micro: clinical bacteriology Flashcards
staph identification
on the staph retreat, there was NO StRESs: NOvobiocin - Saprophyticus = Resistant, Epidermidis = Sensitive
strep identification: Optochin
OVRPS: Optochin: Viridans = Resistant; Pneumoniae = sensitive
strep identification: Bacitracin
B-BRAS: Bacitracin - group B = Resistant, group A = Sensitive
alpha-hemolytic
green ring around colonies on blood agar: strep pneumo and viridans
Strep pneumo identification
catalase -, optochin sensitive, alpha-hemolytic
Viridens streptococci identification
catalase -, optochin resistant, alpha-hemolytic
beta-hemolytic
clear area of hemolysis on blood agar: staph aureus, step pyogenes, step agalactiae, listeria monocytogenes
staph aureus identification
catalase and coagulase +, beta-hemolytic
strep pyogenes identification
group A strep, catalase -, bacitracin sensitive, beta-hemolytic
strep agalactiae identification
group B strep, catalase -, bacitracin resistant, beta-hemolytic. produces CAMP factor (enlarges S. aureus hemolysis). Hippurate test +.
listeria monocytogenes
tumbling motility, meningitis in newborns, unpasteurized milk, beta-hemolytic
staph epidermidis
infects prosthetic devices and IV catheters by producing biofilms. component of normal skin flora, common contaminant. novobiocin sensitive
staph saprophyticus
2nd most common cause of UTI in young women. novobiocin resistant
strep pneumo
common cause of MOPS: meningitis, Otitis media, Pneumonia, Sinusitis. MOPS are Most OPtochin Sensitive. lancet-shaped, GP diplococci. encapsulated. IgA protease
strep pyogenes
pyogenic, toxigenic, and immunologic. bacitracin sensitive, beta-hemolytic, PYR +. Abs to M protein -> inc. host defenses and rheumatic fever. ASO titer detects recent infection
enterococci
group D strep. normal colonic flora. PCN G resistant. -> UTI, biliary infxns, subacute endocarditis. variable hemolysis. include VRE.
strep bovis
Bovis in the blood = cancer in the colon: colonizes gut,can -> bacteremia and subacute endocarditis. associated w/colon CA.
corynebacterium diphteriae
club-shaped. black colonies on cystine-tellurite agar. ABCDEFG: ADP-ribosylation (inhibits protein synthesis via), Beta-prophage, Corynebacterium Diptheriae, Elongation Factor 2 (what ADP-ribosylates), Granules (metachromatic). + Elek test for toxin. toxoid vaccine.
bacterial spores
kill w/autoclave. have dipicolonic acid in their core. no metabolic activity. dzs: anthrax, food poisoning (B. cereus), botulism, abx-associated colitis, gas gangerene, tetanus, Q fever (coxiella burnetii)
C. tetani
tetanospasmin: exotoxin = protease that cleaves SNARE, blocking GABA and glycine from Renshaw cells in spinal cord. -> spastic paralysis, trismus, + risus sardonicus. Tx w/vaccine, antitoxin, and diazepam
C. botulinum
preformed, heat-labile toxin that inhibits ACh release and NMJ. toxin in adults, spores in babies. flaccid paralysis. Tx w/antitoxin
C. perfringens
Perfringens Perforates a gangrenous leg. produces alpha toxin (lecithinase, a phospholipase) that can -> myconecrosis and hemolysis
C. difficile
2 toxins: A = enterotoxin, binds bb in gut. B = cytotoxin, -> cytoskeletal disruption via actin depolymerization -> pseudomembranous colitis. Dx by stool PCR toxin detection
anthrax
caused by GP, spore-forming rod that produces toxin. only bacterium w/polypeptide capsule (contains D-glutamate)
cutaneous anthrax
painless papule surrounded by vesicles -> ulcer w/black eschar. painless, necrotic. -> bacteremia + death = uncommon
pulmonary anthrax
inhalation of spores -> flu-like Sx -> fever, pulmonary hemorrhage, mediastinitis, and shock
B. cereus
reheated rice. spores survive cooking. keeping rice warm -> germination and toxin formation. cereulide = preformed toxin -> emetic type (w/rice + pasta). diarrheal type is slower onset
listeria monocytogenes
facultative intracellular microbe. unpasteurized dairy and deli meats. forms “rocket tails” via actin polymerization that -> intracellular mvmnt and cell-to-cell spread, avoiding Ab. tumbling motility. only GP that -> endotoxin. -> amnionitis, septicemia, spontaneous abortion, granulomatosis infantiseptica, meningitis, gastroenteritis. Tx. w/amp in infants, immunocompromised, and elderly w/meningitis.
