Test 4
What bacteria are classified as a) urgent threats, b) serious threats, and c) concerning threats by the CDC?
urgent threats: C. diff serious: MDR Acinetobacter, ESBLs, VREs, MRSA, MDR/XDR TB concerning: VRSA
How do halides kill?
work as a disinfectant; include I-, Cl-, and NaClO Oxidizing agents
Describe the glycopeptide class of drugs
Mech: inhibit transglycosylation and transpeptidation steps in peptidoglyca synth by bining D-Ala-D-Ala Resistance mech: Gram - outer membrane, modification of trager (substitude D-Ala-D-lactate for D-Ala-D-Ala) Spectrum of activity: most effective against Gram + Common names: vancomycin, teichoplanin, daptomycin
What is the classical definition of an opportunistic pathogen?
Microorganism that rarely causes infection in healthy people Requires impairment of host defense(s) to initiate infection --physical breach like a burns, cuts, surgery --Immuno-compromised bc cancer, immunosuppressive drugs, etc --Co-infection or underlying genetic predisposition (AIDS, Cystic Fibrosis)
How do polar flagella work as a PA virulence factor?
Motility, dissemination, initiation of innate immune response
Describe the potential of smallpox as a bioterror agent
Naive population, extremely contagious and lethal Has been used as a bioweapon before ability to vaccinate exposed persons key in control of disease spread; vaccine can prevent disease even if administered 3-4 days after exposure
What is pharmacokinetics?
Pharmacokinetics (distribution of antimicrobial compound in host body) Toxicity dictates external vs. internal use Something that's safe to use on skin may not be safe to ingest absorption, dosage, distribution/dissemination, route of administration, stability also effects which antimicrobial compound should be used in each situation
How does cholera damage your body?
Pili‐mediated attachment to GI epithelium activated after penetration, co‐regulated with Cholera toxin production (ADP‐ribosylase type of toxin) → Gs protein ribosylated by cholera toxin (host cell adenylate cyclase protein which controls cAMP levels; when it's ribosylated, ↑ cyclic AMP levels) → loss of ion flow control → extreme water loss diarrhea, dehydration "rice water stool", which has its appearance due to mucus, epithelial cells, high concentration of V. cholerae
Describe drug resistant PA
Resistant to nearly all antibiotics, inclding aminoglycosides, cephalosporins, fluoroquinolones, and carbepenems 8% of healthcare associated infections caused by PA 13% of severe healthcare-associated infections caused by PA are MDR
What are the extended spectrum B-lactamase (ESBL) producing Enterobacteriaceae?
Klebsiella pneumonia E. coli
Where is V. fischeri found?
in the light organ of the bobtail squid; V. harvii may also be responsible for some light production Symbiosis developed so squid can hide from predators, emitting a degree of light by opening/closing opening on light organs that matches ambient light above
When did MRSA first become noticable to the public?
1990s because of hospital acquired MRSA Hospitals have lots of methicillin/multidrug resistant MRSA; some now becoming resistant to vancomycin NY, 1990s Prohibitive treatment costs (insurance companies, HMOs)-- cost almost a billion dollars to bring outbreak of MRSA under control Insurance companies and HMOs pay for patient stays, isolations, etc Interested in new antibiotic development
How does UV radiation kill bacteria?
A disinfectant; blocks DNA replication and transcription by damaging DNA
What is a bacteriostatic compound?
Bacteriostatic- antimicrobial compounds that inhibit bacterial growth, don't necessarily kill bacteria Bacteria can frequently recover once treatment is removed; best used in patients with intact immune systems bc their immune systems can take over for the drug
What is the result of S. pneumoniae's QS system?
Cells in competent cell-population produce enzymes that protect them from these lysins Incompetent subpopulations can be degraded, killed, and have their DNA taken up (allolysis, fratricide) Thought to be a population-control behavior Strep pneumoniae doesn't have a repair response, so may take up neighboring cells' DNA to fix theirs Ability to take up/ recombine DNA allows genome to be flexible and survive various pressures
Which exotoxins does B. anthracis use?
Edema Factor: adenylate cyclase → high levels of intracellular cAMP → disturbance of H20 homeostasis, disruption of intracellular signaling pathways Lethal Factor: zinc metalloprotease → selectively inactivates mitogenactivated protein kinase kinases (MAPKKs) → deregulation of numerous cell processes → abnormal ion transport, loss of electrolytes and water, blockage of cellular signal transduction pathways, improper functioning of immune response Net result: shock and lethality (precise mechanisms still under investigation) Highly-purified toxins administered to animals cause symptoms typical for anthrax
How do phospholipases work as a PA virulence factor?
Hydrolysis of phospholipids in host membranes, tissue damage, phosphate acquisition
How do alcohol disinfectants kill?
Includes ethanol, isopropanol Denature proteins
What are the general characterstics of antibiotics?
Low-medium MW compounds that kill or inhibit bacterial growth Can be ingested or injected into humans or animals with minimal side effects Generally interfere with a specific cellular process or enzyme
How do we treat S. pneumoniae?
PPSV‐23 vaccine (23 capsule types) recommended for at‐risk adults, elderly --Other vaccines available for <2‐years old Primarily antibiotic treatment (~15% of strains resistant to B‐lactam antibiotics)
How are AIPs produced?
Processed within cell and translated as part of precursor peptide, which may stay linear or cyclize Transported actively with ABC-type energy driven transporting system
What are DNA replication and transcription inhibitors?
Quinolones inhibit DNA gyrase and replication Rifampin inhibits RNA enzyme
How is the expression of blaZ regulated?
blaZ: an efflux pump which provides B-lactam resistance Only expressed in presence of antibiotic; repressed by blaI DNA binding protein when B-lactams aren't there ---Also autoregulates own expression --blaI encoded by operon BlaR1 in resistant strains catches B-lactams when they diffuse through cell wall --Serine residue covalently binds to B-lactam, triggers BlaR1 conformational change and blaR2 disassociates from blaR1 into cytosol blaR2: protease, cleaves blaI, converting it from dimer → monomer and allowing expression of blaZ
How does LPS work as a PA virulence factor?
endotoxic shock, sepsis, serum resistance
Describe the disease caused by anthrax in the GI tract
from consuming raw/ undercooked meat from infected animals fever and chills, swelling of neck/neck glands, hoarseness, nausea and bloody vomiting, flushing and red eyes, stomach pain, swelling of abdomen
What are sources of natural biological threats?
persistant infectious diseases High-impact infectious disease (new/reemerging, MDR, anthroponosis, vectorborne and epizootic, foreign animal zoonotic transmission, food/water borne, increasing # immunocompromised ppl) invasive species
What factors make TB difficult to treat?
slow growth of organism Can cause inherent tolerance to certain treatments Intracellular Limits antibiotic choice patient compliance treatment time can be from 2-9 months, depending on resistance profile Undesirable side effects can also be seen Populations that usually fall ill may make it harder to treat in patients in unstable areas, with mental illnesses, etc
How does procyanin work as a PA virulence factor?
small molecule w/ toxic blue green pigment; redox-active cmpd which generates ROS; disrupts ciliary action and phagocytic function
How does regulation of the tetB efflux pump work?
tetB: provides tetracycline resistance Fitness cost with resistance mechanism --Can result in slower growth of bacteria --Bacteria fine-tune/ carefully regulate expression of genes TetR DNA binding protein: binding to promoter represses transcription; tetR expression is autoregulated Mg2+ + tetracycline → TetR binding → falls off promoter, allows tetB transcription
What are the virulence factors of B. anthracis?
