Emergence of the Phenicol Exporter Gene fexA in Campylobacter coli and Campylobacter jejuni of Animal Origin.
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ABSTRACT:
SUBMITTER: Liu D
PROVIDER: S-EPMC7269465 | biostudies-literature | 2020 May
REPOSITORIES: biostudies-literature
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Emergence of the Phenicol Exporter Gene <i>fexA</i> in Campylobacter coli and Campylobacter jejuni of Animal Origin.
Liu Dejun D Li Xing X Wang Yang Y Schwarz Stefan S Shen Jianzhong J
Antimicrobial agents and chemotherapy 20200521 6
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Project description:The prototype fexA gene confers combined resistance to chloramphenicol and florfenicol. However, fexA variants mediating resistance only to chloramphenicol have been identified, such as in the case of a Staphylococcus aureus isolate recovered from poultry meat illegally imported to Germany. The effects of the individual mutations detected in the fexA sequence of this isolate were investigated in this study. A total of 11 fexA variants, including prototype fexA and variants containing the different previously described mutations either alone or in different combinations, were generated by on-chip gene synthesis and site-directed mutagenesis. The constructs were inserted into a shuttle vector and transformed into three recipient strains (Escherichia coli, Staphylococcus aureus, and Salmonella Typhimurium). Subsequently, minimal inhibitory concentrations (MIC) of florfenicol and chloramphenicol were determined. In addition, protein modeling was used to predict the structural effects of the mutations. The lack of florfenicol-resistance mediating properties of the fexA variants could be attributed to the presence of a C110T and/or G98C mutation. Transformants carrying fexA variants containing either of these mutations, or both, showed a reduction of florfenicol MICs compared to those transformants carrying prototype fexA or any of the other variants. The significance of these mutations was supported by the generated protein models, indicating a substitution toward more voluminous amino-acids in the substrate-binding site of FexA. The remaining mutations, A391G and C961A, did not result in lower florfenicol-resistance compared to prototype fexA.
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Project description:Florfenicol belongs to a class of phenicol antimicrobials widely used as feed additives and for the treatment of respiratory infections. In recent years, increasing resistance to florfenicol has been reported in Campylobacter spp., the leading foodborne enteric pathogens causing diarrheal diseases worldwide. Here, we reported the identification of fexA, a novel mobile florfenicol resistance gene in Campylobacter Of the 100 Campylobacter jejuni strains isolated from poultry in Zhejiang, China, 9 were shown to be fexA positive, and their whole-genome sequences were further determined by integration of Illumina short-read and MinION long-read sequencing. The fexA gene was found in the plasmid of one strain and chromosomes of eight strains, and its location was verified by S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern blotting. Based on comparative analysis, the fexA gene was located within a region with the tet(L)-fexA-catA-tet(O) gene arrangement, demonstrated to be successfully transferable among C. jejuni strains. Functional cloning indicated that acquisition of the single fexA gene significantly increased resistance to florfenicol, whereas its inactivation resulted in increased susceptibility to florfenicol in Campylobacter Taken together, these results indicated that the emerging fexA resistance is horizontally transferable, which might greatly facilitate the adaptation of Campylobacter in food production environments where florfenicols are frequently used.
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Project description:The florfenicol-chloramphenicol exporter gene fexA is part of the novel transposon Tn558 from Staphylococcus lentus. Similarities between Tn558 and Tn554 from Staphylococcus aureus included the arrangement of the transposase genes tnpA to -C and an att554-like target sequence. Circular forms of Tn558 were detected and suggest the functional activity of this transposon.
