Outbreak of carbapenem-resistant Klebsiella pneumoniae in Puerto Rico associated with a novel carbapenemase variant

Abstract

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is resistant to almost all antimicrobial agents, and CRKP infections are associated with substantial morbidity and mortality.

Objective: To describe an outbreak of CRKP in Puerto Rico, determine risk factors for CRKP acquisition, and detail the successful measures taken to control the outbreak.

Design: Two case-control studies.

Setting: A 328-bed tertiary care teaching hospital.

Patients: Twenty-six CRKP case patients identified during the outbreak period of February through September 2008, 26 randomly selected uninfected control patients, and 26 randomly selected control patients with carbapenem-susceptible K. pneumoniae (CSKP) hospitalized during the same period.

Methods: We performed active case finding, including retrospective review of the hospital's microbiology database and prospective perirectal surveillance culture sampling in high-risk units. Case patients were compared with each control group while controlling for time at risk. We sequenced the bla(KPC) gene with polymerase chain reaction for 7 outbreak isolates and subtyped these isolates with pulsed-field gel electrophoresis.

Results: In matched, multivariable analysis, the presence of wounds (hazard ratio, 19.0 [95% confidence interval {CI}, 2.5-142.0]) was associated with CRKP compared with no K. pneumoniae. Transfer between units (adjusted odds ratio [OR], 7.5 [95% CI, 1.8-31.1]), surgery (adjusted OR, 4.0 [95% CI, 1.0-15.7]), and wounds (adjusted OR, 4.9 [95% CI, 1.1-21.8]) were independent risk factors for CRKP compared to CSKP. A novel K. pneumoniae carbapenemase variant (KPC-8) was present in 5 isolates. Implementation of active surveillance for CRKP colonization and cohorting of CRKP patients rapidly controlled the outbreak.

Conclusions: Enhanced surveillance for CRKP colonization and intensified infection control measures that include limiting the physical distribution of patients can reduce CRKP transmission during an outbreak.