Incidence, risk factors and outcome of multi-drug resistant Acinetobacter baumannii nosocomial infections during an outbreak in a burn unit

Abstract

Background: Multidrug-Resistant Acinetobacter baumannii (MR-AB) can cause outbreaks in burn units. We aimed to study the incidence, risk factors and outcome of MR-AB infections in a burn unit (BU).

Methods: A prospective study was conducted from April to November, 2014 during an outbreak in a BU in Paris. Weekly surveillance cultures were performed to determine MR-AB colonization. MR-AB nosocomial infections, discharge or death without MR-AB infection were considered as competing events. To identify risk factors for MR-AB infection, baseline characteristics and time-dependent variables were investigated in univariate analyses using Cox models.

Results: Eighty-six patients admissions were analyzed during the study period. Among them, 15 (17%) acquired MR-AB nosocomial infection. Median time to infection was 22days (interquartile range: 10-26 days). Cumulative incidence of MR-AB infections was 15% at 28days (95% CI=8-24). Risk factors for MR-AB infection in univariate analysis were SAPS II (Hazard Ratio (HR):1.08; 95% CI:1.05-1.12; P<0.0001) and ABSI (Abbreviated Burn Severity Index) scores (HR:1.32; 95% CI:1.12-1.56; P=0.001), MR-AB colonization (HR:10.2; 95%CI:2.05-50.3; P=0.004), invasive procedures (ventilation, arterial and/or venous catheter) (P=0.0001) and ≥2 skin grafts (HR:10.2; 95% CI:1.76-59.6; P=0.010). MR-AB infection was associated with an increased risk of death (HR: 7.11; 95%CI: 1.52-33.2; P=0.013) and longer hospital stay with a median estimated increase of 10days (IQR: 6; 14).

Conclusions: Incidence of MR-AB nosocomial infection was high during this outbreak, and was associated with prolonged hospitalization and increased risk of death. High patient severity scores, prior MR-AB colonization, invasive procedures and repeated skin grafts were associated with an increased risk of nosocomial infection.

Keywords: Acinetobacter baumannii; Antibiotic resistance; Burns; Infection; Risk factors.