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Novel macrolide‐resistance genes, mef ( C ) and mph ( G ), carried by plasmids from V ibrio and P hotobacterium isolated from sediment and seawater of a coastal aquaculture site
Author(s) -
aka L.,
Maruyama F.,
Suzuki S.,
Masuda M.
Publication year - 2015
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/lam.12414
Subject(s) - plasmid , photobacterium , biology , microbiology and biotechnology , vibrio , macrolide antibiotics , erythromycin , escherichia coli , oleandomycin , vibrionaceae , bacteria , gene , antibiotics , genetics
The aim of this study was to determine whether mef (C) and mph (G), originally found on the transferable multi‐drug plasmid pAQU 1 from Photobacterium damselae subsp. damselae isolated from seawater of a fish farm, are responsible for conferring macrolide resistance. Since these genes are localized head‐to‐tail on pAQU 1 and only four nucleotides exist between them, the single‐ and combination‐effect of these genes was examined. When mph (G) alone was introduced to Escherichia coli , the minimum inhibitory concentrations ( MIC s) against erythromycin, clarithromycin and azithromycin increased, whereas introduction of mef (C) alone did not influence macrolide susceptibility. Introduction of both mef (C) and mph (G) dramatically increased the MIC s to the same three macrolides, i.e. >512 μ g ml −1 , >512 μ g ml −1 and 128 μ g ml −1 respectively. These results suggest that the macrolide phosphotransferase encoded by mph (G) is essential for macrolide resistance, while the efflux pump encoded by mef (C) is required for high‐level macrolide resistance. The tandem‐pair arrangements of the mef (C) and mph (G) genes were conserved on plasmids ranging in size from 240 to 350 kb of the 22 erythromycin‐resistant strains belonging to Vibrio and Photobacterium obtained from the fish farm. Sixteen of 22 plasmids ranged in size from 300 to 350 kb. This is the first report of novel macrolide resistance genes originating from a marine bacterium. Significance and Impact of the Study In this study, mef (C) and mph (G) were found to be novel macrolide‐resistance genes, and this is the first report of macrolide‐resistance genes originating from a marine bacterium. These genes may be responsible for previously reported cases of the emergence of erythromycin‐resistant bacteria in aquaculture sites by an unknown mechanism. The introduction of the tandem arrangement of the mef (C) and mph (G) genes in Escherichia coli increased the MIC s to erythromycin, clarithromycin and azithromycin, suggesting a novel mechanism conferring high‐level macrolide resistance via combined expression of the efflux pump and macrolide phosphotransferase.