High Occurrence of Multidrug-Resistant Escherichia coli Strains in Bovine Fecal Samples from Healthy Cows Serves as Rich Reservoir for AMR Transmission

Abstract

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 E. coli 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 E. coli 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 E. coli 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 mcr1, 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 E. coli isolates. The β-lactamase genotyping of E. coli isolates showed that 47% of isolates harbored either blaCTX or blaTEM. 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 E. coli isolates was phylogroup B1 (57%), followed by phylogroups A (33%), D (6%), and B2 (4%). The most prevalent virulence-associated genes in fecal E. coli were fimH, iss and tatT. Results showed that ten isolates (5%) harbored the stx1 gene, the genetic marker of enterohemorrhagic E. coli. This study provides insights into the antibiotic resistance and virulence profiling of the fecal E. coli 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.

Prevalence of Extended-Spectrum β-Lactamases (ESBLs) Producing Aeromonas spp. Isolated from Lamellidens marginalis (Lamark, 1819) of Sewage-Fed Wetland: A Phenotypic and Genotypic Approach

“…and both the MAR index and R-score, speculating the significant clinical concern for these resistance patterns. These findings align with the results of a study conducted by Jalil et al [54], where similar trends of higher MAR index and R-score in E. coli isolates were reported. Our finding is consistent with other studies on bacteria of marine bivalves conducted in different parts of Korea [17,32,35,55] with a higher MAR index in Aeromonas spp.…”

Extended-Spectrum β-Lactamase-Producing Escherichia coli Isolated from Food-Producing Animals in Tamaulipas, Mexico

“…E. coli is an interesting study model given its omnipresence in nature as a commensal and pathogen, being one of the primary vehicles that can transmit resistance and virulence genes between different species [ 15 ]. The monitoring of antibiotic-resistant E. coli strains from food animals and products is vital to determine its potential risk to humans [ 16 ]. This study found that 5.0% of strains recovered from livestock samples (cattle, pigs, chickens and sheep) were ESBL-EC.…”

“…The health risk associated with the spread of antibiotic resistance in the environment is estimated using the multiple antibiotic resistance index (MARI) [ 16 , 30 ]. In this study, all of the values obtained show that the MARI was greater than 0.2, suggesting that the ESBL-EC strains originated from an environment with a high contamination or overuse of antibiotics.…”

“…E. coli ATCC 25,922 and ATCC 3518 were used as the control strains. The results were used to calculate the Antibiotic Resistance Index (ARI) and Multiple Antibiotic Resistance (MAR) index for the bacteria according to Jalil et al [ 16 ]. Strains showing a MAR index above 0.2 indicate high resistance in that specific isolate [ 16 ].…”

“…ESBL-producing isolates were classified in phylogenetic groups by amplifying fragments of the chuA (279 bp) and yjaA (211 bp) genes, and the DNA fragment TspE4.C2 (152 bp) as described by Clermont et al [ 16 ]. Briefly, groups were assigned on the basis of different combinations of the presence and/or absence of the three amplicons (A, B1, B2 and D).…”