1. Capsule: poly-y-D-glutamic acid polypeptide; protects against phagocytosis 2. Exotoxins 3. Ability to achieve high microbial concentrations in infected hosts
What are the forms of disease caused by B. anthracis?
1. Cutaneous (most common; ~95% of reported cases) Least fatal, can occur with animal contact 2. Inhalation Can also occur with animal contact 3. Gastrointestinal From contaminated meat products, especially undercooked meat 4. Injectional (drug use) (2009-2010 outbreaks in UK and Germany - 54 cases, 18 deaths) More serious than cutaneous anthrax bc skin layer bypassed Heroin likely contaminated and then used Similar symptoms to cutaneous anthrax but much more rapid
How does the tube dilution method for MIC determination work?
A series of increasing concentrations of antibiotic is prepared in the culture medium. --Each tube is inoculated, and incubation is allowed to proceed. Growth (turbidity) occurs in those tubes with antibiotic concentrations below the MIC. --The first clear tube indicates the MIC To determine MBC, you'd have to plate and look for growth after being exposed to antibiotic --No growth? MBC reached
What are some examples of genetic antibiotic resistance in TB?
1. Rifampin-resistance: mutations in β subunit of RNA polymerase Resistance quite common, especially if rifampin is the only thing you're using 2. Streptomycin-resistance: mutations in genes encoding S12 protein and 16S rRNA 3. Fluoroquinolone-resistance: mutations in DNA gyrase gene
How are virulence factors encoded in B. anthracis?
2 plasmids encode virulence factors, pXO1 (toxins; has edema factor, lethal factor, and protective antigen) and pXO2 (capsule) A fully virulent strain has both Can't use this as a vaccine bc it'll be lethal; strains lacking either pXO1 or pXO2 display greatly reduced virulence If pXO1 is lost, you won't be virulent; cure of pXO2 and leave pXO1, you have vaccine
Describe the 1979 anthrax epidemic in Sverdlovsk (former Soviet Union)?
68 confirmed deaths Largest documented outbreak of human inhalational anthrax Later investigation revealed outbreak was likely due to widespread inhalation of anthrax spores accidentally released from a military facility
How do phenols kill bacteria?
A disinfectant; denatures proteins and disrupts cell membranes by intercalating them
What is quorum sensing?
A population density based method of intercellular bacterial communication --As bacterial density increases, quorum sensing is activated Uses autoinducers Usually produced under positive regulatory feedback control Can be used to sense population densities of "self" (within same species) as well as "non‐self" (other species)
How is pneumolysin a virulence factor for S. pneumoniae?
A toxin that assembled in cholesterol containing host membranes, makes large pores and can inhibit ciliary movement and induce chemotaxis ComD phosphorylates transcription regulator, binds COmABCDE locus Bids to comx1 and comx2, alternative sigma factors that regulate competence Autolysins and bacteriocins also regulated by this quorum sensing system Some are competent, some are not Pneumoysin from non-competent cells targets host; can induce pro-inflammatory reactions, complement, etc at low levels May be example of immune distraction At high levels, direct tissue damage; level grows as bacteria grows
How does ExoA work as a PA virulence factor?
AB toxin that ADP-ribosylates EF-2, inhibits host cell protein synth, causes cell death
Describe NNMEC (neonatal-meningitis-causing E. coli)
ADULTS: Abdominal trauma → bloodstream → inflammation/septic shock → organ damage Modified LPS main virulence factor (endotoxin); poorly recognized by TLRs/innate immune cells INFANTS: Abdominal trauma or translocation across GI mucosa → bloodstream → cerebral spinal fluid → neurological complications (cerebral palsy, learning disability, hearing loss) K1 polysialic acid capsule (mimics host sialic acid), confers serum resistance, helps bacteria cross the blood-brain barrier
What are acyl-homoserine lactones (AH1)?
AHLs are small, hydrophobic, membrane‐ diffusible Produced within cell, but can freely diffuse out/in of cells
What is AI2?
AI2 - furanosyl borate diester; byproduct of SAM (S-adenosyl methionine metabolism) degradation, a natural byproduct common to all bacteria and not specifically a quorum sensing molecule but can act as one because it diffuses out of cells of all bacteria --General way for bacteria of all species to sense each other --May be important for colonization --Common to all bacteria; clear indicator of presence of other bacteria --small, hydrophobic, diffusible across cell membrane
Describe AIPs
AIPs are small and hydrophilic, need a transporter Can't passively transport across membrane, need to be secreted and transported Don't diffuse into cell to elicit activity; bind to sensor in cell membrane that sticks into environment AIPs retained in extracellular environment
How do heavy metals kill bacteria?
Act as a disinfectant; include Hg2+, Ag+ Bind -SH groups, denaturing proteins
How does primary Gram - intraspecies communication work?
Acyl-homoserine lactones/ AH1 used No active transporters or accessory proteins needed More bacteria= more autoinducer= when threshold is reached, autoinducers move into cell and bind transcription factor (LuxR in bioluminescence example)= changes conformation so it can interact with and regulate target genes --Often requires dimerization --Binding of AHL to receptor regulator protein within cell protein → dimerization → regulation of target genes
How do Type IV pili work as a PA virulence factor?
Adherence, twitching motility
How do infants and adults receive an S. pneumoniae vaccine?
Adults: vaccine consists of the 23 most common antigenic capsular types. Very safe, routinely given to the elderly (at most risk of contracting pneumonia), efficacy ~60%. This vaccine is useless in infants (lack T-cell independent responses to generate antibodies to long chain polysaccharides) Infants: a protein conjugated-capsule vaccine (7 most prevalent serotypes "PCV-7") was introduced in 2000. Covalently linking carbohydrates to protein segments can induce a major histocompatibility complex type II-mediated T-cell-dependent response to the carbohydrates, even in infants PCV -7 (pneumococcal conjugated seven valent vaccine) has been highly successful in the United States and other developed countries. Invasive pneumococcal diseases have dropped about 70 to 80% for infants under 2 years of age, and most infants in the United States now routinely receive this vaccine
How does TB spread? Symptoms?
