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 _blaKPC 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 _blaKPC 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.