Molecular Epidemiology of Escherichia coli Producing CTX-M and pAmpC 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

Genomic epidemiology of third-generation cephalosporin-resistant Escherichia coli from Argentinian pig and dairy farms reveals animal-specific patterns of co-resistance and resistance mechanisms

Control measures are being introduced globally to reduce the prevalence of antibiotic resistance (ABR) in bacteria on farms. However, little is known about the current prevalence and molecular ecology of ABR in bacterial species with the potential to be key opportunistic human pathogens, such as Escherichia coli, on South American farms. Working with 30 dairy cattle farms and 40 pig farms across two provinces in central-eastern Argentina, we report a comprehensive genomic analysis of third-generation cephalosporin-resistant (3GC-R) E. coli, which were recovered from 34.8% (cattle) and 47.8% (pigs) of samples from fecally contaminated sites. Phylogenetic analysis revealed substantial diversity suggestive of long-term horizontal and vertical transmission of 3GC-R mechanisms. CTX-M-15 and CTX-M-2 were more often produced by isolates from dairy farms, while CTX-M-8 and CMY-2 and co-carriage of amoxicillin/clavulanate resistance and florfenicol resistance were more common in isolates from pig farms. This suggests different selective pressures for antibiotic use in these two animal types. We identified the β-lactamase gene blaROB, which has previously only been reported in the family Pasteurellaceae, in 3GC-R E. coli. blaROB was found alongside a novel florfenicol resistance gene, ydhC, also mobilized from a pig pathogen as part of a new composite transposon. As the first comprehensive genomic survey of 3GC-R E. coli in Argentina, these data set a baseline from which to measure the effects of interventions aimed at reducing on-farm ABR and provide an opportunity to investigate the zoonotic transmission of resistant bacteria in this region.

IMPORTANCE

Little is known about the ecology of critically important antibiotic resistance among bacteria with the potential to be opportunistic human pathogens (e.g., Escherichia coli) on South American farms. By studying 70 pig and dairy cattle farms in central-eastern Argentina, we identified that third-generation cephalosporin resistance (3GC-R) in E. coli was mediated by mechanisms seen more often in certain species and that 3GC-R pig E. coli were more likely to be co-resistant to florfenicol and amoxicillin/clavulanate. This suggests that on-farm antibiotic usage is key to selecting the types of E. coli present on these farms. 3GC-R E. coli and 3GC-R plasmids were diverse, suggestive of long-term circulation in this region. We identified the de novo mobilization of the resistance gene blaROB from pig pathogens into E. coli on a novel mobile genetic element, which shows the importance of surveying poorly studied regions for antibiotic resistance that might impact human health.

One health transmission of fluoroquinolone-resistant Escherichia coli and risk factors for their excretion by dogs living in urban and nearby rural settings

Rates of fluoroquinolone resistance in Escherichia coli, a key opportunistic human pathogen, are problematic. Taking a One Health approach, we investigated the excretion of fluoroquinolone-resistant (FQ-R) E. coli by 600 dogs (303 from rural and 297 from urban environments) recruited from a 50 × 50 km region where we have also surveyed FQ-R E. coli from cattle and from human urine. FQ-R E. coli were detected in faeces from 7.3% (rural) and 11.8% (urban) of dogs. FQ-R E. coli from rural dogs tended to be of sequence types (STs) commonly excreted by cattle, whilst those from urban dogs tended to carry plasmid-mediated quinolone resistance genes, common in human E. coli in our study region. Phylogenetic evidence was obtained for sharing FQ-R E. coli - particularly for STs 10, 162 and 744 - between cattle, dogs and humans. Epidemiological analysis showed a strong association between feeding dogs uncooked meat and the excretion of FQ-R E. coli, particularly for STs 10, 162 and 744. This practice, therefore, could serve as a transmission link for FQ-R E. coli from farmed animals entering the home so we suggest that dogs fed uncooked meat should be handled and housed using enhanced hygiene practices.

Detection and genetic characterization of blaESBL-carrying plasmids of cloacal Escherichia coli isolates from white stork nestlings (Ciconia ciconia) in Spain

OBJECTIVES

This study aimed to characterize Escherichia coli isolates from cloacal samples of white stork nestlings, with a special focus on extended-spectrum β-lactamases (ESBLs)-producing E. coli isolates and their plasmid content.