Aerosols from infected individuals (**Efficient!) → alveoli → internalized by macrophage, where it initially grows → inhibition of lysosomal fusion → SLOW replication --Transmission is highly efficient even if growth is slow once you're infected Potential outcomes dictated by the health status of infected individual: --Person young/ robust/ healthy → Infecting microbes are killed/cleared, usually --Infecting microbes remain viable but controlled in granuloma for many years Latent TB -Can reactivate with age, immune deficiency, etc -Growth, lung damage, dissemination and destruction of other organs -In old/ immunocompromised/ genetically more susceptible (inherent differences in cell-mediated response, which kills TB)
What are some contributers to antibiotic resistance besides human use?
Agricultural use of antibiotics in feed Some antibiotics have growth-enhancing properties and are used to supplement stock feeds Discovery of new antibiotics nearly ceased; not a big $$ maker for industry 1980s research effort (mechanisms of resistance, regulation of resistance genes) came to be viewed as "old-fashioned" → de-emphasis of work and funding
How do we treat/prevent anthrax poisoning?
All forms of disease treatable with antibiotics; "the sooner the better" (especially for inhalational or GI anthrax) A vaccine is also available, but only recommended for certain at-risk adult groups (i.e. military, researchers) Anti-toxin strategies still under investigation
Describe EHEC (enterohemorrhagic E. coli)
Also causes diarrhea, but it's bloody --Can cause further complications (kidney failure (HES), irreversible kidney failure in old and young) --Hamburger disease bc it can be transferred in hamburgers O157:H7 pathogenicity island encodes virulence factors EAE remodeling occurs after delivery of Shiga toxin (ST) Shiga-like toxin (ST) responsible for HES and bloody diarrhea; removes adenine base from cell, killing it --Depurination (removal of adenine base from backbone of host 28S rRNA) blocks protein synth, kills cell --Encoded by lysogenic phage Adherence is mediated by Type I pili, results in actin rearrangement Occurs in large intestine/ colon
What are translation inhibitors?
Animoglycosides, tetracyclines (50S0; chloramphenicol, macrolides, streptogramins, eveminomycins, oxazolidinones, lincosamides (30S) Most are bacteriostatic, some bactericidal Usually inhibit some bit of ribosome during translation
How could anthrax be used as a bioweapon?
Anthrax spores are easily found in nature, can be produced in a lab, and can last for a long time in the environment. Could be released quietly and without anyone knowing. Microscopic spores could be put into powders, sprays, food, and water. Invisible, odorless, tasteless
How does the MDR efflux system (MexEF, OprMN, and MexT) work as a PA virulence factor?
Antibiotic efflux pump (MexEF-OprMN) and its regulator (MexT); confers resistance
What are side effects?
Antimicrobial agent specificity for bacterial target without affecting mammalian cells (differential toxicity) is preferred Some do have some side effects "risk vs. reward" Are the side effects worth it to treat a patient?
How does the El Tor quorum sensing system work?
At low cell density conditions, neither system (A1 or AI2) bind QS molecules --HKs involves in each cascade retain kinase activity, phosphorylating LuxU which phosphorylates LuxO which produces small RNAs that destabilize HapR RNA (central regulator) --When HapR is low, high levels of cyclic ci-di-GMP form, increasing biofilms and cholera toxin --So, in early infection, toxins and biofilms produced to colonize Once Vibrio reaches high population density, Ai1 and Ai2 bind to their HKs, turning off this system -Binding turns kinases to phosphatase, allows HapR to become more highly expressed -Lowers levels of cyclic di-GMP (also called ci-di-GMP), turns off biofilms and cholera toxin (CT), turns on virulence factors important for exiting host/ being transmitted, like metalloproteases and other genes important for transmission/ shedding
What is the anthrax vaccine like?
Attenuated live vaccine strain developed by Sterne in 1937 is still the basis of most anthrax vaccines for livestock; lacks pX02 and is therefore Cap- Tox+. Protection related primarily to antibodies specific for the protective antigen component of the toxin
Describe the B-lactam class of drugs
B-lactams: include penicillins, cephalosporins, carbapenems, monobactams Mech: inhibit transpeptidation step in peptidoglycan synth; bind penicillin-binding proteins and stimulate autolysins Resistance mechs: Gram - outer membrane, porin mutations, B-lactamase, modification of penicillin-binding site Spectrum of activity: Gram + and/or Gram -, depending on agent Common name: penicillin, ampicillin, cefobid, augmentin
What are examples of biofilm infections?
Dialysis catheter infection Intravascular catheter infection Prosthetic valve endocarditis Pacemaker infection Chronic sinusitis Pulmonary infection in cystic fibrosis patient
How does enzymatic inactivation of an antibiotic work?
Bacteria express an enzyme that cleaves/ otherwise inactivates antibiotic --B-lactamase → penicillin resistance --Chloramphenicol → streptogramin acetyltransferases
How do we treat TB? How many VRSA strains are there?
Bc of resistance (primarily modification of drug targets), a four-drug regimen (incl. rifampin) is recommended for persons in US with slight to moderate risk for infection with multidrug TB. There have been 11 VRSA (Vancomycin-resistant S. aureus) strains isolated in the USA, resistance from VREs --VanX derived from VREs via transposons --HGT of VanA/B has also occurred
What are the cell wall synthesis inhibitors?
Beta lactams have 4-membered ring that kill bacteria by inhibiting last step in peptidoglycan synthesis by preventing crosslinking of side chains in final transpeptidation reaction --Bind and inhibit penicillin-binding proteins, enzymes which facilitate last crosslinking reactions --Autolysins become hyperactive, chew up cell wall and kill Vancomycin block transpeptidation and transphosphorylation step
Describe S. pneumonia biofilm formation
Biofilm formation associated with nasopharynx colonization, otitis media, fomite transmission in vitro biofilm formation most enhanced in mutants lacking capsular polysaccharide(CPS) --CPS needed for virulence (prevention of opsono-phagocytosis) --If you inject these in vitro biofilms into an animal, you get weaker disease and a weaker immune response --Balance between ability to colonize and ability to become more invasive by producing capsule; needs capsule to live in nasopharynx Mice infected with planktonic bacteria progressed to bacteremia; most challenged with biofilm bacteria did not Biofilm inoculum also induced weaker immune response
What is bioterrorism? A dual-use agent?
Bioterrorism: The intentional release of viruses, bacteria, or other germs that can sicken or kill people, livestock, or crops. Dual-use agents: Those biological agents (bacteria, virus, toxin) that are used non-malicious ways (therapeutic development, educational purposes) but could also be used as bio-weapons (i.e. botulinum toxin, staphylococcal enterotoxins, B. anthracis, many others)
What is the primary virulence factor used by S. pneumoniae?
CPS
How is natural competence in S. pneumoniae regulated?
CSP produces comABCDE genes --> competent S. pneumoniae commit fratricide and take up DNA of noncompetent S. pneumoniae Noncompetent S. pneumonia use pneumolysin to lyse other cells
How does Gram+/- interspecies communication occur?
