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Microbiology-Bacteria

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mtmtmt's version from 2016-07-28 05:49

Toxins

Question Answer
C. tetaniblocks release of glycine, GABA from inhibitory interneurons
C. botulinuminhibits ACh release from motor neuron at NM junction
V. choleraeactivates adenylate cyclase --> increased NaCl secretion (watery diarrhea)
E. coli heat labile toxinactivates adenylate cyclase --> increased NaCl secretion (watery diarrhea)
E. coli heat stable toxinactivates guanylate cyclase --> increased cGMP --> inhibits NaCl reabsorption (watery diarrhea)
S. dysenteriaeinactivates 60S ribosomal subunit --> inhibits protein synthesis --> kills intestinal epithelial cell (bloody, mucousy diarrhea)
EHEC, EIECinactivates 60S ribosomal subunit --> inhibits protein synthesis --> kills intestinal epithelial cell (bloody, mucousy diarrhea)
S. aureus enterotoxinfood poisoning (diarrhea + vomiting less than 24 hrs)
B. cereus enterotoxinfood poisoning (vomiting less than 24 hrs)
S. pyogenes pyrogenic toxinactivates endogenous IL-1 production (Scarlet fever) ; stimulate T cells to release inflammatory cytokines (streptococcal toxic shock syndrome)
S. aureus pyrogenic toxinactivates endogenous IL-1 and TNF production ; toxin-MHC II complex causes massive T cell response/cytokine production (TSST-1)
S. pyogenestissue invasive toxins (hemolysin, streptokinase, DNAase, hyaluronidase); M protein inhibits activation of complement and prevents phagocytosis of organism
S. aureustissue invasive toxins (hemolysin, streptokinase, DNAase...)
C. perfringenshydrolyzes lecithin in cell membranes --> cell death (gas gangrene)
B. anthracis edema factora calmodulin-dependent adenylate cyclase that increases cAMP --> impairs PMN function + causes massive edema
B. anthracis protective antigenpromotes entry of EF into phagocytic cells
B. anthracis lethal factorzinc metalloprotease that inactivates protein kinase --> induces macrophage to release TNF-alpha, IL-1 (death)
C. diphtheriae exotoxin[A subunit] inactivates elongation factor (EF2) --> inhibits protein translation (myocarditis, peripheral nerve palsies, CNS effects). [B subunit] provides entry into cardiac/neural tissue
B. pertussisactivates membrane adenylate cyclase + inserts own adenylate cyclase --> inhibits PMN phagocytosis (cough)
C. difficilecytotoxic to colonic epithelial cells (bloody diarrhea, fever, abdominal pain)
P. aeruginosainhibits elongation factor (EF2) --> inhibits protein translation (targets liver)
MRSAacquired chromosomal DNA segment (mecA gene) --> encodes penicillin binding protein 2a (PBP2a) --> continues peptidoglycan wall assembly even though transpeptidase is inhibited by penicillin
VREacquired chromosomal transposon DNA element (vanA) --> encodes proteins that modify cell wall (from D-alanine-D-alanine to D-alanine-D-lactate) to lower its affinity for vancomycin
S. aureus exfoliatinexfoliative toxin A and B estalishes localized infection and relases diffusible toxin (cleavage of middle epidermis, exposing underlying flesh)
N. meningitidis endotoxincauses blood vessel destruction (hemorrhaging seen as petechiae) and sepsis
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Classification

