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

Abstract

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]; P = .026), previous receipt of a carbapenem drug (OR, 1.83 [95% CI, 1.02–3.27]; P = .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]; P = .029). All CRKP isolates carried the blaKPC gene. Approximately 90% of the tested isolates carried the blaKPC-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.