Investigation of nosocomial Staphylococcus aureus sepsis in a neonatal intensive care unit: Absence of clonal spread

Abstract

BACKGROUND: In September 2004, five patients were identified with nosocomial Staphylococcus aureus (SA) sepsis in our 40-bed level III neonatal intensive care unit (NICU), compared to one in the prior 3 years. The initial patient expired before we had a positive blood culture. It has been estimated that each case of nosocomial sepsis imposes an additional cost of $25,000. OBJECTIVES: Identify, prevent and control nosocomial transmission of SA. METHODS: Within 1 week, three patients were septic with SA. Two weeks later, two additional patients had SA sepsis. Control measures included cohorting and re-emphasis of hand hygiene and barrier techniques. A questionnaire describing skin infections was distributed to nursing, physicians, respiratory, phlebotomy, and radiology staff, and to volunteer cuddlers and rehabilitation therapy personnel. Of 194 questionnaires returned, four personnel who described skin infections were cultured. At the request of the department of health, point prevalence cultures of the nares of all other neonates were collected. Of 25 screened, 4 (16%) were SA positive and were moved to the cohort. RESULTS: The outbreak of SA sepsis was limited to five patients; one was secondary to pneumonia, one secondary to omphalitis, and the remaining three were catheter-related bloodstream infections. These five neonates had been transferred from two unrelated facilities. Among the 25 neonates screened, four were colonized with SA. Four neonatal nurses with a history of skin infections were cultured and one grew SA. The five cases, four colonized infants and the single nurse isolate, were shown to be unrelated as analyzed by pulsed-field gel electrophoresis (PFGE). The outbreak was controlled by enhanced infection control measures before the root cause analysis process was completed 5 weeks after the index case. Four patients did well and were discharged home. CONCLUSIONS: This outbreak did not reflect clonal spread or the effects of point source transmission. In the screening and cultures collected, healthcare workers were not linked to transmission of cases. Prompt recognition and heightened awareness of the risks of spread within the NICU led to prevention of continued cases. SA colonization is not unusual and maybe increasing in frequency. The implementation of enhanced infection control measures can be effective.