Week 1 - Historical Perspective of Infectious Diseases and Medical Microbiology
what is the size of viruses?
tiny fukcers. 18-300 nanometers in diameter
what does species mean in microbial classification?
groups of bacteria sharing many common properties
what does genus mean in microbial classification?
groups of related species
normal flora may be _____ or _____ (time)
resident (months to life) or transient (hours to days)
True or False: the "parasites" are multicellular eukaryotes
False: some are unicellular
give an example of a pathogen that enters the body by inhalation
Mycobacterium tuberculosis
give an example of a pathogen that enters the body by ingestion
Salmonella
give an example of a pathogen that enters the body by needlestick
Staphylococcus aureus
fungi (do/do not) have a thick carbohydrate cell wall
do
what significance does Robert Koch hold for the field of microbiology?
this guy was boss. -proof of Germ Theory - published criteria now known as Koch's postulates
True or False: Koch's postulates are still used today
to establish link between particular microorganism and particular disease
what is the normal flora?
total microbial population routinely found associated with a healthy human
True or False: bacteria are eukaryotes, all other organisms are prokaryotes
False: bacteria are prokaryotes, all other cellular organisms are eukaryotes
what is the difference between prokaryotic and eukaryotic ribosomes?
prokaryotes = 70S, eukaryotes = 80S
what advantages are conferred on intracellular pathogen?
protected against many of host's defense mechanisms (i.e. antibodies)
all organisms other than _____ are made up of cells
viruses, prions, and related entitites
what is the definition of infectious disease in the context of microbiology?
where the interaction between microbe and host leads to pathologic process characterized by damage to the host
what are strict pathogens?
zey arr verrry STRICT! zey vil ALVAYZ be associated viz human dizzes! for example, mycobacterium tuberculosis neisseria gonorrhoeae and AMERICANZ
what are the general stages of an infectious disease?
• Attachment (+/- entry into body) • Spread within the body (local or general) • Multiplication • Evasion of host defenses • Exit (shedding from the body) •Transmission (source and/or reservoir) • Cause damage to host (not obligatory but often occurs)
give an example of a pathogen that enters the body by trauma
Clostridium tetani
what are the groups of organisms/agents under microbes?
(1) bacteria (2) fungi (3) protozoa (4) helminths (5) arthropods (6) viruses (7) prions
transmission depends on three factors. what are they?
(1) number of microbes shed (2) stability of microbe in the environment (3) number of microbes required to infect fresh host (i.e. infectious dose and efficient of infection)
what significance does Louis Pasteur hold for the field of microbiology?
-mild heating of foods (pasteurization) delays spoilage --> processes for microbial control in foods -came up with "Germ Theory" of disease = microbes can invade other organisms and *cause* disease -studied chicken cholear and developed procedure for attenuating organisms for use as vaccine -developed rabies vaccine made of dried spinal cord from rabbits infected with rabies --> immunology and vaccine development
what significance does Joseph Lister hold for the field of microbiology?
-provided indirect evidence that microorganisms were the causal agents of disease -was a believer of Semmelweis' theories -developed a system of surgery designed to prevent microorganisms from entering wounds as well as methods for treating instruments and surgical dressings --> his patients had fewer postoperative infections -*first applications of aseptic surgery & infection control*
True or False: Infectious diseases are a major problem in the developing world
2009: 8.1 million deaths in children <5 years of age globally - at least half of these were due to infection and the overwhelming majority of these occurred in Africa, SE Asia and the Eastern Mediterranean
what significance does Edward Jenner hold for the field of microbiology?
Discovered that previous infection by cowpox prevents later infection by smallpox --> immunology and vaccine development
why should we care about "subspecies"?
E. coli strain K12 - does not normally cause disease; E. coli strain O157 - causes intestinal disease (carries a toxin gene) → *identification of subspecies is very important in clinical microbiology*
what significance does Anton van Leeuwenhoek hold for the field of microbiology?
He was the first microbiologist to rock a badass wig. (Netherlands,1632-1723) uses simple microscopes to see "animalcules" (little animals) in variety of natural environments = First direct observation of microbes (≤300 X magnification)
True or False: research has shown that probiotics are the bees knees.
