Antimicrobial resistance in commensal faecal Escherichia coli of hospitalised horses

Antimicrobial susceptibility of Salmonella and Escherichia coli from equids sampled in the NAHMS 2015-16 equine study and association of management factors with resistance

Several studies have investigated antimicrobial resistance (AMR) in Salmonella spp. and Escherichia coli isolated from hospitalized horses, but studies conducted on community-based populations of equids are limited. The factors associated with AMR in these bacteria in the general horse population are not well understood. The primary objective of our study was to estimate the prevalence of Salmonella and describe antimicrobial susceptibility of Salmonella and E. coli from equids across the United States. The second objective was to identify associations between health management and biosecurity practices and AMR. Fecal samples submitted from 1357 equids on 199 operations were tested for Salmonella, identifying 27 positive samples with 29 isolates belonging to 18 serotypes. Fecal sample and operation-level prevalence of Salmonella was 2.0% (27/1357) and 7.0% (14/199), respectively. Most (25/29) isolates were pan-susceptible while four isolates exhibited resistance, three of which were multidrug resistant. Of the 721 samples cultured for E. coli, 85% (613/721) were positive. Eighty-six percent of the E. coli isolates recovered were pan-susceptible (529/612). Ten isolates were intermediate to one antimicrobial drug and susceptible to all others. Seventy-three E. coli isolates (11.9%, SE=1.3) were resistant to one or more antimicrobials, corresponding to a 33.0% (64/194) operation-level prevalence. Resistance to sulfonamide drugs was most common with 63 isolates (10.3%) resistant to sulfisoxazole, 57 of which (9.3%) were resistant to trimethoprim-sulfamethoxazole. MDR in E. coli was rare (1.8%, SE=0.5). Univariate and multivariable regression were used to evaluate associations between health management and biosecurity questionnaire items and AMR in E. coli. The outcome modeled was resistance to any of the 14 tested antimicrobials. Depending on the operation type, operations with greater than 20 resident equids were significantly associated with resistance. In addition, performance operations were significantly associated with resistance when compared to farm/ranch operations. Operations with feed containers that prevent fecal contamination and those that had treated any equids for illness or injury were associated with a lower AMR. The study results suggest that equids in the general population appear to pose low risk of shedding antimicrobial resistant strains of Salmonella and E. coli, and therefore low transmission potential to other equids, animals, humans, or the environment. However, it is prudent to practice good hand hygiene to prevent spread of Salmonella as well as AMR, and to protect both animal and human health. Despite study limitations, potential management factors that may influence prevalence and prevent spread of AMR shed by equids were identified.

Longitudinal study of the short- and long-term effects of hospitalisation and oral trimethoprim-sulfadiazine administration on the equine faecal microbiome and resistome

BACKGROUND

Hospitalisation and antimicrobial treatment are common in horses and significantly impact the intestinal microbiota. Antimicrobial treatment might also increase levels of resistant bacteria in faeces, which could spread to other ecological compartments, such as the environment, other animals and humans. In this study, we aimed to characterise the short- and long-term effects of transportation, hospitalisation and trimethoprim-sulfadiazine (TMS) administration on the faecal microbiota and resistome of healthy equids.

METHODS

In a longitudinal experimental study design, in which the ponies served as their own control, faecal samples were collected from six healthy Welsh ponies at the farm (D0-D13-1), immediately following transportation to the hospital (D13-2), during 7 days of hospitalisation without treatment (D14-D21), during 5 days of oral TMS treatment (D22-D26) and after discharge from the hospital up to 6 months later (D27-D211). After DNA extraction, 16S rRNA gene sequencing was performed on all samples. For resistome analysis, shotgun metagenomic sequencing was performed on selected samples.

