Molecular epidemiology of staphylococcal scalded skin syndrome in premature infants

Abstract

Outbreaks of nosocomial staphylococcal scalded skin syndrome (SSSS) in infants have been well-described associated with the well baby nursery or delivery room. We describe two cases of SSSS in very low birth weight infants in a neonatal intensive care unit (NICU) and the success of infection control strategies used to prevent an outbreak. Staphylococcal scalded skin syndrome was diagnosed in two infants in the NICU: Case I (a 47-day-old, formerly 530-g female); and Case II diagnosed 48 h later (a 41-day old, formerly 706-g female). Multiple infection control measures were implemented: (1) isolation and intravenous antibiotic treatment of cases; (2) placement of exposed infants into a cohort; (3) prophylactic mupirocin treatment of the anterior nares of all infants in the NICU and staff colonized with Staphylococcus aureus; and (4) personnel hand washing with hexachlorophene. Detection of exfoliative toxin A and studies to determine the genetic relatedness of S. aureus strains isolated from patients and staff were performed. In addition to the two SSSS cases, S. aureus was isolated from 2 of 12 (17%) exposed asymptomatic infants, 2 of 20 (10%) ancillary staff, 8 of 30 (27%) nurses and 6 of 24 (25%) physicians. Exfoliative toxin A-producing strains were isolated from both cases and one asymptomatic infant. No toxin was expressed by strains isolated from staff. Pulse field gel electrophoresis demonstrated genetically identical strains of S. aureus from the two SSSS cases and the asymptomatic infant, whereas three staff members harbored strains genetically related to the case strain. Unexpectedly two additional unique clusters of genetically related S. aureus strains were identified from the surveillance cultures. This report documents the rare occurrence of nosocomial SSSS attributed to transmission in the NICU among extremely low birth weight infants. Multiple infection control strategies were effective in limiting the out-break. Molecular epidemiology investigation supported a unique S. aureus strain responsible for this event and the presence of bidirectional spread between staff and patients of non-toxin-producing strains.