Acinetobacter Infections Associated with the War in Iraq — Unusual Cases
Abstract & Commentary
By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor, Stanford University School of Medicine, is Associate Editor for Infectious Disease Alert.
Dr. Winslow serves as a consultant for Siemens Diagnostics, and is on the speaker's bureau for Boehringer-Ingelheim and GSK.
Synopsis: Eight cases of skin and soft-tissue infections (SSTI) due to A. baumannii were identified in patients treated on a US Navy hospital ship during early 2003. A large proportion was associated with gunshot wounds or external fixators. These infections presented as cellulitis with overlying vesicles, and when untreated, progressed to necrotizing infection with bullae. All isolates were multidrug-resistant but remained susceptible to carbapenems. In a separate report, a 55-year-old health care worker (HCW) with diabetes developed a severe pneumonia. Molecular analysis revealed the source patient to have been a wounded US serviceman with a ventilator-associated pneumonia on whom the HCW had performed tracheal suction.
Sources: Sebeny PJ, et al. Acinetobacter baumannii skin and soft-tissue infection associated with war trauma. Clin Infect Dis 2008;47:444-449; Whitman TJ, et al. Occupational transmission of Acinetobacter baumannii from a United States serviceman wounded in Iraq to a health care worker. Clin Infect Dis. 2008;47:439-443.
A retrospective review of 211 inpatients admitted to the US Navy hospital ship USNS Comfort in early 2003 revealed 57 patients with A. baumannii infection. Of those, eight cases of A. baumannii skin/skin structure infections (SSTIs) were identified; seven occurred in Iraqi nationals and one was in an American serviceman. All patients had been evacuated from field hospitals in Iraq, where they had undergone initial resuscitation and emergent stabilizing surgical procedures. All but one of the patients received perioperative antibiotics (first or second generation cephalosporins) before admission to the USNS Comfort.
All eight patients had a similar clinical presentation as cellulitis, with a well-demarcated, erythematous and "peau d'orange" edematous rash. In seven cases, the cellulitis appeared to arise from the adjacent wound. Cellulitis progressed to a sandpaper-like appearance containing multiple tiny vesicles. Two patients subsequently became bacteremic and developed hemorrhagic bullae, suggesting necrotizing infection.
All of the A. baumannii isolates were multidrug-resistant but retained susceptibility to imipenem. Co-pathogens were identified in five of eight patients, and included most commonly Enterobacter cloacae and Proteus species.
All eight patients required 1-6 wound debridements each; seven patients survived and one patient died of sepsis after receiving just two doses of imipenem.
The second paper describes the case of a health care worker (HCW) at National Naval Medical Center (NNMC) in Washington, DC, with poorly controlled diabetes (on metformin), who developed a severe Acinetobacter pneumonia complicated by hypotension requiring vasopressors, respiratory failure, and a large empyema requiring decortication. The patient had cared for (specifically performed endotracheal suctioning while wearing gown and gloves but no mask) a US Navy sailor who had sustained polytraumatic injuries in an explosion of an improvised explosive device (IED) in Iraq. The source patient was intubated and initially resuscitated at the Air Force Theater Hospital in Balad, then transferred to Landstuhl Regional Medical Center (LRMC) in Germany before arriving at NNMC. The source patient was shown to be colonized with A. baumannii, which was isolated from his sputum, abdominal wound, axilla, and nares. Pulse field gel electrophoresis (PFGE) demonstrated molecular identity between the isolates of A. baumannii cultured from the HCW and the source patient. The isolates were highly antibiotic-resistant and demonstrated in vitro susceptibility to only carbapenems, amikacin, and colistin.
Commentary
These papers highlight the importance of A. baumannii as a pathogen in patients wounded in the ongoing wars in Afghanistan and Iraq, the source of which appears to be the field hospital environment.1 The clinical observation of multidrug-resistant A. baumannii as a cause of SSTI in trauma patients is important. This pathogen should be suspected in patients with hospital-acquired SSTI who present with edematous cellulitis with overlying vesicles. Empiric coverage with a carbapenem and surgical debridement should be promptly instituted.
While the HCW who developed a complicated pneumonia due to A. baumannii may have had some degree of systemic immunocompromise due to her diabetes, the development of pneumonia in this individual and SSTI in the other patients suggest that certain strains of A. baumannii contain virulence factors worthy of further characterization.
References
- Scott P, et al. An outbreak of multidrug-resistant Acinetobacter baumannii-calcoaceticus complex infection in the US military health care system associated with military operations in Iraq. Clin Infect Dis. 2007; 44:1577-1584.
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