Seasonal and Temperature-Associated Increase in Community-Onset Acinetobacter baumannii Complex Colonization or Infection

Identifying the trends in community-onset Acinetobacter baumannii complex isolation and diversity according to temperature could help provide insight into the behavior of the A. baumannii complex. We performed a retrospective analysis of A. baumannii complex (Acinetobacter baumannii, Acinetobacter nosocomialis, Acinetobacter pittii, and Acinetobacter calcoaceticus) isolates obtained from patients at a Korean community hospital from 2006 to 2015 with reference to seasonal temperatures. The incidence rates were compared between warm (June–September) and cold (November–March) months, defined as an average mean temperature ≥20℃ and ≤5℃, respectively. Incidence rate was calculated as the number of cases per month, converted to cases/10(5) admissions for healthcare-acquired isolates and cases/10(3) outpatients for community-onset isolates. Approximately 3,500 A. baumannii complex cases were identified, and 26.2% of them were community-onset cases. The median (interquartile range) number of community-onset A. baumannii complex cases was significantly higher (P=0.0002) in warm months at 13.8 (9.5–17.6) than in cold months at 10.1 (6.3–13.2). There was a strong correlation between community-onset A. baumannii complex cases and temperature (Pearson's r=0.6805, P=0.0149). Thus, we identified a seasonality pattern for community-onset A. baumannii complex colonization or infection, but not for healthcare-acquired cases.