actinomyces and nocardia
both form long, branching filaments resembling fungi. Tx is a SNAP: Sulfonamides - Nocardia, Actinomyces - PCN
actinomyces
GP anaerobe, not acid fast, normal oral flora, -> oral/facial abscesses w/sinus tracts, -> yellow, sulfur granules. Tx w/PCN.
nocardia
GP aerobe, weakly acid fast, found in soil, -> pulm infxn in immunocompromised, cutaneous after trauma in healthies. Tx w/sulfonamides
primary TB
nonimmune host (often child). hilar nodes + ghon focus (usually lower-mid lung) = ghon complex. -> heals by fibrosis -> immunity + hypersensitivity -> tuberculin +. or progressive lung dz (HIV, malnutrition) -> death (rare). or severe bacteremia -> miliary TB -> death. or preallergic lymphatic or hematogenous dissemination -> dormant tubercle bacilli in several organs -> reactivation in adult life.
secondary TB
reinfection or reactivation in partially immune hypersensitized host (often adult). fibrocaseous cavitary lesion (upper lobes) extrapulmonary TB: CNS (parenchymal tuberculoma or meningitis), vertebral body (Pott dz), lymphadenitis, renal, GI, adrenals
+PPD
if current infxn or past exposure. false positives w/BCG vaccination (further w/u required)
-PPD
if no infection or anergic (steroids, malnutrition, immunocompromise) and in sarcoidosis.
mycobacteria
all are acid-fast pink rods.
cord factor
in virulent strains of mycobacteria. inhibits macrophage maturation and induces release of TNF-alpha. sulfatides (surface glycolipids) inhibit phagolysosomal fusion
leprosy
= hansen dz. caused by mycobacterium leprae. likes cool temps -> glove and stocking skin and superficial nerves. cannot be grown in vitro. armadillos. Tx w/dapsone and rifampin, adding clofazimine if lepromatous form.
lepromatous hansen dz
presents diffusely over the skin w/leonine facies. is communicable. characterized by low cell-mediated immunity w/humoral Th2 response
tuberculoid hansen dz
limited to few hypoesthetic hairless skin plaques, characterized by high cell-mediated immunity w/largely Th1 reponse
differentiates GN diplococci
maltose. fermenter = N. meningitidis. nonfermenter = N. gonorrhoeae
differentiates GN rods
1st: lactose. fermenter = fast: Klebsiella, E coli, enterobacter. slow: citrobacter, serratia
differentiates GN rod lactose nonfermenters
1st: oxodase. + = peudomonas. -: TSI agar: produces H2S = salmonella, proteus, yersinia. doesn’t produce H2S = shigella
GN coccoid rods
H flu, pasteurella, brucella, bordetella pertussis
GN comma-shaped
oxidase +. grows in 42C = campylobacter. grows in alkaline media = v. cholerae. produces urease = H pylori.
lactose fermenting enterics
lactose = key. test w/macConKEE’S agar (forms pink colonies). Citrobacter, Kelbsiella, E coli, Enterobacter, Serratia (weak). grow as purple/black on EMB agar. E coli grows w/green sheen
Neisseria
GN diplococci. both ferment glucose and produce IgA proteases. MeninGococci ferment Maltose and Glucose. Conococci ferment Glucose.
Gonococci
no polysaccharide capsule. no maltose fermentation. no vaccine (Ag variation of pilus proteins). sexually or perinatally transmitted. -> gonorrhea, septic arthritis, neonatal conjunctivitis, PID, fitz-hugh-curtis. condoms help. erythromycin eye ointment for neonates. Tx: ceftriaxone (+ azythro or doxy for possible chlamydia)
Meningococci
polysaccharide capsule. maltose fermentation. vaccine. transmitted via respiratory + oral secretions. -> meningococcemia + meningitis, waterhouse-friderichsen syndrome (hemorrhagic adrenalitis). rifampin, cipro, or ceftriaxone PPx in close contacts. Tx: ceftriaxone or PCN G
H flu
small GN coccobacillus. aurosol transmittion. -> IgA protease. Cx on chocolate agar (w/factors V (NAD+) and X (hematin)) or grow w/staph aureus (-> factor V via hemolysis). haEMOPhilus -> Epiglottitis, Meningitis, Otitis media, and Pneumonia. Tx: mucosal infxns: amox +/- clav. meningitis: ceftriaxone. PPx w/rifampin (close contacts)
H flu vaccine
only against type b. contains capsular polysaccharide conjugated to diphtheria toxoid. given between 2-18 months.
