Hyper-expression of the efflux pump gene adeB was found in Acinetobacter baumannii with decreased triclosan susceptibility.

OBJECTIVES: Triclosan is usually employed as a disinfectant in a wide range of medical and consumer care products, which may have imposed a selective pressure on bacteria. This study was designed to evaluate the resistance mechanisms of triclosan and molecular epidemiology of triclosan-resistant isolates of Acinetobacter baumannii in Wenzhou, China. METHODS: A collection of 626 A. baumannii were isolated from the First Affiliated Hospital of Wenzhou Medical University during 2016-2017 and antimicrobial susceptibility testing of these isolates were performed via agar dilution method. Molecular mechanisms of triclosan resistance, including the existence of mutations in reductase (FabI) were investigated by PCR and sequencing. Furthermore, quantitative RT-PCR was conducted to evaluate the expression levels of the fabI gene and efflux pump genes (adeB, adeG, adeJ, abeM, amvA and abeS) at normal condition and sub-inhibitory concentration of triclosan, and the epidemiological characteristics were analyzed by PFGE and MLST. RESULTS: 2.7% (17/626) of A. baumannii exhibited resistance to triclosan. The FabI mutation Gly95Ser was found in one triclosan resistant strain. The expression of fabI and adeB gene were significant difference between triclosan-resistant and susceptible strains (P < 0.05). The expression of fabI, adeG, adeJ and abeM were increased after triclosan induction. The clones of these resistant isolates were diverse and sporadic. CONCLUSIONS: The hyper-expression of fabI was probably the main mechanism of triclosan resistance in this study, and the efflux pump AdeB, AdeG, AdeJ and AbeM might also be related to decreased triclosan susceptibility.