High Occurrence of Multidrug-Resistant <i>Escherichia coli</i> Strains in Bovine Fecal Samples from Healthy Cows Serves as Rich Reservoir for AMR Transmission
Objectives: Antibiotics are valuable therapeutics. However, the unwarranted and excessive use of these antimicrobials in food animals and the consequent contamination of the environment have been associated with the emergence and spread of antimicrobial resistance. Continuous surveillance and monito...
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| Main Authors: | , , , , |
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| Format: | Book |
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MDPI AG,
2022-12-01T00:00:00Z.
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| Summary: | Objectives: Antibiotics are valuable therapeutics. However, the unwarranted and excessive use of these antimicrobials in food animals and the consequent contamination of the environment have been associated with the emergence and spread of antimicrobial resistance. Continuous surveillance and monitoring of antimicrobial resistance among <i>E. coli</i> isolates is recommended, not only for bovine health but also for public health. This study aims to assess the antimicrobial resistance profile, virulence potential, and genetic characterization of fecal <i>E. coli</i> isolates from healthy cows. Methodology: The in vitro, phenotypic antibiotic resistance of isolates was measured via the Kirby-Bauer disc-diffusion method against twenty-seven antibiotics. The β-lactamase enzymatic activities of the strains were also investigated. For the assessment of virulence potential, fecal <i>E. coli</i> isolates were subjected to several in vitro pathogenicity assays, including biofilm formation ability, blood hemolysis, complement resistance, and growth in human urine. Phylogroup determination and virulence-associated genes were detected via multiplex PCR. Results: In vitro antibiotic resistance profiling showed that 186/200 (93%) of the isolates were multidrug-resistant (MDR), with the highest resistance against penicillin, tetracycline, fluoroquinolone, and macrolide classes of antibiotics. Of particular concern was the phenotypic resistance to colistin in 52/200 isolates (26%), though 16% of the total isolates harbored <i>mcr1</i>, the genetic determinant of colistin. Despite the scarce use of fluoroquinolone, cephalosporin, and carbapenem in the agricultural sector, resistance to these classes was evident due to the presence of extended-spectrum β-lactamase (ESBL) in 41% of <i>E. coli</i> isolates. The β-lactamase genotyping of <i>E. coli</i> isolates showed that 47% of isolates harbored either <i>bla</i>CTX or <i>bla</i>TEM. Approximately 32% of isolates were resistant to serum complement, and their growth in human urine was evident in 18% of isolates, indicating a possible infection of these isolates in high nitrogenous condition. Phylogrouping showed that the most prevalent phylogenetic group among fecal <i>E. coli</i> isolates was phylogroup B1 (57%), followed by phylogroups A (33%), D (6%), and B2 (4%). The most prevalent virulence-associated genes in fecal <i>E. coli</i> were <i>fimH</i>, <i>iss</i> and <i>tatT</i>. Results showed that ten isolates (5%) harbored the <i>stx1</i> gene, the genetic marker of enterohemorrhagic <i>E. coli.</i> This study provides insights into the antibiotic resistance and virulence profiling of the fecal <i>E. coli</i> isolates from healthy cows. These results emphasize the need for imposing regulations on the proper use of antibiotics and growth promoters in food-producing animals. |
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| Item Description: | 10.3390/antibiotics12010037 2079-6382 |