Reduction in chlorhexidine efficacy against multi-drug-resistant Acinetobacter baumannii international clone II.
BACKGROUND
Nosocomial infections caused by Acinetobacter baumannii international clone II (IC II) can cause severe clinical outcomes.


OBJECTIVE
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 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.


RESULTS
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 log10for 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.


CONCLUSIONS
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.
Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Aichi, Japan.
M
M
Hayashi
Department of Pathophysiological Laboratory Sciences, Nagoya University Graduate School of Medicine, Aichi, Japan. Electronic address: kumiko@met.nagoya-u.ac.jp.
K
K
Kawamura
Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan.
M
M
Matsui
Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan.
M
M
Suzuki
Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan.
S
S
Suzuki
Department of Bacteriology II, National Institute of Infectious Diseases, Tokyo, Japan.
K
K
Shibayama
Department of Bacteriology, Nagoya University Graduate School of Medicine, Aichi, Japan.
Y
Y
Arakawa
D000151:Acinetobacter Infections / Q000382:microbiology; D040981:Acinetobacter baumannii / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D002710:Chlorhexidine / Q000494:pharmacology*; D002999:Clone Cells; D004202:Disinfectants / Q000494:pharmacology*; D024901:Drug Resistance, Multiple, Bacterial; D005838:Genotype; D008826:Microbial Sensitivity Tests; D050296:Microbial Viability / Q000187:drug effects
D004202:Disinfectants; D002710:Chlorhexidine
Acinetobacter baumannii; Benzethonium chloride; Chlorhexidine gluconate; Disinfection; International clone II