Spread of Clones of Multidrug-Resistant, Coagulase-Negative Staphylococci Within a University Hospital

Abstract

Objective: : To detect putative clonal dissemination of multidrug-resistant, coagulase-negative staphylococci (CNS) in a university hospital in northern Sweden.Methods: : All consecutive routine clinical samples from our hospital were screened during two periods (November and December 2001 and September and October 2002) for the presence of multidrug-resistant (defined as resistant to oxacillin, clindamycin, co-trimoxazole, gentamicin, and fusidic acid, but susceptible to vancomycin) isolates of CNS. Genetic similarity between isolates was analyzed using pulsed-field gel electrophoresis (PFGE) and a computer program.Results: : Seventy multidrug-resistant isolates from 62 patients were identified, 28 during the 2001 period and 42 during the 2002 period. All isolates except one, which wasStaphylococcus haemolyticus, were identified asS. epidermidis. Multidrug-resistant CNS were isolated in samples obtained from 24 different wards. Two subgroups (group A and group B) ofS. epidermidisthat differed by approximately 40% in PFGE band similarity were identified. Group A consisted of 44 isolates with a PFGE band similarity of greater than 70% that included 6 subgroups consisting of 3 to 16 isolates that expressed a 100% similarity. These isolates were identified during both sampling periods in cultures performed in 18 different wards. A clonal origin could not be excluded for some of the remaining 26 isolates belonging to group B, but none had identical PFGE patterns, suggesting a more diverse origin.Conclusion: : The results of this study suggest clonal spread of multidrug-resistant CNS within our hospital and that some clones are endemic in the hospital environment.