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Flashcards in micro: basic bacteriology Deck (74):
1

peptidoglycan

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

2

cell wall

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

3

outer membrane (GN)

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

4

plasma membrane

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

5

periplasm

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

6

pilus/fimbria

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

7

capsule

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

8

spore

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

9

glycocalyx

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

10

GP cell walls

have lipoteichoic acid. cell wall is on the outside.

11

GN cell walls

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

12

GPCs

staph, streph

13

GNCs

moraxella catarrhalis, neisseria

14

GPRs

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

15

GNRs: enterics

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

16

GNRs: respiratory

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

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GNRs: zoonic

bartonella, brucella, francisella, pasteurella

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branching filamentous GPs

actinomyces, nocardia (weakly acid fast)

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pleomorphic GNs

chlamydiae (giemsa), rickettsiae (giemsa)

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spiral GNs

borrelia (giemsa), leptospira, treponema

21

no cell wall

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

22

bugs that don't gram stain well mnemonic

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)

23

giemsa bugs mnemonic

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

24

PAS (periodic acid-Schiff) mnemonic

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

25

ziehl-neelsen (carbol fuchsin)

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

26

india ink

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

27

silver stain

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

28

H flu Cx

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

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neisseria Cx

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

30

B pertussis Cx

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

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C diphtheria Cx

tellurite agar or loffler medium

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M pneumonia Cx

eaton agar: requires cholesterol

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lactose-fermenting enterics Cx

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

34

E coli Cx

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

35

legionella Cx

charcoal yeast extract agar buffered w/cysteine and Fe

36

fungi Cx

Sab's a fun guy: Sabouraud agar

37

aerobes mnemonic

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

anaerobes mnemonic

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

obligate intracellulars

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

40

facultative intracellulars

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

41

encapsulated bacteria

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

vaccines against encapsulated bacteria

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

urease-positive bugs

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

44

catalase-positive organisms

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

pigment-producing bacteria

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

protein A

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

47

IgA protease

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

48

M protein

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

type II secretion system

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

exotoxins

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

endotoxins

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

corynebacterium diphtheria toxin

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

53

pseudomonasauruginosa toxin

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

54

shigella toxin

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

EHEC toxin

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

ETEC toxins and mnemonic

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

bacillus anthracis toxin

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

vibrio cholera toxin

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

bordetella pertussis toxin

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

clostridium tetani toxin

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

clostridium botulinum toxin

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

clostridium perfringens toxin

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

streptococcus pyogenes toxin

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

staph aureus toxin

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

strep pyogenes toxin

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

endotoxin mnemonic

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

67

actions of endotoxins

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

transformation

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

F+ x F- conjugation

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

Hfr x F- conjugation

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

transposition

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

generalized transduction

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

specialized transduction

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

bacterial toxin genes encoded in lysogenic packages

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