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BacT, Virology, Parasit > Bacteriology Exam 1 > Flashcards

Bacteriology Exam 1 Flashcards

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
Q

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?

A

primary pathogens & opportunists

26
Q

direct detection methods:
non-selective media
selective media
differential media
specific Ab
molecular detection of bacteria/fungal DNA

A

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
Q

MacConkey Agar

A

selective for gram - bacteria
differential for lactose fermentation

28
Q

Pheylethyl alcohol agar

A

selective gram + bacteria

29
Q

indirect detection methods

A

detection of host Ab directed against bacterial or fungal antigen

30
Q

When would we want to choose a serological test versus culture?

A

serological test for…
pathogens with chronic carrier state
surveillance and control of regulatory diseases
difficult to-cultivate pathogens (e.g. neuro or ophtho)

31
Q

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?

A
32
Q

examples of cell wall disruptors (beta-lactams)

bactericidal or bacteriostatic

A

penicillins
cephalosporins
carbapenems

penicillins are bactericidal

33
Q

examples of DNA synthesis inhibitors

bactericidal or bacteriostatic

A

sulfonamides - bacteriostatic unless combined with trimethoprim, then bactericial
nitroimidazoles - bactericidal
fluoroquinolones - bactericidal

34
Q

examples of protein synthesis inhibitors

bactericidal or bacteriostatic

A

aminoglycosides - bactericidal
tetracyclins - bacteriostatic
macrolides/lincosamides - bacteriostatic
aceamides - bacteriostatic

35
Q

what antibiotics should you NOT give food animals

A

chloramphenicol
metronidazole

36
Q

which agents have at least some activity in all 4 quadrants?

A

carbapenems
macrolides/lincosamides
tetracyclines
acetamides
ampicillin
piperacillin

37
Q

which agents have activity ONLY against intracellular bacteria and Mycoplasma

A

fluoroquinolones
tetracyclins
chloramphenicol
some macrolides

38
Q

which protein synthesis inhibitors act on 30s ribosomes?

A

aminoglycosides
tetracyclines

39
Q

which protein synthesis inhibitors act on 50s ribosomes?

A

macrolides/lincosamides
acetamides

40
Q

which agents work only against both gram - and gram + obligate anaerobes

A

nitroimidazoles

41
Q

which agents work only against both gram - and gram + aerobe facultatives

A

cephalosporins
sulfonamides/trimethoprim
fluoroquinolones
aminoglycosides

42
Q

which agent works against everything except gram - aerobe facultative

A

benzylpenicillin

43
Q

general mechanisms of antimicrobial resistance

A
  1. inactivation of drugs via bacterial enzymes
  2. modification of drug targets
  3. preventing access to cell
  4. efflux pumps
44
Q

mechanisms of acquired resistance

A

transformation
transduction
conjugation
mutation

45
Q

methods of antibiotic susceptibility testing (AST)

A

broth microdilutions (e.g. MIC)
Kirby-Bauer disc diffusion

46
Q

What is exactly in an MIC and what does the laboratory observe to determine that value.

A

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

BacT, Virology, Parasit (23 decks)

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