Resistance to disinfectants in epidemiologically defined clinical isolates of Acinetobacter baumannii H. Wisplinghoff a, *, R. Schmitt a ,A.Wo¨hrmann b , D. Stefanik a , H. Seifert a a Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Cologne, Germany b Department I of Internal Medicine, University of Cologne, Cologne, Germany Received 3 August 2006; accepted 22 February 2007 Available online 10 May 2007 KEYWORDS Acinetobacter baumannii; Resistance; Disinfectants Summary Decreased susceptibility to biocides may contribute to epi- demic spread of Acinetobacter baumannii in the hospital. This study was conducted to evaluate the susceptibility of different clinical A. bau- mannii strains to disinfectants. Twenty A. baumannii strains were exam- ined, ten of which were outbreak-related and ten that were sporadic. Clinical isolates were selected on the basis of demonstrating a unique pulsed-field gel electrophoresis pattern. The in-vitro activities of propa- nol, combination of 1-propanol, 2-propanol and mecetronium ethylsul- phate, polyvinylpyrrolidone (PVP)-iodine, triclosan and chlorhexidine were determined using a broth macrodilution method. Exposure times to the disinfectant ranged from 15 s to 2 min and concentrations ranged from undiluted to a 1:4000 dilution in order to investigate the impact of inadvertent dilution that might occur in clinical practice. Five American Type Culture Collection (ATCC) type strains (A. baumannii, Escherichia coli, Pseudomonas aeruginosa, Enterococcus faecalis and Staphylococcus aureus) were used as controls. All disinfectants inhibited growth of all isolates at concentrations and contact times recommended by the respective manufacturer. With most of the disinfectants tested, a relevant number of viable bacteria remained if contact times <30 s or diluted agents were used. No significant differences in susceptibility between outbreak-related and sporadic strains were detected, but larger studies would be required to confirm this. Resistance to currently used * Corresponding author. Address: Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Goldenfelsstr. 19e21, 50935 Cologne, Germany. Tel.: þ49 221 478 32100; fax: þ49 221 478 32002. E-mail address: h.wisplinghoff@uni-koeln.de 0195-6701/$ - see front matter ª 2007 The Hospital Infection Society. Published by Elsevier Ltd. All rights reserved. doi:10.1016/j.jhin.2007.02.016 Journal of Hospital Infection (2007) 66, 174e181 www.elsevierhealth.com/journals/jhin