METHODS

Cloacal samples of 88 animals were seeded on MacConkey-agar and chromogenic-ESBL plates to recover E. coli and ESBL-producing E. coli. Antimicrobial susceptibility was screened using the disc diffusion method, and the genotypic characterization was performed by polymerase chain reaction (PCR) and subsequent sequencing. S1 nuclease Pulsed-Field-Gel-Electrophoresis (PFGE), Southern blotting, and conjugation essays were performed on ESBL-producing E. coli, as well as whole-genome sequencing by short- and long-reads. The four blaESBL-carrying plasmids were completely sequenced.

RESULTS

A total of 113 non-ESBL-producing E. coli isolates were collected on antibiotic-free MacConkey-agar, of which 27 (23.9%) showed a multidrug-resistance (MDR) phenotype, mainly associated with β-lactam-phenicol-sulfonamide resistance (blaTEM/cmlA/floR/sul1/sul2/sul3). Moreover, four white stork nestlings carried ESBL-producing E. coli (4.5%) with the following characteristics: blaSHV-12/ST38-D, blaSHV-12/ST58-B1, blaCTX-M-1/ST162-B1, and blaCTX-M-32/ST155-B1. Whole-genome sequencing followed by Southern blot hybridizations on S1-PFGE gels in ESBL-positive isolates proved that the blaCTX-M-1 gene and one of the blaSHV-12 genes were carried by IncI1/pST3 plasmids, while the second blaSHV-12 gene and the blaCTX-M-32 gene were located on IncF plasmids. The two blaSHV-12 genes and the two blaCTX-M genes had similar but non-identical close genetic environments, as all four genes were flanked by a variety of insertion sequences.

CONCLUSION

The role played by several genetic platforms in the mobility of ESBL genes allows for interchangeability on a remarkably small scale (gene-plasmid-clones), which may support the spread of ESBL genes.

Molecular ecology of highest priority critically important antibiotic resistant Escherichia coli from mammals housed at an urban zoo

OBJECTIVES

Zoos are environments where species of highly valued animals are kept largely separated from others and the wider world. We report the molecular ecology of critically important antibiotic resistant (ABR) Escherichia coli carried by 28 mammalian species housed in a zoo located in an urban residential district.

METHODS

Over 3 months we collected 167 faecal samples from captive mammals and processed for E. coli resistant to third-generation cephalosporins (3GC-R) and fluoroquinolones (FQ-R). Isolates were sequenced using Illumina.

RESULTS

We identified high rates of faecal sample-level positivity, with 50%, 57% and 36% of mammalian species excreting 3GC-R, FQ-R or dual 3GC-R/FQ-R E. coli, respectively. Isolates represented multiple ST and ABR mechanisms; CTX-M-15 and CMY-2 dominated for 3GC-R, and target-site mutation caused 75% of FQ-R. We identified multiple examples of ABR E. coli transmission between mammalian species in separate enclosures, and a variant of the epidemic plasmid pCT within the zoo. There was no evidence for ABR E. coli leaving the zoo, based on comparative analysis with E. coli from humans, cattle and dogs isolated from the 50 × 50 km region in which the zoo is located. Amoxicillin/clavulanate was the most widely used antibiotic in the zoo, and we identified four widely disseminated amoxicillin/clavulanate resistance mechanisms, including a previously unreported inhibitor-resistant TEM, and the carbapenemase OXA-181.

CONCLUSIONS

We conclude that the zoo studied here is a 'melting pot' for the selection and circulation of 3GC-R and FQ-R E. coli, but these circulating E. coli appear captive within the zoo.

