Thomas W. Maddox

Cross-sectional study of antimicrobial-resistant bacteria in horses. Part 1: Prevalence of antimicrobial-resistant Escherichia coli and methicillin-resistant Staphylococcus aureus

REASONS FOR PERFORMING STUDY The increasing prevalence of antimicrobial-resistant bacteria such as methicillin-resistant Staphylococcus aureus (MRSA) and antimicrobial-resistant Escherichia coli represents a significant problem. However, the carriage of such bacteria by horses in the UK has not been well characterised. OBJECTIVES To estimate the prevalence of nasal carriage of MRSA and faecal carriage of antimicrobial-resistant E. coli amongst horses in the general equine community of the mainland UK. METHODS A cross-sectional study of horses recruited by 65 randomly selected equine veterinary practices was conducted, with nasal swabs and faecal samples collected. Faecal samples were cultured for antimicrobial-resistant E. coli. Nasal swabs were cultured for staphylococcal species; methicillin-resistant isolates identified as S. aureus were characterised by SCCmec and spa gene typing. Multilevel logistic regression models were used to calculate prevalence estimates with adjustment for clustering at practice and premises levels. Spatial variation in risk of antimicrobial resistance was also examined. RESULTS In total, 650 faecal samples and 678 nasal swabs were collected from 692 horses located on 525 premises. The prevalence of faecal carriage of E. coli with resistance to any antimicrobial was 69.5% (95% CI 65.9-73.1%) and the prevalence of extended-spectrum β-lactamase (ESBL)-producing E. coli was 6.3% (95% CI 4.1-9.6%). The prevalence of nasal carriage of MRSA was 0.6% (95% CI 0.2-1.5%). Spatial analysis indicated variation across the UK for risk of carriage of resistant and multidrug-resistant (resistant to more than 3 antimicrobial classes) E. coli. CONCLUSIONS AND POTENTIAL RELEVANCE Carriage of MRSA by horses in the community appears rare, but the prevalence of antimicrobial-resistant E. coli (including ESBL-producing E. coli) is higher. A high prevalence of antimicrobial-resistant bacteria could have significant health implications for the horse population of the UK.

Prevalence of antimicrobial-resistant Escherichia coli in dogs in a cross-sectional, community-based study

The prevalence of carriage of antimicrobial-resistant (AMR) and extended-spectrum β-lactamase (ESBL)-producing Escherichia coli was determined in 183 healthy dogs from a semi-rural community in Cheshire. Isolates were tested against a panel of antimicrobials and by PCR to detect resistance genes. In the suspected ESBL-producing isolates, the presence of blaSHV, blaTEM, blaCTX-M and blaAmpC genes was determined by PCR and sequencing. A total of 53 (29 per cent, 95 per cent confidence interval [CI] 22.4 to 35.5 per cent) dogs carried at least one AMR E coli isolate. Twenty-four per cent (95 per cent CI 17.9 to 30.2 per cent) of dogs carried isolates resistant to ampicillin, 19.7 per cent (95 per cent CI 13.9 to 25.4 per cent) to tetracycline and 16.9 per cent (95 per cent CI 11.5 to 22.4 per cent) to trimethoprim. A blaTEM gene was detected in 39 of 54 ampicillin-resistant isolates, a tet(B) gene in 12 of 45 tetracycline-resistant isolates, and a dfr gene in 22 of 33 trimethoprim-resistant isolates. Multidrug-resistant isolates were demonstrated in 15 per cent (28 of 183; 95 per cent CI 10.1 to 20.5 per cent) of dogs. Nine suspected ESBL-producing E coli were isolated, of which only one was confirmed by double disc diffusion testing. Two of these isolates carried the blaTEM-1 gene and seven carried the blaCMY-2 gene.

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.

Carriage of Staphylococcus species in the veterinary visiting dog population in mainland UK: Molecular characterisation of resistance and virulence

This study investigated the prevalence of nasal carriage of staphylococci in dogs and determined the characteristics of the isolates. A total of 724 dogs from 87 veterinary practices across the mainland UK were screened for carriage of Staphylococcus spp. All isolates were examined for meticillin resistance (MR) and the presence of the mecA gene investigated in those isolates showing resistance. All coagulase-positive staphylococci and MR coagulase-negative staphylococci (MRCoNS) were subjected to antimicrobial susceptibility testing. Spa typing and DNA microarray analysis of resistance and virulence genes was carried out on all MR S. aureus (MRSA) and a subset of meticillin susceptible S. aureus (MSSA). Staphylococci were isolated from 399 (55.1%) of the dogs; only seven (1%) carried MRSA, all of which were identified as the dominant UK healthcare-associated strain (EMRSA-15, ST22). MSSA was identified in 47 (6.5%) dogs, the sequence types of which have been suggested as precursors to successful MRSA clones. Forty (5.5%) dogs carried MRCoNS, while no dogs carried MR S. pseudintermedius, although this is increasingly reported in mainland Europe. Resistance to antimicrobials among the isolates varied between species, with multidrug resistance (MDR) in 87.5% of MRCoNS and 21.8% of coagulase positive staphylococci. Microarray analysis of MRSA and a subset of MSSA isolates identified numerous virulence genes associated with pathogenesis, which are commonly identified in isolates of human origin. However, no isolates carried Panton-Valentine leukocidin (PVL) genes. This study suggests that MRSA carriage is low in the vet visiting dog population, but there is a diverse range of virulence and resistance determinants in canine S. aureus and MRCoNS isolates.

