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Colistin resistance is a global concern warning for a one health approach to combat the challenge. Colistin resistant E. coli and their resistance determinants are widely distributed in the environment, and rats could be a potential source of these isolates and resistant determinants to a diverse environmental setting. This study was aimed to determine the presence of colistin resistant E. coli (CREC) in wild rats, their antimicrobial resistance (AMR) phenotypes, and genotypic analysis of mcr-1 CREC through whole genome sequencing (WGS). A total of 39 rats were examined and CREC was isolated from their fecal pellets onto MacConkey agar containing colistin sulfate (1 μg/ mL). AMR of the CREC was determined by disc diffusion and broth microdilution was employed to determine MIC to colistin sulfate. CREC were screened for mcr genes (mcr-1 to mcr-8) and phylogenetic grouping by PCR. Finally, WGS of one mcr-1 CREC was performed to explore its genetic characteristics especially resistomes and virulence determinants. 43.59% of the rats carried CREC with one (2.56%) of them carrying CREC with mcr-1 gene among the mcr genes examined. Examination of seventeen (17) isolates from the CREC positive rats (n = 17) revealed that majority of them belonging to the pathogenic phylogroup D (52.94%) and B2 (11.76%). 58.82% of the CREC were MDR on disc diffusion test. Shockingly, the mcr-1 CREC showed phenotypic resistance to 16 antimicrobials of 8 different classes and carried the ARGs in its genome. The mcr-1 gene was located on a 60 kb IncI2 plasmid. On the other hand, ARGs related to aminoglycosides, phenicols, sulfonamides, tetracyclines and trimethoprims were located on a 288 kb mega-plasmid separately. The mcr-1 CREC carried 58 virulence genes including genes related to adhesion, colonization, biofilm formation, hemolysis and immune-evasion. The isolate belonged to ST224 and closely related to E. coli from different sources including UPEC clinical isolates from human based on cgMLST analysis. The current research indicates that rats might be a possible source of CREC, and the presence of mcr-1 and other ARGs on plasmid increases the risk of ARGs spreading and endangering human health and other environmental components through this infamous pest. [ABSTRACT FROM AUTHOR]

This study was designed to identify Enterococcus faecalis from clinical mastitis of cattle and determine their antimicrobial resistance and virulence determinants to evaluate their potential public health significance. A total of 105 composite milk samples (80 from cattle with clinical mastitis and 25 from apparently healthy cattle) were analyzed. E. faecalis were isolated by culturing on enterococcal selective media and identified by PCR and sequencing. Antimicrobial resistance phenotype was elucidated by the disc diffusion method, and MIC was determined by broth microdilution method according to CLSI guidelines. Detection of antimicrobial resistance and virulence genes was done by PCR. E. faecalis were isolated from 11.25% (9/80) of the clinical mastitis and 4% (1/25) of the apparently healthy cattle milk samples. The disc diffusion test revealed 40% isolates as resistant to tetracycline and azithromycin, respectively. Among them, 20% (2/10) of isolates showed resistance to both tetracycline and azithromycin. Tetracycline-resistant isolates showed MIC ranging from ≥64 to >128 μg/ml and carried tetracycline-resistant genes tetK, tetL, and tetM in 25%, 25%, and 50% of the resistant isolates, respectively. On the other hand, all the isolates were sensitive to amoxicillin, ampicillin, bacitracin, chloramphenicol, gentamicin, penicillin, and vancomycin. In addition, the isolates carried at least one of the nine virulence genes screened with pil having the highest frequency, followed by fsrB, fsrC, ace, sprE, gelE, and agg genes. Positive correlations were evident between ace, fsrC, gelE, and sprE genes that are associated with the attachment and biofilm formation in E. faecalis. E. faecalis isolated in this study carried antibiotic resistance and virulence determinants which explain their competence to be potential human pathogens. [ABSTRACT FROM AUTHOR]