micro 6

Question 1

Legionella pneumophila 🤷🏻‍♀️🤷🏻‍♀️🤷🏻‍♀️

Answer 1

Gram ⊝ rod. Gram stains poorly—use silver stain. Grow on charcoal yeast extract medium with iron and cysteine. Detected by presence of antigen in urine. Labs may show hyponatremia.

Aerosol transmission from environmental water source habitat (eg, air conditioning systems, hot water tanks). No person-to-person transmission.

Question 2

Legionella pneumophila (diseases and 💊💊)

Answer 2

Treatment: macrolide or quinolone. Legionnaires’ disease—severe pneumonia (often unilateral and lobar A ), fever, GI and CNS symptoms. Common in smokers and in chronic lung disease.

Pontiac fever—mild flu-like syndrome.

Question 3

Pseudomonas aeruginosa

Answer 3

Aeruginosa—aerobic; motile, gram ⊝ rod. Non-lactose fermenting. Oxidase ⊕ . Frequently found in water. Has a grape-like odor. 🦋PSEUDOMONAS is associated with: Pneumonia, Sepsis, Ecthyma gangrenosum, UTIs, Diabetes, Osteomyelitis, Mucoid polysaccharide capsule, Otitis externa (swimmer’s ear), Nosocomial infections (eg, catheters, equipment), Addicts (drug abusers), Skin infections (eg, hot tub folliculitis, wound infection in burn victims).

🦋Mucoid polysaccharide capsule may contribute to chronic pneumonia in cystic fibrosis patients due to biofilm formation.

🦋Produces PEEP: Phospholipase C (degrades cell membranes); Endotoxin (fever, shock); Exotoxin A (inactivates EF-2); Pigments: pyoverdine and pyocyanin (blue-green pigment A ; also generates reactive oxygen species).
Corneal ulcers/keratitis in contact lens wearers/ minor eye trauma.

Ecthyma gangrenosum—rapidly progressive, necrotic cutaneous lesion B caused by Pseudomonas bacteremia. Typically seen in immunocompromised patients.

Question 4

Pseudomonas aeruginosa💊💊

Answer 4

Treatments include “CAMPFIRE” drugs:

ƒ Carbapenems ƒ Aminoglycosides ƒ Monobactams ƒ Polymyxins (eg, polymyxin B, colistin) ƒ Fluoroquinolones (eg, ciprofloxacin,

levofloxacin) ƒ ThIRd- and fourth-generation

cephalosporins (eg, ceftazidime, cefepime) ƒ Extended-spectrum penicillins (eg,

piperacillin, ticarcillin)

Question 5

167

مهم كلش

Answer 5

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Question 6

Yersinia enterocolitica

Answer 6

Gram ⊝ rod. Usually transmitted from pet feces (eg, puppies), contaminated milk, or pork. Causes acute diarrhea or pseudoappendicitis (right lower abdominal pain due to mesenteric adenitis and/ or terminal ileitis).

Question 7

Lactose-fermenting enteric bacteria

Answer 7

Fermentation of lactose Ž pink colonies

on MacConkey agar. Examples include Citrobacter, Klebsiella, E coli, Enterobacter, and Serratia (weak fermenter). E coli produces β-galactosidase, which breaks down lactose into glucose and galactose.

Lactose is key.

Test with MacConKEE’S agar.

EMB agar—lactose fermenters grow as purple/ black colonies. E coli grows colonies with a green sheen.

Question 8

Escherichia coli🤷🏻‍♀️

Answer 8

Gram ⊝ rod. E coli virulence factors: fimbriae—cystitis and pyelonephritis (P-pili); K capsule—pneumonia, neonatal meningitis; LPS endotoxin—septic shock.

Question 9

Enteroinvasive E coli

Answer 9

Microbe invades intestinal mucosa and causes necrosis and inflammation.

Presentation//EIEC is Invasive; dysentery. Clinical manifestations similar to Shigella.

Question 10

Enterotoxigenic E coli

Answer 10

Produces heat-labile and heat-stable enteroToxins. No inflammation or invasion.
Presentation//ETEC; Traveler’s diarrhea (watery).

Question 11

Enteropathogenic E coli

Answer 11

No toxin produced. Adheres to apical surface, flattens villi, prevents absorption.
Presentation//Diarrhea, usually in children (think EPEC and Pediatrics).

Question 12

Enterohemorrhagic E coli

Answer 12

O157:H7 is most common serotype in US. Often transmitted via undercooked meat, raw leafy vegetables.

Shiga-like toxin causes hemolytic-uremic syndrome: triad of anemia, thrombocytopenia, and acute renal failure due to microthrombi forming on damaged endothelium Ž mechanical hemolysis (with schistocytes on peripheral blood smear), platelet consumption, and  renal blood flow.
Presentation//Dysentery (toxin alone causes necrosis and inflammation).

Does not ferment sorbitol (vs other E coli). Hemorrhagic, Hamburgers, Hemolytic-uremic syndrome.

Question 13

Klebsiella🤷🏻‍♀️🤷🏻‍♀️

Answer 13

Gram ⊝ rod; intestinal flora that causes lobar pneumonia in alcoholics and diabetics when aspirated. Very mucoid colonies A caused by abundant polysaccharide capsules. Dark red “currant jelly” sputum (blood/mucus).

Also cause of nosocomial UTIs. Associated with evolution of multidrug resistance (MDR).

Question 14

Klebsiella five

Answer 14

5 A’s of KlebsiellA:

Aspiration pneumonia 
Abscess in lungs and liver 
Alcoholics 
DiAbetics 
“CurrAnt jelly” sputum