Bacillus bacteria are found so commonly in the environment that sometimes finding them in medical specimens is considered routine and of no concern. However, certain types of these bacteria can cause serious, sometimes fatal, disease in newborns, especially those born prematurely.
A report on a new study concludes that contamination with this organism should not be routinely dismissed. Severe and lethal Bacillus cereus infections have been described in newborn infants, with higher frequency among premature infants. These infants are on ventilators and intubated to treat severe respiratory compromise.
The Missouri Department of Health and Senior Services investigated Bacillus cereus–positive tracheal aspirates from infants on ventilators in a neonatal intensive care unit. Multilocus sequence typing determined a genetic match between strains isolated from samples from a case-patient and from the air flow sensor in the ventilator.
The types of B. cereus infections in newborns included central nervous system, respiratory tract, primary bacteremia, and sepsis. Nosocomial outbreaks of B. cereus implicating hospital linens, manual ventilation balloons, contaminated diapers, and contaminated ventilator equipment have also been reported.
The Missouri Department of Health and Senior Services conducted this investigation in response to the hospital’s identification of an increased number of tracheal aspirates that were positive for B. cereus collected from newborns who were on ventilators during March–May, 2011. All tracheal aspirate culture results obtained in the Neonatal Intensive Care Unit (NICU) during January 2010–June 2011 were reviewed. NICU data was also searched for positive B. cereus culture from other specimens, such as blood, body fluids, or tissues. Investigators thoroughly evaluated respiratory management practices in the unit by direct observation, respiratory records review, and an interview with the respiratory therapist.
Investigation of the ventilation procedures in the NICU revealed that most equipment used for respiratory care was disposable, designated for single-patient use. The sensor closest to the baby’s mouth was an air flow sensor located inside the disposable ventilation circuit.
Investigators found that air flow sensors were routinely disinfected by placing them in a container with 70% alcohol solution for 60 minutes.
After discovery of the air flow sensor contaminated with B. cereus, the disinfection policy was changed. All air flow sensors were first soaked in Enzol enzymatic detergent solution and then sent for steam autoclave sterilization at 134°C (273.2°F). Changing the sterilization method for sensors to steam autoclaving stopped transmission. After implementation of new disinfection and sterilization procedures, no new cases of B. cereus tracheal colonization were identified in the nursery.
Bacillus species in tracheal aspirate cultures should not be routinely viewed as clinically insignificant; further testing to determine the exact strain should be considered under appropriate clinical and epidemiologic circumstances. Proper disinfection of the entire ventilator circuit as recommended by the equipment manufacturer is crucial in avoiding potentially lethal B. cereus infections.
See the CDC Report
See also Medical Law Perspectives, January 2012 Report: Hospital-Acquired Infections: Who Is Liable and Why?