Differential characteristics of Acinetobacter baumannii colonization and infection: risk factors, clinical picture, and mortality

OBJECTIVES: The objectives of this study were to detect those characteristics that were specifically associated with infection or colonization by Acinetobacter baumannii, describe the clinical manifestations of those patients in whom the infection was detected in intensive care unit (ICU) or non-ICU wards, and analyze the prognosis-associated factors in patients from whom A. baumannii was isolated. PATIENTS AND METHODS: A sample of 122 patients from whom A. baumannii was recovered during an endemic period in a teaching hospital was included. Only those cases in which A. baumannii was recovered as the unique microbe were considered. Demographic data; ward of admission; intrinsic and extrinsic risk factors for infection or colonization; chronic underlying condition severity, as evaluated by the McCabe classification or Charlson index and Acute Physiology and Chronic Health Evaluation (APACHE) II score; and clinical manifestations were analyzed to differentiate specific characteristics of colonized or infected patients. Factors independently associated with the mortality at 30 days were also analyzed by Cox regression. RESULTS: A total of 73 (60%) patients were colonized and 49 (40%) individuals were infected with A. baumannii. A non-fatal McCabe class (when compared to ultimately and rapidly fatal), days of hospitalization prior to isolation of A. baumannii, and present ICU admission were associated with the diagnosis of infection. The more frequent clinical picture was respiratory infection (tracheobronchitis, 16 [33%] cases; pneumonia, 27 [55%] cases). Mortality at 30 days was 24% (n=29). A non-fatal McCabe class (Exp[B] 2.44, 95% confidence interval [CI] 1.05–5.66, p=0.039) and the absence of infection (Exp[B] 2.75, 95% CI 1.18–6.38, p=0.019) were independently associated with survival. CONCLUSION: Parameters associated with infection by A. baumannii in an endemic situation are the admission at ICU and the number of days of hospitalization. Mortality of patients from whom A. baumannii was isolated was independently influenced by the chronic underlying basal state and the presence of infection by A. baumannii.