Question Answer
S. pyogenesgram+ coccus in chains; beta-hemolytic; bacitracin sensitive
S. agalactiaegram+ coccus; beta-hemolytic; bacitracin resistant
Enterococcusgram+ coccus; no hemolysis (normal colonic flora); LAP+, PYR+
S. viridansgram+ coccus; alpha-hemolytic; optochin resistant; not bile soluble (normal oral flora)
S. pneumoniaegram+ diplococci "lancet" ; alpha-hemolytic; optochin sensitive; bile soluble; positive Quelling reaction
S. aureusgram+ coccus in clusters; catalase +; coagulase +; beta-hemolytic
S. epidermidisgram+ coccus in clusters; catalase +; coagulase -; novobiocin sensitive
S. saprophyticusgram+ coccus in clusters; catalase +; coagulase -; novobiocin resistant ; non-hemolytic
B. anthracisgram+ rod; spore-forming; aerobic; non-motile; non-hemolytic
B. cereusgram+ rod; spore-forming; aerobic; motile
Clostridiumgram+ rod; spore-forming; anaerobic
Corynebacteriumgram+ rod "club-shaped"; non spore-forming
Listeriagram+ rod; non spore-forming; tumbling motility
N. meningitidisgram- diplococci; glucose+maltose fermenter; can be part of normal flora of nasopharynx-5%
N. gonorrhoeaegram- diplococci; ferments glucose; maltose non-fermenter
H. influenzaegram- coccobacillus; dependent on Factor X + V for growth
Actinomycesgram+ rod; branching; has sulfur granules
Nocardiagram+ rod; branching; partially acid-fast
E. coligram- rod; fast lactose fermenter; motile
K. pneumoniaegram- rod; fast lactose fermenter; non-motile; indole -
Proteusgram- rod; lactose non-fermenter; oxidase -
Shigellagram- rod; lactose non-fermenter; oxidase -; non-motile
Salmonellagram- rod; lactose non-fermenter; oxidase -; motile; produce H2S
V. choleraegram- comma-shaped rod; oxidase +
C. jejunigram- comma-shaped rod; oxidase +; grows at 42 degrees C
H. pylorigram- comma-shaped rod
P. aeruginosagram- rod; aerobic; oxidase +; "metallic sheen", tortilla smell
B. pertussisgram- coccobacillus
Rhodococcus equigram+ rod; aerobic, nonmotile; partially acid-fast
Listeria monocytogenessmall gram+ rod (diphtheroid-like); tumbling motility; cold enrichment (often cultured at 4-10C)
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Presentation

