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step 1 > micro: basic bacteriology > Flashcards

micro: basic bacteriology Flashcards

1
Q

peptidoglycan

A

fxn: gives rigid support, protects against osmotic pressure. made of sugar backbone w/peptide side chains x-linked by transpeptidase

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2
Q

cell wall

A

fxn: major surface Ag. made of peptidoglycan for support, lipoteichoic acid induces TNF and IL-1

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3
Q

outer membrane (GN)

A

fxn: site of endotoxin (lipopolysaccharide (LPS)); major surface Ag. made of lipid A - induces TNF and IL-1. O polysaccharide = Ag

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4
Q

plasma membrane

A

fxn: site of oxidative and transport enzymes. made of phospholipid bilayer

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5
Q

periplasm

A

fxn: space between cytoplasmic and outer membranes in GNs. contains many hydrolytic enzymes, including beta-lactamases

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6
Q

pilus/fimbria

A

fxn: mediate adherence of bacteria to cell surface; sex pilus forms attachment between 2 bacteria during conjugation. made of glycoproteins

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7
Q

capsule

A

fxn: protects against phagocytosis. made of organized, discrete polysaccharide layer (except anthrax, which contains D-glutamate)

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8
Q

spore

A

fxn: resistant to dehydration, heat, and chemicals. made of keratin-like coat; dipicolinic acid, peptidoglycan

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9
Q

glycocalyx

A

fxn: mediates adherence to surfaces, especially foreign surfaces (e.g. indwelling catheters). made of loose network of polysaccharides

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10
Q

GP cell walls

A

have lipoteichoic acid. cell wall is on the outside.

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11
Q

GN cell walls

A

cell wall = between plasma and outer membranes. outer membrane has porins.

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12
Q

GPCs

A

staph, streph

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13
Q

GNCs

A

moraxella catarrhalis, neisseria

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14
Q

GPRs

A

bacillus, clostridium, corynebacterium, gardnerella (gram variable), lactobacillus, listeria, mycobacterium (acid fast), propionibacterium

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15
Q

GNRs: enterics

A

bacteriodes, campylobacter, E coli, enterobacter, helicobacter, klebsiella, proteus, pseudomonas, salmonella, serratia, shigella, vibrio, yersinia

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16
Q

GNRs: respiratory

A

bordetella, haemophilus (pleomorphic), legionella (silver stain)

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17
Q

GNRs: zoonic

A

bartonella, brucella, francisella, pasteurella

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18
Q

branching filamentous GPs

A

actinomyces, nocardia (weakly acid fast)

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19
Q

pleomorphic GNs

A

chlamydiae (giemsa), rickettsiae (giemsa)

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20
Q

spiral GNs

A

borrelia (giemsa), leptospira, treponema

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21
Q

no cell wall

A

mycoplasma, ureaplasma (contain sterols, which do not gram stain)

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22
Q

bugs that don’t gram stain well mnemonic

A

These Microbes May Lack Real Color: Treponema (too thin), Mycobacteria (high lipid content), Mycoplasma (no cell wall), Legionella pneumophila (intracellular), Rickettsia (intracellular), Chlamydia (intracellular, lacks classic peptidoglycan b/c of low muramic acid)

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23
Q

giemsa bugs mnemonic

A

Certain Bugs Really Try my Patience: Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium

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24
Q

PAS (periodic acid-Schiff) mnemonic

A

PASs the sugar: stains glycogen, mucopolysaccharides. used to Dx whipple dz: tropheryma whipplei

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25
Q

ziehl-neelsen (carbol fuchsin)

A

acid-fast bacteria: nocardia, mycobacteria, protozoa (cryptosporidium oocysts). alternative is auramine-rhodamine stain for screening (cheaper, more sensitive, less specific)

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26
Q

india ink

A

cryptococcus neoformans (mucicarmine can also be used to stain thick polysaccharide capsule red)

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27
Q

silver stain

A

fungi (e.g. pneumocystis), legionella, helicobacter pylori

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28
Q

H flu Cx

A

chocolate agar w/factors V (NAD+) and X (hematin)

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29
Q

neisseria Cx

A

thayer-martin agar w/Very Typically Cultures Neisseria: Vancomycin (inhibits GPs), Trimethoprim, Colistin (inhibits GNs except neisseria), and Nystatin (inhibits fungi)

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30
Q

B pertussis Cx

A

bordet-gengou agar: BORDET for BORDETella, w/potato. or regan-lowwe medium, w/charcoal, blood, and Abx

31
Q

C diphtheria Cx

A

tellurite agar or loffler medium

32
Q

M pneumonia Cx

A

eaton agar: requires cholesterol

33
Q

lactose-fermenting enterics Cx

A

macconkey agar: fermentation produces acid, causing colonies to turn pink

34
Q

E coli Cx

A

eosin-methylene blue (EMB) agar: colonies w/green metallic sheen

35
Q

legionella Cx

A

charcoal yeast extract agar buffered w/cysteine and Fe

36
Q

fungi Cx

A

Sab’s a fun guy: Sabouraud agar

37
Q

aerobes mnemonic

A

Nagging Pests Must Breathe: Nocardia, Pseudomonas, MycoBacterium tuberculosis. use O2-dependent system to generate ATP. tuberculosis likes lung apices b/c they have highest PO2.