Can be AI1 or AI2 dependent; both types are hydrophobic. We focus on AI2 AI2 sensed by a TCS --> Binding of AI2 to membrane receptor protein (HK) → phosphorylation of RR → regulation of target genes
How does B. anthracis activate?
Can live in environment for decades; might just have to quaruntine pasture for long time spores dormant in soil under high O2, low temp conditions --> spores get into body of animal/person, high CO2 and high temp trigger germination --> bacteria multiply, spread out in body, produce toxins and cause illness
Describe UPEC (uropathogenic E. coli)
Causes UTIs, especially in women Hemolysins Tropism for UT/bladder due to Type I pili containing FimH and P pili containing PapG --Both FimH and PapG are specific proteins at the tip of the pili that get into bladder Adherence → invasion/intracellular replication → host cell lysis/exfoliation
Describe EIEC (enteroinvasice E. coli)
Causes bloody diarrhea/ dysentery Also in colon E. coli itself invades epithelial cells, facilitated by binding and uptake by M cells Bacteria spread laterally via the host cell's manipulated actin tails like Listeria/ Shigella
Describe how E. coli K1 utilizes breaches to act as an opportunistic pathogen
Causes infant meningitis Colonizes infants in vaginal tract during birth
Describe how P. aeruginosa utilizes breaches to act as an opportunistic pathogen
Causes lung infections Colonizes built-up mucus present in cystic fibrosis patients
Describe how P. gingivalis utilizes breaches to act as an opportunistic pathogen
Causes periodontal disease, internal infections Uses a shift in microbiota of gums --> inflammation
Describe how A. baumanni utilizes breaches to act as an opportunistic pathogen
Causes wound infections Seen in traumatic war wounds in Iraq vets
How are E. coli strains classified?
Classification via serotyping (O antigen - LPS, H antigen - flagella, K capsule type) Serotyping often not sensitive enough to detect differences between clinical strains (i.e. same serotype, different virulence properties), therefore virotyping can be used (profiling based on virulence factor production, effects on host cells, clinical symptoms)
Describe general characteristics of Gram - opportunists
Come from either normal microbiota, soil, insects (insects are controversial) Usually requires a specific type of "breach" to initiate infection (i.e. they respond to a more limited range of opportunities relative to Gram +ve opportunists) --Many demonstrate a tropism for types of breaches Many are multidrug resistant → difficult to treat Include E. coli K1, P. gingivalis, P. aeruginosa, A. baumanni, etc
What are some exceptions to the classic definition of an opportunistic pathogen?
Community-acquired infections (MRSA, C. difficile ) Strains with increased virulence properties (S. pyogenes "flesh-eating disease") Even in the case of "true" pathogens, there exists a wide variation in host susceptibility (i.e. TB - asymptomatic infection)
How does serine B-lactamase work as a mechanism of B-lactam resistance?
Covalent bond formation between active site serine and B lactam ring (analogous to covalent bond formed between serine residues in PBPs) B-lactamase secreted enzyme cleaves B-lactam ring and is covalently attached to antibiotic H2O can come in and attack ring, opening it up and released B-lactamase
What are different C. diff infection outcomes?
Disruption of normal flora--> protective factors present (high serum antibody response to toxin A, mild underling disease) active 40-60% of time--> asymptomatic colonization --> low likelihood of infection, may at as nosocomial reservoir Disruption of normal flora--> risk factors present (low serum antibody response to toxin A, severe underlying disease, 40-60% of cases) --> C. diff diarrhea --60-95% of time, risk of recurrent infection is low after treatment (<65, no exposure to antibiotics) --5-40% of time, increased risk of recurrent infection after treatment, 50% due to infection and 50% to relapse (>65, exposure to antibiotics)
Describe ESBLs
ESBLs can hydrolyze the B-lactam ring of various cephalosporins, not just penicillins --Usually associated with active site mutations of plasmid-encoded β- lactamase genes --These plasmids often encode other antibiotic-resistance genes (i.e. aminoglycosides), making treatment choices limited --Carbapenems usually used to treat these infections but some are becoming resistant to those 19% of healthcare-associated Enterobacteriaceae infections are caused by ESBL-producing Enterobacteriaceae. Patients with bloodstream infections caused by ESBL-producing Enterobacteriaceae are about 57% more likely to die than those with bloodstream infections caused by a non ESBL-producing strain
What are the two cholera biotypes?
El Tor: -Responsible for 7th pandemic (1960s - early 1990s) -Milder disease compared to Classical strain -Has slightly different quorum sensing that regulates virulence than classical type -Has an AI1 and an AI2 system Classical: -Responsible for 6 pandemics (1817‐ 1923) -Similar to El Tor, but QS system is a little different
What factors contribute to Acinetobacter baumanni environmental persistence, host infection, and colonization?
Environment: resistant to dessication, able to use many substrates for growth, QS sensing for biofilm formation Colonization: adherence to host cells, resistance to inhibitory agents, biofilm formation and QS Infection: elicitation of inflammatory responses, cytotoxicity , iron acquisition, resistance to serum and complement activation Can cause pneumonia, skin infections, sepsis, UTIs, infect wounds, etc
What are the characteristics of a good antibiotic?
Few or no side effects to the host; lacks "differential toxicity" Broad spectrum of activity (but can have drawbacks...i.e. C. difficile infection usually occurs after native gut microbiota killed off) --Good: you can wipe out lots of different things to treat a patient immediately before labs come back --Bad: may cause further problems down the line, like subsequent infections from wiping out normal microbiota and resistance Appropriate bioavailability (rate or amount of drug that reaches the infection site) and pharmacokinetics to get to site(s) of infection Ex: might be different to reach an abscess, so some antibiotics taken via pills may have trouble getting to it Pill/ingested form Low cost
How do PA biofilms form?
Free living cells attach to cell surface → become sessile (attached) and biofilm genes upregulated, those for motility turned down → microcolonies → mushroom-type towers form, protective matrix forms --Visualized under microscope --Mature biofilm takes about a week to form --Doesn't look same in vivo All wild-type P. aeruginosa strains are capable of synthesizing alginate --Mucoid phenotype (high alginate production) is not observed outside the human host --Conversion to an overtly mucoid phenotype appears to depend on host environmental pressures --Mucoid forms very resistant to drugs; nearly all in lung eventually convert to mucoid over time
What is cholera?
GI disease causing voluminous watery diarrhea; life threatening (dehydration) Fecal‐oral transmission; aquatic environments natural reservoir of bacteria (algae, copepods, crustacean shells) --Bacteria bind to a number of organisms in the water --Can be ingested, go into your GI tract, and cause illness Mortality rate without treatment 25% ‐50% Asymptomatic carriers also important reservoir
What are some factors that have exacerbated the development of resistance?