Question Answer
S. pyogenes direct infection/exotoxin releasepharyngitis, skin infection, scarlet fever, TSS
S. pyogenes antibody-mediated infectionrheumatic fever (fever, myocarditis, arthritis, chorea, subcutaneous nodules, rash) ; glomerulonephritis
S. agalactiaeneonatal meningitis, pneumonia, sepsis
EnterococcusUTI ; nosocomial infections
S. bovissubacute endocarditis
S. viridansdental caries, subacute bacterial endocarditis
S. pneumoniaepneumonia, meningitis (adults), sepsis, otitis media (children)
S. aureus toxin mediatedgastroenteritis, TSS, scalded skin syndrome
S. aureus direct invasion mediatedpneumonia, meningitis, osteomyelitis (children), acute endocarditis, septic arthritis, skin infection, sepsis, UTI
S. epidermidisnosocomial infections (prothetic joints, intravenous lines, UTIs, etc); frequent skin contaminant in blood cultures
S. saprophyticusUTI
B. anthracispainless black ulcer on skin; pulmonary hemorrhage (woolsorter's disease); abdominal pain/bloody diarrhea
B. cereusfood poisoning
C. botulinumcranial nerve palsies, muscle weakness, respiratory paralysis
C. tetanimuscle spasm, lockjaw, risus sardonicus, respiratory paralysis
C. perfringensgas gangrene
C. difficilepseudomembranous colitis
C. diphtheriaesore throat (pseudomembrane); myocarditis (AV block); peripheral nerve palsy, cranial neuropathies
Listerianeonatal meningitis, pneumonia, sepsis
N. meningitidismeningitis (petechial rash), disseminated intravascular coagulation (DIC), Waterhouse-Friderichsen syndrome (adrenal gland failure; severe sepsis)
Actinomycesoral/ facial abscesses
Nocardiapneumonia in immunocompromised
N gonorrhoaeurethritis, PID, bacteremia (septic arthritis, rash); ophthalmia neonatorum (1st 5 days after birth)
Moraxella catarrhalisotitis media (children)
E. colineonatal meningitis; UTI; hospital acquired pneumonia/ sepsis; diarrhea
K. pneumoniaepneumonia (necrosis, bloody sputum common in alcoholics)
ProteusUTI, bladder stones
Shigellabloody diarrhea
Salmonella typhityphoid fever (fever, abd pain, hepatosplenomegaly, rose spots on abdomen); gastroenteritis; osteomyelitis (HbS patients)
Y. enterocoliticagastroenteritis
V. choleraesevere rice-water diarrhea (no pus)
C. jejunibloody diarrhea
H. pyloriduodenal ulcers; chronic gastritis
BacteroidesGI tract, pelvic, lung abscesses
Fusobacteriumnecrotizing pneumonia, periodontal abscess, abdominal abscess, otitis media
Pseudomonasburn infection, hot tub folliculitis, endocarditis, pneumonia, sepsis, malignant otitis externa, UTI, diabetic osteomyelitis
Burkholderiahospital acquired pneumonia (CF, chronic granulomatous disease)
Stenotrophomonashospital acquired pneumonia (respirator patients)
Acinetobacterhospital acquired pneumonia, UTI
H. influenzae type Bmeningitis (children), acute epiglottitis, septic arthritis (infants), sepsis, pneumonia
H. influenzae nontypeableotitis media, sinusitis
H. ducreyichancroid
Gardnerellabacterial vaginitis (fishy smell)
B. pertussislow grade fever, runny nose --> intense cough with whoop
Legionellapontiac fever (headache, myalgias, fatigue); legionnaire's disease (pneumonia, fever, cough)
Y. pestishot, swollen lymph nodes, high fever, conjunctivitis; sepsis, pneumonia (bubonic plague)
Francisellatularemia (ulceroglandular, pneumonia, oculoglandular)
Brucellaundulant fever
Pasteurellacellulitis
Borrelia recurrentisrecurrent fever
BartonellaCat scratch fever
Chlamydia trachomatis; types A-Cconjunctivitis, corneal scarring, blindness
Chlamydia trachomatis; types D-Kurethritis, cervicitis, PID, epididymitis, prostatitis
Chlamydia trachomatis; types L1-L3lymphogranuloma venereum
Chlamydia pneumoniaeatypical pneumonia
R. rickettsiifever, conjunctival injection, severe headache, rash (wrists, ankles --> generalized)
R. prowazekiiepidemic typhus (fever, headache, rash, delirium, extremity gangrene)
R. typhiendemic typhus (fever, headache, rash)
Coxiella burnetiiQ fever (headache, atypical pneumonia)
Borrelia burgdorferiLyme disease (erythema chronicum migrans --> Bell's palsy, peripheral neuropathy; heart block; arthritis --> chronic arthritis, encephalopathy)
Leptospiraflu-like symptoms; Weil's disease (renal failure, hepatitis-jaundice, hemorrhage)
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Virulence Factors

Question Answer
S. pyogenesM-protein (adherence, anti-phagocytic, antigenic); tissue invasive toxins
S. pneumoniaecapsule
S. epidermidisbiofilm ; polysaccharide capsule
B. anthracisprotein (poly-D-glutamic acid) capsule; plasmid pXO1 (toxins) and pXO2 (poly-glutamyl capsule)
Clostridiumspore
Bacillusgerminated spores release enterotoxins (heat-labile and heat-stable)
N. meningitidisantiphagocytic capsule, endotoxin (LPS), IgA protease (found in pathogenic species of Neisseria), pili (attach to host cells, allow antigenic variation)
N. gonorrhoaepili (antigenic variation); IgA protease
E. colipili, capsule (K-antigen)
K. pneumoniaecapsule
Proteusurease
Salmonellacapsule
Y. enterocoliticasurvives refrigeration
H. pyloriurease
H. influenzaecapsule, IgA protease
B. pertussiscapsule, pili
Chlamydia trachomatiselementary body (infective); reticulate body (reproductive)
Listerialisteriolysin O allows it to escape phagolyosomes of macrophages and avoid intracellular killing; facultative intracellular organism (survive inside/outside cells); cell-mediated immunity
C. diphtheriaepseudmomenbrane forms in pharnx- serves as base from where toxins are secreted
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Treatment