RESULTS

Hospitalisation without antimicrobial treatment did not significantly affect microbiota composition. Oral TMS treatment reduced alpha-diversity significantly. Kiritimatiellaeota, Fibrobacteres and Verrucomicrobia significantly decreased in relative abundance, whereas Firmicutes increased. The faecal microbiota composition gradually recovered after discontinuation of TMS treatment and discharge from the hospital and, after 2 weeks, was more similar to pre-treatment composition than to composition during TMS treatment. Six months later, however, microbiota composition still differed significantly from that at the start of the study and Spirochaetes and Verrucomicrobia were less abundant. TMS administration led to a significant (up to 32-fold) and rapid increase in the relative abundance of resistance genes sul2, tetQ, ant6-1a, and aph(3")-lb. lnuC significantly decreased directly after treatment. Resistance genes sul2 (15-fold) and tetQ (six-fold) remained significantly increased 6 months later.

CONCLUSIONS

Oral treatment with TMS has a rapid and long-lasting effect on faecal microbiota composition and resistome, making the equine hindgut a reservoir and potential source of resistant bacteria posing a risk to animal and human health through transmission. These findings support the judicious use of antimicrobials to minimise long-term faecal presence, excretion and the spread of antimicrobial resistance in the environment. Video Abstract.

Innovative next-generation therapies in combating multi-drug-resistant and multi-virulent Escherichia coli isolates: insights from in vitro, in vivo, and molecular docking studies

Despite notable advances in vaccine and antimicrobial therapies, treatment failure has been increasingly reported worldwide. Of note, multi-drug-resistant (MDR) Escherichia coli (E. coli) strains have a considerable share in the evolution of this crisis. So, current practice guidelines are directed towards complementary and alternative therapies. Therefore, we evaluated the antibacterial and antivirulence activities of curcumin, thymol, and eugenol essential oils (EOs) as well as EOs-EOs and EOs-antibiotics interactions on MDR and multi-virulent E. coli isolates. Unfortunately, MDR E. coli could be isolated with a prevalence rate of 95.6% (86/90). Additionally, the majority of our isolates harbored both fimH (95.6%) and ompA (91.1%) genes, and half of them (45/90) were multi-virulent. Interestingly, all the tested EOs, especially curcumin, exhibited inhibitory activities against all MDR and multi-virulent E. coli isolates. The addition of thymol enhanced the antibacterial activities of curcumin and eugenol. Moreover, the activities of piperacillin/tazobactam and imipenem were increased by adding any one of the tested EOs. Regarding the antivirulence activities of the tested EOs, the cell surfaces of treated E. coli isolates under transmission electron microscope (TEM) were uneven. The cells appeared damaged and lost their appendages. Furthermore, EOs strongly reduced the transcription of ompA and fimH genes. The antibacterial and antivirulence activities of the used EOs were confirmed by in silico and mice protection assays. Hereby, we introduced the promising uses of curcumin, thymol, and eugenol oils as complementary and alternative therapies for combating MDR and multi-virulent E. coli isolates. KEY POINTS: • Our promising results confirmed that we were right for renewed interest of EOs. • The EOs, especially curcumin, can be used to prevent treatment failure. • We supposed a new pharmaceutical formulation of antibiotic powders dissolved in EOs.

Antibiotic prescription practices and attitudes towards the use of antimicrobials among veterinarians in the City of Tshwane, South Africa

BACKGROUND

Understanding the prescription practices and attitudes of veterinarians towards antimicrobial resistance (AMR) is crucial in guiding efforts to curb AMR. This study investigated prescription practices and attitudes towards AMR among veterinarians in the City of Tshwane, South Africa.

METHODS

Out of the 83 veterinarians invited to participate in the study, 54 signed the consent form and completed the questionnaire. Percentages and 95% confidence intervals of all categorical variables were computed. A multinomial logistic model was used to identify predictors of the veterinarians' view towards antimicrobial use.