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Project description:In a structured survey of all major chicken-meat producers in Australia, we investigated the antimicrobial resistance (AMR) and genomic characteristics of Campylobacter jejuni (n = 108) and C. coli (n = 96) from cecal samples of chickens at slaughter (n = 200). The majority of the C. jejuni (63%) and C. coli (86.5%) samples were susceptible to all antimicrobials. Fluoroquinolone resistance was detected among both C. jejuni (14.8%) and C. coli (5.2%), although this only included three sequence types (STs) and one ST, respectively. Multidrug resistance among strains of C. jejuni (0.9%) and C. coli (4.1%) was rare, and fluoroquinolone resistance, when present, was never accompanied by resistance to any other agent. Comparative genome analysis demonstrated that Australian isolates were found dispersed on different branches/clusters within the international collection. The major fluoroquinolone-resistant STs of C. jejuni (ST7323, ST2083, and ST2343) and C. coli (ST860) present in Australian chickens were similar to those of international isolates and have been reported previously in humans and animals overseas. The detection of a subpopulation of Campylobacter isolates exclusively resistant to fluoroquinolone was unexpected since most critically important antimicrobials such as fluoroquinolones are excluded from use in Australian livestock. A number of factors, including the low level of resistance to other antimicrobials, the absence of fluoroquinolone use, the adoption of measures for preventing spread of contagion between flocks, and particularly the genomic identities of isolates, all point to humans, pest species, or wild birds as being the most plausible source of organisms. This study also demonstrates the need for vigilance in the form of surveillance for AMR based on robust sampling to manage AMR risks in the food chain.IMPORTANCECampylobacter is one of the most common causes of gastroenteritis in humans, with infections frequently resulting from exposure to undercooked poultry products. Although human illness is typically self-limiting, a minority of cases do require antimicrobial therapy. Ensuring that Campylobacter originating from meat chickens does not acquire resistance to fluoroquinolones is therefore a valuable outcome for public health. Australia has never legalized the use of fluoroquinolones in commercial chickens and until now fluoroquinolone-resistant Campylobacter has not been detected in the Australian poultry. This structured survey of meat chickens derived from all major Australian producers describes the unexpected emergence of fluoroquinolone resistance in Campylobacter jejuni and C. coli Genetic characterization suggests that these isolates may have evolved outside the Australian poultry sector and were introduced into poultry by humans, pest species, or wild birds. The findings dramatically underline the critical role of biosecurity in the overall fight against antimicrobial resistance.
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Project description:Campylobacter jejuni subsp. jejuni and Campylobacter coli are leading causes of gastroenteritis, with virulence linked to cell surface carbohydrate diversity. Although the associated gene clusters are well studied for C. jejuni subsp. jejuni, C. coli has been largely neglected. Here we provide comparative analysis of the lipooligosaccharide (LOS) and capsular polysaccharide (CPS) gene clusters, using genome and cluster sequence data for 36 C. coli strains, 67 C. jejuni subsp. jejuni strains and ten additional Campylobacter species. Similar to C. jejuni subsp. jejuni, C. coli showed high LOS/CPS gene diversity, with each cluster delineated into eight gene content classes. This diversity was predominantly due to extensive gene gain/loss, with the lateral transfer of genes likely occurring both within and between species and also between the LOS and CPS. Additional mechanisms responsible for LOS/CPS diversity included phase-variable homopolymeric repeats, gene duplication/inactivation, and possibly host environment selection pressure. Analyses also showed that (i) strains of C. coli and Campylobacter upsaliensis possessed genes homologous to the sialic acid genes implicated in the neurological disorder Guillain-Barré syndrome (GBS), and (ii) C. coli LOS classes were differentiated between bovine and poultry hosts, potentially aiding post infection source tracking.
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Project description:Campylobacter coli and C. jejuni, the causing agents of campylobacteriosis, are described to be undergoing introgression events, i.e., the transference of genetic material between different species, with some isolates sharing almost a quarter of its genome. The participation of phages in introgression events and consequent impact on host ecology and evolution remain elusive. Three distinct prophages, named C. jejuni integrated elements 1, 2, and 4 (CJIE1, CJIE2, and CJIE4), are described in C. jejuni. Here, we identified two unreported prophages, Campylobacter coli integrated elements 1 and 2 (CCIE1 and CCIE2 prophages), which are C. coli homologues of CJIE1 and CJIE2, respectively. No induction was achieved for both prophages. Conversely, induction assays on CJIE1 and CJIE2 point towards the inducibility of these prophages. CCIE2-, CJIE1-, and CJIE4-like prophages were identified in a Campylobacter spp. population of 840 genomes, and phylogenetic analysis revealed clustering in three major groups: CJIE1-CCIE1, CJIE2-CCIE2, and CJIE4, clearly segregating prophages from C. jejuni and C. coli, but not from human- and nonhuman-derived isolates, corroborating the flowing between animals and humans in the agricultural context. Punctual bacteriophage host-jumps were observed in the context of C. jejuni and C. coli, and although random chance cannot be fully discarded, these observations seem to implicate prophages in evolutionary introgression events that are modulating the hybridization of C. jejuni and C. coli species.
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