Multi-drug resistant Acinetobacter infections in critically injured Canadian forces soldiers

Abstract

Background: Military members, injured in Afghanistan or Iraq, have returned home with multi-drug resistant Acinetobacter baumannii infections. The source of these infections is unknown.

Methods: Retrospective study of all Canadian soldiers who were injured in Afghanistan and who required mechanical ventilation from January 1 2006 to September 1 2006. Patients who developed A. baumannii ventilator associated pneumonia (VAP) were identified. All A. baumannii isolates were retrieved for study patients and compared with A. baumannii isolates from environmental sources from the Kandahar military hospital using pulsed-field gel electrophoresis (PFGE).

Results: During the study period, six Canadian Forces (CF) soldiers were injured in Afghanistan, required mechanical ventilation and were repatriated to Canadian hospitals. Four of these patients developed A. baumannii VAP. A. baumannii was also isolated from one environmental source in Kandahar - a ventilator air intake filter. Patient isolates were genetically indistinguishable from each other and from the isolates cultured from the ventilator filter. These isolates were resistant to numerous classes of antimicrobials including the carbapenems.

Conclusion: These results suggest that the source of A. baumannii infection for these four patients was an environmental source in the military field hospital in Kandahar. A causal linkage, however, was not established with the ventilator. This study suggests that infection control efforts and further research should be focused on the military field hospital environment to prevent further multi-drug resistant A. baumannii infections in injured soldiers.

Figure 1

DNA fingerprint profiles of Acinetobacter baumannii after ApaI-digested pulsed-field gel electrophoresis. Lanes 1 and 12: Lambda DNA ladder (New England Biolabs, Mississauga, ON) Lanes 2 and 11: Unrelated A. baumannii strains Lane 3: Patient 1 (bronchoalveolar lavage (BAL) from LRMC) Lane 4: Patient 1 (Tracheal aspirate, Canada) Lane 5: Patient 2 (Tracheal aspirate, LRMC) Lane 6: Patient 2 (Tracheal aspirate, Canada) Lane 7: Patient 3 (Tracheal aspirate, LRMC) Lane 8: Patient 3 (BAL, Canada) Lane 9: Patient 4 (BAL, Canada) Lane 10: A. baumannii isolate from air intake filter, Kandahar.