Carbapenem-resistant Acinetobacter baumannii and Klebsiella pneumoniae across a hospital system: impact of post-acute care facilities on dissemination.

Background: Resistance to carbapenems among Acinetobacter baumannii and Klebsiella pneumoniae presents a serious therapeutic and infection control challenge. We describe the epidemiology and genetic basis of carbapenem resistance in A. baumannii and K. pneumoniae in a six-hospital healthcare system in Northeast Ohio.

Methods: Clinical isolates of A. baumannii and K. pneumoniae distributed across the healthcare system were collected from April 2007 to April 2008. Antimicrobial susceptibility testing was performed followed by molecular analysis of carbapenemase genes. Genetic relatedness of isolates was established with repetitive sequence-based PCR (rep-PCR), multilocus PCR followed by electrospray ionization mass spectrometry (PCR/ESI-MS) and PFGE. Clinical characteristics and outcomes of patients were reviewed.

Results: Among 39 isolates of A. baumannii, two predominant genotypes related to European clone II were found. Eighteen isolates contained bla(OXA-23), and four isolates possessed bla(OXA-24/40). Among 29 K. pneumoniae isolates with decreased susceptibility to carbapenems, two distinct genotypes containing bla(KPC-2) or bla(KPC-3) were found. Patients with carbapenem-resistant A. baumannii and K. pneumoniae were elderly, possessed multiple co-morbidities, were frequently admitted from and discharged to post-acute care facilities, and experienced prolonged hospital stays (up to 25 days) with a high mortality rate (up to 35%).

Conclusion: In this outbreak of carbapenem-resistant A. baumannii and K. pneumoniae across a healthcare system, we illustrate the important role post-acute care facilities play in the dissemination of multidrug-resistant phenotypes.