Bacteriology Exam 1 Flashcards

(46 cards)

1
Q

basic roles of bacteria and fungi in health and disease

A

Host immunity
environment
organism pathogenicity

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2
Q

primary pathogen

A

normal host defenses overcome

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3
Q

opportunistic pathogen

A

sentinels of underlying problems with host management

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4
Q

prokaryote cell structure and organization

A

bacteria
no membrane bound organelles
70S ribosomes
DNA = singular circular chromosome, plasmid
no nuclear membrane/nucleolus
replicates via binary fission
haploid genome
no introns
polycistronic operons

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5
Q

eukaryotes cell structure and organization

A

fungi, protozoa, algae
membrane bound organelles
70 & 80S ribosomes
DNA linear chromosomes
nuclear membrane/nucleolus
replicates via mitosis
diploid genome
introns
monocistronic transcription (no operons)

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6
Q

what is a cell wall made up of? what is the difference between gram + and gram - cell walls?

A

peptidoglycan (murein) - a crosslinked polymer with repeating subunits of NAG & NAM
gram + has thick peptidoglycan layer
gram - has thin layer, doesn’t uptake gram stain as well

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7
Q

Cell wall structure: how do gram + and gram - bacteria differ?

A

gram +: thin cytoplasmic membrane + thick peptidoglycan layer
gram -: thin cytoplasmic membrane + thin peptidoglycan layer + outer bilipid membrane

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8
Q

What won’t a gram stain allow us to see?

A

spores
mollicutes (E.G. MYCOPLASMA)

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9
Q

What is different about Mycoplasma?

A

type of mollicute = no cell wall = cannot be stained via gram stain

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10
Q

obligate aerobe

A

must use O2 as terminal e- acceptor

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11
Q

aerotolerant anaerobe

A

don’t use O2 but can survive in the presence of O2 with help of superoxide dismutase & peroxidase

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12
Q

facultative anaerobe

A

prefer no O2, but can use it if present; many have catalase, SOD and peroxidase

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13
Q

obligate anaerobe

A

no enzymes dealing with O2

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14
Q

what protective enzymes do bacteria have to protect them from reactive oxygen species?

A

superoxide dismutase
peroxidase
catalase

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15
Q

Anaerobe

A

uses other terminal e- acceptor (SO4)

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16
Q

Koch’s Postulates

A

1.Microorganism must be found in abundance in all organisms suffering from the disease, but should not be found in healthy organisms
2.The microorganism must be isolated from a diseased organism and grown in pure culture
3.The cultured microorganism should cause disease when introduced into a healthy organism
4.The microorganism must be reisolated from the inoculated, diseased experimental host and identified as being identical to the original specific causative agent

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17
Q

limitations of Koch’s postulates

A

diseases may be caused by ingestion of a preformed toxin
many microorganisms are difficult to grow in culture
some agents require another factor (i.e. stress) to cause disease
there are carrier states for some microorganisms

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18
Q

exotoxins

A

gram + & gram - bacteria
proteins/polypeptides
pharmacologically-specific effects
distinct in structure
lethal in minute amounts
labile to heat/chemicals
convertible to toxoids

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19
Q

endotoxins

A

gram - bacteria
lipopolysaccharide (lipid A) - toxic
many effects
similar in structure
lethal in large amounts
stable in heat/chemicals
not convertible to toxoids

20
Q

saprophytes

A

environmental organisms

21
Q

commensals

A

colonize tissue without disease

22
Q

symbionts

A

colonize host tissue but a mutually beneficial relationships exists

23
Q

opportunists

A

colonize host tissue but cause disease with tissue injury or an environmental change

24
Q

primary pathogens

A

infection directly causes disease, but host species predilections may exist

25
Thinking back to childbed fever in Semmelweis’s day, before we knew what bacteria were, what kinds of bacteria do you think actually caused the infections in the post-parturient women?
primary pathogens & opportunists
26
direct detection methods: non-selective media selective media differential media specific Ab molecular detection of bacteria/fungal DNA
non-selective media: nothing added to inhibit microbes selective media: additives to inhibit specific groups of microbes differential media: additives to aid differentiation of microbial growth of microbial growth
27
MacConkey Agar
selective for gram - bacteria differential for lactose fermentation
28
Pheylethyl alcohol agar
selective gram + bacteria
29
indirect detection methods
detection of host Ab directed against bacterial or fungal antigen
30
When would we want to choose a serological test versus culture?
serological test for... pathogens with chronic carrier state surveillance and control of regulatory diseases difficult to-cultivate pathogens (e.g. neuro or ophtho)
31
When submitting a sample from a non-sterile site for culture, what other laboratory methods and clinical thinking are helpful in interpreting the significance of microorganisms isolated?
32
examples of cell wall disruptors (beta-lactams) bactericidal or bacteriostatic
penicillins cephalosporins carbapenems penicillins are bactericidal
33
examples of DNA synthesis inhibitors bactericidal or bacteriostatic
sulfonamides - bacteriostatic unless combined with trimethoprim, then bactericial nitroimidazoles - bactericidal fluoroquinolones - bactericidal
34
examples of protein synthesis inhibitors bactericidal or bacteriostatic
aminoglycosides - bactericidal tetracyclins - bacteriostatic macrolides/lincosamides - bacteriostatic aceamides - bacteriostatic
35
what antibiotics should you NOT give food animals
chloramphenicol metronidazole
36
which agents have at least some activity in all 4 quadrants?
carbapenems macrolides/lincosamides tetracyclines acetamides ampicillin piperacillin
37
which agents have activity ONLY against intracellular bacteria and Mycoplasma
fluoroquinolones tetracyclins chloramphenicol some macrolides
38
which protein synthesis inhibitors act on 30s ribosomes?
aminoglycosides tetracyclines
39
which protein synthesis inhibitors act on 50s ribosomes?
macrolides/lincosamides acetamides
40
which agents work only against both gram - and gram + obligate anaerobes
nitroimidazoles
41
which agents work only against both gram - and gram + aerobe facultatives
cephalosporins sulfonamides/trimethoprim fluoroquinolones aminoglycosides
42
which agent works against everything except gram - aerobe facultative
benzylpenicillin
43
general mechanisms of antimicrobial resistance
1. inactivation of drugs via bacterial enzymes 2. modification of drug targets 3. preventing access to cell 4. efflux pumps
44
mechanisms of acquired resistance
transformation transduction conjugation mutation
45
methods of antibiotic susceptibility testing (AST)
broth microdilutions (e.g. MIC) Kirby-Bauer disc diffusion
46
What is exactly in an MIC and what does the laboratory observe to determine that value.
a two-fold dilution series of gorillacillin in Mueller-Hinton broth where a standard amount of bacteria of interest is added to each tube and then incubated at 35o for 16-24 hours lowest dilution tested with no visible growth = MIC