Prevalence and clinical relevance of Staphylococcus warneri in the neonatal intensive care unit

OBJECTIVE. To describe the prevalence of Staphylococcus warneri on the hands of nurses and the clinical relevance of this organism among neonates in the neonatal intensive care unit ( NICU). DESIGN. Prospective cohort study that examined the microbial flora on the hands of nurses and clinical isolates recovered from neonates during a 23- month period ( March 1, 2001, through January 31, 2003). SETTING. Two high- risk NICUs in New York City. PARTICIPANTS. All neonates hospitalized in the NICUs for more than 24 hours and all full- time nurses from the same NICUs who volunteered to participate. INTERVENTION. At baseline and then every 3 months, samples for culture were obtained from each nurse's cleaned dominant hand. Pulsed- field electrophoresis compared S. warneri isolates from neonates and staff. RESULTS. Samples for culture (n=834) were obtained from the hands of 119 nurses; 520 ( 44%) of the 1,195 isolates of coagulase-834 negative staphylococci recovered were identified as S. warneri. Of the 647 clinically relevant isolates recovered from neonates, 17 ( 8%) of the 202 isolates that were identified to species level were S. warneri. Pulsed- field electrophoresis revealed a common strain of S. warneri that was shared among the nurses and neonates. Furthermore, 117 ( 23%) of 520 S. warneri isolates from nurses' hands had minimum inhibitory concentrations for vancomycin of 4 mu g/mL, which indicate decreasing susceptibility. CONCLUSIONS. Our findings that S. warneri can be pathogenic in neonates, is a predominant species of coagulase- negative staphylococci cultured from the hands of nurses, and has decreased vancomycin susceptibility underscore the importance of continued surveillance for vancomycin resistance and pathogenicity in pediatric care settings.