legionella mnemonic
think of a french soldier (legionnaire) w/silver helmet, sitting around a campfire (charcoal) w/his iron dagger. he is no sitty (cysteine).
legionella
GNR (poorly) so use silver stain. grow on charcoal yeast extract culture w/iron and cysteine. Dx: Ag in urine. hyponatremia. aurosol transmission from environmental water source (e.g. airconditioning). no person-person transmission. Tx: macrolide or quinolone.
legionnaire’s dz
severe pna, often unilateral and lobar, fever, GI + CNS Sx
pontiac fever
mild flu-like syndrome caused by legionella
pseudomonas mnemonic
PSEUDDOmonas: Pneumonia, Sepsis, otitis Externa, UTIs, Drug use, Diabetics, Osteomyelitis (e.g. puncture wounds).
pseudomonas
aerobic, motile, GNR. non-lactose fermenting. oxidase +. produces pyocyanin (blue-green pigment). has grape-like odor. produces endotoxin (fever, shock) and exotoxin A (inactivates EF-2). burn victims. mucoid polysaccharide capsule -> chronic pna in CF (forms biofilms). hot tub folliculitis
pseudomonas Tx
extended spectrum beta-lactams: pip-tazo, ticarcillin, cefepime
carbapenems
monobactams: aztreonam
fluoroquinolones
aminoglycosides: gent, tobramycin
for multidrug resistent: colistin, polymyxin B
ecthyma gangrenosum
rapidly progressive, necrotic cutaneous lesion caused by pseudomonas. typically seen in immunocompromised.
EIEC
Invasive. dysentery. microbe invades intestinal mucosa -> intestinal necrosis + inflammation. similar to shigella
ETEC
Traveler’s diarrhea (watery). produces heat-labile and heat-stable enteroToxins. no inflammation/invasion
EPEC
Pediatrics. no toxin. adheres to apical surface, flattens villi, prevents absorption -> diarrhea
EHEC
shiga toxin. O157:H7 = most common serotype in US.
-> dysentery. doesn’t germent sorbitol (unlike other E coli)
causes HUS: anemia, thrombocytopenia, acute renal failure: microthrombi form on damaged endothelium -> mechanical hemolysis (schistocytes), plt consumption, dec. renal blood flow.
klebsiella mnemonic
4 As: Aspiration pna, Abscess in lungs + liver, Alcoholics, di-A-betics
klebsiella
intestinal flora -> lobar pna in alcoholics and diabetics when aspirated. very mucoid colonies caused by abundant polysaccharide capsules. currant jelly sputum. also -> nosocomial UTIs
campylobacter jejunum
major cause of bloody diarrhea, esp. children. fecal-oral transmission or from poultry, meat, unpasteurized dairy or contact w/infected animals. comma or S-shaped, oxidase +, grows at 42C. common cause of GBS and reactive arthritis
salmonella typhi
humans only. hematogenous dissemination. produces H2S. has flagella (salmon swim). virulence factors: endotoxin + Vi capsule. high infectious dose. abx prolong duration of fecal excretion. monocyte-predominant response. -> constipation, then diarrhea. live attenuated oral vaccine. -> typhoid fever. Tx w/ceftriaxone or fluoroquinolone. carrier state w/gallbladder colonization.
typhoid fever
rose spots on abdomen, constipation, abd. pain, fever
salmonella except typhi
humans and animals. hematogenous dissemination. produces H2S. has flagella (salmon swim). virulence factor: endotoxin. high infectious dose. abx prolong duration of fecal excretion. PMN-predominant response (in disseminated dz). -> bloody diarrhea. no vaccine. found in poultry, eggs, pets, and turtles. more common cause of gastroenteritis
shigella
humans only. cell to cell, not hematogenous spread. no H2S. no flagella. virulence factors: endotoxin, shiga toxin. low infectious dose. abx shortens duration of fecal excretion. PMN-predominant response. -> bloody diarrhea (bacillary dysentery). no vaccine. 4 Fs: Fingers, Flies, Food, Feces. Severity: dysenteriae > boydii > sonnei. invasion = key to pathogenicity in organisms that produce less toxin
v. cholera
produces profuse rice-water diarrhea via enterotoxin that permanently activates Gs -> inc. cAMP. comma-shaped, oxidase +, grows in alkaline media. endemic to developing countries. requires prompt oral rehydration
salmonella and shigella..
