Carbapenem Resistance Among Klebsiella pneumoniae Isolates: Risk Factors, Molecular Characteristics, and Susceptibility Patterns

BACKGROUND. Carbapenem resistance among isolates of Klebsiella pneumoniae has been unusual. OBJECTIVES. To identify risk factors for infection with carbapenem-resistant K. pneumoniae (CRKP) and to characterize microbiological aspects of isolates associated with these infections. DESIGN. Retrospective case-control study. SETTING. A 900-bed tertiary care hospital. RESULTS. From January 2006 through April 2007, K. pneumoniae was isolated from 461 inpatients; 88 had CRKP infection (case patients), whereas 373 had carbapenem-susceptible K. pneumoniae infection (control subjects). The independent risk factors for infection with CRKP were prior fluoroquinolone use (odds ratio [OR], 1.87 [95% confidence interval {CI}, 1.07-3.26]; Pp. 026), previous receipt of a carbapenem drug (OR, 1.83 [95% CI, 1.02-3.27]; Pp. 042), admission to the intensive care unit (OR, 4.27 [95% CI, 2.49-7.31]; P <.001), and exposure to at least 1 antibiotic drug before isolation of K. pneumoniae (OR, 3.93 [95% CI, 1.15-13.47]; Pp. 029). All CRKP isolates carried the bla(KPC) gene. Approximately 90% of the tested isolates carried the bla(KPC)-2 allele, suggesting patient-to-patient transmission. Almost all CRKP isolates were resistant to all antibiotics, except to colistin (resistance rate, 4.5%), gentamicin (resistance rate, 7%), and tigecycline (resistance rate, 15%). CONCLUSIONS. CRKP should be regarded as an emerging clinical threat. Because these isolates are resistant to virtually all commonly used antibiotics, control of their spread is crucial.