2188. Evaluation of biocide susceptibilities of clinical isolates of Acinetobacter baumannii

BACKGROUND: Carbapenem-resistant Acinetobacter baumannii (CRAB) is an urgent antimicrobial resistant threat due to its resistance to many antibiotics. There is a concern that some antibiotic-resistant strains of A. baumannii might also express resistance to biocides, including disinfectants and antiseptics. However, relatively little information is available on the susceptibility of A. baumannii to disinfectants. METHODS: Thirty well-characterized clinical A. baumannii isolates were studied, including 24 (%) CRAB isolates and 11 (37%) with qacE1 and amvA efflux pump genes. The efficacy of sodium hypochlorite (1:10 dilution of household bleach) and virex-II 256 (quaternary ammonium disinfectant) was evaluated using a standard disk-based quantitative carrier test method (ASTM E2197-11) in the presence of 5% fetal calf serum. The disinfectants were tested at in-use concentrations with the manufacturer-recommended exposure times. Minimum inhibitory concentrations (MICs) to virex-II 256, povidone-iodine, chlorhexidine, and were determined using a broth microdilution method. Serial passage of A. baumannii in subinhibitory concentrations of virex-II 256 were performed to assess the potential for emergence of resistance. RESULTS: All 30 A. baumanii isolates were reduced to undetectable levels (>5.4 log(10) reduction) by both disinfectants. MICs for povidone-iodine, chlorhexidine, and virex-II 256 were 2343.75 to 9375 µg/ml, 0.62 to 12.5 µg/ml, 1.06 to 2.03µg/ml, respectively. With serial passage in subinhibitory concentrations of virex-II 256, the MICs of virex-II 256 increased 4-fold from 2.03 to 8 µg/ml, and some strains developed increases in chlorhexidine MICS from 12.5 to 50 µg/ml. CONCLUSION: Sodium hypochlorite and a quaternary ammonium disinfectant were effective at in-use concentrations against A. baumannii, including CRAB strains and isolates with efflux pumps. Exposure to subinhibitory concentrations of quaternary ammonium compounds may result in increases in MICs in these disinfectants and other biocides. DISCLOSURES: All Authors: No reported disclosures