Investigation of Suspected Nosocomial Clusters of Staphylococcus haemolyticus Infections

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Abstract
Objective: To determine whether typing methods can discriminate amongStaphylococcus haemolyticusisolates.Design: Molecular epidemiological evaluation of Shaemolyticusisolates obtained from patients hospitalized on a hematology service and in a surgical intensive-care unit (SICU).Setting: A large Midwestern teaching hospital.Interventions: None.Results: Over 22 days,S haemolyticuswas isolated from five patients on the hematology service. Isolates from four patients had the same unusual antibiogram and biotype. Ribotyping, restriction endonuclease digestion of plasmid DNA (REAP), and whole chromosomal DNA analysis by pulsed-field gel electrophoresis (PFGE) confirmed that these isolates were identical and different from the fifth patient's isolate and from 6 control isolates. In a second cluster, 11S haemolyticusisolates obtained from eight patients in the SICU had similar antibiograms and biotypes. By REAP and ribotype analysis, isolates from four patients were identical. However, PFGE indicated that only two of these patients shared a common strain.Conclusions: Antibiograms or biotyping may discriminate among isolates ofS haemolyticusif the results of these tests are unusual. Many clinical isolates can be differentiated by REAP analysis, ribotyping, or PFGE. However, some isolates are identical by all of these methods, suggesting that they may have been transmitted nosocomially.