MICRO - EXAM 2

Define microbial death rate, and describe its significance in microbial control

Microbial Death Rate is usually found to be constant over time for any particular microbe under a particular set of conditions. It is important in order to develop standard protocols for disinfection which will facilitate the sterilization routine in many industries.

Define mutation

Mutation is the change in the nucleotide base sequence of a genome.

Describe the antimicrobial action of nucleotide and nucleoside analogs, quinolones, drugs that bind to DNA or RNA, and reverse transcriptase inhibitors

NUCLEOTIDE/NUCLEOSIDE ANALOGS: can distort shapes of nucleic acid molecules and prevent further replication, transcription, or translation QUINOLONES: act against prokaryotic DNA gyrase DRUGS THAT BIND TO DNA OR RNA: inhibit the action of RNA polymerase during transcription REVERSE TRNASCRIPTASE INHIBITORS: act against reverse transcriptase, an enzyme HIV uses early in its replication cycle

Compare and contrast the release of viral particles by lysis and budding

Naked viruses are extruded by exocytosis or may cause lysis and death of host cell Enveloped viruses often release via budding because the host cell was not quickly lysed and is causing persistent infections

Describe the actions of drugs that affect the cell walls of bacteria and fungi

BACTERIA: most agents act by preventing the cross-linkage of NAM subunits; another drug blocks transport of NAG and NAM from the cytoplasm out to the wall FUNGI: drugs inhibit the enzyme that synthesizes glucan

Contrast incidence and prevalence

INCIDENCE: the number of new cases of a disease in a given area or poopulation during a given period of time PREVALENCE: the total number of cases, both new and already existing, in a given area or population during a given period of time

Contrast contact, vehicle, and vector transmission

1. CONTACT: Direct contact - involves body contact between hosts (person-to-person; touching, kissing, biting, scratching, sexual intercourse; mother to fetus) Indirect contact - pathogens spread from one host to another by formites (neeldes, toothbrushes, kleenex, toys, money, diapers, medical equipment) Droplet - droplets expelled when we exhale, cough, and sneeze 2. VEHICLE: the spread of pathogens via air, drinking water, and food, as well as bodily fluids being handled outside the body Airborne - sneezing, coughing, AC systems, sweeping, mopping, changing clothes Waterborne - fecal-oral infection Foodborne - foods that are inadequately processed, undercooked, poorly reefrigerated / fecal-oral transmission Bodily fluid - blood, urine, saliva, and other 3. VECTOR: arthropods that transmit disease from one host to another Biological - transmit pathogens and serve as hosts for the multiplication of a pathogen during some stage of the pathogen's life cycle Mechanical - passively carry pathogens to new hosts on their feet or other body parts (fly on roadkill -> potato salad)

Describe three types of healthcare associated infections and how they may be prevented

1. Central line-associated bloodstream infection 2. Catheter-associated urinary tract infections 3. Surgical site infection Make sure medical equipment is being sterilized properly

Describe the importance, advantages and disadvantages, and use of the six types of physical methods of microbial control

1. Heat-related Methods Denature of proteins, interference with integrity of cytoplasmic membrane and cell walls, disruption of structure and function of nucleic acids Moist heat - used to disinfect, sanitize, sterilize, and pasteruize -Boiling - kills vegetative cells of bacteria and fungi, protozoan trophozoitesm and most viruses within 10 minutes at sea level -Autoclaving - pressure applied to boiling water prevents steam from escaping -Pasteurization - not sterilization; heat-tolerant and heat-loving microbes survive; the combination of time and temperature required for effective pasteurization varies with the product -Ultrahigh-temperature sterilization - sterilization; liquid is passed through superheated steam at 140°C for 1-3 seconds and then rapidly cooled Dry heat - denatures proteins and oxidizes metabolic and structural chemicals; requires higher temperatures for longer time than moist heat because dry heat penetrates more slowly 2. Refrigeration and Freezing Decrease microbial metabolism, growth, and reproduction Psychrophlic microbes can multiply in refrigerated foods Refrigeration halts growth of most pathogens which are predominantly mesophiles Slow freezing more effective than quick freezing 3. Desiccation and Lyophilization Drying inhibits growth because metabolism requires liquid water Lyophilization is used for long-term preservation of microbes and other cells 4. Filtration Traps particles and separates them from the fluid Traps microbes larger than the pore size 5. Osmotic Pressure Cell desiccates in cells with a hypertonic solution of salt or sugar lose water Fungi have greater ability than bacteria to tolerate hypertonic environments with little moisture 6. Radiation Particulate radiation - consists of high-speed subatomic particles that have been freed from their atoms Electromagnetic radiation - energy without mass traaveling in waves at the speed of light

