Reduced antibacterial drug resistance and bla_CTX-M β-lactamase gene carriage in cattle-associated Escherichia coli at low temperatures, at sites dominated by older animals and on pastureland: implications for surveillance

Abstract

16Little is known about the drivers of critically important antibacterial resistance in 17 species with zoonotic potential present on farms (e.g. CTX-M ꞵ-lactamase-positive 18 Escherichia coli). There is also debate about the influence of farms on the circulation 19 of resistance in local human populations. This was a two-year surveillance study on 20 53 dairy farms. E. coli positive for blaCTX-M were detected in 224/4145 (5.4%) of all 21 samples from faecally-contaminated sites. E. coli positive for blaCTX-M were more 22 prevalent (98/631; 15.5%) in calf samples and less prevalent (12/630; 1.9%) in 23 samples collected from pastureland, including publicly accessible sites. Multilevel, 24 multivariable logistic regression showed antibiotic dry cow therapeutic choice to be 25 associated with risk of blaCTX-M positivity, including use of cefquinome or framycetin; 26 74% of blaCTX-M-positive E. coli were framycetin-resistant. Low temperature was 27 associated with low risk of blaCTX-M positivity. This was additional to the effect of 28 temperature on total E. coli density, a finding with profound implications for 29 surveillance. There was no evidence that study farms had a significant impact on 30 circulating blaCTX-M plasmids in the local human population: across 296 fully 31 sequenced E. coli isolates, two cattle isolates shared blaCTX-M plasmids with eight 32 urinary isolates collected in parallel.33 34 Antimicrobial resistance (AMR) -and particularly antibacterial resistance (ABR) -is a 35 significant global challenge. Many countries are implementing plans to reduce the 36 use of antibacterial drugs (ABs) in food-producing animals. For example, the most 37 recent UK five-year National Action Plan includes a target to reduce AB use (ABU) in 38the treatment of food-producing animals by 25% (1). In Europe, AB sales for food-39 producing animals fell by 20% from 2011 to 2016 (2). In the UK dairy industry, 40 overall ABU dropped from 24 mg/kg in 2015 to 17 mg/kg in 2017 (3, 4). In 2018, 41 additional industry-led policies were enforced in the UK that aim to almost eliminate 42 the use of highest priority critically important antimicrobials (HP-CIAs) such as third-43 and fourth-generation cephalosporins (3GCs and 4GCs) and fluoroquinolones on 44 dairy farms. One reason for reducing ABU in farming is the belief that such 45 measures will reduce the prevalence of ABR bacteria carried by farm animals. 46 However, there is a need for better data on drivers of ABR in farming. More 47 granularity of understanding is required concerning the risks of using individual ABs 48 and other management practices. This is especially important in terms of drivers of 49 HP-CIA resistance. One key focus is on 3GC resistance in Escherichia coli, a 50 species commonly found in animal faeces and considered one of the most significant 51 potential zoonotic threats to humans (5). 523GC-resistance is increasingly common in E. coli causing infections in humans (6) 53 and is also found in farmed and domestic animals around the world (7). The...

Molecular epidemiology of Escherichia coli producing CTX-M and plasmid AmpC-type β-lactamases from dairy farms identifies a dominant plasmid encoding CTX-M-32 but no evidence for transmission to humans in the same geographical region

“…Of these, 4145 samples were positive for detectable levels of E. coli and 384 samples were positive for growth of CTX-R E. coli . 18 From these, 1226 colonies were taken forward for PCR testing for possible cephalosporinase genes of interest (GOIs): bla CTX-M (groups 1, 2, 8, 9 and 25), bla CMY , bla DHA , and bla SHV . Over half (648/1226; 52.7%) of all CTX-R isolates tested were found to harbour bla CTX-M genes.…”

“…Details of farm sample collection and microbiological analysis has recently been reported. 18 In brief, samples of faecally contaminated sites were collected using sterile overshoes on 53 dairy farms located in South West England between January 2017 and December 2018. Samples were plated onto TBX agar (Sigma-Aldrich, Poole, UK) containing 16 mg/L cephalexin.…”

Limited Phylogenetic Overlap Between Fluoroquinolone-Resistant Escherichia coli Isolated on Dairy Farms and those Causing Bacteriuria in Humans Living in the Same Geographical Region

“…We have recently reported a survey of resistant E. coli in faecal samples from 53 dairy farms in South West England. 23 Of 4145 faecal samples collected from vicinities near animals, 263 were positive for FQ-R E. coli , representing 49 of 53 farms surveyed. 23 Of 42 farms located within a 50 x 50 km region, which included the homes of the people providing the urinary samples discussed above, 245 FQ-R E. coli isolates from this earlier study 23 were taken forward for further analyses, representing one unique isolate from each positive sample.…”

“…23 Of 4145 faecal samples collected from vicinities near animals, 263 were positive for FQ-R E. coli , representing 49 of 53 farms surveyed. 23 Of 42 farms located within a 50 x 50 km region, which included the homes of the people providing the urinary samples discussed above, 245 FQ-R E. coli isolates from this earlier study 23 were taken forward for further analyses, representing one unique isolate from each positive sample. Multiplex PCRs showed that aac(6’)Ib-cr (found to be highly prevalent in the human urinary E. coli isolates) was entirely absent from the farm isolates and only nine isolates carried a PMQR gene (5 qnrS , 2 qnrA and 2 qnrD) .…”

“…Collection of FQ-R E. coli from dairy farms in South West England has been described previously. 23 Briefly, 4145 samples were collected from faecally contaminated sites around 53 dairy farms (49 farms yielded FQ-R E. coli ). Samples were collected at monthly visits between January 2017 and December 2018.…”