Genomic plasticity of bacteria (core genome mutation acquisition/ accumulation, intra-/interspecies genetic exchange, mobile genetic elements) --Bacteria have very fluid genomes --Lots of mutations, horizontal gene transfers, plasmids/ transposons can cause antibiotic resistance Resistant strains outcompete naive strains 50% of antibiotic use in US estimated to be inappropriate --Antibiotics prescribed for viral or inappropriate bacteria --Use of antibiotics to enhance growth of livestock Crowding, homelessness, poor nutrition/sanitation --Make it very easy for antibiotic resistance to develop/ spread International travel
How does P. gingivalis affect teeth?
Gingipains aid in destruction of host antibodies and complement, contribute to localized tissue destruction --> bone loss reduction in cytokine production interferes w/ neutrophil recruitment to periodontal pocket --> modification of local host responses to biofilm flora results in skewed immune response that drives periodontitis progression
What is streptococcus pneumoniae?
Gram +ve diplococci, inhabits upper respiratory tract of up to 40% humans Can cause pneumonia, bacterial meningitis, otitis, various upper respiratory infections --~60% of all bacterial pneumonia Capsule very important in its virulence --> 83 types of polysaccharide capsule; major contributor to invasive potential (bloodstream, cerebral spinal fluid) --Avoids phagocytosis, complement, etc --Capsule production highly positively correlated with infectious ability At risk populations have less natural antibodies (6 months‐2 years, elderly) or immunocompromised, recovering from viral infection Aerosol spread (community)
How common is S. pneumonia colonization? What can it cause? Vaccines?
Gram +ve diplococci, inhabits upper respiratory tract of up to 40% humans When it goes into places it shouldn't be, you can get pneumonia, bacterial meningitis, otitis, various upper respiratory infections ~60% of all bacterial pneumonia > 83 types of polysaccharide capsule; major contributor to invasive potential (bloodstream, cerebral spinal fluid) At risk populations have less natural antibodies ( 6 months -2 years, elderly) or immunocompromised, recovering from viral infection Aerosol spread (community pneumonia) Having the flu before puts you at risk PPSV-23 vaccine (23 capsule types) recommended for at-risk adults, elderly Other vaccines available for <2-years old Primarily antibiotic treatment (~15% of strains resistant to B-lactam antibiotics) More than ½ of deaths in the great 1918 influenza epidemic died of invasive pneumococcal disease
Describe Enterococcus faecalis
Gram +ve facultative anaerobe Causative agent of UTIs, abdominal/pelvic wound infections, bacteremia --Opportunistic pathogen usually infections are hospital-acquired Can normally be found in external environment and human GI tract Grown on bile esculin agar: esculin hydrolysis + ferric citrate = iron salts (black)
Describe Clostridium difficile
Gram +ve rod; spore former Endogenous or environmental (spores) It's more common in the environment but can be commensal; as an opportunistic pathogen or microbial shift disease, can be severe Causes bloody diarrhea; pseudomembranous colitis Overgrowth in the colon a result of normal flora disruption (antibiotics) Recurrence common; little protective immunity
Describe A. baumannii
Gram -ve rod, aerobic, non-motile High incidence among immunocompromised individuals, especially those who have experienced a prolonged ( > 90 day) hospital stay Ubiquitous in soil and aquatic environments; can also colonize skin Became well-known during Iraq war --Both colonized and lethal wound infections (soldiers) → Iraq strains brought to US via colonized wounded soldiers → Walter Reed hospital treated soldiers (veteran hospital = initial treatment) → spread to other US hospitals Wound infections (primarily), also bloodstream and pneumonia Has been categorized as a "superbug" (along with TB and MRSA) because they are extensively drug resistant Also inherently resistant to disinfectants and various environmental conditions like dessication → hampers decontamination efforts Aggressive sterilization and patient isolation required (1 patient = 1 doctor/1 nurse rule)
Describe the characteristics of Escherichia coli
Gram -ve rod, motile Pink colonies on MacConkey agar bc they ferment lactose Many strains!!! Problem in immunocompromised/ breached patients
Describe Vibrio cholera
Gram -ve, motile, halophilic (likes to be salty, lives in ocean) Causative agent of cholera; penetration of intestinal epithelium facilitated by flagellar motility, mucinase
Describe B. anthracis
Gram-positive, non-motile, aerobic, facultative anaerobic, large rod-shaped bacterium capable of forming dormant spores Found in soil → herbivore mammals ← humans Spores clump together naturally but can be refined for inhalation
How do biofilms contribute to antibiotic resistance?
Growth of biofilm confers tolerance Growth of bacteria slows/ stops in presence of antibiotic, but cells aren't killed so they can proliferate once treatment is stopped --Protective matrix may limit diffusion of a few antibiotics, but not a universal mechanism May be destroyed by matrix enzymes Some may be inactivated by metabolic waste, low pH, high CO2/ low O2, etc --Some have very hard time with slow growing-bacteria normally (esp b-lactams) Biofilm-specific resistance genes may be an issue Because biofilms grow in response to stress, enzymes associated with stres response may inactivate antibiotic --Antibiotic tolerance: growth of bacteria stops in the presence of antibiotic, but cells are not killed
What components does the El Tor quorum sensing system have?
Has an AI1 and AI2 A2 system requires binding to TCS, does not generally diffuse --Once QS molecule interacts with TCS, they inhibit phosphorylation (has a phosphatase activity)
What lessons were learned from the 2001 US anthrax attack?
Important for there to be an official organized network of scientific experts to communicate with media and the public Minimize hype and propagation of mis-information (i.e. needless destruction of anthrax strains at ISU) Appreciation that a bioweapon attack does not have to be "a large-scale exposure with catastrophic outcomes" (Pre-2001 era scenario) Increased scrutiny, reporting requirements for obtaining and working with select agents Better medical infrastructure and crisis management plans now in place: --In 2002, decision made to acquire enough smallpox vaccine for the entire U.S. population --currently more than 300 million doses of stockpiled FDA-approved vaccine, which was made using modern cell culture methods
Hows does quorum sensing LasR system work as a PA virulence factor?
Key role in controlling virulence factor production biofilm formaton, swarming motility, expression of efflux pumps
What is the minimum bactericidal concentration (MBC)?
Lowest [antibiotic] that will kill bacteria
What is the minimum inhibitory concentration (MIC)?
Lowest [antibiotic] that will prevent bacterial growth --Determined via a dilution susceptibility assay
What diseases does P. aeruginosa (PA) cause?
