Micro 2 USMLE Flashcards
dermatophyte has a reservoir in pets
microsporum
this obligate anaerobic bacilli is gram positive, spore forming
clostridia
this clostridium species produces an exotoxin
clostridium tetani
C tetani exotoxin works by blocking ________ release [inhibitory neurotransmitter] from Renshaw cells in the spinal cord
glycine
this clostridia bacilli forms a preformed, heat-labile toxin that inhibits ACh release
C. botulinum
mneu: BOTulinum is from bad BOTtles of food (causes a flacid parralysis)
this clostridia bacilli produces an alpha toxin (lethinasse) that causes myonecrosis, gas gangrene, or hemolysis.
C. Perfringes
mneu: PERFringes PERForates a gangrenous leg
this clostridia bacilli produces a cytotoxin, an exotoxin that kills enterocytes, causing psudomembranous colitis. It is often secondary to antibiotic use, especially clindamycin or ampicillin.
C. difficile
mneu: DIfficile causes DIarrhea.
how do you tx C. difficile
metronidazole.
Diptheria is caused by _________ via exotoxin encoded by a Beta-prophage.
Corynebacterium diptheriaee
the potent diptheria exotoxin works by inhibiting what via ADP ribosylation of EF-2
Protein synthesis
coryne=______
club shaped
Symptoms of infection with this bug include pseudomembranous pharyngitis (grayish-white membrane) with lymphadenopathy)
C. diptheriae.
C diptheriae identified in the lab as a Gram ___, _____ with metachromatic ranules.
G+, rod
C diptheriae grows on a ______ agar
tellurite
What are the ABCDEG of diptheria and its exotoxin
ADP ribosylation Beta-prophage Corynebacterium Diphtheriae Elongation Factor 2 Granules
pt presents with painless black skin lesions (vesicular papules covered by black eschar). He developes sepsis and dies. What G+ sporeforming rod that produces a toxin do you suspect
Bacillus anthracis
Inhalation of anthrax spores from contaminated wool can lead to flulike symptoms that rapidly progress to fever, pulmonary hemorrhage, and shock. what is the name of this dz.
woolsorters dz.
these two bugs are both gram + rods forming long branching filaments resembling fungi
actinomyces v. nocardia.
this bug forms yellow “sulfur granules’ in sinus tracts
A. israelii
this bug is a G+ ANAEROBE, that causes oral/facial abscesses with “sulfur granules” that may drain through sinus tracts in the skin. It is part of the normal oral flora.
Actinomyces israelii
this bug is a gram + and weakly acid fast aerobe in the soil taht causes pulmonary infection in immunocompromized pts
Nocardia asteroides
How do you tx nocardia? actinomyces?
mneu: SNAP Sulfa for Nocardia; Actinomyces use Penicillin
Gram negative outer membrane layer inhibits entry of these 2 AB. Therefore G - bugs are resistant to these 2 drugs
Penicillin G
Vancomycin
T or F. G- bugs are resistant to all derivitives of penicillin such as ampicillin
F–just resistant to PCN & Vanco.
Neisseria is a gram ___, ____
neg, cocci
Neisseria Gonococci or Meningococci?
Polysaccharide capsule
Meningococci
Neisseria Gonococci or Meningococci?
No Polysaccharide capsule
Gonococci
Neisseria Gonococci or Meningococci?
No maltose fermintation
Gonococci
Neisseria Gonococci or Meningococci?
maltose fermintation
Meningococci
Neisseria Gonococci or Meningococci?
No Vaccine
Gonococci
Neisseria Gonococci or Meningococci?
Vaccine
Meningococci
Neisseria Gonococci or Meningococci?
causes gonorrhea, septic arthritis, neonatal conjunctivitis, PID
Gonococci
Neisseria Gonococci or Meningococci?
causes meningococcemia and meningitis, Waterhouse-Friderichsen syndrome
Meningococci
this bug is a small gram negative (coccobacillary) rod spread via aerosol transmission.
