ABSTRACT
Several variants of the plasmid-carried tigecycline resistance gene cluster, tmexCD-toprJ, have been identified. This study characterized another novel variant, tmexC6D6-toprJ1b, located on the chromosome of environmental-origin Pseudomonas mendocina. TMexC6D6-TOprJ1 mediates resistance to multiple drugs, including tigecycline. The promoter activity of tmexC6D6-toprJ1b and negative transcriptional repression by the upstream regulator tnfxB6 are crucial for the expression of tmexC6D6-toprJ1b. tmexC6D6-toprJ1b was found in the plasmids or chromosomes of different Pseudomonas species from six countries. Two genetic backgrounds, class 1 integrons and int-carrying integrase units, were found adjacent to the tmexC6D6-toprJ1b gene cluster and might mediate the transfer of this novel efflux pump gene cluster in Pseudomonas. Further phylogenetic analysis revealed Pseudomonas as the major reservoir of tmexCD-toprJ variants, warranting closer monitoring in the future. IMPORTANCE Tigecycline is one of the treatment options for serious infections caused by multidrug-resistant bacteria, and tigecycline resistance has gained extensive attention. The emergence of a transferable tigecycline resistance efflux pump gene cluster, tmexCD-toprJ, severely challenged the efficiency of tigecycline. In this study, we identified another novel tmexCD-toprJ variant, tmexC6D6-toprJ1b, which could confer resistance to multiple classes of antibiotics, including tigecycline. Although tmexC6D6-toprJ1b was found only in Pseudomonas species, tmexC6D6-toprJ1b might spread to Enterobacteriaceae hosts via mobile genetic elements resembling those of other tmexCD-toprJ variants, compromising the therapeutic strategies. Meanwhile, novel transferable tmexCD-toprJ variants are constantly emerging and mostly exist in Pseudomonas spp., indicating Pseudomonas as the important hidden reservoir and origin of tmexCD-toprJ variants. Continuous monitoring and investigations of tmexCD-toprJ are urgent to control its spread.
Subject(s)
Anti-Bacterial Agents , Pseudomonas , Tigecycline/pharmacology , Pseudomonas/genetics , Pseudomonas/metabolism , Phylogeny , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/metabolism , Plasmids , Microbial Sensitivity TestsABSTRACT
Arginine metabolism in wine malolactic bacteria may increase the concentration of ethyl carbamate (EC, a known carcinogen with the potential toxicological effects) in wine, which makes a profound impact on wine hygienic quality. In fact, recent advanced studies have proved that arginine metabolism in wine malolactic bacteria is via arginine deiminase pathway (ADI pathway), and this pathway is composed of three enzymes: arginine deiminase (ADI), ornithine transcarbamylase (OTC), carbamate kinase (CK). The possible mechanisms of arginine transport and the regulation of major enzymes for arginine metabolism as well as the mechanism of ADI pathway and its molecular characteristics are reviewed. The study on arginine metabolism in wine malolactic bacteria has practical and theoretical significance for the safety and high quality of wine.