Compare and contrast the nine major types of antimicrobial chemicals, and discuss the positive and negative aspects of each

1. Phenol/Phenolics Denature proteins and disrupts cell membranes Intermediate-low level disinfectants 2. Alcohols Denature proteins and disrupt cell membranes Intermediate-level disinfectants 3. Halogens Damage enzymes via oxidation or by denaturing them Intermediate-level antimicrobial chemicals 4. Oxidizing Agents Denature proteins by oxidation High-level disinfectants and antisepctics 5. Surfactants//Soaps/Detergents Decrease surface tension of water and disrupt cell membranes Low-level agents 6. Heavy Metals Denature proteins Low-level agent 7. Aldehydes Denature proteins and inactivate nucleic acids High agent level 8. Gaseous Agents Denature proteins and DNA cross-linking functional groups High agents

List seven ways by which microbes can be resistant to antimicrobial drugs

1. Resistance cells may produce an enzyme that destroys or deactivates the drug 2. Resistant microbes may slow or prevent the entry of the drug into the cell 3. Resistant cells may alter the target of the drug so that the drug either cannot attach to it or binds it less effectively 4. Resistant cells may alter their metabolic chemistry, or they may abandon the sensitive metabolic step altogether 5. Resistant cells may pump the antimicrobial out of the cell before the drug can act 6. Bacteria within biofilms resist antimicrobials more effectively than free-living cells 7. Protection of the target of an antimicrobial drug

List and differentiate between the three effects of point mutations

A change to a different amino acid, called a missense mutation A change to a termination codon, called a nonsense mutation Creation of a new sequence that is silent with regard to protein sequence but alters some aspect of gene regulation

Discuss the relative frequency of deleterious and useful mutations

A deleterious mutation is a genetic alteration that increases an individual's susceptibility or predisposition to a certain disease or disorder. It occurs in >70% in most species.

Define point mutation, and describe three types

A point mutation is when a single base pair is affected (most common type of mutation). Base Pair Substitutions: replacement or substitution of a single nucleotide base with another in DNA or RNA molecule Insertions (Frameshift Mutation): involves the addition of one or more nucleotides into a segment of DNA Deletions (Frameshift Mutation): involves the loss of one or more nucleotides from a segement of DNA Frameshift mutations affect proteins much more seriously than mere substitutions because a frame shift affects all codons subsequent to the mutation.

Describe three types of reservoirs of infection of humans

ANIMAL RESERVOIR: acquire zoonoses through various routes (direct contact with animals or their wastes, eating animals, bloodsucking arthropod vectors) HUMAN RESERVOIR: humans with active disease; some individuals will eventually develop illness; others remain a continued source of infection without ever becoming sick NONLIVING RESERVOIR: soil, water, and food; fecal or urine contamination

Sketch and describe the five stages of the lytic replication cycle as it typically occurs in bacteriophages

ATTACHMENT: random collision, tail fibers attach, chemical attraction and precise fit ot receptor sites ENTRY: virus overcomes barrier, tail sheath forces its' way into bacterial cell SYNTHESIS: DNA -> constituent nucleotides, transcription&translation of phage mRNA, phage marks viral DNA and proteins ASSEMBLY: not completely understood RELEASE: bacterium disintegrates

