Cluster of bloodstream infections caused by KPC-2 carbapenemase-producing Klebsiella pneumoniae in Manhattan

Background Carbapenems are considered the agents of choice for treatment of serious infections caused by resistant gram-negative organisms. A new group of class A β-lactamases, known as KPC-type carbapenemases, has recently been described and poses a serious clinical challenge. Methods Seven patients with bloodstream infections caused by Klebsiella pneumoniae isolates with decreased susceptibility to carbapenems were identified between January and April 2005 in the intensive care units of a hospital in Manhattan. Isolate identification and susceptibility testing were performed according to National Committee for Clinical Laboratory Standards methodology. All isolates were ribotyped and screened for bla KPC by polymerase chain reaction. The polymerase chain reaction product underwent nucleotide sequencing for one of the isolates. Medical records were reviewed retrospectively. Results Six isolates were carbapenem-resistant with minimum inhibitory concentrations for imipenem of >8 μg/mL. Ribotyping showed that all isolates belonged to a single clone. All isolates possessed bla KPC and nucleotide sequencing identified the allelic type KPC-2. Patients' median age was 68 years. The median duration of hospitalization was 25.5 days before the first positive blood culture. Five of 6 patients received previous broad-spectrum β-lactam antibiotics but none received prior carbapenems. Five of 6 isolates were susceptible to polymyxin B. Three of the 5 patients were treated with polymyxin B and 1 survived. Overall, only 2 of the 6 patients survived. Conclusion This report describes the first outbreak of KPC-2 carbapenemase-producing K pneumoniae bloodstream infections in a hospital in Manhattan.