Haemophilus influenzae
HaEMOPhilus Influenzae causes (4)
Epiglottis, Meningitis, Otitis media & Pneumonia.
Most invasive form of H. influenzae is caused by capsular type ___
B.
H. influenzae produces ____ protease.
IgA.
how do you culture H. influenzae
chocolate agar w/ factors V (NAD) & X (hematin) for growht
mneu: when child has “flu” mom goes to five(V) & dime (X) to buy some chocolate.
H. flu vaccine contains type B capsular polysaccharide conjugated to diptheria toxoid or other protien. It is given between ____ and _____ mo of age.
2 and 18
this group is a diverse family including E. coli, salmonella, shigella, klebsiella, enterobacter, serratia, porteus
enterobacteriaceae.
all enterobacteriaceae have somatic (__) Ag (polysaccharide of endotoxin. The capsular (__)Ag related to virulence of the bug. The flagellar (__) Ag is found in motile species
O
K
H
enterobacteriaceae ferment ____ and are oxidase ____
glucose
negative
with enterobacteriaceae think COFFEe.
Capsular O Ag Flagellar Ag Ferment glucose Enterobacteriaceae
these bacteria grow pink colonies on MacConkey’s agar. Examples include Klebsiella, E. coli, Enterobacter, and Citrobacter
Lactose fermenters
Lactose is KEE
These 2 organisms are similar in that both are non-lactose fermenters. Both invade intestinal mucosa and can cause bloody diarrhea
Salmonella v. Shigella
Salmonella v. Shigella:
Only _______ is motile and can invade further and disseminate hematogenously. Symptoms may be prolonged with AB treatments, and there is typically a monocyte response.
Salmonella
mneu: Salmon swim (motile and disseminate
_____ has an animal reservoir
salmonella.
Shigella is transmitted via the 4 Fs
Food, fingers, feces, & fliies
usually transmitted from pet feces (e.g., puppies), contaminated milk, or pork. Outbreaks are common in day-care centers. Can mimic Crohn’s or appendicitis, can disseminate to produce lymphadenitis.
Yersinia enterocolitica.
Bugs causing food poisoning:
contaminated seafood
Vibrio parahaemolyticus & V. vulnificus
Bugs causing food poisoning:
reheated rice
Bacillus cereus
Bugs causing food poisoning:
meats, mayonaise, custard
s/s starts quickly and ends quickly
S. aureus
Bugs causing food poisoning: reheated meat dishes
clostridium perfringes
Bugs causing food poisoning: undercooked meat
E. Coli O157:H7
Bugs causing food poisoning: poultry, meat, & eggs
Salmonella
Pt presents with bloody diarrhea. culture shows comma or S- shaped, oxidase positive organisms that grow at 42*C. What is the species
Campylobacteria
Pt presents with bloody diarrhea. culture shows motile organisms What is the species
Salmonella
Pt presents with bloody diarrhea & dysentery. Culture shows nonmotile species with very low ID50. What is the species
Shigella.
What is more virulent Shigella or Salmonella
Shigella (only 100 organisms causes dz)
Pt presents with bloody diarrhea which progresses to HUS. culture shows shiga-like toxin. What is the species
Enterohemorrhagic E. coli
Pt presents with bloody diarrhea. culture shows O157:H7 which has invaded the colonic mucosa What is the species
Enteroinvasive E. coli
child at day care center presents with bloody diarrhea and pain that mimicks appendicitis. What is the bug?
Yersinia enterocolitica
Pt presents with bloody diarrhea & pseudomembranous colitis. What is the species
C. dificile
Pt presents with bloody diarrhea. culture shows protozoa. What is the species
entamoeba histolytica
Pt presents with watery diarrhea. Hx of traveling out of the country. No preformed toxin. What is the species
Enterotoxigenic E. coli (ETEC)
Pt presents with rice watery diarrhea . culture shows comma shaped organisms. What is the species
V. cholerae
Pt presents with watery diarrhea and gas gangrene. What is the species
C. perfringes
Immunocompromized pt presents with watery diarrhea. what do you suspect.
protazoa (e.g., giardia, cryptosporidium)
Pt presents with watery diarrhea . What viruses could cause this
Rotavirus, adenovirus, Norwalk virus
This toxin acts via ADP ribosylation that perminantly activates adenyl cyclase (increase cAMP). It perminantly activates G(s)causing rice-water diarrhea.