Question Answer
S. saprophyticusvancomycin
MRSAvancomycin
B. cereusno treatment (toxin only) ; resistant to penicillin
B. anthracisciprofloxacin or doxycycline
C. botulinumantitoxin
C. tetaniantitoxin, vaccine
N. meningitidisvaccine; rifampin prophylxis in close contacts
H. pylorimetronidazole + bismuth + tetracycline/ amoxicillin
Bacteroidesmetronidazole, clindamycin
gardnerellametronidazole
Chlamydiadoxycycline (adults); erythromycin (children, pregnancy)
Rickettsiaedoxycycline
mycobacterium tuberculosisisoniazid, rifampin, ethambutol, pyrazinamide, streptomycin
Corynebacterium diphtheriaeantitoxin (inactivates circulating toxin), penicillin/erythromycin, DPT (diphtheria/pertussis/tetanus) vaccine
Listeriaampicilin or trimethoprim-sulfamethoxazole
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Special culture media growth patterns/requirements

Question Answer
Corynebacteriumtellurite plate, Loeffler's media (methylene blue stain)
E. coliMacConkey's agar (pink); eosin-mthylene blue agar (blue-black)
N. gonorrhoeaeThayer-Martin media (Vancomycin, Polymyxin, Nystatin)
V. choleraealkaline media
C. jejunigrow media at 42 degrees C
H. influenzachocolate agar with factor V, factor X
B. pertussispotato agar
Legionellacharcoal-yeast extract with Fe, cysteine
M. tuberculosisLowenstein-Jensen agar
M. pneumoniaeEaton's agar
Fungisabouraud's agar
H. parahaemolyticusgrowth with Factor V, beta-hemolysis on rabbit's blood; -no-growth with Factor X only
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Source

Question Answer
Legionellawater sources (A/C)
Y. pestisflea bite, rodents, prairie dogs
Y. entercoliticaunpasteurized milk
Francisellarabbits
Borrelia burgdorferiIxodes tick
Borrelia recurrentishuman body louse
Pasteurellacats, dogs
Bartonellacat scratch
Coxiella burnetiicattle, sheep, goats
Rickettsia rickettsiaetick
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IMViC Reactions- used to identify organisms in coliform group

Question Answer
E. coli ++--
Edwardsiella tarda++--
Proteus vulgaris++--
Klebsiella pneumoniae--++
Enterobacter spp--++
Klebsiella oxytoca+-++
Serratia marcescens--++
Citrobacter freundii-+-+
Citrobacter koseri++-+
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Biochemical Testing

Question Answer
Bile esculin agarable to grow in presence of bile and hydrolyze esculin to form esculetin --> dark brown when esculetin reacts with iron salt
Catalasehydrolysis of hydrogen peroxide by the enzyme catalase into water + oxygen --> bubbling
Catarrhalis Test DiskHydrolysis of bromo-chloro-ondolyl butyrate in the disc by the enzyme butyrate esterase --> blue/green compound
Citrate agargrowth of organisms able to use ammonium dihydrogen phosphate and sodium citrate as sole sources of nitrogen and carbon --> blue (alkaline reaction)
Lysine decarboxylase (Moeller) brothdecarboxylation/hydrolysis of amino acid produces amine --> increased pH (purple/alkaline); lysine is decarboxylated to form cadaverine [neg rxn=yellow/acidic]
Arginine decarboxylase (Moeller) brotharginine is first hydrolyzed to form ornithine, then decarboxylated to form putrescine --> purple/alkaline [neg rxn=yellow/acidic]
Ornithine decarboxylase (Moeller) brothornithine is decarboxylated to form putrescine --> purple/alkaline [neg rxn=yellow/acidic]
Desoxycholate reagentbile solubility test; lysis occurs because bile soluble organisms contain an autolytic amidase that (when activated by bile salts) cleaves the bond between alanine and muramic acid in the cell wall
Haemophilus Quad Platefor fastidious organisms; quad I-requires hemin for growth but not NAD, II-require NAD but not hemin, III-both hemin+NAD, IV-require both hemin+NAD & displays hemolysis
Spot Indolemetabolism of tryptophan results in indole as a degradation product
LAP diskleucine-B-naphthylamide (substrate) hydrolyzed by leucine aminpeptidase (enzyme) to release beta-naphthylamine
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