Reduction in chlorhexidine efficacy against multi-drug resistant Acinetobacter baumannii international clone II

Research paper by Michiko Hayashi, Kumiko Kawamura; Mari Matsui; Masato Suzuki; Satowa Suzuki; Keigo Shibayama; Yoshichika Arakawa

Indexed on: 28 Dec '16Published on: 16 Dec '16Published in: Journal of Hospital Infection


Publication date: Available online 10 December 2016 Source:Journal of Hospital Infection Author(s): Michiko Hayashi, Kumiko Kawamura, Mari Matsui, Masato Suzuki, Satowa Suzuki, Keigo Shibayama, Yoshichika Arakawa Background Nosocomial infections caused by Acinetobacter baumannii international clone II (IC II) can cause severe clinical outcomes. Aim Differential evaluation of bactericidal efficacy of chlorhexidine gluconate (CHX) and benzethonium chloride (BZT) disinfectants against IC II and non-IC II isolates. Methods Minimum inhibitory concentrations (MICs) of CHX and BZT were determined for 137 A. baumannii IC II, 99 non-IC II, and 69 non-baumannii Acinetobacter isolates, further classified according to MIC values into disinfectant-reduced susceptible (DRS) and disinfectant-susceptible (DS) groups. Time-kill curve and minimum bactericidal concentration (MBC) were evaluated for representative isolates in each group. Results CHX and BZT MIC90s for IC II isolates were 100 and 175 mg/L, respectively, but those for non-IC II and non-baumannii isolates were <100 mg/L. Nevertheless, time-kill curves indicated that CHX and BZT reduced live bacterial cell number by 5 log10 for IC II and non-IC II isolates within 30 s, when used at 1000 mg/L, comparable to practical use concentrations. CHX MBC at 30 s was 1000 mg/L for IC II and non-IC II isolates, and was uninfluenced by 3% BSA addition; BZT MBC at 30 s was 100 mg/L without BSA and increased up to 500 mg/L upon BSA addition. No significant differences of BSA were found between DRS and DS isolates. Conclusion CHX and BZT were effective against Acinetobacter spp. including IC II at a concentration of 1000 mg/L and exposure for at least 30 s, but their concentrations should be carefully considered to ensure sufficient effects in both clinical and healthcare settings.