GN bacilli, non-lactose fermenting, oxidase -.
yersinia enterocolitica
transmitted from pet feces (e.g. puppies), contaminated milk, pork. -> acute diarrhea or pseudoappendicitis (RLQ pain due to mesenteric adenitis and/or terminal ileitis)
H pylori
-> gastritis + peptic ulcers (esp. duodenal). risk factor for peptic ulcer, gastric adenocarcinoma, + MALT lymphoma. curved GNR. catalase, oxidase, and urease +. Dx: urea breath test or fecal Ag test. creates alkaline environment. Tx: PPI + clarithromycin + amoxicillin (or flagyl if PCN allergy)
spirochetes
BLT: Borrelia (big), Leptospira, Treponema. only borrelia can be seen using aniline dyes (wright or giemsa) in light microscopy due to size. treponema is seen on dark-field microscopy
leptospira interrogans
found in water containing animal urine. -> leptospirosis and weil dz
leptospirosis
flu-like Sx, myalgias (classically calves), jaundice, photophobia w/conjuctival suffusion (erythema w/o exudate). prevalent among surfers and in tropics
weil dz
icterhemorrhagic leptospirosis = severe form w/jaundice + azotemia from liver and kidney dysfxn, fever, hemorrhage, and anemia.
lyme mnemonic
key lime pie to the FACE: Facial nerve palsy (typically b/l), Arthritis, Cardiac block, Erythema chronicum migrans
lyme dz
caused by borrelia burgdorferi. transmitted by Ixodes deer tick (same as babesia). mouse = natural reservoir. common in NE united states. initial Sx: erythema chrocum migrans, flu-like Sx, +/- facial nerve palsy. later Sx: monoarthritis (large joints), AAV nodal block, neurologic (meningitis, facial palsy, polyneuropathy). Tx: doxycycline, ceftriaxone.
primary syphilis
painless chancre. Dx: dark-field microscopy of chancre-fluid. VDRL + in 80%
secondary syphilis
disseminated dz w/constitutional Sx, maculopapular rash including palms and soles, condylomata lata. Dx: can still use dark-field microscopy
tertiary syphilis
gummas, aortitis (vasa vasorum destruction), neurosyphilis (tabes doraslis ,”general paresis”), argyll robertson pupil. signs: board-based ataxia, + romberg, charcot joint, stroke w/o HTN. Dx for neurosyphilis: test CSF w/VDRL and PCR
congenital syphilis
facial abnormalities: rhagades (linear scars at mouth angle), snuffles, saddle nose, notched hutchinson teeth, mulberry molars, short maxilla, saber shins, CN VIII deafness. PPx: treat mother early in pregnancy: transmission usually occurs after 1st trimester
VDRL false positives
VDRL: Viral infection (mono, hepatitis), Drugs, Rheumatic fever, Lupus/Leprosy. inexpensive, widely available, quantitative. sensitive but not specific. Ab reacts w/beef cardiolipin
jarisch-herxheimer reaction
flu-like Sx after Abx started due to killed bacteria (usually spirochetes) releasing endotoxins
anaplasma
zoonotic bacteria -> anaplasmosis (anemia, hematuria, diarrhea, B Sx). source: ixodes ticks (live on deer + mice)
bartonella
zoonotic bacteria -> cat scratch dz (tender lymphadenitis, B Sx), bacillary angiomatosis (tumor-like blood vessels), source: cat scratch
borrelia burgdorferi
zoonotic bacteria -> lyme dz. source: ixodes ticks (deer + mice)
borrelia recurrentis
zoonotic bacteria -> relapsing fever. source: louse. recurrent due to variable surface Ags
brucella
zoonotic bacteria -> brucellosis/undulant fever (sweating, migratory arthralgia/myalgia, fever). source: unpasteurized dairy
campylobacter
zoonotic bacteria -> bloody diarrhea. source: puppies, livestock (fecal-oral, ingestion of undercooked meat)
chlamydophila psittaci
zoonotic bacteria -> psittacosis (atypical pna that mimics typhoid fever). source: parrots, other birds
coxiella burnetii
zoonotic bacteria -> Q fever (fever, malaise, sweating, pain, dry cough, headache, confusion, GI Sx). source: aerosols of cattle/sheep amniotic fluid
ehrlichia chaffeensis
zoonotic bacteria -> ehlichiosis (headache, myalgia, fatigue +/- rash. can -> opportunistic infxns). source: ambylomma (lone star tick)
francisella tularensis
zoonotic bacteria -> tularemia (high fever, lethargy, dec. appetite, rash, supporative lymphadenopathy, septicemia). source: ticks, rabbits, deer fly
leptospira
zoonotic bacteria -> leptospirosis (headache, myalgia, fever, hemoptisis, meningitis, jaundice, azotemia. source: animal urine
mycobacterium leprae
zoonotic bacteria -> leprosy. source: humans w/lepromatous leprosy, armadillo
pasteurella multocida
zoonotic bacteria -> cellulitis, osteomyelitis. source: animal bite: cats/dogs
rickettsia prowazekii
zoonotic bacteria -> epidemic typhus (sustained high fever, cough, rash, severe muscle pain, chills, falling blood pressure, stupor, sensitivity to light, delirium and death). source: louse
ricketssia rickettsii
zoonotic bacteria -> rocky mountain spotted fever (fever, headache, centripetal rash). source: dermacentor (dog tick).
