Community-acquired Acinetobacter baumannii infections in Santa Clara County, California

Background: Acinetobacter baumannii is an emerging pathogen which causes serious healthcare-associated infections, and less commonly, community-acquired infections, especially in tropical and subtropical climates. Hospital-acquired A. baumannii infections are characterized by high mortality and multi-drug resistance.

Objective: To describe the epidemiological, microbiological and clinical characteristics of patients with A. baumannii community-acquired infections, and compare them to cases of healthcare-associated A. baumannii infections.

Methods: A retrospective study of patients diagnosed with A. baumannii infections and treated in Regional Medical Center of San Jose, California, a 247-bed trauma medical center serving Santa Clara County, from January, 2009, until July, 2010, was performed. Patients with positive A. baumannii culture within 48 hours of admission, without hospitalization or residence in a skilled nursing facility in the preceeding 30 days, were compared to hospitalized cases of healthcare-associated A. baumannii infections during the same time period.

Results: A total of 46 cases of A. baumannii infections were identified. Of these, 7 (15%) were community-acquired, and consisted of wound infections (43%), urinary tract infections (UTI, 29%), pneumonia (14%) and bacteremia (14%). The single case of bacteremia was associated with septic shock and died. Healthcare-associated infections (39 cases) included a predominance of pneumonia (56%), and less wound infections (28%), UTI (13%), and bacteremia (3%). Hospital-acquired infections were associated with longer hospital lenght of stay. Community-acquired infections occurred in younger patients (average age 54 years compared to 70 years), and were not associated with antibiotic resistance. Males predominated in both groups.

Conclusions: In contrast to healthcare-associated infections, more than half of which were associated with pneumonia, community-acquired A. baumannii infections caused a variety of serious clinical syndromes, including wound infection, pneumonia, UTI and septic shock, in a younger age group. Although multi-drug resistance was seen in 18% of healthcare-associated infections, none of the community-acquired infections were caused by A. baumannii strains resistant to third generation cephalosporins or carbapenems.