Culture Media for Detection of Acinetobacter baumannii Selective Media for Detection of A baumannii

Abstract

Detection of Acinetobacter baumannii is of crucial importance to the prevention of the development of nosocomial infections. CHROMagar Acinetobacter® is a new selective medium recently developed for the rapid identification of A. baumannii. This medium incorporates enzymatic substrates that enable colour- based preliminary identification of bacterial colonies recovered within 18 to 24 h of inoculation. Sheep blood agar (SBA) supplemented with ertapenem contains few modifications and has not yet been defined in the literature. The aim of this study was to evaluate CHROMagar Acinetobacter® for detection of A. baumannii and compare its performance to that of SBA supplemented with ertapenem. A total of 73 Gram-negative bacteria were evaluated. A. baumannii, Pseudomonas aeruginosa, Stenotrophomonas maltophilia and carbapenemase-positive Klebsiella pneumoniae were grown on CHROMagar Acinetobacter® and supplemented SBA media. Susceptible clinical isolates and standard strains of Enterobacteriaceae were inhibited by both CHROMagar Acinetobacter® and supplemented SBA. C. albicans isolates, inoculated with mixed samples, did not grow on CHROMagar Acinetobacter® after 24 or 48 h, but did grow on supplemented SBA after 24 h and exhibited distinct colony morphology. A. baumannii, the most clinically relevant of the bacteria tested, have a particular propensity for nosocomial transmission, due in part to their sustained survival on environmental surfaces as well as their multidrug resistance. The prevalence of infection with A. baumannii has increased significantly during the last decade. Due to well-designed solid selective culture media are required for detection of Acinetobacter spp. We advise the use of supplemented SBA and CHROMagar Acinetobacter® medium for rapid detection of nosocomial infection in the absence of a confirmatory procedure. Investigation into the metabolism of A. baumannii will facilitate the development of chromogenic media.