RESULTS

The majority (88%) of respondents indicated that improper use of antimicrobials contributed to selection for AMR. Veterinarians relied on clinical signs and symptoms (88%, 48/54) to decide whether to prescribe antimicrobials or not. However, the choice of antimicrobials depended on the cost of antibiotics (77.2%), route of administration (81.5%), and risk of potential adverse reactions (79.6%; 43/54). Many (61.5%) veterinarians were of the view that often antimicrobials are appropriately prescribed and 88.7% agreed that improper use of antimicrobials contributed to selection for antimicrobial resistant organisms. Compared to females, males were significantly more likely (Relative Risk Ratio (RRR) = 9.0; P = 0.0069) to agree rather than to "neither agree nor disagree" that their colleagues over-prescribed antimicrobials.

CONCLUSIONS

The decisions to prescribe antimicrobials by the veterinarians depended on clinical presentation of the patient, while the choice of antimicrobial depended on cost, route of administration, and risk of potential adverse reactions. Most veterinarians were of the view that antimicrobials were prescribed judiciously.

Antimicrobial resistance profiles and phylogenetic groups of Escherichia coli isolated from healthy Thoroughbred racehorses in Japan

In this study, we investigated the occurrence of antimicrobial resistance in commensal Escherichia coli isolated from healthy Thoroughbred (TB) racehorses in Japan. A total of 212 fecal samples were individually collected from TB racehorses from March 2017 to August 2018 at Japan Racing Association training centers. E. coli was isolated by using selective agar media, deoxycholate-hydrogen sulfide-lactose (DHL) and eosin methylene blue (EMB). A total of 417 E. coli isolates were examined against 10 antimicrobial agents by using the broth microdilution method. The 417 E. coli isolates were phylogenetically grouped using a multiplex polymerase chain reaction. The highest proportion of resistance was observed for streptomycin (30.9%, 129/417) followed by ampicillin (19.4%, 81/417), trimethoprim (15.8%, 66/417), tetracycline (8.4%, 35/417), chloramphenicol (2.6%, 11/417), kanamycin (1.2%, 5/417), nalidixic acid (0.5%, 2/417), cefazolin (0.2%, 1/417), colistin (0.2%, 1/417), and gentamycin (0%). Multidrug-resistant (MDR) E. coli was detected in 7.9% (33/417) of isolates. The proportions of resistance against ampicillin, streptomycin, kanamycin, and chloramphenicol and of multidrug-resistant phenotypes in E. coli belonging to phylogenetic group B2 were significantly higher than those of other groups. This study clarified the distribution of antimicrobial-resistant (AMR) E. coli in Japanese racehorses. A continuous monitoring program for antimicrobial resistance is required to control the spread of AMR bacteria in racehorses.

Identification of risk factors associated with antimicrobial resistance in equine fecal Escherichia coli isolates

Antimicrobial resistance is a growing global problem that will need a multinational collaborative effort to overcome this serious challenge. The aim of the study is to investigate the potential risk factors associated with the prevalence and distribution of antimicrobial-resistance genes (ARGs) of Escherichia coli isolates obtained from equine fecal samples. One hundred and eighteen horses from different geographical locations and management systems were enrolled in the study and a questionnaire containing information about each individual horse was designed and filled. The enrolled horses belonged to 2 main categories (Hospitalized horses (n = 31), and Non hospitalized horses (n = 87)). In total, 103 E. coli isolates were collected from the 118 horse fecal samples. Genes that are responsible for resistance to β-lactams, tetracyclines, aminoglycosides, and trimethoprim were detected using uniplex and multiplex polymerase chain reaction (PCR). The prevalence of antimicrobial resistance was significantly higher in hospitalized horses compared to non-hospitalized ones (p ≤ .05), particularly against (trimethoprim, doxycycline, oxytetracycline, and amoxicillin-clavulanic acid). The most prevalent antimicrobial-resistant genes were aminoglycoside resistant genes (strA, strB, and aadA) in percentages; 89%, 85%, and 84%, respectively. Statistical analysis revealed a significant association between risk factors and occurrence of ARGs (p ≤ .05). Significant risk factors include the last treatment and history of antimicrobial administration, breed of horses, use of horses, type of diet fed for horses, practice management and history of last illness. Tetracycline-resistance gene (tetA) was 23 times more likely to be found in the Arabian and local breeds of horses compared to English and warmblood breed. TetA is also 8 times more likely to be found in horses that were fed a natural diet compared to other horses that were fed manufactured/ processed feed. In conclusion, E. coli bacterium can harbor high resistance to different classes of antimicrobials which increases the risk of potential uncontrolled transmission of the multi-drug resistant E. coli bacterium to veterinarians and horse handlers, as well as to the equine population itself.

