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Flashcards in Gram negatives Deck (25):

bartonella henselae: presentation, classification

gram negative rods
cause "cat scratch fever." May cause a rash with unilateral LAD. or endocarditis. may also cause bacilliary angiomatosis: proliferation of blood vessels.


vibrio cholera: presentation, classification, toxin

vibrio: gram negative, comma shaped, oxidase positive, grows in alkaline media.
causes rice water diarrhea.
cholera toxin is carried on a bacteriophage and permanently activates Gs. This causes increased cAMP and increased secretion of Cl- in the gut. ultimately, this leads to osmotic water loss.


Legionella pneumonia: presentation, classification

2 diseases:
1. Pontiac fever: mild, flu-like syndrome
2. Legionnaire's disease: severe, atypical pneumonia with fever, GI, and CNS symptoms.
classification: gram negative rod, but usually requires silver stain on CHARCOAL yeast extract with IRON and CYSTEINE. usually clinically detected by antigen in the urine.
spread: aerosol transmission from an environmental water source; no person-to-person transmission.


Treatment of legionella pneumonia: name, mechanism, side effects

Macrolide or quinolone.
macrolides work by binding 23S rRNA and preventing translocation (this is part of the 50S subunit). could cause GI motility issues, arrhythmias, cholestatic hepatitits, rash, eosinophilia, increased serum conc. of theophyllines and anticoagulants.
quinolone: inhibit DNA gyrase (topoisomerase II) and topoisomerase IV; bacterialcidal. can't be taken with antacids. may cause tendon rupture; contraindicated in pregnancy and childhood becasue of cartilage damage.


pseudomonas aeruginosa: classification, toxins

classification: gram negative rod; non-lactose fermenting, oxidase positive. makes pyocanin (blue-green pigment) and smells like grapes. comes from water.
toxins: endotoxin that can cause shock and fever, and exotoxin A that inactivates EF-2 (like the diphtheria toxin). in CF patients, pseudomonas is associated with a BIOFILM formation and an antiphagocytic capsule.


pseudomonas aeruginosa: diseases

wound and burn infections, pneuomia in CF, sepsis, external otitis, UTIs, drug use and diabetes, osteomyelitis, and hot tub folliculitis. external otitis may be malignant in diabetics (may spread to the mastoid bone)
ecthyma gangrenosum: rapidly progressive, necrotic cutaneous lesions caused by pseudomonas bacteremia. seen in immunocompromized.


treatment of pseudomonas

aminoglycoside pluse piperacillin, ticarcillin, cefepime, imipenem, or meropenem (-penems are beta lactamase resistant drugs, but use is limited by seizures. always give with cilastine to decrease inactivation in the renal tubules)


E coli virulence factors and classification

fimbriae/attachement pili: cause cystitis and pylonephritis
K capsule (inhibits complement, phagocytosis): pneumonia, neonatal meningitis
LPS endotoxin (specifically, lipid A): septic shock
classification: gram negative rod that ferments lactose (pink on MacConkey agar)



EIEC: microbe invades intestinal mucosa and causes necrosis and inflammation. will cause dysentery with leukocytes in stool (looks like shigella)
EPEC (enetropathogenic): No toxin. adheres to apical surface, FLATTENS VILLI, and prevents absorption. does NOT invade. usually in KIDS



produces heat-labile and heat-stable toxins. no inflammation or invasion.
heat labile toxin: overactivates adenylate cyclase to incr. cAMP and incr. Cl secretion
heat stable toxin: overactivates guanylate cyclase to increase cGMP and decrease NaCl resorption in the gut.
causes watery traveler's diarrhea.
no invasion



O157:H7 is the most common serotype. it produces a shiga-like toxin that causes HUS (anemia, thrombocytopenia, and acute renal failure).
it causes dysentery because the toxin causes necrosis and inflammation. toxin INACTIVATES 60S RIBOSOME BY REMOVING ADENINE FROM rRNA.
microthrombi form on endothelim damaged by toxin causing mechanical hemolysis and decr. renal blood flow. microthrombi consume platelets and cause thrombocytopenia. `


klebisella: disease, categorization

gram negative, lactose fermenting rod.
3 As:
1. aspiration lobar pneumonia: mucoid colonies casued by abundant polysaccharide capsules with red currant jelly sputum.
2. abscesses in lungs and linver
3. alcoholics and diabetics.
also casues nosocomial UTIs