Characterization of Escherichia coli and Other Enterobacterales Resistant to Extended-Spectrum Cephalosporins Isolated from Dairy Manure in Ontario, Canada

Extended-spectrum cephalosporins (ESCs) resistance genes, such as bla_CTX-M, bla_CMY, and bla_SHV, have been found regularly in bacteria from livestock. However, information on their distribution in dairy cattle in Canada and on the associated genome sequences of ESC-resistant Enterobacterales is sparse. In this study, the diversity and distribution of ESC-resistant Escherichia coli throughout manure treatments in six farms in Southern Ontario were assessed over a one-year period, and their ESC-resistance plasmids were characterized. The manure samples were enriched using selective media. The resulting isolates were screened via polymerase chain reaction for bla_CTX-M, bla_CMY, and bla_SHV. No E. coli carrying bla_SHV were detected. Escherichia coli (n = 248) carrying bla_CTX-M or bla_CMY underwent whole-genome sequencing using an Illumina MiSeq/NextSeq. These isolates were typed using multilocus sequence typing (MLST) and their resistance gene profiles. A subset of E. coli (n = 28) were sequenced using Oxford Nanopore Technologies. Plasmids were assembled using Unicycler and characterized via the resistance genes pattern, replicon type, plasmid MLST, phylogenetic analysis, and Mauve alignments. The recovery of ESC-resistant Enterobacterales (18 species, 8 genera) was drastically reduced in manure outputs. However, multiple treatment stages were needed to attain a significant reduction. 62 sequence types were identified, with ST10, ST46, ST58, ST155, ST190, ST398, ST685, and ST8761 being detected throughout the treatment pipeline. These STs overlapped with those found on multiple farms. The ESC-resistance determinants included CTX-M-1, -14, -15, -17, -24, -32, -55, and CMY-2. The plasmids carrying bla_CTX-M were more diverse than were the plasmids carrying bla_CMY. Known "epidemic plasmids" were detected for both bla_CTX-M and bla_CMY. IMPORTANCE The increase in antimicrobial resistance is of concern for human and animal health, especially when resistance is conferred to extended-spectrum cephalosporins, which are used to treat serious infections in both human and veterinary medicine. Bacteria carrying extended-spectrum cephalosporin resistance genes, including bla_CTX-M and bla_CMY, are frequently found in dairy manure. Manure treatment influences the loads and diversity of bacteria, including those carrying antimicrobial resistance genes, such as Enterobacterales and Escherichia coli. Any bacteria that survive the treatment process are subsequently applied to the environment. Enterobacterales carrying bla_CTX-M or bla_CMY can contaminate soil and crops consumed by humans and animals, thereby increasing the potential for antimicrobial resistance genes to integrate into the human gut microflora through horizontal gene transfer. This furthers the dissemination of resistance. Therefore, it is imperative to understand the effects manure treatments have on ESC-resistance in environmentally applied manure.

Surveillance for multidrug resistant Escherichia coli carriage in cattle, dogs and humans reveals predominance of CMY-2, CTX-M-15 and CTX-M-9 groups of β-lactamases

Global spread of antimicrobial multidrug resistance (MDR) in human and veterinary medicine relies upon diagnostics, surveillance and stewardship to guide mitigation. Utilizing surveillance of fecal samples from our service area for detecting MDR Escherichia coli carriage in humans (2143), dogs (627), and cattle (130), we found isolates resistant to third/fourth generation cephems present in 3.7 %, 13.1 %, and 51.5 %, respectively. CMY-2, CTX-M-15-like and CTX-M9 group genes in descending order were predominant in all hosts and accounted for 83.3 % of non-wild-type gene targets. MDR carriage mirrored cephem non-susceptibility rates as published in annual antibiograms for humans and dogs; notably, no carbapenem-resistant carriage isolates were detected. Given the scale of MDR E. coli carriage in cattle (14X) and dogs (3.5X) compared to humans, bench-marking of the resistance gene pool by host species utilizing regional One Health surveillance may aid in assessing occupational and geographic risks for acquiring resistance and for monitoring of mitigation strategies.

Occurrence and transfer characteristics of blaCTX-M genes among Escherichia coli in anaerobic digestion systems treating swine waste

