Evaluation of carriage and environmental contamination by carbapenem-resistant Acinetobacter baumannii

Abstract

We evaluated the sensitivity of surveillance cultures for carbapenem-resistant Acinetobacter baumannii (CRAB) in patients and in their environment. Patients with a CRAB-positive clinical culture were sampled within 7 days; the buccal mucosa and rectum were sampled using swabs, and skin was sampled using pre-moistened sterile sponges. Sponges were also used to sample the surrounding environment. Specimens were inoculated onto CHROMagar MDR Acinetobacter plates both directly and after overnight enrichment. CRAB load was scored semi-quantitatively and composite scores for patient colonization and environmental contamination were calculated. Thirty-four patients were included. Screening sensitivity was 28/34 (82%) for buccal mucosa, 30/34 (88%) for skin, and 25/34 (74%) for rectum. Combined sensitivity was 32/34 (94%). Among patients with CRAB-positive respiratory cultures, sensitivity for buccal mucosa was 20/20 (100%). Direct inoculation had excellent sensitivity: 25/28 (89%) for all three sites combined. In the subgroup of patients who did not have a respiratory source for CRAB, direct inoculation sensitivity was lower than among patients with CRAB-positive respiratory cultures: 5/8 (63%) versus 20/20 (100%). The environment of all patients was contaminated with CRAB. There was a positive correlation between the patient colonization score and the environmental contamination score (r = 0.63, p <0.001; r = 0.4, p 0.04 for buccal mucosa, r = 0.7, p <0.001 for skin, and r = 0.46, p 0.14 for rectum). In conclusion, screening for CRAB carriers can be performed by direct plating of skin and buccal mucosa samples. Environmental contamination is common and can be monitored. Implementing screening may facilitate infection control efforts to limit the spread of CRAB.

Keywords: Active surveillance; Carbapenem-resistant Acinetobacter baumannii; Carriage; Environmental contamination; Screening.