Spread of a vancomycin-intermediate, methicillin-resistant Staphylococcus caprae in a neonatal intensive care unit

Abstract number: 1733_824

John M., Kenny D., Diagre D., Hussain Z.

Objectives: We report spread and control of a strain of a methicillin-resistant and vancomycin intermediate Staphylococcus caprae strain in a 38 bed neonatal intensive care unit (NICU), following isolation from a blood culture of one of a triplet.

Methods: Specimens from the nose and respiratory tract were collected from all neonates and cultured. Coagulase negative staphylococci (CoNS) were screened for vancomycin resistance using BHI plates with 6 mg/L vancomycin. Susceptibility to vancomycin was confirmed by E-test (AB Biodisk) according to the manufacturer's instructions. Susceptibility to other antimicrobials was determined using the VITEK system and the presence of the mecA gene was ascertained by an in-house PCR. CoNS that grew on screen plates were identified using long set sugars (Kloos method) and were typed using restriction enzyme digestion (Sma1) and Pulsed Field Gel Electrophoresis (PFGE). Infected and colonised neonates were cohorted in the same room and placed on contact precautions. Staff and families were instructed regarding good hand hygiene.

Results: CoNS from five babies grew on screen plates and were identified as most closely resembling Staphylococcus caprae. Three were blood isolates, one was from an endotracheal aspirate and one was a colonising organism. All displayed vancomycin intermediate resistance and carried the mecA gene. The isolates had an MIC of 8 mg/L of vancomycin by E-test. The profile of PFGE of all five isolates was identical. All five babies with this strain, including a sibling of the index case were linked epidemiologically and had been in the same room at the same time.

Conclusion: CoNS resistant to b-lactam antimicrobials have emerged as important causes of bloodstream infection in NICUs. Vancomycin is commonly chosen in the treatment of these infections. The outbreak in our NICU demonstrates the importance of screening isolates of CoNS for decreased vancomycin susceptibility, which automated methods and disc diffusion methods may fail to detect. Institution of strict hand disinfection and contact precautions was successful in preventing further spread of this organism within our NICU