Rickettsia typhi
zoonotic bacteria -> endemic typhus. source: fleas (on rats)
salmonella
zoonotic bacteria -> diarrhea (can be bloody), vomiting, fever, abd cramps. source: reptiles + poultry
yersinia pestis
zoonotic bacteria -> plague (bubonic, septicemic, pneumonic). source: fleas (rats + prairie dogs = reservoirs)
gardnerella vaginalis
-> BV. Tx: flagyl or clinda
rocky mountain spotted fever
rickettsia rickettsii. tick vector. found in/near north carolina. Sx: classic triad = headache, fever, rash. rash starts on wrists/ankles, spreads to trunk, palms, soles. Tx: doxycycline
palms + soles rash mnemonic
you drive CARS with your palms + soles: Coxsackievirus A (hand, foot, mouth), Rocky mountain spotted fever, secondary Syphilis.
typhus
endemic (fleas): R. typhi. epidemic (lice): R. prowazekii. rash starts centrally and spreads out, sparing palms + soles. Tx: doxy
centripetal/centrifugal rash mnemonic
Rickettsii on the wRists, Typhus on the Trunk.
ehrlichiosis
vector = tick. rash is rare. monocytes w/morulae (berry-like inclusions) in cytoplasm. Tx: doxy
anaplasmosis
vector = tick. granulocytes w/morulae in cytoplams. Tx: doxy
Q fever
coxiella burnetii. no arthropod vector. spores inhaled from cattle-sheep amniotic fluid. presents as pna. most common cause of Cx neg endocarditis. Q fever = Queer: no rash, no vector, organism can survive outside (as endospore).
chlamydia
cannot make ATP so they are obligate intracellular pathogens. chamys = cloak (intracellular). lab Dx: cytoplasmic inclusions seen on giemsa or fluorescent Ab-stained smear. cell wall lacks classic peptidoglycan (less muramic acid) so beta-lactams are less effective.
chlamydia forms
Elementary body (small, dense) = Enfectious, Enters cell via Endocytosis. transforms into retuculate body Reticulate body Replicates in cell by fission; Reorganizes into elementary bodies
C. trachomatic
-> reactive arthritis (reiter syndrome), follicular conjunctivitis, nongonococcal urethritis, PID. Tx: azythromycin (1 dose) or doxy
C. pneumoniae/C. psittaci
-> atypical pna. transmitted via aerosol. Tx: azythromycin (1 dose) or doxy. psittaci has avian reservoir
chlamydia trachomatis serotypes A, B, C
-> chronic infection, blindness 2/2 follicular conjunctivitis (mostly in africa). ABC: Africa, Blindness, Chronic infection
chlamydia trachomatis serotypes D-K
-> everything else: urethritis/PID, ectopic pregnancy, neonatal pna (staccato cough) w/eosinophilia, neonatal conjuctivitis.
chlamydia trachomatis serotypes L1, L2, L3
-> lymphogranuloma venereum: small, painless genital ulcers -> swollen, painful inguinal lymph nodes that ulcerate (buboes). Tx: doxy
mycoplasma pneumonia
no cell wall. not seen on gram stain. pleomorphic. bacterial membrane contains sterols for stability. more common in young people, military recruits, prisons. -> atypical, walking pna. X-ray is worse that Sx. high titer of cold agglutinins (IgM): can agglutinate or lyse RBCs. grown on eaton agar. Tx: macrolides, doxy, or fluoroquinolones