The effect of different antimicrobial treatment regimens on the faecal shedding of ESBL-producing Escherichia coli in horses

Fourth-generation cephalosporins can select for extended-spectrum β-lactamase (ESBL)-producing Enterobacteriaceae in horses, but it is unknown to what extent this occurs compared to penicillin/gentamicin combination treatment. The objective was to evaluate the effect of different antimicrobial treatments on faecal shedding and diversity of ESBL-producing Escherichia coli (ESBL-EC) in horses. Upon hospital admission, 86 horses in need of antimicrobial treatment or prophylaxis were randomly allocated to receive penicillin and gentamicin (PG) or cefquinome (CEF). Untreated horses were included as controls (NOAMD, n = 33). Faecal samples from admission (T1), 3 days after admission (T2), and faecal swabs 28 days after discharge (T3) were cultured selectively. Differences in prevalence (T1, T2, T3) and counts (T1, T2) of ESBL-EC between groups and over time were analysed. On a subset of ESBL-EC isolates, antimicrobial susceptibility testing (n = 45) and whole-genome sequencing followed by SNP-analysis (n = 46) were performed. The prevalence of ESBL-EC at T1 was 12 % with no significant difference between groups. In all groups, significantly higher carriage rates were observed at T2 and T3 compared to T1. Carriage and counts of ESBL-EC at T2 were significantly higher in treated compared to untreated horses. There was no significant difference between PG and CEF at any time points. Despite a large genetic diversity, indistinguishable ESBL clones were observed in different horses over time. In conclusion, antimicrobial treatment and hospitalization increased prevalence and counts of ESBL-EC, and transmission of ESBL-EC in the hospital was suspected. These findings highlight the importance of antimicrobial stewardship and infection control practices in equine medicine.

Differences in isolation rate and antimicrobial susceptibility of bacteria isolated from foals with sepsis at admission and after ≥48 hours of hospitalization

Background

Antimicrobial treatment protocols for foals with sepsis that do not improve clinically often are adjusted based on bacteriological and antimicrobial susceptibility testing results from samples collected at hospital admission.

Objectives

To evaluate whether hospitalization for ≥48 hours affects bacteriological and antimicrobial susceptibility testing results.

Animals

Two‐hundred sixty‐seven foals <30 days of age admitted to a neonatal intensive care unit and diagnosed with sepsis.

Methods

Medical records were reviewed retrospectively to identify foals with sepsis and positive bacteriological cultures. Results from samples collected at hospital admission were compared to those collected ≥48 hours after admission. Logistic regression for clustered data and exact logistic regression were used for statistical analysis.

Results

Three‐hundred fifty‐three unique bacterial isolates were obtained from 231 foals at hospital admission and 92 unique bacterial isolates were obtained from 57 foals after ≥48 hours of hospitalization. Relative isolation frequency after ≥48 hours of hospitalization increased for Acinetobacter spp., 0.6% versus 3.3% (odds ratio [OR], 7.63; 95% confidence interval [CI], 1.28‐45.45); Enterococcus spp., 4.8% versus 19.6% (OR, 5.37; 95% CI, 2.64‐10.90); Klebsiella spp., 5.1% versus 10.9% (OR, 2.27; 95% CI, 1.05‐4.89); Pseudomonas spp., 3.0% versus 7.6% (OR, 3.49; 95% CI, 3.49‐240.50); and Serratia spp., 3.0% versus 5.4% (OR, 20.23; 95% CI, 2.20‐186.14). Bacteria isolated after ≥48 hours of hospitalization were less susceptible to all tested antimicrobial drugs, except for imipenem.

