A Carbapenem-Resistant Acinetobacter baumannii Outbreak in an Intensive Care Unit: Detection Before Recognition and Persistence After Containment.

Background

We analyzed a carbapenem-resistant Acinetobacter baumannii (CRAB) outbreak in an intensive care unit (ICU) to improve insight into how this pathogen spreads within health care facilities and to inform the development of targeted control procedures.

Methods

A CRAB outbreak in a tertiary referral center was investigated over a 5-month window with clinical data, molecular typing (AP-PCR, PFGE), and one month of environmental sampling. All ICU patients (n=31) were compared-epidemic-clone-positive (n=7) versus -negative (n=24)-using Mann-Whitney/Fisher tests and Firth penalized logistic regression.

Results

Although the outbreak spanned 6 days clinically, index patients had been colonized up to 41 days earlier. CRAB was recovered from high-touch surfaces; 6/7 patients developed pneumonia/VAP and 6/7 died (4 CRAB-attributable). Prior A. baumannii isolation (57% vs 0%) was the only independent risk factor (Firth odds ratio 34.7; P=.004). Despite treatment, infected patients redeveloped epidemic-clone infection up to 3.5 months later.

Conclusions

In CRAB outbreaks, spread may begin weeks before clinical recognition, and-even months after the outbreak is contained-the epidemic clone can cause reinfection in previously treated patients; only high-resolution analyses spanning an extended period can document this. Multidisciplinary and administrative collaboration, extended and effective environmental disinfection, and effective isolation of positive patients are important for containing CRAB outbreaks.