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.

Management of cranial cruciate ligament rupture in small dogs: A questionnaire study

OBJECTIVES To survey the current management of cranial cruciate ligament rupture in small dogs (<15 kg) by veterinarians. METHODS A questionnaire was distributed to veterinarians attending the British Veterinary Orthopaedic Association Spring meeting and British Small Animal Veterinary Association Annual Congress which took place in April 2010. Respondents were surveyed on their management of small dogs with cranial cruciate ligament rupture. RESULTS Immediate surgical management was chosen by 15.5% of the respondents. Following that, 77.6% of respondents suggested that case management would depend on severity of lameness (81%), age (72.6%), bodyweight (70.4%), degree of instability (64.8%), and duration of lameness (64.0%). Conservative management included non-steroidal anti-inflammatory drugs (91.1%), short leash walks (91.1%), weight loss (89.0%), hydrotherapy (53.6%), physiotherapy (41.9%), and cage rest (24.2%). Where surgical management was chosen, 71.4% would perform the procedure rather than refer it to another practice. Surgical techniques included extra-capsular stabilisation (63.4%), corrective osteotomies (32.9%), and intra-articular stabilisation (6.8%). The demographic characteristics of the responding veterinarians had no effect on their initial management of the case. General practice veterinarians were less likely to perform a corrective osteotomy than to refer the case, but were no less likely to perform an extracapsular technique. CLINICAL SIGNIFICANCE Conservative management is still widely used for treatment of cranial cruciate ligament rupture in dogs weighing less than 15 kg; this is in agreement with previous publications on the management of this condition in small dogs.

Postoperative Complications after Surgical Management of Incomplete Ossification of the Humeral Condyle in Dogs

Objective: To describe incidence and type of postoperative complications in the surgical management of incomplete ossification of the humeral condyle (IOHC) and identify any risk factors associated with development of these complications. Study Design: Case series. Methods: Clinical records of dogs (n=57) that had prophylactic transcondylar screw insertion for treatment of IOHC (79 elbows) at 6 UK referral centers were reviewed. Signalment, presentation, surgical management, postoperative care, and complications were recorded. Postoperative complications were divided into seroma, surgical site infections (SSI) and implant complications. Results: Spaniel breeds and entire males were overrepresented. The overall complication rate was 59.5%. Seroma (n=25) and SSI (24) were the most commonly encountered complications. Implant failure occurred in 2 dogs. Labrador retrievers were at greater risk of developing a postoperative complication than other breeds (P=.03). Increasing bodyweight was a significant risk factor for development of a SSI (P=.03). Placement of the transcondylar screw in lag fashion rather than as a positional screw reduced the incidence of postoperative SSI (P=.007). Conclusions: Surgical management of IOHC is associated with a high rate of postoperative complications. Placement of the transcondylar screw in lag fashion may limit postoperative complications and warrants further consideration.OBJECTIVE To describe incidence and type of postoperative complications in the surgical management of incomplete ossification of the humeral condyle (IOHC) and identify any risk factors associated with development of these complications. STUDY DESIGN Case series. METHODS Clinical records of dogs (n=57) that had prophylactic transcondylar screw insertion for treatment of IOHC (79 elbows) at 6 UK referral centers were reviewed. Signalment, presentation, surgical management, postoperative care, and complications were recorded. Postoperative complications were divided into seroma, surgical site infections (SSI) and implant complications. RESULTS Spaniel breeds and entire males were overrepresented. The overall complication rate was 59.5%. Seroma (n=25) and SSI (24) were the most commonly encountered complications. Implant failure occurred in 2 dogs. Labrador retrievers were at greater risk of developing a postoperative complication than other breeds (P=.03). Increasing bodyweight was a significant risk factor for development of a SSI (P=.03). Placement of the transcondylar screw in lag fashion rather than as a positional screw reduced the incidence of postoperative SSI (P=.007). CONCLUSIONS Surgical management of IOHC is associated with a high rate of postoperative complications. Placement of the transcondylar screw in lag fashion may limit postoperative complications and warrants further consideration.

