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

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.

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).

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.

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.

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.