Livestock waste is a known reservoir of Escherichia coli (E. coli) carrying clinically important CTX-M-type extended-spectrum β-lactamase genes (bla_CTX-M), however, the occurrence and transfer characteristics of bla_CTX-M genes during anaerobic digestion (AD) remain unclear. Herein, four full-scale and two parallel lab-scale AD systems treating swine waste under ambient and mesophilic conditions were investigated by both molecular- and culture-based methods to reveal the occurrence and transfer behaviors of bla_CTX-M genes during AD. Real-time TaqMan polymerase chain reaction revealed 1.3 × 10⁴-6.8 × 10⁵ and 3.0 × 10⁴-7.0 × 10⁵ copies/mL of bla_CTX-M groups 1 and 9 in all feeding substrates. While AD reduced the absolute abundance of groups 1 and 9 by 0.63-2.24 and 0.08-1.30 log (P < 0.05), 5.0 × 10²-4.1 × 10³ and 1.1 × 10⁴-3.5 × 10⁴ copies/mL of groups 1 and 9 remained in the anaerobic effluent, respectively. In total, 141 bla_CTX-M-carrying E. coli isolates resistant to cefotaxime were obtained from the AD reactors. Whole-genome sequencing showed that bla_CTX-M-65 mainly carried by E. coli ST155 was the most frequently detected group 9 subtype in the feeding substrate; whereas bla_CTX-M-14 associated with the dominant clones E. coli ST6802 and ST155 became the major subtype in AD effluent. Furthermore, bla_CTX-M-14 was flanked by ΔIS26 upstream and ΔIS903B downstream. The ΔIS26-bla_CTX-M-14-ΔIS903B element was mainly located on the IncHI2 plasmid in E. coli ST48 and ST6802 and also the IncFIB plasmid in ST155 in anaerobic effluent. Conjugation assays showed that the plasmids harboring bla_CTX-M-14 could be successfully transferred at a frequency of 10^-3-10^-2 cells per recipient cell. This study revealed that bla_CTX-M genes remained in both the full-scale and lab-scale AD effluents of swine waste. Thus, additional efforts should be implemented to block the discharge and spread of antibiotic resistance genes to the environment.

Molecular ecology and risk factors for third-generation cephalosporin-resistant Escherichia coli carriage by dogs living in urban and nearby rural settings

Objectives

To compare faecal third-generation cephalosporin-resistant (3GC-R) Escherichia coli isolates from dogs living in a city and in a rural area ∼30 km away; to compare isolates from dogs, cattle and humans in these regions; and to determine risk factors associated with 3GC-R E. coli carriage in these two cohorts of dogs.

Methods

Six hundred dogs were included, with faecal samples processed to recover 3GC-R E. coli using 2 mg/L cefotaxime. WGS was by Illumina and risk factor analyses were by multivariable linear regression using the results of an owner-completed survey.

Results

3GC-R E. coli were excreted by 20/303 rural and 31/297 urban dogs. The dominant canine 3GC-R ST was ST963 (bla_CMY-2), which also accounted for 25% of CMY-2-producing E. coli in humans. Phylogenetic overlap between cattle and rural dog CTX-M-14-producing E. coli ST117 was observed as well as acquisition of pMOO-32-positive E. coli ST10 by a rural dog, a plasmid common on cattle farms in the area. Feeding raw meat was associated with carrying 3GC-R E. coli in rural dogs, but not in urban dogs, where swimming in rivers was a weak risk factor.

Conclusions

Given clear zoonotic potential for resistant canine E. coli, our work suggests interventions that may reduce this threat. In rural dogs, carriage of 3GC-R E. coli, particularly CTX-M producers, was phylogenetically associated with interaction with local cattle and epidemiologically associated with feeding raw meat. In urban dogs, sources of 3GC-R E. coli appear to be more varied and include environments such as rivers.

Evidence that faecal carriage of resistant Escherichia coli by 16-week-old dogs in the United Kingdom is associated with raw feeding

We report a survey (August 2017 to March 2018) and risk factor analysis of faecal carriage of antibacterial-resistant (ABR) Escherichia coli in 223 16-week-old dogs in the United Kingdom. Raw feeding was associated with the presence of fluoroquinolone-resistant (FQ-R) E. coli and those resistant to tetracycline, amoxicillin, and streptomycin, but not to cefalexin. Whole genome sequencing of 36 FQ-R E. coli isolates showed a wide range of sequence types (STs), with almost exclusively mutational FQ-R dominated by ST744 and ST162. Comparisons between E. coli isolates from puppies known to be located within a 50 × 50 km region with those isolated from human urinary tract infections (isolated in parallel in the same region) identified an ST744 FQ-R lineage that was carried by one puppy and caused one urinary tract infection. Accordingly, we conclude that raw feeding is associated with carriage of ABR E. coli in dogs even at 16 weeks of age and that bacteria carried by puppies are shared with humans. We therefore suggest that those who feed their dogs raw meat seriously consider the potential ABR-transmission threat their pet may become as a result and deploy appropriate hygiene practices in mitigation.

