Deciphering the role of calcium peroxide on the fate of antibiotic resistance genes and mobile genetic elements during bioelectrochemically-assisted anaerobic composting of excess dewatered sludge

Aeromonas salmonicida subsp. salmonicida, the causative agent of furunculosis in salmonids, is an issue especially because many isolates of this bacterium display antibiotic resistances, which limit treatments against the disease. Recent results suggested the possible existence of alternative forms of pAsa4, a large plasmid found in A. salmonicida subsp. salmonicida and bearing multiple antibiotic resistance genes. The present study reveals the existence of two newly detected pAsa4 variants, pAsa4b and pAsa4c. We present the extensive characterization of the genomic architecture, the mobile genetic elements and the antimicrobial resistances genes of these plasmids in addition to the reference pAsa4 from the strain A449. The analysis showed differences between the three architectures with consequences on the content of resistance genes. The genomic plasticity of the three pAsa4 variants could be partially explained by the action of mobile genetic elements like insertion sequences. Isolates from Canada and Europe that bore similar antibiotic resistance patterns than pAsa4-bearing strains were genotyped and specific pAsa4 variants could be attributed to phenotypic profiles. pAsa4 and pAsa4c were found in Europe, while pAsa4b was found in Canada. The plasticity of pAsa4 variants related to the acquisition of antibiotic resistance indicates that these plasmids may pose a threat in terms of the dissemination of antimicrobial-resistant A.salmonicida subsp. salmonicida bacteria.

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The shared resistome of human and pig microbiota is mobilized by distinct genetic elements

Applied and Environmental Microbiology ◽

10.1128/aem.01910-20 ◽

2020 ◽

Author(s):

Chao Wang ◽

Yuqin Song ◽

Na Tang ◽

Gang Zhang ◽

Sébastien Olivier Leclercq ◽

...

Keyword(s):

Antibiotic Resistance ◽

Intestinal Microbiota ◽

Resistance Genes ◽

Pathogenic Bacteria ◽

Antibiotic Resistance Genes ◽

Mobile Genetic Elements ◽

Human Pathogens ◽

Genetic Elements ◽

Metagenomics Data ◽

Genetic Context

The extensive use of antibiotics in hospitals and in the animal breeding industry has promoted antibiotic resistance in bacteria, which resulted in the emergence of a large number of antibiotic resistance genes in the intestinal tract of human and farmed animals. Genetic exchange of resistance genes between the two ecosystems is now well documented for pathogenic bacteria, but the repertoire of shared resistance genes in the commensal bacterial community and by which genetic modules they are disseminated are still unclear. By analyzing metagenomics data of human and pig intestinal samples both collected in Shenzhen, China, a set of 27 highly prevalent antibiotic resistance genes was found to be shared between human and pig intestinal microbiota. The mobile genetic context for 11 of these core antibiotic resistance genes could be identified by mining their carrying scaffolds constructed from the two datasets, leading to the detection of seven integrative and conjugative/mobilizable elements and two IS-related transposons. The comparison of the relative abundances between these detected mobile genetic elements and their associated antibiotic resistance genes revealed that for many genes, the estimated contribution of the mobile elements to the gene abundance differs strikingly depending on the host. These findings indicate that although some antibiotic resistance genes are ubiquitous across microbiota of human and pig populations, they probably relied on different genetic elements for their dissemination within each population. IMPORTANCE There is growing concern that antibiotic resistance genes could spread from the husbandry environment to human pathogens through dissemination mediated by mobile genetic elements. In this study, we investigated the contribution of mobile genetic elements to the abundance of highly prevalent antibiotic resistance genes found in commensal bacteria of both human and pig intestinal microbiota originating from the same region. Our results reveal that for most of these antibiotic resistance genes, the abundance is not explained by the same mobile genetic element in each host, suggesting that the human and pig microbial communities promoted a different set of mobile genetic carriers for the same antibiotic resistance genes. These results deepen our understanding of the dissemination of antibiotic resistance genes among and between human and pig gut microbiota.

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