Compare and contrast the lysogenic replication cycle of viruses with the lytic cycle

ATTACHMENT: same as lytic cycle ENTRY: same as lytic cycle PROPHAGE FORMATION: prophage is inserted into DNA and becomes part of chromosome REPLICATION OF CHROMOSOMES & CELL DIVISION: prophage is replicated when cell is replicated INDUCTION: prophage might have been excised, so it reenters SYNTHESIS: same as lytic cycle ASSEMBLY: same as lytic cycle RELEASE: same as lytic cycle

Explain the importance of adhesion in the establishment of an infection

Adhesion is the process by which microorganisms attach themselves to cells. Inability to make attachment proteins or adhesions renders the microorganisms avirulent.

Compare and contrast viruses of animals and bacteria

Animal viruses do not have to penetrate a cell wall to gain access to the host cell. Animal viruses have the same five basic steps in their replication pathway as bacteriophages except for: the presence of envelope around some viruses, eukaryotic nature of animal cells (transcription occurs in the nucleus), and a lack of cell wall in animal cells. Animal cells use different mechanisms for entry and uncoating of animal viruses.

Describe the basic activities of drugs that interfere with protein synthesis

Antimicrobial agents selectively target bacterial protein translation without significantly affecting eukaryotes.

Compare and contrast the terms in Table 9.1 and describe their practical uses

Antisepsis: reduction in the number of microorganisms and viruses, particularly potential pathogens, on living tissue Aseptic: refers to an environment or procedure free of pathogenic contaminants Degerming: removal of microbes by mechanical means Disinfection: destruction of most microorganisms and viruses on nonliving tissue Pasteurization: use of heat to destroy pathogens and reduce the number of spoilage microorganisms in foods and beverages Sanitization: removal of pathogens from objects to meet public health standards Sterilization: destruction of all microorganisms and viruses in or on an object

Describe the action of antimicrobial attachment antagonists

Attachment antagonists are when attachment can be blocked by peptide and sugar analogs of attachment or receptor proteins.

Distinguish narrow-spectrum drugs from broad-spectrum drugs in terms of their targets and side effects

BROAD-SPECTRUM: killing or normal flora reduces microbial antagonism; may allow for secondary infections (transient pathogen) or superinfections (member of normal flora) NARROW-SPECTRUM: means it will have a more specific target

Describe the relationship between contamination and infection

CONTAMINATION: the mere presence of microbes in or on the body Can remain without causing harm INFECTION: a successful invasion of the body by a pathogen Can result in disease When some microbes overcome the body's external defenses, multiply, and become established in the body is when contamination turns into infection.

Define genetic recombination

Genetic recombination refers to the exchange of nucleotide sequences between two DNA molecules between one bacterial cell and another.

Discuss the structure and function of the viral capsid

Capsids are protein coats that provide protection for viral nucleic acid and meanas of attachment to host's cells. Capsids are composed of proteinaceous subunits called capsomeres; some capsomeres are composed of only a single type of protein, whereas others are composed of several different kinds of proteins. A viral capsid attaches and sinks into the cytoplasmic membrane, creating a pore through which the genome alone enters the cell. The capsid always has to enter the host cell. 1. It protects the nucleic acid from digestion by enzymes 2. Contains special sites on its surface that allow the virion to attach to a host cell 3. Provides proteins that enable the virion to penetrate the host cell membrane and inject the infectious nucleic acid

Describe in general how cells regulate protein synthesis

Cells may stop transcription of mRNA or can stop translation directly.

List two ways that genes for drug resistance are spread between bacteria

Cross resistance Multiple resistance

Define cross resistance, and distinguish it from multiple resistance

Cross resistance is the resistance to one antimicrobial agent that may confer resistance to similar drugs; typically occurs when drugs are similar in structure. Multiple resistance pathogens (superbugs) are resistant to three or more types of antimicrobial agents.

