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

Abstract

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-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.

Figure 1

Pulsed-field gel electrophoresis patterns of Staphylococcus warneri isolates. Asterisk indicates unrelated isolates. Lanes 1-4, isolates from study neonates; lanes 5 and 6, isolates from nurses in neonatal intensive care unit 2; lanes 7 and 8, isolates from nurses in neonatal intensive care unit 1; lanes 9-11, isolates from adult patients; and lanes 12-14, isolates from adults from the community.