Risk factors for endemic Acinetobacter Baumannii colonization: A case-case study

Acinetobacter baumannii causes increasingly resistant nosocomial infections worldwide. Although some patients are already colonized with A baumannii on hospital admission, others become colonized with endemic strains that are more likely to be antibiotic-resistant. Colonization increases risk of infection and transmission to others. This study aimed to identify risk factors for colonization with endemic compared to sporadic A baumannii among hospitalized patients.

The study population were patients colonized with A baumannii at a single medical center during a 17-month period of active surveillance. Endemic A baumannii (cases) had a repetitive extragenic palindromic (REP) type that occurred 10 or more times during the surveillance period. Cases carrying 1 of the 5 endemic REP types were matched to comparison cases (controls) carrying sporadic strains by facility and time.

There were 69 cases with REP-1, and 64 with REP-2-5. After adjustment, each unit increase in Schmid score was associated with a 70% increase in REP-1 carriage (P = .04) and a 50% increase in REP-2-5 (P = .07). Days in the intensive care unit prior to colonization, longer length of stay, immunosuppression, and the Charlson comorbidity index were not significantly associated with carriage of endemic strains.

Following best practices for antibiotic stewardship and hygiene will help minimize the emergence and persistence of A baumannii strains adapted to the health care environment.