38
Q

anaerobes mnemonic

A

anaerobes Frankly Can’t Breathe Air: Fusobacterium, Clostridium, Bacteroides, Actinomyces. they lack catalase and/or superoxide dismutase so they are susceptiple to oxidative damage. foul smelling, difficult to Cx, produce gas in tissue. aminO2glycosides are ineffective b/c they require Ox to enter bacteria

39
Q

obligate intracellulars

A

stay inside when it is Really CHilly and COld: Rickettsia, CHlamydia, COxiella. rely on host ATP

40
Q

facultative intracellulars

A

Some Nasty Bugs May Live FacultativeLY: Salmonella, Neisseria, Brucella, Myscobacterium, Listeria, Francisella, Legionella, Yersinia

41
Q

encapsulated bacteria

A

SHiNE SKis: Strep pneumo, H flu (type B), Neisseria meningitidis, E coli, Salmonella, Klebsiella, group B Strep. their capsules serve as an antiphagocytic virulence factor. capsule + protein conjugate serves as an Ag in vaccines. they are opsonized and clearly by spleen so asplenics need S pneumo, H flu, and N meningitidis vaccines

42
Q

vaccines against encapsulated bacteria

A

contain polysaccharide capsule Ags conjugated to carrier proteins -> T-cell activation -> class switching -> inc. immunogenicity. lone polysaccharide Ag can’t be presented to T cells. prevnar (PVC), pneumovax (PPSV), H flu type B, meningococcus vaccine

43
Q

urease-positive bugs

A

CHuck norris hates PUNKSS: Cryptococcus, H pylori, Proteus, Ureaplasma, Nocardia, Klebsiella, S epidermidis, S saprophyticus

44
Q

catalase-positive organisms

A

Cats Needs PLACESS to hide: Nocardia, Pseudomonas, Listeria, Aspergillus, Candida, E coli, Staph, Serratia. Catalase degrades H2O2 -> H2O and O2 before it can be converted to microbicidal products by myeloperoxidase. catalase + organisms infect people w/chronic granulomatous dz (NADPH oxidase deficiency).

45
Q

pigment-producing bacteria

A

actinomyces israelii -> yellow “sulfur” granules: filaments of bacteria: israel has yellow sand
S aureus -> yellow pigment: Au = gold
pseudomonas aeruginosa -> blue-green: aerugula = green
serratia marcescens -> red: marceschino cherries

46
Q

protein A

A

virulence factor: binds Fc region of IgG. prevents opsonization and phagocytosis. expressed by staph aureus

47
Q

IgA protease

A

virulence factor: enzyme that cleaves IgA. secreted by strep pneumo, H flu type B, and Neisseria (SHiN) in order to colonize respiratory mucosa

48
Q

M protein

A

virulence factor: helps prevent phagocytosis. expressed by group A strep. shares similar epitopes to human cellular proteins. might underly autoimmune response in rheumatic fever: molecular mimicry

49
Q

type II secretion system

A

virulence factor. aka “injectisome” = needle-like protein appendage facilitating direct delivery of toxins from certain GNs (e.g. pseudomonas, salmonella, shigella, E coli) to eukaryotic host cell

50
Q

exotoxins

A

polypeptides secreted by certain bacteria (GNs and GPs) coded for by plasmid or bacteriophage that are highly toxic (fatal at low dose). variety of clinical effects and MoAs. induce high-titer Abs = antitoxins. toxoid vaccines. destroyed at 60C (except staph enterotoxin). e.g. tetanus, botulism, diphtheria

51
Q

endotoxins

A

lipopolysaccharides on outer membrane of most GNs, coded for in bacterial chromosome. low toxicity. causes fever, shock, DIC by inducing TNF, IL-1, and IL-. poorly antigenic. no vaccines available. stable at 100C. e.g. meningococcemia, GN sepsis

52
Q

corynebacterium diphtheria toxin

A

diphtheria exotoxin: inhibits protein synthesis by inactivating elongation factor (EF-2) -> pharyngitis w/pseudomembranes in throat and severe lymphadenopathy (bull neck)

53
Q

pseudomonasauruginosa toxin

A

exotoxin A: inhibits protein synthesis by inactivating elongation factor (EF-2) -> host cell death

54
Q

shigella toxin

A

shiga exotoxin (ST): inhibits protein synthesis by inactivating 60S ribosome by removing adenine from rRNA -> GI mucosal damage -> dysentery; ST also enhances cytokine release -> HUS

55
Q

EHEC toxin

A

shiga-like exotoxin (SLT): inhibits protein synthesis by inactivating 60S ribosome by removing adenine from rRNA -> enhanced cytokine release -> HUS. unlike shigella, does NOT invade host cells. typically EHEC serotype O157:H7

