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J Hosp Infect. 2017 Mar;95(3):318-323. doi: 10.1016/j.jhin.2016.12.004. Epub 2016 Dec 10.

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

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Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Aichi, Japan.
Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Aichi, Japan. Electronic address:
Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan.
Department of Bacteriology, Nagoya University Graduate School of Medicine, Aichi, Japan.



Nosocomial infections caused by Acinetobacter baumannii international clone II (IC II) can cause severe clinical outcomes.


Differential evaluation of bactericidal efficacy of chlorhexidine gluconate (CHX) and benzethonium chloride (BZT) disinfectants against IC II and non-IC II isolates.


Minimum inhibitory concentrations (MICs) of CHX and BZT were determined for 137 A. baumannii IC II, 99 non-IC II and 69 non-baumannii isolates, further classified according to MIC values into disinfectant-reduced susceptible (DRS) and disinfectant-susceptible (DS) groups. Time-kill curves and minimum bactericidal concentrations (MBCs) were evaluated for representative isolates in each group.


CHX and BZT MIC90s for IC II isolates were 100 and 175mg/L, respectively, but those for non-IC II and non-baumannii isolates were <100mg/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 30s when used at 1000mg/L, comparable to practical use concentrations. CHX MBC at 30s was 1000mg/L for IC II and non-IC II isolates, and was not influenced by addition of 3% bovine serum albumin (BSA); BZT MBC at 30s was 100mg/L without BSA and increased up to 500mg/L upon addition of BSA. No significant differences in BSA were found between DRS and DS isolates.


CHX and BZT were effective against Acinetobacter spp. including IC II at a concentration of 1000mg/L and exposure for at least 30s, but their concentrations should be considered carefully to ensure sufficient effects in both clinical and healthcare settings.


Acinetobacter baumannii; Benzethonium chloride; Chlorhexidine gluconate; Disinfection; International clone II

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