Vibrio cholerae toxin
Cholera turns the “on” on
This toxin acts via ADP ribosylation that perminantly activates adenyl cyclase (increase cAMP). It perminantly disables G(i)causing whooping cough. It also promotes lymphocytosis by inhibiting chemokine receptors
Pertussis toxin
Pertussis turns the “off” off
This bug is a gram neg. rod that gram stains poorly. It is spread via aerosol transmission from enviornmental water source hapitat. It is not spread person to person.
Legionella pneumophelia
How do you cx & stain Legionella pneumophelia
grow on charcoal yeast extract culture with iron and cysteine
stain with silver stain.
mneu: Think of French legionnaire (ssoldier) with his silver hlmet, sitting around a campfire (charcoal) with is iron dagger–he is no sissy (cysteine)
How do you tx Legionnaires’ dz
erythromycin
this bug is associated with wound and burn infections. It is an aerobic gram negative rod. It is non lactose fermenting, oxidase positive. it produces pyocyanin which is a blue green pigment and is usually associated with a water source.
Pseudomonas aeruginosa.
mneu: AERuginosa–AERobic. think water connnection & blue green pigment.
Pseudomonas aeruginosa causes pneumonia in these patients
CF
Pseudomonas aeruginosa causes black lesions on the skin when this happens
sepsis
When pseudomonas aeruginosa causes external otitis, it is also known as
swimmers ear
Pseudomonas aeruginosa produces an endotoxin which causes (2)
fever & shock
Pseudomonas aeruginosa produces an exotoxin (A) which does this to EF-2
inactivates it
how do you tx Pseudomonas aeruginosa
aminoglycoside plus extended-spectrum penicillin (e.g., Piperacillin, ticarcillin.
this gram - rod causes gastritis and up to 90% of duodenal ulcers.
Helicobacter pylori
Is H. pylori urease + or -
+ think the urease breath test.
what other bug is urease +
Proteus
cleaves urea to amonia
H. pylori is a risk factor for (2)
peptic ulcer and gastric carcinoma
H. pylori creates this kind of envirnment (acid or alkaline)
alkaline
tx H. pylori w/ triple therapy-what is it
1) bismuth (pepto-bismol)
2) metronidazole
3) tetracycline or amoxycillin
or (more expensive)
1) metronidazole
2) omeprazole
3) clarithromycin
this zoonotic bacteria causes lyme dz and is transmitted by the bite of the Ixodes tick that live on deer and mice
Borrelia Burgdorferi
this zoonotic bacteria causes Undulant fever and is transmitted by dairy products and contact with animals
Brucella species
this zoonotic bacteria causes Tularemia and is transmitted by ticks that live on rabbits & deer
Francisella tularensis
this zoonotic bacteria causes plague and is spread via flease that live on rodents, especially prarie dogs
Yersinia pestis
this zoonotic bacteria causes cellulitis and is spread via bites from cats and dogs
pasteurella multocida
On pelvic exam you note a greenish vaginal discharge with a fishy smell. Pt reports no pain. Smear shows clue cells and cx grows out a pleomorphic, gram variable rod. What is the dx and the bug.
Bacterial Vaginosis
Gardnerella vaginalis
What anaerobe is also involved with B.V
Mobiluncus.
How do you tx B.V.
metronidazole
what are clue cells
vaginal epithelial cells covered with bacteria, visable under microscope
TB granulomas with lobar and perihilar lymph node involvement. Reflects primary infection or exposure
Ghon complex
pt presents with fever, night sweats, weight loss & hemoptysis. What mycobacterium do you suspect
mycobacterium tuberculosis
pt presents with TB like symptoms but it is not mycobacterium tuberculosis, what other mycobacterium could it be
M. kansasii
child presents with cervical lymphadenitis. What mycobacterium?