Shigella: classification, disease, diagnosis, treatment

gram negative rod that does oxidase negative and does not ferment lactose.
causes dysentery.
carried only by humans and primates.
invades and causes a PMN infiltration. cell to cell transmission only- NO hematogenous spread.
Dx: nonmotile (vs. salmonella), does not produce H2S (vs. salmonella),
Tx: abx shorten the duration of fecal excretion of the orgnanism.


salmonella enteritidis: classification, disease,diagnosis, treatment.

many animal reservoirs
causes gastroenteritis, may or may not be bloody
invades and causes a MONOCYTIC response. can disseminate hematogenously.
gram neg rods in stool or urine. motile and produce H2S. does not ferment lactose.
antibiotics may prolong the carrier state, so only use them if the patient is at risk for invasive disease.


salmonella typhi: classification, disease, diagnosis

only found in humans.
people may be asymptomatic carriers, have thypoid fever, or have osteomyelitis in sickle cell patients.
classification: gram negative motile rod that makes H2S and does not ferment lactose.
typhoid fever: rose spots on abdomen, fever, headache, and diarrhea. may remain in gallbladder and cause carrier state.


Haemaphilus influenza: transmission, classification, diseases

small gram negative coccobacilli with aerosol transmission.
grow on chocolate agar with factor V (NAD+) and factor X (hematin), or grow with S. aureus, which provides factor V.
non-typable strains casue mucosal infections like OM, conjunctivitis, and bronchitis.
type B casues epiglottitis, meningitis, OM, and pneumonia.


HiB tx and prevention

tx: amoxicillin +/- clavulanate for mucosal infections
meningitis: ceftriaxone; rifampin prophylaxis for close contacts.
vaccine has type B capsular polysaccharide (polyribosylribitol phosphate) conjugated to diphtheria toxoid or other protein. given btw 2 or 18 months of age.


Neisseria: how do you distinguish btw the types, what do they have in common>

both ferment glucose and produce IgA proteases
meningitidis only ferments maltose. Meningitidis also has a polysaccharide capsule and a vaccine exists.


Waterhouse friederichsen syndrome

caused by neisseria meningitidis. causes vascular necrosis and hemorrhagein adrenal glands, leading to adrenal insufficiency, shock ,DIC


treatment of N. gonococci

ceftriaxone + azithromycin or doxycyline for chlamydia.
erythromycin ointment prevents neonatal transmission/neonatal conjunctiviits


treatment of meningococci

ceftriaxone or penicillin G


B. pertussis: carriers, toxin, disease, classification

only human carriers
3 stages:
1-2 wks: catarrhal. flu-like symptoms, very contagious
3 wks- 2 mo: paroxysmal stage
2-3 months: recovery stage
gram neg coccobacilli, Bordet-Gengou medium.
pertussis toxin: inactivates Gi proteins, which causes uninhibited adenylate cyclase, incr. cAMP. this impairs phagocytosis to enhance organism survival.


H. pylori: disease, classification, tx

may cause acute gastritis or chronic antral gastritis, pangastritis, or peptic ulcers. also associated with MALT lymphoma
this is a catalase, oxidase, urease positive organism.
Tx: PPI + amoxicillin/metronidazole + clarithromycin


campylobacter jejuni

oxidase positive comma shaped gram negative organism. grows in 42C. moves in a "corkscrew" fashion.
causes bloody or secretory diarrhea, esp. in kids. transmitted fecal-oral or unpasteurized milk. can be transmitted from a domestic animal to a human.
common antecedent to reactive arthritis or Guillan-Barre


yersinia enterocolitica

causes bloody diarrhea nad mesenteric adenitits that can mimic Crohn's disease or appendicitis. gram negative motile rod that does not fermident lactose.