Abstract
The production of extended-spectrum β-lactamases (ESBLs) conferring resistance to new derivatives of β-lactams is a major public health threat if present in pathogenic Gram-negative bacteria. The objective of this study was to characterize ceftiofur (TIO)- or cefotaxime (FOX)-resistant Escherichia coli isolated from dairy cow manure. Twenty-four manure samples were collected from four farms and incubated under anaerobic conditions for 20 weeks at 4 °C or at 25 °C. A total of 37 TIO- or FOX-resistant E. coli were isolated from two of the four farms to determine their susceptibility to 14 antibiotics. Among the 37 resistant E. coli, 10 different serotypes were identified, with O8:H1 being the predominant serotype (n = 17). Five isolates belonged to each of serotypes O9:NM and O153:H42, respectively. All 37 cephalosporin resistant isolates were multi-resistant with the most prevalent resistance spectrum being amoxicillin-clavulanic acid-ampicillin-cefoxitin-ceftiofur-ceftriaxone-chloramphenicol-streptomycin-sulfisoxazole-tetracycline-trimethoprim-sulfamethoxazole. The genomes of 18 selected isolates were then sequenced and compared to 14 selected human pathogenic E. coli reference genomes obtained from public repositories using different bioinformatics approaches. As expected, all 18 sequenced isolates carried at least one β-lactamase bla gene: TEM-1, TEM-81, CTX-M115, CTX-M15, OXA-1, or CMY-2. Several other antibiotic resistance genes (ARGs) and virulence determinants were detected in the sequenced isolates and all of them harbored antimicrobial resistance plasmids belonging to classic Inc groups. Our results confirm the presence of diverse ESBL producing E. coli isolates in dairy cow manure stored for a short period of time. Such manure might constitute a reservoir of resistance and virulence genes for other bacteria that share the same environment.
Highlights
The dairy cow industry in Canada generates ~10 million kilograms of manure annually, which is applied to agricultural fields as fertilizer [1]
As reported in several previous studies, manure generated by dairy cattle may contain resistance profiles of to characterize ceftiofur (TIO) and FOX resistant E. coli isolates from dairy cattle manure samples were potentially harmful antibiotic resistant E. coli [36,37,38]
The contribution of food producing animals in the spread of ESBL-CTX-M15 E. coli to humans is not well established, the present study showed that multiple antibiotics resistant ESBL-CTX-M15 E. coli can be found in dairy cow manure
Summary
The dairy cow industry in Canada generates ~10 million kilograms of manure annually, which is applied to agricultural fields as fertilizer [1]. This manure is a valuable source of nutrients for crops; it can be a source of manure-borne bacteria that could contaminate the environment. The bacterial pathogens that are commonly found in bovine manure can pose a major risk of infections for humans [3,4]. Dairy cows are frequently treated with cephalosporin antibiotics to prevent or cure mastitis that is caused largely by Escherichia coli or other pathogenic bacteria [5,6,7]. Dairy cow manure could be an important reservoir of several antibiotic resistant bacteria (ARB) and their corresponding antibiotic resistance genes (ARGs)
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