Factors influencing the detection of antibacterial-resistant Escherichia coli in faecal samples from individual cattle

AIMS

To investigate whether on-farm antibacterial usage (ABU), environmental antibacterial-resistant (ABR) Escherichia coli prevalence, sampling and sample handling methodologies are associated with ABR E. coli positivity in individual faecal samples from dairy heifers.

METHODS AND RESULTS

Three hundred and sixty-four heifers from 37 farms were sampled via rectal or faecal pat sampling. Samples were stored at -80°C for variable periods before microbiological analysis. Data analysis was done through a multilevel, multivariable logistic regression approach. Individual rectal samples had increased odds of positivity for amoxicillin-, cefalexin- and tetracycline-resistant E. coli. Sample storage for 6-12 months was associated with decreased odds of finding amoxicillin- and tetracycline-resistant E. coli. On-farm ABU had little influence, and environmental ABR E. coli prevalence had no significant influence on the odds of sample-level positivity for ABR E. coli.

CONCLUSIONS

Sampling methodology and sample handling have a greater association than on-farm factors with the detection of ABR E. coli in individual faecal samples from dairy heifers.

SIGNIFICANCE AND IMPACT OF THE STUDY

Sampling and storage methodologies should be considered carefully at the point of designing ABR surveillance studies in livestock and their environments and, where possible, these methodologies should be standardized between and within future studies.

Limited phylogenetic overlap between fluoroquinolone-resistant Escherichia coli isolated on dairy farms and those causing bacteriuria in humans living in the same geographical region

BACKGROUND

Our primary aim was to test whether cattle-associated fluoroquinolone-resistant (FQ-R) Escherichia coli found on dairy farms are closely phylogenetically related to those causing bacteriuria in humans living in the same 50 × 50 km geographical region suggestive of farm-human sharing. Another aim was to identify risk factors for the presence of FQ-R E. coli on dairy farms.

METHODS

FQ-R E. coli were isolated during 2017-18 from 42 dairy farms and from community urine samples. Forty-two cattle and 489 human urinary isolates were subjected to WGS, allowing phylogenetic comparisons. Risk factors were identified using a Bayesian regularization approach.

RESULTS

Of 489 FQ-R human isolates, 255 were also third-generation-cephalosporin-resistant, with strong genetic linkage between aac(6')Ib-cr and blaCTX-M-15. We identified possible farm-human sharing for pairs of ST744 and ST162 isolates, but minimal core genome SNP distances were larger between farm-human pairs of ST744 and ST162 isolates (71 and 63 SNPs, respectively) than between pairs of isolates from different farms (7 and 3 SNPs, respectively). Total farm fluoroquinolone use showed a positive association with the odds of isolating FQ-R E. coli, while total dry cow therapy use showed a negative association.

CONCLUSIONS

This work suggests that FQ-R E. coli found on dairy farms have a limited impact on community bacteriuria within the local human population. Reducing fluoroquinolone use may reduce the on-farm prevalence of FQ-R E. coli and this reduction may be greater when dry cow therapy is targeted to the ecology of resistant E. coli on the farm.

Prevalence and Characterization of ESBL/AmpC Producing Escherichia coli from Fresh Meat in Portugal

The present study aimed to characterize the extended-spectrum β-lactamases and plasmid-mediated AmpC β-lactamases (ESBL/PMAβ) among Escherichia coli producers isolated from beef, pork, and poultry meat collected at retail, in Portugal. A total of 638 meat samples were collected and inoculated on selective medium for the search of E. coli resistant to 3rd generation cephalosporins. Isolates were characterized by antimicrobial susceptibility testing, molecular assays targeting ESBL/AmpC, plasmid-mediated quinolone resistance (PMQR), and plasmid-mediated colistin resistance (PMCR) encoding genes. The highest frequency of E. coli non-wild type to 3rd generation cephalosporins and fluoroquinolones was observed in broiler meat (30.3% and 93.3%, respectively). Overall, a diversity of acquired resistance mechanisms, were detected: bla_ESBL [bla_CTX-M-1 (n = 19), bla_CTX-M-15 (n = 4), bla_CTX-M-32 (n = 12), bla_CTX-M-55 (n = 8), bla_CTX-M-65 (n = 4), bla_CTX-M-27 (n = 2), bla_CTX-M-9 (n = 1), bla_CTX-M-14 (n = 11), bla_SHV-12 (n = 27), bla_TEM-52 (n = 1)], bla_PMAβ [bla_CMY-2 (n = 8)], PMQR [qnrB (n = 27), qnrS (n = 21) and aac(6')-Ib-type (n = 4)] and PMCR [mcr-1 (n = 8)]. Our study highlights that consumers may be exposed through the food chain to multidrug-resistant E. coli carrying diverse plasmid-mediated antimicrobial resistance genes, posing a great hazard to food safety and a public health risk.

