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

Abstract

To detect putative clonal dissemination of multidrug-resistant, coagulase-negative staphylococci (CNS) in a university hospital in northern Sweden. 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. 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 was Staphylococcus haemolyticus, were identified as S. epidermidis. Multidrug-resistant CNS were isolated in samples obtained from 24 different wards. Two subgroups (group A and group B) of S. epidermidis that 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. 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.