High-level tolerance to triclosan may play a role in <it>Pseudomonas aeruginosa </it>antibiotic resistance in immunocompromised hosts: evidence from outbreak investigation

• Main Authors: D'Arezzo Silvia, Lanini Simone, Puro Vincenzo, Ippolito Giuseppe, Visca Paolo
• Format: Article
• Language: English
• Published: BMC 2012-01-01
• Series: BMC Research Notes
• Online Access: http://www.biomedcentral.com/1756-0500/5/43

<p>Abstract</p> <p>Background and methods</p> <p><it>Pseudomonas aeruginosa </it>is a major infectious threat to immunocompromised patients. We recently reported a fatal epidemic of multidrug-resistant <it>P. aeruginosa </it>in an onchoematology unit, linked to massive contamination of a triclosan-based disinfectant. The aim of this study is to evaluate the antimicrobial activity of triclosan and chlorhexidine digluconate against the epidemic strain of <it>P. aeruginosa</it>, to confirm the hypothesis that the soap dispenser acted as a continuous source of the infection during the outbreak, and to explore the potential role of triclosan in increasing the level of resistance to selected antibiotics.</p> <p>Susceptibility tests and time-kill assays for disinfectans were performed using two commercial formulations containing triclosan and chlorhexidine digluconate, respectively. Antibiotic susceptibility testing was performed by the broth microdilution method.</p> <p>Findings</p> <p>The <it>P. aeruginosa </it>epidemic strain exhibited an extremely high level of triclosan resistance (apparent MIC = 2,125 mg/L), while it was markedly susceptible to chlorhexidine digluconate (apparent MIC = 12.5 mg/L). Upon gradual adaptation to triclosan, the epidemic strain survived for a long period (> 120 h) in the presence of 3,400 mg/L (equivalent to 1.6 × MIC) of triclosan, concomitantly increasing the resistance to six antibiotics that are typical substrates of drug efflux pumps of the resistance nodulation division family. This effect was reversed by efflux pump inhibitors.</p> <p>Conclusions</p> <p>The epidemic <it>P. aeruginosa </it>strain was resistant to triclosan and its previous exposure to triclosan increases antibiotic resistance, likely through active efflux mechanisms. Since <it>P. aeruginosa </it>can become tolerant to elevated triclosan concentrations, the use of triclosan-based disinfectants should be avoided in those healthcare settings hosting patients at high risk for <it>P. aeruginosa </it>infection.</p>