Conclusions and Clinical Importance

Decreased antimicrobial susceptibility of bacteria isolated after ≥48 hours of hospitalization provides a rationale for repeated bacteriological culture and susceptibility testing in hospitalized foals with sepsis.

Extended-spectrum β-lactamase-producing Escherichia coli isolated from healthy Thoroughbred racehorses in Japan

Extended-spectrum β-lactamase-producing Escherichia coli (ESBLEC) have become a major health concern in both human and veterinary medicine. These bacteria could become a critical problem in equine medicine due to the limited number of antimicrobial drugs available. However, there are no previous reports of ESBLEC isolated from horses in Japan. The objectives of this study were to investigate the occurrence of ESBLEC isolated from feces in healthy Thoroughbred racehorses in Japan. Feces samples were collected from 147 healthy Thoroughbred racehorses by equine veterinarians at the Japan Racing Association (103 from Miho Training Center and 44 from Ritto Training Center) between March 2017 and April 2018. Samples were screened for ESBLECs using MacConkey agar supplemented with 1 µg/ml cefotaxime. Detection of ESBL genes was performed by PCR and confirmed by DNA sequencing. Horizontal transmission was demonstrated by conjugation assay. In this study, 24 ESBLECs were isolated from twelve horse feces samples (8.2%). All ESBLECs harbored bla_CTX-M-2, and both bla_TEM-1 and bla_CTX-M-2 were detected in nine isolates (37.5%). ESBLECs showed resistance to all β-lactam antibiotics (100%) tested, followed by trimethoprim (66.7%), streptomycin (62.5%), tetracycline (25.0%), and oxytetracycline (25.0%). Horizontal transmission was successfully demonstrated by conjugation assay in eight of 13 isolates, and bla_CTX-M-2 was detected by PCR in all transconjugants. This study showed that racehorses in Japan are potential reservoirs of ESBLECs.

Characterization of intestinal Escherichia coli isolated from calves with diarrhea due to rotavirus and coronavirus

PURPOSE

To address more information about changes in commensal Escherichia coli during virus intestinal infection, we characterized 30 faecal E. coli isolates from calves (21 to 60 days old) with diarrhea due to rotavirus and coronavirus, which received, before diagnosis, tetracycline, gentamicin and enrofloxacin drugs.

METHODOLOGY

Clermont's phylogenetic classification; presence of genes for curli, cellulose, fimbriae (F4, F5, F6, F18, F41); and antimicrobial susceptibility were used to characterize the isolates. Disk diffusion technique and PCR were used as methodologies.

RESULTS

E. coli isolates from calves with diarrhea were phylogenetically classified as B1 (70%, 21/30), B2 (3.33%, 1/30), C (3.33%, 1/30), D (3.33%, 1/30), E (13.33%, 4/30) and unknown (6.7 %; 2/30), whereas E. coli isolates from the control group were classified only as B1 (83.3%, 25/30), E (10 %; 3/30) and unknown (6,7 %; 2/30). E. coli isolates from calves with diarrhea showed a much higher resistance profile with 16 (53.3%) multiresistant isolates. Only isolates (30%-9/30) from diarrheic calves were also positive for fimbriae, specifically 16.7% (5/30) for F5 and 13.3% (4/30) for F18.

CONCLUSION

To sum up, E. coli isolates from calves with diarrhea showed differences in relation to the control group, confirming changes in commensal E. coli during virus intestinal infection. It can be emphasized that some care should be taken to manage diarrheic calves: the pathological agent must be diagnosed prior to treatment; antibacterial treatment should be with antimicrobials with a different mechanism of action; and finally, treated animals should be maintained separately from others because they can carry micro-organisms with a resistant profile.

Antimicrobial resistance in horses

Cajsa Isgren and colleagues from the University of Liverpool discuss issues around the problem of antimicrobial resistance in bacteria associated with horses and introduce a new surveillance initiative.