Lung infections in cystic fibrosis (CF) patients; causes infections in skin (burn wounds, chronic wounds), eye, bone, heart, UTI, meningitis Frequent caue of nosocomial infections
Describe the macrolide/ lincosamide class of drugs
Mech: Bind 23S rRNA in 50S subunit of bacterial ribosome Resistance mech: methylation of target, efflux Spectrum: bacteriostatic, can be bactericidal for some Gram + Common names: erythromycin (macrolide), linomycin, clindamycin (lincosamide)
Describe the rifampin class of drugs
Mech: Binds B subunit of bacterial RNA polymerase Resistance mech: mutation in RNA pol Spectrum of activity: broadly antibacterial, effective against mycobacteria Names: rifampin (inhibits RNA enzymes), rifadin
Describe the tetracycline class of drugs
Mech: bind 16S rRNA in 30S subunit of bacterial ribosome; disrupt bacterial membrane Resistance mech: inactivation of antibiotic, ribosome protection, efflux Spectrum of activity: Broadly bacteriostatic, some protozoans Common names: tetracycline, doxycycline
Describe the flouroquinolone class of drugs
Mech: bind DNA gyrase Resistance mechs: efflux, reduced uptake, mutations in DNA gyrase Spectrum of activity: broadly bactericidal, can enter phagocytes and kill intracellular bacteria Common names: ciprofloxacin (common for anaphylaxis), norfloxacin
Describe the streptogramin class of drugs
Mech: bind to 23S rRNA in 50S subunit of bacterial ribosome Resistance mech: inactivation of antibiotic by removing groups Spectrum: bacteriostatic individually; bactericidal in combination; used for MDR enterococcal infections Common names: synercid
Describe the genetics of S. pneumoniae
Naturally competent → genetic diversity Genomes of different serotype strains differ by ~10%, these differing regions often contain pathogenic islands with genes that mediate invasive diseases. Was one of the first model bacterial systems used to study fundamental molecular genetic processes Avery, MacLeod and McCarty used the natural transformation of S. pneumoniae to demonstrate that DNA is the genetic material Most people are usually colonized by only one serotype at a time, due to intraspecies competition (partly mediated by bacteriocin/pneumocin production → regulating by QS)
Are all Gram + opportunistic strains equally infectious?
No; Each bacterial species is actually composed of many subgroups that contain profound differences in their genomes and virulence properties. ''Pangenome'' or ''total composite genome'': Core set of genes shared by all (~80%) + ~20% extrachromosomal elements (transposons, pathogenicity islands, prophage, plasmids) that tend to carry specific virulence genes, toxin genes, antibiotic resistance genes, etc. These 20% ''accessory'' genes usually dictates the pathogenic potential of a particular subgroup of a given species (commensal → opportunistic pathogen → disease severity)
Describe the general characteristics of Gram + opportunistic pathogens
Normal commensal inhabitants of the human body (either majority of the population (i.e. S. epidermidis) or a portion of the adult population at any one time (i.e. S. aureus, S. pneumoniae, Clostridium difficile) Like the Gram -ve opportunistic pathogens, multi-drug resistance can a problem (i.e. MRSA) The "line" between opportunistic pathogen and other categories of disease can be blurred (i.e. community-acquired MRSA, C. difficile, S. mutans)
Describe Porphyromonas gingivalis
Obligate anaerobic bacterium located in oral cavity Occupies periodontal pocket (region between teeth and gums) , which is pretty anoxic Involved in gingivitis (inflammation of gums) ↑anaerobes (incl. P. gingivalis) → inflammation → deepening periodontal pockets → bleeding gums → tooth loss Can also occasionally cause internal abscesses Association between P. gingivalis and coronary heart disease, as well as various autoimmune diseases (diabetes, arthritis)
Both disinfectants and antiseptics...
Often also active against viruses, fungi, protozoa Often several targets in bacterial cell so harder to form resistance --10% bleach will kill almost anything Most effective against actively growing bacteria In general, resistance mechanisms poorly understood relative to antibiotics --Membrane-active agents less effective against Gram -ve bacteria --Membrane pumps (Quaternary Ammonium Cation resistance in staphylococci) can be used to form resistance because they pump out QACs
How does protected antigen (PA) allow both edema factor (EF) and lethal factor (LF) of B. anthracis to act upon a host?
PA needed for binding specific host cell receptors; docks toxin to cell and delivers EF and LF into host cell through proteolytic cleavage events --Makes heptamer which recruits up to 3 subints of EF or LF, induces endocytosis --Endosome acidifies, allows heptameric complex to translocate Ef and LF into cytosol of cell Ef causes high levels of cAMP and → edema
How does modification/protection of a target function as a mechanism of antibiotic resistance?
PBPs (S. aureus methicillin resistance) --Methicillin targets PBPs (penicillin binding proteins) so S. aureus acquired a modified PBPs glycopeptide resistance in vancomycin resistant enterococcus (VRE) tetracycline resistance (widespread) macrolide resistance (widespread)
Describe K. pneumonia
Part of normal GI microbiota but can cause healthcare-associated infections, including pneumonia, bloodstream infections, wound or surgical site infections, and meningitis
How quickly did penicillin, methicillin, and vancomycin resistance develop?
Penicillin introduced in 1943, but staph resistance noticed before implementation --Many other bacteria now resistant Only took 2 years for methicillin resistance to develop Long time to develop vancomycin resistance; first resistance didn't occur for around 15 years
What is the persister cell hypothesis?
Persister cells aren't slow-growing bacteria; instead subpopulation of dormant/non-growing cells that survive antibiotic treatment --Always present (~1%) --Metabolic processes cause change into these phenotypes --In some bacteria, certain signaling molecules → dormancy ---Toxin-antitoxin modules → ppGpp induced in subpopulation → inhibit macromolecular synthesis processes → dormancy --Biofilm penetrated, persisters may survive treatment to cause new infection Helps explain why biofilms can cause chronic, hard to treat infections
What is pneumolysin and how is it helpful?
Pneumolysin is also produced as part of QS system; a pore-forming toxin important for virulence, regulated by competence development Also released from non-competent cells, targets eukaryotic cells Sublytic concentrations: induction of host cell apoptosis, activation of host complement, induction of proinflammatory reactions in immune cell. Higher lytic concentrations: Potential for widespread direct cellular and tissue damage via pore forming properties
How does the Lux system in V. fischeri operate?
Positive feedback! At low cell density, vibrio have low level LuxI expression for AI1 and low expression of LuxR transcription factor for AI1 binding → cells grow an daccumulate, threshold concentration of AI1 increases and goes back into cell → goes back to LuxR, dimerizes → upregulates LuxR expression and divergent loci which upregulates LuxI (makes AI1) → downstream genes required for luciferase formation/ light formation activated
How do we prevent/detect cholera?
Prevent by keeping water sources sterile, clean food Stool sample testing important Grows on specific agar plate as yellow colony ELISA or eukaryotic cell culture tested for toxin based on change in eukaryotic cell lines in response to toxin
What is a two-component system (TCS)?
Production of AIPs coupled to this; has 2 components: HK and RR Sensor component (sensor kinase, HK): special membrane embedded protein with AIP binding pocket; AIPs bind here once critical threshold is reached --HK has phosphorylation ability, phosphorylates response regulator (RR) Response regulator (RR) targets genes used by quorum system
What are the notable virulence factors of PA?
