Short communication: Extended-spectrum AmpC-producing Escherichia coli from milk and feces in dairy farms in Brazil

Occurrence of extended-spectrum β-lactamase-producing Enterobacteriaceae in raw milk from cows with subclinical mastitis in northeast Brazil

Extended-spectrum β-lactamase (ESBL)-producing Gram negative bacteria are becoming increasingly important in veterinary and human medicine because they can hydrolyze the third generation β-lactams, penicillins, and monobactams. The aim of this study was to identify ESBL-producing Enterobacteriaceae in raw cow milk samples from northeast Brazil. Twenty-six bacterial isolates belonging to the Enterobacteriaceae family were obtained from milk samples from 257 cows with subclinical mastitis. Using microbiological tests, 53.85% (14/26) were identified as Escherichia coli, 15.38% (4/26) as Proteus mirabilis, 26.92% (7/26) as Klebsiella spp., and 3.85% (1/26) as Citrobacter spp. Of all the isolates, 61.54% (16/26) were positive in the ESBL screening test, of which 12.5% (2/16) were positive in the double-disc synergy test using three types of cephalosporins and amoxicillin/clavulanic acid. The two isolates were identified as Klebsiella spp. Among all the isolates, 53.85% (14/26) were positive for one or both ESBL-encoding genes, blaSHV and blaTEM; among these, 71.43% (10/14) were identified as E. coli. This study demonstrates that ESBL-producing bacteria can be found in raw cow milk from northeast Brazil. Cows with subclinical mastitis should be recognized as reservoirs of these strains, which can propagate to humans.

Prevalence and distribution of extended-spectrum β-lactamase and AmpC-producing Escherichia coli in two New Zealand dairy farm environments

Antimicrobial resistance (AMR) is a global threat to human and animal health, with the misuse and overuse of antimicrobials being suggested as the main driver of resistance. In a global context, New Zealand (NZ) is a relatively low user of antimicrobials in animal production. However, the role antimicrobial usage on pasture-based dairy farms, such as those in NZ, plays in driving the spread of AMR within the dairy farm environment remains equivocal. Culture-based methods were used to determine the prevalence and distribution of extended-spectrum β-lactamase (ESBL)- and AmpC-producing Escherichia coli from farm environmental samples collected over a 15-month period from two NZ dairy farms with contrasting management practices. Whole genome sequencing was utilised to understand the genomic epidemiology and antimicrobial resistance gene repertoire of a subset of third-generation cephalosporin resistant E. coli isolated in this study. There was a low sample level prevalence of ESBL-producing E. coli (faeces 1.7%; farm dairy effluent, 6.7% from Dairy 4 and none from Dairy 1) but AmpC-producing E. coli were more frequently isolated across both farms (faeces 3.3% and 8.3%; farm dairy effluent 38.4%, 6.7% from Dairy 1 and Dairy 4, respectively). ESBL- and AmpC-producing E. coli were isolated from faeces and farm dairy effluent in spring and summer, during months with varying levels of antimicrobial use, but no ESBL- or AmpC-producing E. coli were isolated from bulk tank milk or soil from recently grazed paddocks. Hybrid assemblies using short- and long-read sequence data from a subset of ESBL- and AmpC-producing E. coli enabled the assembly and annotation of nine plasmids from six E. coli, including one plasmid co-harbouring 12 antimicrobial resistance genes. ESBL-producing E. coli were infrequently identified from faeces and farm dairy effluent on the two NZ dairy farms, suggesting they are present at a low prevalence on these farms. Plasmids harbouring several antimicrobial resistance genes were identified, and bacteria carrying such plasmids are a concern for both animal and public health. AMR is a burden for human, animal and environmental health and requires a holistic “One Health” approach to address.

The epidemiology of AmpC-producing Escherichia coli isolated from dairy cattle faeces on pasture-fed farms

Introduction. Antibiotic use, particularly amoxicillin-clavulanic acid in dairy farming, has been associated with an increased incidence of AmpC-hyperproducing Escherichia coli.Gap statement. There is limited information on the incidence of AmpC-hyperproducing E. coli from seasonal pasture-fed dairy farms.Aim. We undertook a New Zealand wide cross-sectional study to determine the prevalence of AmpC-producing E. coli carried by dairy cattle.Methodology. Paddock faeces were sampled from twenty-six dairy farms and were processed for the selective growth of both extended-spectrum beta-lactamase (ESBL)- and AmpC-producing E. coli. Whole genome sequence analysis was carried out on 35 AmpC-producing E. coli.Results. No ESBL- or plasmid mediated AmpC-producing E. coli were detected, but seven farms were positive for chromosomal mediated AmpC-hyperproducing E. coli. These seven farms were associated with a higher usage of injectable amoxicillin antibiotics. Whole genome sequence analysis of the AmpC-producing E. coli demonstrated that the same strain (<3 SNPs difference) of E. coli ST5729 was shared between cows on a single farm. Similarly, the same strain (≤15 SNPs difference) of E. coli ST8977 was shared across two farms (separated by approximately 425 km).Conclusion. These results infer that both cow-to-cow and farm-to-farm transmission of AmpC-producing E. coli has occurred.