Klebsiella Species

A 68-year-old man with diabetes mellitus type 2 presents to the emergency department with fever (39.2°C), dysuria, and flank pain for 3 days. He has a history of recurrent urinary tract infections. Urinalysis shows pyuria, bacteriuria, and nitrites. Urine culture on MacConkey agar grows large, mucoid, pink colonies. Gram stain of the isolate shows gram-negative rods. The organism is oxidase-negative, indole-negative, and ferments lactose. What is the most likely causative organism?

Klebsiella pneumoniae is differentiated from Escherichia coli primarily by which biochemical characteristic?

A 55-year-old man admitted to the ICU with sepsis secondary to aspiration pneumonia develops a secondary infection. Sputum culture grows a gram-negative rod that is mucoid, non-motile, and produces a positive string test (capsule test). The organism ferments glucose, lactose, and sucrose but is negative for urease and indole. It is resistant to ampicillin but susceptible to ceftriaxone. Which organism is most likely responsible for this nosocomial respiratory infection?

Which capsular polysaccharide antigen is most commonly associated with virulence and mucoid phenotype in Klebsiella pneumoniae?