f Typing of Mycobacterium avium subspecies paratuberculosis strains presents a challenge, since they are genetically monomorphic and traditional molecular techniques have limited discriminatory power. The recent advances and availability of wholegenome sequencing have extended possibilities for the characterization of Mycobacterium avium subspecies paratuberculosis, and whole-genome sequencing can provide a phylogenetic context to facilitate global epidemiology studies. In this study, we developed a single nucleotide polymorphism (SNP) assay based on PCR and restriction enzyme digestion or sequencing of the amplified product. The SNP analysis was performed using genome sequence data from 133 Mycobacterium avium subspecies paratuberculosis isolates with different genotypes from 8 different host species and 17 distinct geographic regions around the world. A total of 28,402 SNPs were identified among all of the isolates. The minimum number of SNPs required to distinguish between all of the 133 genomes was 93 and between only the type C isolates was 41. To reduce the number of SNPs and PCRs required, we adopted an approach based on sequential detection of SNPs and a decision tree. By the analysis of 14 SNPs Mycobacterium avium subspecies paratuberculosis isolates can be characterized within 14 phylogenetic groups with a higher discriminatory power than mycobacterial interspersed repetitive unit-variable number tandem repeat assay and other typing methods. Continuous updating of genome sequences is needed in order to better characterize new phylogenetic groups and SNP profiles. The novel SNP assay is a discriminative, simple, reproducible method and requires only basic laboratory equipment for the largescale global typing of Mycobacterium avium subspecies paratuberculosis isolates. Mycobacterium avium subspecies paratuberculosis causes Johne's disease, a chronic infectious enteritis principally of ruminants. The disease occurs worldwide and is responsible for significant losses to the livestock industry. M. avium subspecies paratuberculosis also has been detected in a subset of human patients with Crohn's disease (1), although the zoonotic role of the bacterium remains controversial.Strain typing is a prerequisite for tracing the sources of infection and for studying the epidemiology, population structure, and evolutionary relationships between isolates. It can also reveal the genetic diversity underlying important phenotypic characteristics, such as host specificity, pathogenicity, antibiotic resistance, and virulence. Typing of M. avium subspecies paratuberculosis strains presents a challenge, since M. avium subspecies paratuberculosis, like Mycobacterium tuberculosis, is genetically monomorphic (2). Genetic diversity among M. avium subspecies paratuberculosis strains has been investigated using molecular techniques, such as restriction fragment length polymorphism (RFLP) and IS900 analysis (IS900 RFLP) (3), pulsed-field gel electrophoresis (PFGE) (4), amplified fragment length polymorphism (AFLP) analysis (5), ran...
The emergence and dissemination of resistance to third- and fourth-generation cephalosporins among Enterobacteriaceae from different sources impose a global public health threat. Here, we characterized by whole-genome sequencing four Escherichia coli strains harboring the blaCTX–M–65 gene identified among 49 isolates from beef and pork collected at retail. The genomic content was determined using the Center for Genomic Epidemiology web tools. Additionally, the prediction and reconstruction of plasmids were conducted, the genetic platform of the blaCTX–M–65 genes was investigated, and phylogenetic analysis was carried out using 17 other genomes with the same sequence type and harboring the blaCTX–M–65 gene. All strains harbored blaCTX–M–65, blaOXA–1, and blaTEM–1B, and one also carried the blaSHV–12 gene. Other resistance genes, namely, qnrS2, aac(6′)-Ib-c, dfrA14, sul2, tetA, and mphA, were present in all the genomes; the mcr-1.1 gene was identified in the colistin-resistant strains. They belong to sequence type 2179, phylogenetic group B1, and serotype O9:H9 and carried plasmids IncI, IncFIC(FII), and IncFIB. All strains share an identical genetic environment with IS903 and ISEcp1 flanking the blaCTX–M–65 gene. It seems likely that the blaCTX–M–65 gene is located in the chromosome in all isolates based on deep in silico analysis. Our findings showed that the strains are clonally related and belong to two sub-lineages. This study reports the emergence of CTX-M-65-producing E. coli in Portugal in food products of animal origin. The chromosomal location of the blaCTX–M–65 gene may ensure a stable spread of resistance in the absence of selective pressure.
The present study aimed to characterize the extended-spectrum β-lactamases and plasmid-mediated AmpC β-lactamases (ESBL/PMAβ) among Escherichia coli producers isolated from beef, pork, and poultry meat collected at retail, in Portugal. A total of 638 meat samples were collected and inoculated on selective medium for the search of E. coli resistant to 3rd generation cephalosporins. Isolates were characterized by antimicrobial susceptibility testing, molecular assays targeting ESBL/AmpC, plasmid-mediated quinolone resistance (PMQR), and plasmid-mediated colistin resistance (PMCR) encoding genes. The highest frequency of E. coli non-wild type to 3rd generation cephalosporins and fluoroquinolones was observed in broiler meat (30.3% and 93.3%, respectively). Overall, a diversity of acquired resistance mechanisms, were detected: blaESBL [blaCTX-M-1 (n = 19), blaCTX-M-15 (n = 4), blaCTX-M-32 (n = 12), blaCTX-M-55 (n = 8), blaCTX-M-65 (n = 4), blaCTX-M-27 (n = 2), blaCTX-M-9 (n = 1), blaCTX-M-14 (n = 11), blaSHV-12 (n = 27), blaTEM-52 (n = 1)], blaPMAβ [blaCMY-2 (n = 8)], PMQR [qnrB (n = 27), qnrS (n = 21) and aac(6’)-Ib-type (n = 4)] and PMCR [mcr-1 (n = 8)]. Our study highlights that consumers may be exposed through the food chain to multidrug-resistant E. coli carrying diverse plasmid-mediated antimicrobial resistance genes, posing a great hazard to food safety and a public health risk.
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