Explain the central dogma of genetics, and explain the roles of DNA and RNA in polypeptide synthesis

DNA is transcribed to RNA and RNA is translated to form polypeptides.

Explain why DNA replication is said to be a semiconservative process

DNA replication is said to be a semiconservative process because new strands are composed of one original strand and one daughter strand.

Contrast droplet transmission and airborne transmission

DROPLET: droplets expelled when we exhale, cough, and sneeze; transmission via droplet nuclei that travel <6 feet AIRBORNE: pathogens travel >6 feet to the respiratory mucous membranes of a new host; may come from sneezing, coughing, AC systems, sweeping, mopping, changing clothes, or flaming inoculating loops

Differentiate among the terms endemic, sporadic, epidemic, and pandemic

ENDEMIC: consistently present but limited to a particular region SPORADIC: occurs infrequently and irregularly EPIDEMIC: unexpected increase in the number of disease cases in a specific geographical area PANDEMIC: when a disease's growth is exponential

Describe the genetic code in general, and identify the relationship between codons and amino acids

Each codon corresponds to a single amino acid (or stop signal), and the full set of codons is called the genetic code.

Discuss the origin, structure, and function of the viral envelope

Enveloped virus acquires its envelope from its host cell during viral replication or release. Envelope is a portion of the membrane system of a host cell. Viral envelope is composed of phospholipid biliary and proteins. Some proteins are virally encoded glycoproteins; other proteins are host proteins. Envelope's proteins and glycoproteins often play a role in host recognition. Envelope provides some protection to the virus from the immune system. Enveloped are more susceptible to detergents, alcohol, and desiccation.

Describe the factors that influence the development of healthcare associated infections

Exogenous - pathogen acquired from the healthcare environment Endogenous - arise from opportunistic normal microbiota within the patient due to factors within the health care setting Iatrogenic - results from modern medical procedures Superinfections - result from the use of antimicrobial drugs that inhibit some resident microbiota and allow others to survive

Explain the roles of an F factor, F+ cells, and Hfr cells in bacterial conjugation

F factor: acts as recipient F+ cells: acts as donor; means with fertility plasmid Hfr cells: acts as donor

Explain how the genotype of an organism determines its phenotype

Genotype (set of genes in the genome) determines phenotype (physical features and functional traits of the organism) by specifying what kinds of RNA and which structural, enzymatic, and regulatory protein molecules are produced. Not all genes are active at all times; the information of a genotype is not always expressed as a phenotype.

Describe four ways to retard development of resistance

High concentration of drug maintained in patient long enough to kill all sensitive cells and inhibit others so immune system can destroy Use antimicrobial agents in combination Limit the use of antimicrobials to necessary cases Develop semisynthetic drugs, search for new antimicrobials, or synthetically designed drugs

Compare and contrast the terms infection, disease, morbidity, pathogenicity, and virulence

INFECTION: the invasion and growth of germs in the body DISEASE: the existence of pathology MORBIDITY: having a disease or symptom of disease, or to the amount of disease within a population PATHOGENICITY: the quality or state of being pathogenic, the potential ability produce disease VIRULENCE: an ability of an organism to infect the host and cause a disease

List and describe the five typical stages of infectious diseases

Incubation period Prodromal period Illness Decline Convalescence

List six mechanisms by which antimicrobial drugs affect pathogens

Inhibition of Cell Wall Synthesis Inhibition of Protein Synthesis Disruption of Cytoplasmic Membranes Inhibition of Metabolic Pathways Inhibition of Nucleic Acid Synthesis Prevention of Virus Attachment and Entry

Describe the three conditions that create opportunities for normal microbiota to cause disease

Introduction of normal microbiota into unusual site in the body Immune suppression Changes in the normal microbiota Stressful conditions