56
Q

ETEC toxins and mnemonic

A

exotoxins: increase fluid secretion.
heat-labile toxin (LT) overactivates adenylate cyclase (-> inc. cAMP) -> inc. Cl secretion in gut and H2O efflux.
heat-stable toxin (ST) overactivates guanylate cyclase (-> inc. cGMP) -> dec. resorption of NaCl and H2O in gut.
-> watery diarrhea. Labile in the Air, Stable on the Ground

57
Q

bacillus anthracis toxin

A

edema exotoxin: increases fluid secretion by mimicing the adenylate cyclase enzyme (-> inc. cAMP). likely responsible for characteristic edematous borders of black eschar in cutaneous anthrax

58
Q

vibrio cholera toxin

A

cholera exotoxin: increases fluid secretion by overactivating adenylate cycle (-> inc. cAMP) by permanently activating Gs -> inc. Cl secretion in guy and H2O efflux -> voluminous rice-water diarrhea

59
Q

bordetella pertussis toxin

A

pertussis exotoxin: inhibits phagocytic ability by overactivating adenylate cyclase (-> inc. cAMP) by diabling Gi, impairing phagocytosis to permit survival of microbe -> whooping cough (100 day cough in adults). toxin might not actually cause cough.

60
Q

clostridium tetani toxin

A

tetanospasmin exotoxin: inhibits release of neurotransmitter by cleaving SNARE (set of proteins required for NT vesicular fusion -> spasticity, risus sardonicus, and lockjaw; toxin prevents release of GABA from renshaw cells in spinal cord

61
Q

clostridium botulinum toxin

A

botulinum exotoxin: inhibits release of neurotransmitter by cleaving SNARE (set of proteins required for NT vesicular fusion -> flaccid paralysis, floppy baby; toxin prevents release of ACh -> flaccid

62
Q

clostridium perfringens toxin

A

alpha exotoxin: lyses cell membranes by phospholipase (lecithinase) that degrades tissue and membranes -> myonecrosis (gas gangrene) and hemolysis (double zone of hemolysis on blood agar)

63
Q

streptococcus pyogenes toxin

A

streptolysin O exotoxin: protein that lyses cell membranes -> lysed RBCs, contributes to beta-hemolysis; host Abs against toxin (ASO) used to Dx rheumatic fever (NOT the same as the immunocomplexes of post-strep glomerulonephritis)

64
Q

staph aureus toxin

A

toxic shock syndrome exotoxin (TSST-1): superAg binds to MHC II and TCR outside of Ag binding site to cause overwhelming release of IL-1, IL-2, IFN-gamma, and TNF-alpha -> shock -> TSS: fever, rash, shock. other toxins cause staph scalded skin and food poisoning.

65
Q

strep pyogenes toxin

A

exotoxin A: superAg binds to MHC II and TCR outside of Ag binding site to cause overwhelming release of IL-1, IL-2, IFN-gamma, and TNF-alpha -> shock -> TSS: fever, rash, shock.

66
Q

endotoxin mnemonic

A

ENDOTOXIN: Edema, NO, DIC/Death, Outer membrane, TNF-alpha, O-Ag, eXtremely heat stable, IL-1, Neutrophil chemotaxis

67
Q

actions of endotoxins

A

activates macrophages: IL-1 -> fever, TNF-alpha -> fever and hypotension, NO -> hypotension
activates complement: C3a -> hypotension, edema, C5a -> neutrophil chemotaxis
activates tissue factor: coagulation cascade -> DIC

68
Q

transformation

A

ability to take up naked DNA (i.e. from cell lysis) = “competence”. a feature of many bacteria, esp. strep pneumo, H flu type B, and neisseria (SHiN). can use any DNA. if deoxyribonuclease is added to the environment, naked DNA degenerates and transformation cannot occur

69
Q

F+ x F- conjugation

A

F+ plasmid contains genes required for sex pilus and conjugation. bacteria without this plasmid = F-. F+ sex pilus contacts F- bacterium, transfers single stranded DNA across mating bridge. no chromosomal DNA is transferred

70
Q

Hfr x F- conjugation

A

F+ plasmid can become incorporated into bacterial chromosomal DNA -> high-frequency recombination (Hfr) cell. replication of incorporated plasmid DNA may include some flanking chromosomal DNA. transfer of plasmid and chromosomal DNA

71
Q

transposition

A

segment of DNA (transposon) that can jump (excision and reintegration) from one location to another, can transfer genes from plasmid to chromosome and vice cersa. when excision occurs, may include some flanking chromosomal DNA, which can be incorporated into plasmid and transferred to another bacterium (e.g. Abx resistance across species)

72
Q

generalized transduction

A

packaging event: lytic phage infects bacterium -> cleavage of bacterial DNA. parts of this can be packaged in viral capsid. phage infects another bacterium and transfers these genes

73
Q

specialized transduction

A

excision event: lysogenic phage infects bacterium; viral DNA incorporates into bacterial chromosome. when phage DNA is excised, flanking bacterial genes come with it, are packaged into viral capsid and can infect another bacterium

74
Q

bacterial toxin genes encoded in lysogenic packages

A

ABCDE: shigA-like toxin, Botulinum toxin, Cholera toxin, Diphtheria toxin, Erythrogenic toxin to strep pyogenes

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