micro: basic bacteriology Flashcards
(74 cards)
1
Q
peptidoglycan
A
fxn: gives rigid support, protects against osmotic pressure. made of sugar backbone w/peptide side chains x-linked by transpeptidase
2
Q
cell wall
A
fxn: major surface Ag. made of peptidoglycan for support, lipoteichoic acid induces TNF and IL-1
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
4
Q
plasma membrane
A
fxn: site of oxidative and transport enzymes. made of phospholipid bilayer
5
Q
periplasm
A
fxn: space between cytoplasmic and outer membranes in GNs. contains many hydrolytic enzymes, including beta-lactamases
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
7
Q
capsule
A
fxn: protects against phagocytosis. made of organized, discrete polysaccharide layer (except anthrax, which contains D-glutamate)
8
Q
spore
A
fxn: resistant to dehydration, heat, and chemicals. made of keratin-like coat; dipicolinic acid, peptidoglycan
9
Q
glycocalyx
A
fxn: mediates adherence to surfaces, especially foreign surfaces (e.g. indwelling catheters). made of loose network of polysaccharides
10
Q
GP cell walls
A
have lipoteichoic acid. cell wall is on the outside.
11
Q
GN cell walls
A
cell wall = between plasma and outer membranes. outer membrane has porins.
12
Q
GPCs
A
staph, streph
13
Q
GNCs
A
moraxella catarrhalis, neisseria
14
Q
GPRs
A
bacillus, clostridium, corynebacterium, gardnerella (gram variable), lactobacillus, listeria, mycobacterium (acid fast), propionibacterium
15
Q
GNRs: enterics
A
bacteriodes, campylobacter, E coli, enterobacter, helicobacter, klebsiella, proteus, pseudomonas, salmonella, serratia, shigella, vibrio, yersinia
16
Q
GNRs: respiratory
A
bordetella, haemophilus (pleomorphic), legionella (silver stain)
17
Q
GNRs: zoonic
A
bartonella, brucella, francisella, pasteurella
18
Q
branching filamentous GPs
A
actinomyces, nocardia (weakly acid fast)
19
Q
pleomorphic GNs
A
chlamydiae (giemsa), rickettsiae (giemsa)
20
Q
spiral GNs
A
borrelia (giemsa), leptospira, treponema
21
Q
no cell wall
A
mycoplasma, ureaplasma (contain sterols, which do not gram stain)
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)
23
Q
giemsa bugs mnemonic
A
Certain Bugs Really Try my Patience: Chlamydia, Borrelia, Rickettsia, Trypanosomes, Plasmodium
24
Q
PAS (periodic acid-Schiff) mnemonic
A
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)
29
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
31
C diphtheria Cx
tellurite agar or loffler medium
32
M pneumonia Cx
eaton agar: requires cholesterol
33
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
