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Microbiology

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Gram Negative Bacilli

Question
10 out of 81
 

A specimen of thick, bloody sputum from a hospitalized 80-year-old patient with diabetes mellitus and difficulty in breathing is sent for laboratory analyses. The tests yield heavy growth of a lactose-positive, nonmotile, gram-negative rod with a large capsule. Which of the following bacteria is most likely to be the cause of the pulmonary problems?



A Enterobacter aerogenes

B Escherichia coli

C Klebsiella pneumoniae

D Pseudomonas aeruginosa

Ans. C Klebsiella pneumoniae

a. Patients with K. pneumoniae infections usually have predisposing conditions such as alcoholism, advanced age, chronic respiratory disease, and diabetes. The "currant-jelly" sputum distinguishes K. pneumoniae from the other organisms. Infections can lead to necrosis and abscess formation.

b. Whereas all of the above listed organisms are gram-negative rods, only Klebsiella pneumoniae fulfill all of the laboratory criteria listed in the question, such as the presence of a very large capsule, which gives a striking mucoid appearance to its colonies, lactose fermenting, non-motile gram negative bacillus.

EXTRA EDGE OF Diarrheagenic E. Coli

ETEC - Heat stable toxin - c-GMP

- Heat labile toxin - c-AMP } Causes traveler’s diarrhea

[It produces cholera like toxin (cholera infantum), Biken test+]

EPEC - Attaches to enterocytes (enteroadherent) &destroy brush border villi.

Inflammation causes infantile diarrhea (remember EPEC affects pediatric population

EIEC - Only E – coli which invades G.I. mucosa (Enteroinvasive) & produces dysentery

likely disease ( DISEASE resembles shigella )

EHEC /VTEC - Produces verotoxin (shiga like toxin) which acts on vascular endothelium &

causes hemorrhagic colitis + HUS (strain H : 157 )

- Does not ferment sorbitol (sorbitol -)

Gram Negative Bacilli Flashcard List

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