Carriage of antimicrobial resistant Escherichia coli in dogs: Prevalence, associated risk factors and molecular characteristics

Resistance to antimicrobials, in particular that mediated by extended spectrum β-lactamases (ESBL) and AmpC β-lactamases are frequently reported in bacteria causing canine disease as well as in commensal bacteria, which could be a potential health risk for humans they come into contact with. This cross-sectional study aimed to estimate the prevalence and investigate the molecular characteristics of ESBL and plasmid encoded AmpC (pAmpC)-producing E. coli in the mainland UK vet-visiting canine population and, using responses from detailed questionnaires identify factors associated with their carriage. Faecal samples were cultured for antimicrobial resistant (AMR), ESBL and pAmpC-producing E. coli. A subset of ESBL and pAmpC-producing isolates were subjected to multi-locus sequence typing and DNA microarray analyses. Multivariable logistic regression analysis was used to construct models to identify risk factors associated with multidrug resistant (MDR, resistance to three or more antimicrobial classes), fluoroquinolone resistant, ESBL and AmpC-producing E. coli. AMR E.coli were isolated from 44.8% (n=260) of samples, with 1.9% and 7.1% of samples carrying ESBL and pAmpC-producing E. coli, respectively. MDR E. coli were identified in 18.3% of samples. Recent use of antimicrobials and being fed raw poultry were both identified as risk factors in the outcomes investigated. A number of virulence and resistance genes were identified, including genes associated with extra-intestinal and enteropathogenic E. coli genotypes. Considering the close contact that people have with dogs, the high levels of AMR E. coli in canine faeces may be a potential reservoir of AMR bacteria or resistance determinants.

COMPARISON BETWEEN SHOULDER COMPUTED TOMOGRAPHY AND CLINICAL FINDINGS IN 89 DOGS PRESENTED FOR THORACIC LIMB LAMENESS

Computed tomography (CT) is an established technique for detecting shoulder lesions in dogs, however the clinical significance of shoulder CT lesions often remains uncertain. The purposes of this retrospective study were to describe the prevalence of CT lesions in both shoulder joints for 89 dogs presenting with thoracic limb lameness and to compare CT lesions with clinical characteristics. For all included dogs, results of a full orthopedic examination, other diagnostic tests, and signalment data were available in medical records. Multilevel, multivariable logistic regression was used to test clinical significance of the most prevalent CT lesions and determine factors associated with their presence. Computed tomographic lesions were detected in one or both shoulder joints for 51/89 dogs (57.3%). Mineralization of one or more surrounding peri-articular soft-tissue structures was identified in 31.5% of dogs, with supraspinatus muscle/tendon mineralization being the most frequently identified (24.7%). The prevalence of humeral head osteochondrosis was 9 and 21.3% of dogs had shoulder osteoarthritis. Border collies (odds ratio [OR] 9.3; 95% CI 1.39-62.1, P = 0.02) and dogs with shoulder pain (OR 4.3; 95% CI 1.08-17.1, P = 0.04) had increased risk of osteochondrosis lesions. Border collies (OR 8.4; 95% CI 1.27-55.6; P = 0.03) and older animals (OR 1.04; 95% CI 1.02-1.1, P < 0.001) had increased risk of osteoarthritis lesions. Female entire dogs had an increased risk of supraspinatus mineralization lesions (OR 6.8; 95% CI 1.55-29.5, P = 0.01). Findings indicated that shoulder CT lesions are common in dogs with thoracic limb lameness, and that some CT lesions are not associated with shoulder pain.

Late presentation of canine nasal tumours in a UK referral hospital and treatment outcomes

OBJECTIVES To determine the computed tomographic stage of dogs with nasal tumours in a UK referral population, and whether stage, time to referral and treatment correlates with outcome. METHODS Retrospective review of clinical records and computed tomography scans of dogs with nasal tumours. RESULTS Dogs (n=78) presented to a referral practice in the UK with suspected nasal tumours are presented with more late stage tumours than dogs in the USA and Japan. Length of time from initial presentation to referral did not correlate with tumour stage at diagnosis. Median survival times for radiotherapy-treated dogs in this population are equivalent to those previously reported for late stage nasal tumours. CLINICAL SIGNIFICANCE Dogs with nasal tumours are presented late in the course of disease in the North West of England. Dogs with clinical signs consistent with a nasal tumour should have timely imaging and biopsy, in order to make prompt treatment decisions. Although survival times are comparable with previous reports and radiotherapy is a valid treatment option for dogs with late stage disease, better outcomes are likely to be achievable with earlier treatment.