M. scrofullaceum
AIDS pt presents with disseminated dz. Bug is resistant to multilple drugs. What mycobacteria
M. avium-intracellulare
all mycobacteria should be stained this way
acid fast
what dz involves loss of eyebrows, nasal collapse, lumpy earlobe, and “leonine facies”
Leprosy (Hansen’s dz)
This bug is an acid fast bacillus that likes cool temperatures (infects skin and superficial nerves) and cannot be grown in vitro.
Mycobacterium leprae
What is the reservoir in US for M. leprae
armadillos.
TB granulomas with lobar and perihilar lymph node involvement. Reflects primary infection or exposure
Ghon complex
pt presents with fever, night sweats, weight loss & hemoptysis. What mycobacterium do you suspect
mycobacterium tuberculosis
pt presents with TB like symptoms but it is not mycobacterium tuberculosis, what other mycobacterium could it be
M. kansasii
child presents with cervical lymphadenitis. What mycobacterium?
M. scrofullaceum
Hansen’s dz (Leprosy) has 2 forms: lepromatous & tubberculoid. Which is worse?
Lepromatous is worse–it involves failed cell mediated immunity; tuberculoid is self limited
mneu: LEpromatous=LEthal.
these are obligate intracellular parasites that cause mmucosal infections
Clamydiae
chlamys=_______
cloak (intracellular
Chlamydiae exists in 2 forms What are they?
1) Elementary body (small, dense) Enters cell via Endocytosis
2) Reticuliate body, which Replicates in cell by fission
This chlamydia species causes reactive arthritis, conjunctivitis, and nongonococcal urethritis
Chlamydia trachomatis
These 2 chlamydia species cause atypical pneumonia, and is transmitted via aerosol droplets
C. pneumoniae & C. psittaci
C. psittaci is notable in that it has an ____ reservior
avian
The clamydial peptidoglycan wall is unusual in that it lacks ______
muramic acid
Dx of clamydia is made by cytoplasmic incusions seen on _______ or fluorescent Ab stained smear
giemsa
how do you tx clamydia
erythromycin or tetracylcine
Clamydia trachomatis serotypes:
A,B,C
ABC=Africa/Blindness/Chronic infection
Clamydia trachomatis serotypes:
D-K
urethritis/PID, ectopic pregnancy, neonatal pneumonia, or neonatal conjunctivitis
D-K=everything else
Clamydia trachomatis serotypes:
L1-L3
Lymphogranuloma venerium
Neonate develops conjunctivits via passage through infected birth canal. How do you tx his chlamydia
erythromycin eye drops
Name 3 spirochetes
Borrelia (Big-can be visualized under light microscopy using aniline dyes (Wright’s or Giemsa stain))
Leptospira
Treponema
mneu: BLT
pt presents with erythema chronicum migrans, an expanding “bull’s eye” red rash with central clearing. Dz may progress to affect joints CNS, & heart.
Lyme dz
Lyme dz caused by what spirochete and what vector
Borrelia burgdorferi, transmitted by the tick Ixodes
important reservoir for Lymme dz
mice
animal required for tick life cycle
deer.
lyme dz transmission is most common during this season
summer
3 stages of Lyme dz
1) erythema chronicum migrans, flulike symptoms
2) neurologic and cardiac manifestations
3) autoimmune migratory polyarthritis
mneu: BAKE a Key LYME pe:
Bells palsy, Arthritis, Kardiac block, Erythema chronicum migranes.
