An episodic outbreak of genetically related Burkholderia cepacia among non-cystic fibrosis patients at a university hospital

OBJECTIVE: To investigate an outbreak of Burkholderia cepacia. DESIGN: Observational study and chart review. PATIENTS: Adult non-cystic fibrosis (CF) patients. SETTING: Intensive care units (ICUs) at a university-affiliated teaching ho spital. METHODS: As part of the epidemiological investigation, we conducted a chart review and collected environmental samples. A review of work schedules of healthcare workers also was performed. We used B cepacia selective agar for preliminary screening for all isolates, which subsequently were confirmed as members of the B cepacia complex by polyphasic analysis employing conven tional biochemical reactions and genus- and species-specific polymerase cha in reaction assays. Pulsed-field gel electrophoresis, randomly amplified po lymorphic DNA typing, and automated ribotyping were used to genotype the is olates. As part of the intervention, contact isolation precautions were ini tiated for all patients identified as having had a culture positive for B c epacia. RESULTS: Between September 1997 and September 1999, B cepacia was isolated from 31 adult patients without CF in ICUs at a university-affiliated teachi ng hospital. Based on geographic clustering and genotypic analysis, three d istinct clusters were observed involving 20 patients. Isolates from 17 of t hese patients were available for testing and were found to be of the same s train (outbreak strain). Further taxonomic analysis indicated that the outb reak strain was B cepacia complex genomovar III. Twelve (71%) of the 17 pat ients were judged to be infected, and 5 (29%) were colonized with this stra in. Six of 200 environmental cultures from multiple sources in the hospital 's ICUs yielded B cepacia. Two of these isolates, both recovered from rooms of colonized patients, were the same genotype as the outbreak strain recov ered from patients. CONCLUSION: Despite an extensive investigation, the source of the B cepacia clone involved in this outbreak remains unknown. The spatial and temporal pattern of cases suggests that cross-transmission of a genetically related strain contributed to clustering among patients. The initiation of contact isolation may have limited the extent of this transmission. Additional stud ies are needed to elucidate better the epidemiology of nosocomial B cepacia infection among non-CF adult patients (Infect Control Hosp Epidemiol 2001; 22:419-422).