Burkholderia cenocepacia bacteremia without respiratory colonization in an adult intensive care unit: epidemiological and molecular investigation of an outbreak

Abstract

Background: To investigate an outbreak of Burkholderia cenocepacia bacteremia. Observational study and chart review in a multidisciplinary adult Intensive Care Unit (ICU) at a tertiary care hospital.

Methods: Patients' demographic variables, comorbid conditions, ICU admission diagnosis, disease severity and outcome were analyzed. In case-patients, time and possible sources of bacteremia, molecular assays, antimicrobial susceptibility and response to therapy were also recorded.

Results: During a 9-month period, 30 episodes of B. cenocepacia bacteremia were diagnosed in 21 patients. Median time for a positive blood culture was 9 days after admission. None of the case-patients had respiratory colonization prior to onset of bacteremia. Pathogen was susceptible to meropenem, piperacillin/tazobactam, ciprofloxacin and trimethoprim /sulphamethoxazole. Surveillance involved environmental and patient/personnel cultures. All samples were negative for B. cenocepacia. However, extensive assessment revealed lapses in infection control procedures. PFGE molecular typing showed that all isolates were indistinguishable. Prior surgery and septic shock on ICU admission were significantly more frequent among case-patients. These patients needed significantly prolonged mechanical ventilation, central venous catheterization and ICU hospitalization. All patients responded to antimicrobial therapy and the attributed mortality was zero. Complete elimination of the outbreak was achieved only after strict enforcement of infection control policies and ICU disinfection.

Conclusion: The outbreak influenced ICU morbidity but it did not affect mortality. Although extensive environmental investigations failed to identify the source of infection, B.cenocepacia disappeared after implementation of control measures. Effective outbreak elimination cannot be limited to offending reservoir removal but needs to extend to efficient infection control practices.

Keywords: Burkholderia cenocepacia; bacteremia; infection control; molecural investigation; outbreak.

Figure 1. Pulsed-field gel electrophoresis (PFGE) of SpeI- digested genomic DNA of representative B.cenocepacia isolates recovered from patients. Lanes 1&15 lambda ladder size marker, lanes 2-12 isolates obtained from patients, lane 13 control A, lane 14 control B (control A & B are B.cenocepacia isolates from patients of Hospital A and Hospital B respectively).

Figure 2. Number of B.cenocepacia bacteremias by month.