Dissemination of Bacillus cereus in a paediatric intensive care unit traced to insufficient disinfection of reusable ventilator air-flow sensors

Abstract

Over a two-week period in November 2006, vancomycin-resistant Bacillus cereus was isolated from respiratory samples from six ventilated paediatric intensive care unit (PICU) patients. To investigate the possibility of a common source and extent of the dissemination, all procedures related to mechanical ventilation were monitored and surveillance cultures performed. B. cereus was isolated from reusable air-flow sensors, before and after on-site disinfection with 70% alcohol. The organism was also isolated from respiratory samples from three other ventilated patients and from two ventilation grids in the ceiling of PICU, as well as from the alcohol solution itself. Using amplified fragment length polymorphism (AFLP) typing, B. cereus strains from the six PICU patients together with isolates recovered from the air-flow sensors and the alcohol solution were shown to be closely related. Isolates from the ventilation grids demonstrated different AFLP patterns to the outbreak strain. Intervening measures, including disinfection by autoclaving all reusable air-flow-guiding parts and the use of disposable non-autoclavable parts, resulted in rapid termination of the outbreak. B. cereus infections can cause significant morbidity, particularly in intensive care patients. Disinfection of all air-flow-guiding reusable parts for mechanical ventilation should be addressed with great care and should include effective autoclaving in order to eradicate spores.