Pyocyanin: blue-green pigment that generates ROS → interferes with cilia action and phagocyte function --Characteristic blue-green pigment of PA on agar plate produced bc of pyocyanin, also glows in UV light Alginate capsule: adherence, resistance against phagocytosis, protection of biofilm, anti-desiccant Biofilm growth - variety of factors Quorum sensing Multi-drug efflux pump Variety of toxins (cytotoxicity, inflammation, antiphagocytic)
What is the S. pneumoniae QS system based on? What are the components?
QS has been related to competence (ability to uptake DNA) --Unknown signal which differentiates populations into those that are and are not competent --Not all members of a pop will become competent System based on Com locus ComABCDE locus encodes.... --Transporter for auto-incuding peptide (ComA, ComB) ComC: encodes precursor for competent-stimulating peptide (AIP) --Com D, ComE: senses AIP --ComD: HK --ComE: RR
Describe vancomycin resistant enterococci (VRE)
Represents about 30% of all hospital-acquired Enterococcus infections Enterococcus sp. intrinsically resistant to various β-lactams, fluoroquinolones, and aminoglycosides VRE infections usually treated with newer antibiotics such as daptomycin HGT is a concern i.e. VRE → MRSA = VRSA Genes that encode vancomycin resistance in other bacteria derived from VREs
How is CPS useful in S. pneumoniae infection?
Resists opsonophagocytosis (opsonization + phagocytosis) Low-level capsule production, increased net negative charge of certain serotypes, helps evade entrapment by mucus (mucopolysaccharides highly negatively charged due to sialic acid and other anionic residues) by electrostatic repulsion Invasive strains of S. pneumoniae are encapsulated; unencapsulated strains are infrequent, usually only associated with topical eye infection CPS production also required for efficient in vivo colonization; suggests that S. pneumoniae must strike a balance between CPS hindrance of biofilm formation and resistance to host defense
What are other S. pneumoniae virulence factors besides CPS?
SPXB: makes hydrogen peroxide, which stimulates cytokine production by surrounding host cells, helps it compete in respiratory tract Oxidizing pyruvate makes ATP; streps can't respire with an electron transport chain, so they ferment, take up carbs, and oxidize pyruvate to make energy Modifying LTA via phosphocholine (ChoP) groups increases ability to bind to PAF, molecular mimicry → inflammation Pneumolysin: assembled in cholesterol-contraining cells bc large transmembrane pores; increase concentration --> inhibit ciliary movement, chemotaxis of immune cells Surface adhesions (PavA, Eno, NanA, PsrP)
Describe PA pathogensis in burns/chronic wounds
Seepage of plasma = rich nutrient source PA is the leading cause of infection of burn wounds Bacteria leak into bloodstream → systemic infection Extremely difficult to treat due to PA antibiotic resistance (biofilm growth, drug efflux pumps) Biofilms impair wound healing by stimulating chronic inflammation, leading to elevated levels of proteases and ROS that degrade proteins that are essential for healing --PA grows back quickly even after debridement Important virulence factors similar to those required for CF lung infection (biofilm formation, toxins, efflux pumps, etc) Pyocyanin production thought to contribute to tissue necrosis --Blue pus fluoresce under long-wave UV light Can also infect toes or fingernails --Pyocyanin causes bluish-gray color
What is an autoinducer? What are the three classes?
Small, diffusible signaling molecules ("autoinducers") 3 major families --Gram +/- interspecies communication --Acyl‐homoserine lactones (AHLs; produced primarily by 1° Gram -ve) --Autoinducing peptides (AIPs; produced mostly by 1° Gram +ve)
Describe the 2001 US anthrax outbreak
Spore-containing envelopes mailed to news and government offices; general consensus is that is was "non-weaponized" (i.e. pores purified and ground up but not mixed with silica/dispersal agents) --11 inhalational and 11 cutaneous cases reported. --All five patients who developed shock with inhalational disease died --Prophylactic antibiotic treatment for many potentially exposed individuals likely mitigated a much higher fatality rate Specific source of the contaminated envelopes is still debated --Two suspects investigated, no one ever formally charged/prosecuted Ames strain used --Caused lots of confusion; used to test vaccines --Not from Ames, Iowa; mislabeled but isolated from TX and was just processed in Iowa; army believed this strain came from Ames Iowa instead --ISU forced to destroy their samples
Describe the potential of B. anthracis as a terrorism agent
Spores extremely stable outside host; can be produced in large quantities but require refinement
How does the quorum sensing system for the classical biotype work?
Still TCS Has special, little characterized system in which ci-di-GMP is not regulated through HapR So, bypasses HapR to more directly regulate ci-di-GMP levels High levels of ci-di-GMP still signal increases biofilms and CT; low levels still seen in later infections
What are the mechanisms of tetracycline resistance? How does tetracycline normally work?
Tetracycline sensitive cell: Tetracycline correctly acts on cell; diffuses into cell, accumulates, intracts with 16S rRNA, stalling translation and blocking protein synth Tetracycline efflux pump (cytoplasmic membrane) Intracellular [tetracycline] remains too low; prevents binding to 16S rRNA Ribosome modification/ protection: TetM GTPase activity perturbs helix in 16S region bound by tetracycline; prevents binding to 16S rRNA
Describe Mycobaterium tuberculosis
Tuberculosis (TB) "Acid-fast" bacillus (Ziehl-Neelsen stain of sputum) Can't be stained traditionally, needs a Ziehl-Neelson stain identified from sputum culture, chest X-ray, or TB skin test (indicates exposure; does not necessarily mean infection) --Tb test: positive result indicated by red welt over 20 cm in diameter
What happens when the S. pneumoniae QS activates?
Turns on at high concentrations ComD phosphorylates ComE → ComE upregulates expression of whole locus and target of alternative sigma actors (ComX1, ComX2) which regulate competence factors (DNA uptake, DNA recombination genes [Allow for DNA uptake from environment and recombination within bacteria]), autolysins/ bacteriocins (degrade bacterial cell walls)
How do ExoS, ExoT, ExoU, and ExoY work as a PA virulence factor?
Type III secretion system effector proteins; cause cytotoxicity in host, inflammation
Describe primary Gram + intraspecies communication?
Uses AIPs, which need a transporter Same basic principle as Gram - type; when critical threshold density reached, released AIPs bind to receptor in cell Binding of AIP to membrane receptor protein (HK) → phosphorelay to RR (response regulator) → regulation of target genes
What are the mechanisms of vancomycin resistance?