Antimicrobial resistance and the presence of extended-spectrum beta-lactamase genes in Escherichia coli isolated from the environment of horse riding centers

The aim of the study was to determine the antimicrobial resistance profile and the occurrence of extended-spectrum beta-lactamase genes and to analyze the genetic diversity of Escherichia coli strains isolated from the environment of horse riding centers. The study was conducted using E. coli strains isolated from the air, manure, and horse nostril swabs in three horse riding centers differing in the system of horse keeping-stable (OJK Pegaz and KJK Szary) and free-range (SKH Nielepice). Resistance to antibiotics was determined using the disk-diffusion method, and the PCR technique was employed to detect the extended-spectrum β-lactamase (ESBL) genes, while the genetic diversity of strains was assessed by rep-PCR. A total of 200 strains were collected during the 2-year study, with the majority isolated from KJK Szary, while the smallest number was obtained from SKH Nielepice. The strains were mostly resistant to ampicillin, aztreonam, and ticarcillin. The tested strains were most frequently resistant to one or two antibiotics, with a maximum of ten antimicrobials at the same time. Two multidrug-resistant (MDR) strains were detected in OJK Pegaz while in KJK Szary there were two MDR and one extensively drug-resistant (XDR) strain. The ESBL mechanism was most frequently observed in OJK Pegaz (20.31% of strains) followed by KJK Szary (15.53% of strains) and SKH Nielepice (15.15% of strains). Among the ESBL-determining genes, only blaTEM and blaCTXM-9 were detected-blaTEM was mostly found in KJK Szary (53.40% of strains), while the second detected gene-blaCTXM-9-was most frequent in SKH Nielepice (6.06% of strains). The rep-PCR genotyping showed high variation among the analyzed strains, whereas its degree differed between the studied facilities, indicating that the type of horse keeping (stable vs. free-range) affects the genetic diversity of the E. coli strains. Having regard to the fact that the tested strains of E. coli were derived from non-hospitalized horses that were not treated pharmacologically, we can assume that the observed antimicrobial resistance may be of both-natural origin, i.e., not the result of the selection pressure, and acquired, the source of which could be people present in the horse riding facilities, the remaining horses which were not included in the study, and air, as well as water, fodder, and litter of the animals. Therefore, it can be concluded that the studied horses are the source of resistant E. coli and it is reasonable to continue monitoring the changes in antimicrobial resistance in those bacteria.

An epidemiologic study of antimicrobial resistance of Staphylococcus species isolated from equine samples submitted to a diagnostic laboratory

Background

Antimicrobial resistance limits traditional treatment options and increases costs. It is therefore important to estimate the magnitude of the problem so as to provide empirical data to guide control efforts. The aim of this study was to investigate the burden and patterns of antimicrobial resistance (AMR) among equine Staphylococcus samples submitted to the University of Kentucky Veterinary Diagnostic Laboratory (UKVDL) from 1993 to 2009. Retrospective data of 1711 equine Staphylococcus samples submitted to the UKVDL during the time period 1993 to 2009 were included in the study. Antimicrobial susceptibility testing, that included 16 drugs, were performed using cultures followed by the Kirby-Bauer disk diffusion susceptibility test. The proportion of resistant isolates by animal breed, species of organism, sample source, and time period were computed. Chi-square and Cochran-Armitage trend tests were used to identify significant associations and temporal trends, respectively. Logistic regression models were used to investigate predictors of AMR and multidrug resistance (MDR).

Results

A total of 66.3% of the isolates were resistant to at least one antimicrobial, most of which were Staphylococcus aureus (77.1%), while 25.0% were MDR. The highest level of resistance was to penicillins (52.9%). Among drug classes, isolates had the highest rate of AMR to at least one type of β-lactams (49.2%), followed by aminoglycosides (30.2%). Significant (p < 0.05) associations were observed between odds of AMR and horse breed, species of organism and year. Similarly, significant (p < 0.05) associations were identified between odds of MDR and breed and age. While some isolates had resistance to up to 12 antimicrobials, AMR profiles featuring single antimicrobials such as penicillin were more common than those with multiple antimicrobials.

