Characteristics of bacteremia between community-acquired and nosocomial Klebsiella pneumoniae infection: risk factor for mortality and the impact of capsular serotypes as a herald for community-acquired infection.

BACKGROUND Although several epidemiological surveys of Klebsiella clinical isolates have been performed, few studies have correlated the clinical isolate with disease. OBJECTIVE To compare the clinical and bacteriological characteristics of Klebsiella pneumoniae bacteremia acquired as community or nosocomial infections. METHODS We prospectively enrolled 158 consecutively hospitalized patients with K pneumoniae bacteremia. Clinical data were reviewed. Antimicrobial susceptibility testing and capsular serotyping were performed. We used the chi(2) test, the Fisher exact test, or the t test for statistic analysis. RESULTS Underlying diabetes mellitus was more common in community-acquired than in nosocomial infection (46/94 [49%] vs. 8/64 [12%]; P<.001). On the other hand, neoplastic disease (34/64 [53%] vs. 13/94 [14%]; P<.001) and antibiotic resistance (P<.01) were more frequent in patients with nosocomial compared with community-acquired infections. Klebsiella pneumoniae liver abscesses, which were all community acquired, accounted for the source of 22 (23%) of 94 community-acquired K pneumoniae infections. No attributable source of infection was found for 37 (58%) of the 64 nosocomial infections vs. 15 (16%) of the 94 community-acquired infections. Only 58 isolates (36.7%) could be serotyped; of these, capsular serotypes K1, K2, and K28 accounted for 37 (23.4%), 8 (5.1%), and 6 (3.8%), respectively, of all strains. However, typeable isolates were significantly more common among community-acquired than nosocomial isolates (42/94 [45%] vs. 16/64 [25%]; P =.01), especially for serotype K1 (28/94 [30%] vs. 9/64 [14%]; P =.02). Significant risk factors for mortality included nosocomial infection, lung infection, thrombocytopenia, leukopenia, ceftazidime resistance, inappropriate antimicrobial therapy, and septic shock. CONCLUSIONS Significant differences were identified between community-acquired and nosocomial K pneumoniae bacteremia. Ceftazidime resistance in nosocomial K pneumoniae bacteremia carried a high risk for mortality, and serotype K1 in K pneumoniae was more prevalent in community-acquired infection, suggesting more virulence.