Vancomycin binds to the C-terminal acyl-D-Ala-D-Ala of the undecaprenol-diphosphate MurNAc-pentapeptide intermediate and inhibits transglycosylation and transpeptidation reactions in cell wall peptidoglycan polymerization and cross-linking --VanH enzyme catalyzes pyruvate → D-lactate --VanA/B (either A or B depending on resistance mechanism) So, makes a D-Ala-D-Lactate repeat that vancomycin can't recognize instead of D-Ala-D-Ala --VanX from Cleaves any remaining D-Ala-D-Ala to single D-Alas Gram -ve bacteria naturally-resistant to Vancomycin (bulky → cannot diffuse through outer membrane porins)
Describe E. coli
Variety of pathogenic strains and diseases depending on toxins (diarrhea, dysentery), UTIs, meningitis, respiratory tract, others) Transmission routes: fecal-oral, contaminated food, birth canal Normal resident of microbiota in some individuals
Describe MDR Acinobacter
Whole genus categorized as serious, not just the species mentioned here about 63% of acinobacter considered MDR (resistant to at least 3 classes of antibiotics) 2% of healthcare associated infections reported to the CDC caused by Acinobacter, with higher proportions (7%) among patients on mechanical ventilators
Can a bactericidal compound ever have a bacteriostatic effect?
Yes! A lot of bactericidal antibiotics depend on growth state of bacteria; fast growing ones very susceptible Those that are slow growing or have a biofilm may survive better and a bactericidal antibiotic may have more a bacteriostatic effect
What are biological threats originated by people?
accidental release of infectious agent deliberate release of infectious agent, bioterrorism
How does limiting access of an antibiotic work as a resistance mechanism?
active efflux of antibiotic (antiporters, ABC transporters) Pump antibiotics out of the cell faster than it can penetrate cell, lowering concentration below a useful amount
How does alginate work as a PA virulence factor?
adherence, protection from dehydration, antiphagocytic, protection of biofilm from host immune response
How do alkylating agents kill?
another category of disinfectants; include formaldehyde, ethylene oxide Form epoxide bridges that inactivate proteins
What is a bactericidal compound?
antimicrobial compounds that kill bacteria Best for patients with compromised immune systems
What are antiseptics?
applied to living skin or tissue Not ingested/ injected Often contain diluted disinfectants
How does antibiotic resistance occur?
basic process: lots of germs in an area, a few are naturally resistant --> antibiotics kill bacteria causing illness as well as good bacteria --> drug-resistant bacteria fill gap, may transfer resistance to other bacteria via HGT Antibiotic-resistant infections can happen anywhere. --Data show that most happen in the general community --However, most deaths related to antibiotic resistance happen in healthcare settings, such as hospitals and nursing homes.
Describe EPEC (enteropathogenic E. coli)
causes diarrhea Alters mucosa when plasmid-encoded BFP is bound, which allows cells to attach and make microcolonies --Not all strains have BFPs Attachment of E. coli to host cell very close; signaling causes actin to rearrange and pedestals form on host cells --EAE (microvillus effacement) also results, alteration of structure of cell 35 kb pathogenicity island encodes genes that alter cell ultrasctructure Toxins (CLDT, CNF) may also be here and cause cell enlargement/ cytoskeletal rearrangement Distal small intestine; also causes diarrhea
Describe ETEC (enterotoxigenic E. coli)
causes traveler's diarrhea Once in GI tract, adhere to mucosal epithelial cells via Type I or Type IV pili, deliver enterotoxins into host mucosal epithelia (heat stable or heat labile toxin) --Make one or both toxins Stimulate Cl channels which results in intestinal cell linkage, small intestine
How do we treat bacteria with a serine B-lactamase mutation? Can bacteria resist these treatments?
clavulanic acid also administered in the presence of serine b-lactamase, prevents b-lactamase from inhibiting ring, killing bacteria --high level β-lactamase expression (i.e. gene duplication) can overcome clavulanic acid supplementation (binding/sequestering ) --clavulanic acid only inhibits serine β-lactamases zinc β-lactamases use a catalytic mechanism that does not involve active-site serine residues to cleave β-lactam ring resistant to clavulanic acid
What are disinfectants?
compounds applied to non-living objects or surfaces i.e. bleach, alcohols, phenolics Never used in/ on human body primarily bactericidal, too toxic for use for external/internal treatment of patients
How do quaternary ammonium cations (QACs) kill bacteria?
disinfectants; disrupt cell membranes by intercalating them
How is erm expression regulated?
emr: provides resistance to erythromycin Low level formation of alternative stem-loop in the absence of antibiotic allows basal expression of methylase (keeps some ribosomes functional when initially encountering Erm) --Stem loop blocks start codon, turning down translation of target gene When erythromycin is there, it prevents translocation of ribosomes, inhibiting translation of stem-loop forming peptide --Then, resistance gene can be expressed; alternative loop forms downstream, exposing the start codon and allowing translation of methylase, which deals with erythromycin
Describe the disease caused by anthrax injection
from drug use Similar to cutaneous but far more rapid
What are the symptoms of anthrax disease caused by inhalation?
from working with infected animals or products anthrax spores less than 5 um are inhaled, reach lower respiratory tract --> fever and chills, chest discomfort, nausea, shortness of breath, vomiting, stomach pains, drenching sweats, fatigue --> shock --> can be highly fatal, moreso than cutaneous
What are the symptoms of cutaneous anthrax?
from working with infected animals/ products symptoms 1 day to 2 months after exposure; cutaneous ulcers can be seen after 6 days small blisters/bumps, may itch --> painless skin sore (ulcer) with black center forms, often on face, neck, arms, or hands--> swelling --> dissemination and death (20%) if left untreated
What is cystic fibrosis?
inherited as an autosomal recessive trait at a rate of 1 in 2,000 live births 5% population are estimated to be heterozygous carriers "CF gene" located on chromosome 7; mutation results in production of a defective transmembrane conductance regulator protein CF airways characterized by inadequate ion transport and defective mucociliary clearance → predisposition to persistent microbial colonization of lungs, bc lungs can't clear Disease of abnormal electrolyte transport and mucous secretion from exocrine glands and secretory epithelia
Describe the potential of Botulinum neurotoxin as a bioterror agent
introduction into water/food supplies, difficulty in initial diagnosis, relative ease and application
How do siderophores work as a PA virulence factor?
iron acquisition
Describe Yersinia pestis's potential as a bioterror agent
known agent of Black Death = fear factor uses flea as a vehicle for transmission bacterium sensitive to antibiotics used as a weapon in WWII
How do hemolysins work as a PA virulence factor?
pore-forming toxins that damage host cell membranes
How do elastase/alkaline protease/ other proteases work as a PA virulence factor?
proteolytic degredation of elastin, collagen, immunoglobulin, complement, immune evasion, nutrient acquisition, tissue damage
Describe P. aeruginosa
ubiquitous in soil and water, plants some humans colonized Diagnosed by culturing on King's medium (**blue and/or yellow pigment production) motile, Gram -ve rod, capable of growth at 42°C.