OmpF Downregulation Mediated by Sigma E or OmpR Activation Confers Cefalexin Resistance in Escherichia coli in the Absence of Acquired β-Lactamases

Cefalexin is a widely used first-generation cephalosporin, and resistance in Escherichia coli is caused by extended-spectrum (e.g., CTX-M) and AmpC β-lactamase production and therefore frequently coincides with third-generation cephalosporin resistance. However, we have recently identified large numbers of E. coli isolates from human infections, and from cattle, where cefalexin resistance is not β-lactamase mediated. Here, we show, by studying laboratory-selected mutants, clinical isolates, and isolates from cattle, that OmpF porin disruption or downregulation is a major cause of cefalexin resistance in E. coli. Importantly, we identify multiple regulatory mutations that cause OmpF downregulation. In addition to mutation of ompR, already known to downregulate OmpF and OmpC porin production, we find that rseA mutation, which strongly activates the sigma E regulon, greatly increases DegP production, which degrades OmpF, OmpC, and OmpA. Furthermore, we reveal that mutations affecting lipopolysaccharide structure, exemplified by the loss of GmhB, essential for lipopolysaccharide heptosylation, also modestly activate DegP production, resulting in OmpF degradation. Remarkably, given the critical importance attached to such systems for normal E. coli physiology, we find evidence for DegP-mediated OmpF downregulation and gmhB and rseA loss-of-function mutation in E. coli isolates derived from human infections. Finally, we show that these regulatory mutations enhance the ability of group 1 CTX-M β-lactamase to confer reduced carbapenem susceptibility, particularly those mutations that cause OmpC in addition to OmpF downregulation.

Role played by the environment in the emergence and spread of antimicrobial resistance (AMR) through the food chain

The role of food-producing environments in the emergence and spread of antimicrobial resistance (AMR) in EU plant-based food production, terrestrial animals (poultry, cattle and pigs) and aquaculture was assessed. Among the various sources and transmission routes identified, fertilisers of faecal origin, irrigation and surface water for plant-based food and water for aquaculture were considered of major importance. For terrestrial animal production, potential sources consist of feed, humans, water, air/dust, soil, wildlife, rodents, arthropods and equipment. Among those, evidence was found for introduction with feed and humans, for the other sources, the importance could not be assessed. Several ARB of highest priority for public health, such as carbapenem or extended-spectrum cephalosporin and/or fluoroquinolone-resistant Enterobacterales (including Salmonella enterica), fluoroquinolone-resistant Campylobacter spp., methicillin-resistant Staphylococcus aureus and glycopeptide-resistant Enterococcus faecium and E. faecalis were identified. Among highest priority ARGs bla CTX -M, bla VIM, bla NDM, bla OXA -48-like, bla OXA -23, mcr, armA, vanA, cfr and optrA were reported. These highest priority bacteria and genes were identified in different sources, at primary and post-harvest level, particularly faeces/manure, soil and water. For all sectors, reducing the occurrence of faecal microbial contamination of fertilisers, water, feed and the production environment and minimising persistence/recycling of ARB within animal production facilities is a priority. Proper implementation of good hygiene practices, biosecurity and food safety management systems is very important. Potential AMR-specific interventions are in the early stages of development. Many data gaps relating to sources and relevance of transmission routes, diversity of ARB and ARGs, effectiveness of mitigation measures were identified. Representative epidemiological and attribution studies on AMR and its effective control in food production environments at EU level, linked to One Health and environmental initiatives, are urgently required.