Control of an outbreak of Acinetobacter baumannii infections using vaporized hydrogen peroxide

Abstract

Background: Multidrug-resistant Acinetobacter baumannii (MRAB) is a serious nosocomial pathogen characterized by its survival on inanimate surfaces for long periods, making control of outbreaks difficult.

Aim: To analyse two hospital outbreaks caused by MRAB, determine their epidemiology, carbapenem-resistance mechanisms and assess the effectiveness of surface disinfection by vaporized hydrogen peroxide (VHP).

Methods: MRAB strains were isolated from patients in two intensive care units (ICUs). Antimicrobial susceptibility testing was performed by E-test. Polymerase chain reaction (PCR) was used to detect the presence of the most common A. baumannii carbapenemases. Epidemiological typing was performed by rep-PCR (DiversiLab) and pulsed-field gel electrophoresis. VHP was used to decontaminate the affected ICUs.

Findings: MRAB was isolated from 28 patients between January 2009 and September 2010. All isolates were resistant to ciprofloxacin and gentamicin. Twenty-one were also resistant to carbapenems. Carbapenem resistance was associated primarily with the acquired OXA-23-like enzyme. Genotyping revealed three clones; the predominant clone corresponded to the international clone (IC) 2. Typing of the isolates pointed to a multifocal outbreak without a single source of infection, with horizontal spread of the dominating clone among ICU patients. A combination of rigorous infection control measures including strict isolation, education of staff, hand hygiene and surface decontamination using VHP halted the outbreak.

Conclusion: The results of this study confirm the importance of rigorous infection prevention and control measures, combined with VHP decontamination in controlling an outbreak of MRAB.