True: may help reduce: bloating and diarrhea from lactose intolerance, diarrhea that is a side effect of antibiotics, diarrhea in infants with rotavirus enteritis, infections in the digestive tract
True or False: smallpox has been eradicated
True: no naturally acquired cases since October 1977
True or False: modern lifestyles and technical developments facilitate transmission of disease
True: population growth, new patterns of travel and trade (especially food), new agricultural practices (e.g. using antibiotics in animal feed), altered sexual behaviour, medical interventions, overuse and misuse of antibiotics, economic, social and political changes, slowing of development of new antimicrobials and vaccines, climate change
True or False: viruses are obligate intracellular parasites
True: require host cells for replication
True or False: peptidoglycan is unique to bacteria
True: target for some antibiotics (e.g. penicillin)
what is an opportunistic pathogen?
a microbe which is *not pathogenic under normal conditions, but may cause infection and disease if introduced into a normally sterile body site (or into a host with a compromised immune system)
how are microbes classified?
according to physical, metabolic, and genetic properties
what is the definition of host in the context of microbiology?
an animal capable of supporting growth of a microbe
what is the definition of pathogen in the context of microbiology?
any virus, bacterium, or other agent that causes disease
how does attachment work to the advantage of bacteria like Vibrio cholera?
attaches to receptors on surface of intestinal epithelial cells - in order to avoid elimination due to peristalsis and excretion, this microbe attaches itself to host cell to colonize and multiply
where is the normal flora found?
found in parts of the body that are exposed to or communicate with the external environment (skin, nose and mouth, intestinal and genitourinary tracts)
what do viruses consist of?
genetic material (either DNA or RNA) +/- proteins required for replication and pathogenesis, enclosed in protein coat +/- lipid "membrane" layer
what is the scientific name of a microbe?
genus name + species name
where does strain fit in among species and genus?
genus → species → strain
_____ take metabolic requirements directly from pool of nutrients inside the cell
intracellular pathogen
which eukaryotes possess a cell wall?
only fungi
what are microbes?
organisms (or agents) that cause infectious diseases
what are some of the beneficial effects of normal flora?
participate in metabolism of food products gut bacteria provide essential growth factors (e.g. vitamin K and B vitamins) stimulates normal development of immune system protects against infection with virulent microbes
what is the purpose of the prokaryotic cell wall?
protects against hostile environments
what are the ranges in size of parasites?
protozoa - single-celled animals ranging from 2-100 μm in size arthropods - invertebrate animals having exoskeletons; most relevant to human disease are insects, ticks and mites - cause disease directly by their feeding and indirectly by transmitting disease helminths - parasitic worms; can be meters in length
what are obligate intracellular pathogens"?
rely on host synthetic machinery so must live within host cells (e.g. viruses, chlamydia, rickettsia)
prions are associated with _____ (causes degenerative changes in brain and motor disturbances)
spongiform enecephalopathies
what is the definition of mutualism in the context of microbiology?
symbiotic relationship in which *both members benefit* from their interaction
what is the definition of commensalism in the context of microbiology?
symbiotic relationship in which *one benefits and the other neither benefits nor is harmed*
which of the following are considered the "larger parasites"? (1) bacteria (2) fungi (3) protozoa (4) helminths (5) arthropods (6) viruses (7) prions
(3) protozoa (4) helminths (5) arthropods
what is a receptor with respect to pathogen entry?
*specific receptor molecules on host cells* that have some specific function in the life of the cell, which are *exploited* by the pathogen
how do the normal flora protect against virulent microbes?
-exclusion of potential pathogens → competition for attachment sites, nutrients, etc. -production of toxic metabolites -production of antibacterial factors
what are some of the potential negative effects of normal flora?
-source of pathogens -metabolic activity of intestinal flora may be detrimental (e.g. biotransformation of natural compounds, release of toxic waste products from bacterial metabolism)
what does the outcome of the interaction between the microbe and host depend on?
-virulence of organism -site of exposure -host's ability to respond to the organism
give some examples of organisms that occur as members of normal flora.
Dear. God. I hope we don't have to memorize this.
_____ was the first person to be immunized against rabies
Joseph Meister
give some examples of prion-associated diseases.
Kuru, Creutzfeldt-Jakob (CJD), scrapie (sheep) and bovine spongiform encephalopathy (mad cow)
give an example of a pathogen that enters the body by sexual transmission
Neisseria gonorrhoeae
what significance does Ignaz Semmelweis hold for the field of microbiology?