Contrast mechanical vectors and biological vectors

MECHANICAL: not required as hosts by the pathogens they transmit; passively carry pathogens to new hosts on their feet or other body parts BIOLOGICAL: transmit pathogens and serve as hosts for the multiplication of a pathogen during some stage of the pathogen's life cycle; pathogens replicate within a biological vector, then enter a new host through a bite; mosquitoes, ticks, lice, fleas, bloodsucking flies, bloodsucking bugs, and mites

Distinguish among the types of symbiosis

MUTALISM: both benefit COMENSALISM: one benefits/nothing happens to other one AMENSALISM: one is harmed/nothing happens to the other one PARASITISM: one benefits/one is harmed

Describe how populations of resistant microbes can arise

Not all pathogens are equally sensitive to a given therapeutic agent; a population may contain a few organisms that are either naturally partially or completely resistant. Resistance by bacteria can be acquired in two ways: (1) new mutations of chromosomal genes (2) acquisitions of resistance genes through horizontal gene transfer - transformation, transduction, or conjugation.

Discuss the advantages and disadvantages of the different routes of administration of antimicrobial drugs

ORAL: simplest; no reliance on health care provider; lower drug concentrations; patients do not always follow prescribing information INTRAMUSCULAR: requires needle; concentration never as high as IV administrationINTRAVENOUS: requires needle or catheter; drug concentration diminishes as liver and kidneys remove drug from circulation

Explain the differences between bacteriophage replication and animal viral replication

Presence of envelope around some viruses Eukaryotic nature of animal cells (transcription occurs in the nucleus) Lack of cell wall in animals

Describe the structure and function of plasmids

Prokaryotic plasmid are small molecules of DNA that replicate independently of the chromosome (1-5% of the prokaryotic chromosome). They carry information required for their own replication, and often for one or more cellular traits. And typically they are not essential for normal metabolism, growth, or reproduction, but can confer survival advantages.

Compare and contrast the structure and function of prokaryotic and eukaryotic DNA

Prokaryotic: 1-2 chromosomes, each cell has 1 copy of chromosome (haploid), circular molecule of DNA in nucleoid, fMet Eukaryotic: 1+ chromosome, each cell has 2 copies of chromosome (diploid), linear DNA in membrane-bound nucleus, Met

Contrast the basic tenets of bacterial transcription with those of eukaryotic transcription

Prokayotic (bacterial) transcription occurs in the nucloid region of the cytoplasm, is a single type of RNA polymerase, and a single transcription factor is required to bind RNA polymerase to DNA. Eukaryotic transcription occurs in the nucleus (nucleolus), mitochondria, and chloroplasts; there are three types of nuclear RNA polymerases (mitochondria uses a fourth type or RNA polymerase); there are several transcription factors that aid in binding eukaryotic RNA polymerase to DNA; elongation factors are required; and mRNA is processed before translation.

Describe the normal microbiota, including resident and transient members, and describe the sites where these are found in humans

RESIDENT MICROBIOTA: remain a part of the microbiome of a person throughout life; most are commensal (feed on excreted cellular wastes and dead cells without causing harm) TRANSIENT MICROBIOTA: remains in the body for only a few hours, days, or months before disappearing; cannot persist in the body (competition from other microorganisms, elimination by the body's defenses, chemical or physical changes in the body that dislodge them) SITES IN HUMANS: the womb is generally an axenic environment; microbiomes begin to develop during the birthing process; much of one's resident microbiota is established during the first months of life

Identify and describe the portals through which pathogens invade and exit the body

SKIN: thick layers of tightly packed, dead, dry cells usually act as barrier to most pathogens (hair follicles, sweat glands, abrasions, cuts, bites, scrapes, stab wounds, surgeries) MUCOUS MEMBRANES: line the body cavities that are open to the environment (respiratory, GI, urinary, and reproductive tracts), nose, mouth, eyes PLACENTA: usually an effective barrier but it is the means of nutrition from mom to fetus

Contrast symptoms, signs, and syndromes

SYMPTOMS: subjective characteristics of disease felt only by the patient SIGNS: objective manifestations of disease that can be observed or measured by others SYNDROMES: group of symptoms and signs that characterize a disease or abnormal condition

Explain the principle of selective toxicity

Selective toxicity is an effective antimicrobial agent that must be more toxic to a pathogen than to the pathogen's host. This is possible because of differences in structure or metabolism between the pathogen and its host.

