INVESTIGATION AND CONTROL OF A MULTI-YEAR MULTI-INTENSIVE CARE UNIT (ICU) OUTBREAK OF ACINETOBACTER BAUMANNII (ACB).

R.Kaul*, L. Cork, J.Burt, H.Didier, M. Kraiden, J.M. Conly,

Department of Microbiology, The Toronto Hospital, University of Toronto, Ontario.

ACB is increasingly recognized as a nosocomial pathogen, but its contribution to morbidity and
mortality is controversial. Between 1990-1993 rates of respiratory ACB isolation from 5 ICUs increased from 1.6 to 13.4/month, representing over a 700% increase. An investigation was initiated to identify risk factors and a potential environmental source for ACB acquisition.

Multiple environmental cultures were obtained from the respiratory therapy (RT) department,
clean respiratory equipment and the Supply Processing and Distribution (SPD) department. Handwashing cultures were taken from 35 ICU was performed. Pulsed-field gel electrophoresis (PFGE) was used to characterize isolates of ACB found during the investigation.

ACB was isolated from multiple environmental sites including "clean" temperature probes,
water traps and ventilator filters. Counts of > 104 CFU/ml were found on temperature probes in use. Seventeen percent of staff carried ACB on their hands. Based on molecular subtyping with PFGE, a single epidemic strain accounted for 88% of environmental and 93.5% of patients isolates. In patients matched on admission for severity of illness, the attributable mortality for ACB acquisition was 50%. Control measures included sterilization of temperature probes, cohorting of patients, changes in RT practices and strict adherence by all staff to good handwashing. Within 2 months, respiratory ACB isolation rates fell to 1.7/month.

We conclude that multiple factors including inadequate disinfection of temperature probes and
respiratory equipment resulted in an ICU outbreak of respiratory ACB colonization and infection, with significant morbidity and mortality.

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