Recognizes connection between autopsies and "childhood fever"
give an example of a pathogen that enters the body by arthropod bite
Rickettsia
True or False: commensalism, mutualism, and parasitism from a continuum
True or False: associations can merge and change given the *circumstances of the relationship*
True or False: globally infectious diseases currently cause > 20% of all deaths
True:
True or False: if large enough extracellular pathogens are protected against phagocytosis
True:
True or False: the middle of the 20th century was an active time for vaccine research and development
True: -antitoxins and vaccines against *diphtheria, tetanus, anthrax, cholera, plague, typhoid, tuberculosis* and more were developed -methods for growing viruses in the lab led to rapid discoveries and innovations, including the creation of vaccines for *polio* -researchers targeted other common childhood diseases such as *pertussis, measles, mumps, and rubella* and vaccines for these diseases reduced the disease burden greatly
True or False: Infections continue to emerge or re-emerge
True: >30 "new" infectious agents identified in last 35 years (e.g. HIV) - diseases formerly considered 'under control' are on the rise due to increasing numbers of immunocompromised individuals and emergence of drug-resistant strains
True or False: presence, absence and concentration of receptors are critical determinants of cell and host susceptibility
True: CD4 molecule for HIV → macrophages and T-cells; Vibrio cholera bind to receptors on surface of intestinal epithelial cells
True or False: normal flora consists primarily of bacteria
True: although minor numbers of viruses, fungi and protozoans may be present
True or False: health authorities predict the eradication of polio through large-scale vaccination programs
True: delayed by temporary suspension of vaccination in Nigeria and some areas of India
True or False: composition of normal flora is in a continual state of flux
True: determined by local physiological conditions (e.g. types and amounts of nutrients, pH, oxygen concentration etc, presence of local antibacterial substances, types of other flora present); systemic host factors
True or False: organisms with poor transmission from person to person will have little impact on the host population as a whole
True: e.g. Ebola virus, Legionella pneumophila
True or False: opportunistic pathogens may be members of patient's normal microbial flora
True: e.g. Staphylococcus aureus, Escherichia coli, Candida albicans
True or False: diet influences normal flora of GI tract
True: e.g. breastmilk is high in lactose → GI flora of breastfed infants contains lactic acid streptococci and lactobacilli; bottle-fed infants show greater variety of organisms
True or False: respiration for bacteria occurs in cytoplasmic membrane
True: lack mitochondria
what options were available for the prevention of disease in early times?
Variolation = dried crusts derived from healed smallpox scabs of mild smallpox cases inhaled into nostrils or inserted into small cut in skin to prevent later acquisition of the disease -- inconsistent, dangerous (10th century China; 18th century Turkey)
what does subspecies mean in microbial classification?
aka strains, serogroups, serotypes, biotypes, groups = members of same species having small physical, metabolic, or genetic differences
what is the definition of symbiosis in the context of microbiology?
all associations in which one species lives in or on the body of another
what are the intentional methods in which the normal flora composition may be disrupted?
bone marrow transplant patients (immunocompromised): give antibiotics to remove normal flora and minimize risk of opportunistic infections; -probiotics
what shapes do bacteria come in? what are the terms for these?
cocci = spherical bacilli = rod spirocetes or spirillum = spiral curved = coma pleomorphic = variable
prokaryotes usually have a _____ (structural component)
complex cell wall containing protein, lipid, and peptidoglycan
what is the definition of pathogenicity in the context of microbiology?
condition or quality of being pathogenic, or the *ability* to cause disease
what is the definition of probiotics?
consumption of *live* bacteria so as to alter the balance of intestinal flora and improve health
what is the definition of colonization in the context of microbiology?
establishment of a site of microbial reproduction on an "external" host *surface* (transiently or permanently) *without observable clinical symptoms* or immune reaction
fungi are _____ (prokaryotes/eukaryotes) that exist in _____ (unicellular/multicellular) form and replicate _____ (sexually/asexually)
eukaryotes either unicellular or filamentous form sexual or asexual form
when does development of normal flora occur?
human fetus lives in protected, sterile environment → during and after birth, colonization of skin, oropharynx, gastrointestinal tract and other mucosal surfaces occurs (from mother;s genital tract flora, flora of medical personnel, environmental flora)
what are prions? how do they cause disease?
lack nucleic acid genome, highly resistant to conventional disinfection; small proteinaceous - thought to be modified forms of a normal cellular protein, and cause disease by converting corresponding normal proteins into further abnormal forms
what are the unintentional methods in which the normal flora composition may be disrupted?
long-term antibiotic use (endogenous flora in GI tract is eliminated → C diff proliferates → diarrhea, colitis) hospitalization - replacement of normally avirulent microbes in the oropharynx with Gram-negative rods (e.g. Klebsiella, Pseudomonas) that can invade lungs → pneumonia
infectious disease may result from _____ or from _____
microbial factors or from host's immune response
what are prebiotics?
non-digestible food ingredients that beneficially affect the host by selectively stimulating the growth and/or activity of one or a limited number of bacteria in the colon, thus improving host health - e.g. inulin, raw oats, unrefined wheat
what significance does Alexander Fleming hold for the field of microbiology?
observed that a colony of penicillium mood contaminating a culture of Staphylococcus bacteria prevented growth of bacteria --> development of *penicillin* for use as safe versatile chemotherapeutic agent
what is the definition of infection in the context of microbiology?
presence and replication of a microbe *in or on* a host
what significance does John Snow hold for the field of microbiology?
some diseases (e.g. cholera) are transmitted by polluted water --> public health microbiology
what is the definition of parasitism in the context of microbiology?
symbiotic relationship in which *one organism derives benefit while harming its host*
how do extracellular pathogens meet their metabolic needs?
take metabolic requirements from tissue fluids or by feeding directly on host cells
what is the definition of virulence in the context of microbiology?
the *degree or intensity* of pathogenicity of an organism as indicated by case fatality rates and/or ability to invade host tissues and cause disease
define microbiology.
the study of microscopic organisms
