Correlation between reduced susceptibility to disinfectants and multidrug resistance among clinical isolates of Acinetobacter species

Department of Medical Technology, Nagoya University Graduate School of Health Science, Nagoya, Japan.
Journal of Antimicrobial Chemotherapy (Impact Factor: 5.31). 09/2010; 65(9):1975-83. DOI: 10.1093/jac/dkq227
Source: PubMed


The aim of this study was to investigate the susceptibility profiles to disinfectants and antimicrobial agents of 283 non-repetitive Acinetobacter clinical isolates obtained in 97 Japanese hospitals in March 2002.
Susceptibility profiles of the above isolates to four disinfectants, six antimicrobial agents and two dyes were investigated. MICs were measured by the agar dilution method recommended by the CLSI (formerly NCCLS). MBC measurements and time-kill assays were performed using a slightly modified quantitative suspension test based on the European Standard EN 1040.
No evident resistance to disinfectants was seen among the 283 strains of Acinetobacter spp. isolated in 2002, but the MIC(90)s of chlorhexidine gluconate, benzalkonium chloride and alkyldiaminoethylglycine hydrochloride were 50, 50 and 400 mg/L, respectively. Interestingly, the MICs of alkyldiaminoethylglycine hydrochloride and benzethonium chloride for four and three clinical isolates, respectively, reached 800 mg/L (approximately half the in-use concentration). The MBCs for the 28 disinfectant reduced susceptibility (DRS) isolates, for which the MICs of at least one of the four disinfectants tested were higher than the MIC(90), were comparable to those for susceptible isolates, in general; however, significant differences (P < 0.01) were observed between disinfectant-susceptible and DRS isolates in the time-kill assays of chlorhexidine gluconate, benzalkonium chloride and benzethonium chloride. Furthermore, DRS isolates tended to demonstrate multiresistance profiles to ceftazidime, ciprofloxacin and amikacin (P < 0.05).
Since several Acinetobacter clinical isolates have developed augmented resistance to multiple antimicrobials and disinfectants, it is worth checking the susceptibility to disinfectants if multidrug-resistant Acinetobacter spp. are recurrently isolated clinically.

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    • "We adjusted the growth medium at three different pHs: 5, 9 and 6.7. The 5 and 9 pHs were chosen to represent mean pH values of the disinfectants most commonly used at a hospital setting (Doidge et al., 2010; Kawamura-Sato et al., 2010; Koburger et al., 2010; Weber et al., 2010). However, the pH 6.7 represents the mean pH value of the lung compartment (Effros and Chinard, 1969), and was chosen since lung infections and pneumonia are the most common infections caused by A. baumannii (Dijkshoorn et al., 2007; Qiu et al., 2009). "
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    • "Moreover, A. baumannii causes community-acquired infections, predominately in Asia and tropic Australia (Falagas et al., 2007). A. baumannii infection is facilitated through biofilm formation on indwelling medical devices and other hospital surfaces and the ability to withstand desiccation and disinfection (Vidal et al., 1996; Wendt et al., 1997; Neely, 2000; Tomaras et al., 2003; Kawamura-Sato et al., 2010; Pour et al., 2011). In addition to the wide repertoire of diseases caused by A. baumannii, this organism has acquired antibiotic resistance at alarming rates. "
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Jun-ichi Wachino