treponemes are ______
spirochetes
________ causes syphilis
Treponema pallidum
_______ causes yaws (a tropical infxn that is not an STD, although VDRL test is +.
T. pertenue
describe primary syphilis
localized dz-painless chancre
describe secondary syphilis
disseminated dz w/ constitutional symptoms, maculopapular rash (palms & soles) condylomata lata
mneu: Secondary syphilis=Systemic
pt preents w/ broad-based ataxia positive Romberg, charcot joints, stroke without hypertension
tertiary syphilis
describe tertiarry syphilis
gummas, aortitis, neurosyphalis (tabes dorsalis), argyl Robertson pupil
child presents with deafness, saber shins, sadddle nose. what dx
congenital syphilis
describe primary siphilis
localized dz-painless chancre
describe secondary syphilis
disseminated dz w/ constitutional symptoms, maculopapular rash (palms & soles) condylomata lata
mneu: Secondary syphilis=Systemic
pt preents w/ broad-based ataxia positive Romberg, charcot joints, stroke without hypertension
tertiary syphilis
describe tertiarry syphilis
gummas, aortitis, neurosyphalis (tabes dorsalis), argyl Robertson pupil
child presents with deafness, saber shins, sadddle nose. what dx
congenital syphilis
constricts with accomodation but is not reactive to light. Pathognomonic for tertiary syphilis
Argyll Robertson Pupil
“prostitute’s pupil” – accommodates but does not react.
FTA-ABS is specific for these. It turns + earliest in dz & remains positive for longest
treponemes
mneu: FTA-ABS=Find The Antibody-ABSolutely:
1) Most specific
2) earliest positive
3) remains positive the longest
VDRL or FTA interpretation:
Active infection
both
VDRL or FTA interpretation:
Probably false positive
VDRL
VDRL or FTA interpretation: positive after successful treatment
FTA
this test detects a nonspecific Ab that reacts with beef cardiolipin
VDRL
VDRL false positive
VDRL Viruses (mono, hepatitis) Drugs Rheumatic fever & arthritis Lupus & leprosy
coccidiomycosis and histoplasmosis are fungus transmitted by _______
inhalation of conidia (asexual fungal spores)
this fungus can cause a systemic of superficial fungal infection. It is dimorphic forming budding yeast with psudohyphae in cx at 20C and germ tube formation at 37C
Candida albicans
alba=_____
white
causes thrush esophagitis with immunocompromized pts (neonates, steroides, diabetes, AIDS), endocarditis in IV drug users, vaginitis (post-antibiotic), diaper rash
Candida albicans
Tx of candida for superfical infxn
nystatin
Tx of candida for systemic infxn
amphotercin B
this dz causes San Joaquin Valley or desert “valley fever.” It is known as desert bumps and on cx you may see a spherule filled with endospores
Coccidiomycosis
this dz is spread by bird or bat droppings in Mississippi and Ohio river valleys. Characterized by tiny yeast inside macrophages
Histoplasmosis
This organism endemic in rural Latin America and is characterized by a “Captain’s wheel” appreance.
PARACOCCIDIOMYCOSIS
This fungis is endemic to states east of Mississippi River & Central America, it is characterized by Big, Broad-Based Budding yeasts
Blastomycosis.
histo, paracoxie, and blastomycoisis are all caused by _______ fungi, which are mold in soil (low temp) adn yeast in tissue (higher temp)
dimorphic
coxie is the exception in that it is a ______ in tissue
spherule
tx coxie, histo, paracoxie, and blastomycoisis locally with
fluconazole or ketoconazole
tx coxie, histo, paracoxie, and blastomycoisis systemically
amphotericin
systemic mycosis can form granulomas and mimick this dz
TB
this dz causes hypopigmented skin lesion and occurs in hot, humid weather.
tinea versicolor
tinea versicolor is caused by
malassezia furfur
tx tinea versicolor with topical
miconazole or selenium sulfide (Selsun)
this dz is an infxn of keratinized leyer of skin. It appears as a brownish spot.
tinea nigra
tinea nigra is caused by this fungus
Cladosporium wernecki.
tx tinea nigra with topical______
salycylic acid
pruritic lesions with central clearing resembling a ring
Tinea (pedis, cruris, corporis, capitis)
Tinea (pedis, cruris, corporis, capitis) caused by
dermatophytes (microsporum, trichophyton, and epidermophyton)