Explain how a biofilm may facilitate contamination and infection

Some bacterial pathogens interact with each other to form a biofilm which adheres to a surface within a host.

Describe the action of drugs that interfere with cytoplasmic membranes

Some drugs act by forming a channel through the membrane. Certain drugs disrupt transport across the cytoplasmic membrane. Certain drugs change the permeability of cytoplasmic membranes of parasites.

Discuss environmental conditions that can influence the effectiveness of antimicrobial agents

Temperature and pH affect death rates and the efficacy of antimicrobial methods: warm disinfectants generally work better than cool ones and acidic conditions enhance the antimicrobial effect of heat. Organic materials interfere with penetration of heat, chemicals, and some forms of traditions, and in some cases these materials inactivate chemical disinfectants.

Describe the action of drugs that disrupt synthesis of folic acid

They produce folate deficiency by inhibiting this enzyme.

Identify three main categories of side effects of antimicrobial therapy

Toxicity Allergies Disruption of Noraml Microbiota

Compare and contrast transformation, transduction, and conjugation

Transformation: the specific process where exogenous genetic material is directly taken up and incorporated by a cell through its cell membrane. Transduction: the process by which a virus transfers genetic material from one bacterium to another. Conjugation: the process by which one bacterium transfers genetic material to another through direct contact.

Contrast vertical gene transfer with horizontal gene transfer

Vertical gene transfer is the process by which prokaryotes and eukaryotes replicate their genomes and supply copies to their descendants (parent cell -> daughter cell//one generation -> next). Horizontal gene transfer is when the donor cell contributes part of genome to recipient cell (an exchange of DNA within the same generation).

Explain how microibal extracellular enzymes, toxins, adhesion factors, and antiphagocytic factors affect virulence

Virulence factors include traits the allow the pathogen to interact with and enter a host, adhere to host cells, gain access to nutrients, and escape detection or removal by the immune system. Virulent pathogens have one or more virulence factors that nonvirulent microbes lack: Adhesion factors extracellular enzymes - dissolve structural chemicals in the body and help pathogen maintain infection, invade further, and avoid body defenses Toxins - chemicals that harm tissues or trigger host immune responses that cause damage Antiphagocytic factors - the longer a pathogen remains in a host, the greater the damage and the more severe the disease

Explain the mechanism by which viruses are specific for their host cells

Viruses have proteins on their capsule that bind preferentially to certain receptors on cells. A virus attaches to a specific receptor site on the host cell membrane through attachment proteins in the capsid or via glycoproteins embedded in the viral envelope.

Compare and contrast latency in animal viruses with phage lysogeny

When animal viruses remain dormant in host cells, viruses involved in latency are called latent viruses or proviruses. It may be prolonged for years with no viral activity, signs, or symptoms. Latency is similar to lysogeny but there are differences: when provirus is incorporated into host DNA, condition is permanent and it becomes physical part of host's chromosome (induction never occurs).

Discuss viral genomes in terms of dsDNA, ssDNA, ssRNA, dsRNA, and number of segments of nucleic acid

dsDNA: double-stranded DNA ssDNA: single-stranded DNA ssRNA: single-stranded RNA dsRNA: double-stranded DNA Number of Segments of Nucleic Acid May be linear and composed of several molecules or singular and circular Usually much smaller than genomes of cells