Conclusion

Demographic factors were significant predictors of AMR and MDR. The fact that some isolates had resistance to up to 12 of the 16 antimicrobials assessed is quite concerning. To address the high levels of AMR and MDR observed in this study, future studies will need to focus on antimicrobial prescription practices and education of both practitioners and animal owners on judicious use of antimicrobials to slow down the development of resistance.

Cross-sectional study of antimicrobial-resistant bacteria in horses. Part 2: Risk factors for faecal carriage of antimicrobial-resistant Escherichia coli in horses

REASONS FOR PERFORMING STUDY

The increasing prevalence of antimicrobial resistant bacteria such as antimicrobial-resistant and extended spectrum β-lactamase (ESBL)-producing Escherichia coli represents a significant problem for human and veterinary medicine. Despite this, the risk factors for faecal carriage of such bacteria by horses in the UK, particularly those in the wider community, have not been well described.

OBJECTIVES

To characterise the risk factors for faecal carriage of antimicrobial-resistant E. coli amongst horses in the mainland UK.

METHODS

A cross-sectional study of horses recruited by 65 randomly selected equine veterinary practices was conducted, with a faecal sample collected and self-administered questionnaire completed by the horse owner. Faecal samples were cultured for antimicrobial-resistant E. coli, with isolates confirmed as E. coli having their antimicrobial resistance profile determined. Multilevel, multivariable logistic regression models were used to investigate risk factors for the carriage of antimicrobial-resistant E. coli in the sample population.

RESULTS

Faecal samples and completed questionnaires were obtained for 627 horses located on 475 premises. Recent hospitalisation, contact with specific types of nonequid animals, the type of premises, the surrounding land use, the reason for veterinary treatment received in the last 6 months and antimicrobial treatment in the previous 10 days were identified as risk factors for many of the antimicrobial-resistance outcomes considered. Being stabled on the same yard as a recently hospitalised horse was identified as a risk factor for increased risk of carriage of ESBL-producing E. coli.

CONCLUSIONS AND POTENTIAL RELEVANCE

Increasing antimicrobial resistance may have significant health implications for the horse population of Great Britain. This form of epidemiological investigation highlights potential risk factors that may be controlled to limit the extent of the problem.

Longitudinal study of antimicrobial-resistant commensal Escherichia coli in the faeces of horses in an equine hospital

The increasing prevalence of antimicrobial resistance in bacteria represents a considerable problem for human and veterinary medicine, causing complications in the treatment of infections. Resistance in Escherichia coli from horses has been documented in commensal and pathogenic strains, but little information exists regarding the prevalence of such bacteria in hospitalised horses or associated risk factors. A longitudinal cohort study was conducted of 103 horses admitted to a referral equine hospital for more than 48 h, with faecal samples collected on hospital admission and subsequently every two days until discharge. Horses undergoing radioactive gamma scintigraphic examination, un-weaned foals and mares with un-weaned foals were excluded. Data were collected from enrolled animals, including antimicrobial treatment history and hospitalisation details. Samples were cultured for resistant E. coli; isolates had their antimicrobial resistance profile determined. High sample prevalence for resistant E. coli was identified for all antimicrobials examined except co-amoxiclav. The prevalence of resistance was consistently lower at admission, rising to a peak 4 days post-admission. Risk factors were analysed using multilevel, multivariable modelling, which identified significant clustering of resistance outcomes within horses. For all outcomes except trimethoprim resistance, the day the sample was obtained was significant, with increased risk of resistance for samples taken on day 2 or later. Antimicrobial treatment in the previous seven days and increased total daily dosages of cotrimoxazole prescribed in the hospital in the previous 24-48 h were associated with increased risk. Location within the hospital and admission reason were significant risk factors for some resistance outcomes. High levels of multidrug-resistant E. coli (47.7% of samples) and extended spectrum β-lactamase-producing E. coli (27.3% of samples) were recovered; such bacteria could significantly complicate treatment if they were the cause of infection and may represent a risk to personnel in close contact with hospitalised horses.