Special Issue-Resistant Staphylococci in Animals

Staphylococci figure prominently among those bacteria demonstrating antimicrobial resistance (AMR) and are thus responsible for significant problems concerning the treatment of the animals and humans that they infect [...].

Climbing the Integration Ladder: A Case Study on an Interdisciplinary and Case-Based Approach to Teaching General Pathology, Parasitology and Microbiology in the Veterinary Curriculum

The School of Veterinary Medicine, University College Dublin, Ireland, restructured the teaching of general pathology, parasitology, and microbiology in third year in 2018 as part of the development of an outcome-based curriculum. A new integrated teaching module was created, called Veterinary Pathobiology, which encompassed the three paraclinical subjects, worth 20 ECTS credits. Subject integration was driven and supported by case-based learning (CBL) activities, and practical classes, which were aimed at facilitating the understanding of basic disease processes, infectious agents, and the application of diagnostic tests. The disciplines maintained their identities within lectures which were aligned by content. The restructuring led to a reduction of contact hours by 20% and of assessment time by 40%. The examinations included integrated questions with an emphasis on the material students had covered in their CBL. Despite positive outcomes, which included equivalent examination scores and positive written feedback by students on teaching and learning, understanding, assessment, relevance, CBL, group work, and generic skills, the average scores for overall student satisfaction dropped dramatically in the second academic year of implementation. This followed the introduction of new regulations by the University relating to student progression, which was capped at "carrying" 10 ECTS credits, thus preventing students that failed the new module from progressing. Other criticisms of the new module by students included too little communication on the changes implemented in its first iteration and a workload perceived to be too heavy. Further restructuring is therefore necessary. This study highlights the process/pitfalls of integration/curricular innovation.

Metabolomic changes in Mycobacterium avium subsp. paratuberculosis (MAP) challenged Holstein-Friesian cattle highlight the role of serum amino acids as indicators of immune system activation

INTRODUCTION

Paratuberculosis, commonly known as Johne's disease, is a chronic granulomatous infection of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). Clinical signs, including reduced milk yields, weight loss and diarrhoea, are typically absent until 2 to 6 years post exposure.

OBJECTIVES

To identify metabolomic changes profiles of MAP challenged Holstein-Friesian (HF) cattle and correlate identified metabolites to haematological and immunological parameters.

METHODS

At approximately 6 weeks of age, calves (n = 9) were challenged with 3.8 × 10⁹ cells of MAP (clinical isolate CIT003) on 2 consecutive days. Additional unchallenged calves (n = 9) formed the control group. The study used biobanked serum from cattle sampled periodically from 3- to 33-months post challenge. The assessment of sera using flow infusion electrospray high resolution mass spectrometry (FIE-HRMS) for high throughput, sensitive, non-targeted metabolite fingerprinting highlighted differences in metabolite levels between the two groups.

RESULTS

In total, 25 metabolites which were differentially accumulated in MAP challenged cattle were identified, including 20 which displayed correlation to haematology parameters, particularly monocyte levels.

CONCLUSION

The targeted metabolites suggest shifts in amino acid metabolism that could reflect immune system activation linked to MAP and as well as differences in phosphocholine levels which could reflect activation of the Th1 (tending towards pro-inflammatory) immune response. If verified by future work, selected metabolites could be used as biomarkers to diagnose and manage MAP infected cattle.

Quantitative microbial risk assessment associated with ready-to-eat salads following the application of farmyard manure and slurry or anaerobic digestate to arable lands

Farmyard manure and slurry (FYM&S) and anaerobic digestate are potentially valuable soil conditioners providing important nutrients for plant development and growth. However, these organic fertilisers may pose a microbial health risk to humans. A quantitative microbial risk assessment (QMRA) model was developed to investigate the potential human exposure to pathogens following the application of FYM&S and digestate to agricultural land. The farm-to-fork probabilistic model investigated the fate of microbial indicators (total coliforms and enterococci) and foodborne pathogens in the soil with potential contamination of ready-to-eat salads (RTEs) at the point of human consumption. The processes examined included pathogen inactivation during mesophilic anaerobic digestion (M-AD), post-AD pasteurisation, storage, dilution while spreading, decay in soil, post-harvest washing processes, and finally, the potential growth of the pathogen during refrigeration/storage at the retail level in the Irish context. The QMRA highlighted a very low annual probability of risk (P_annual) due to Clostridium perfringens, norovirus, and Salmonella Newport across all scenarios. Mycobacterium avium may result in a very high mean P_annual for the application of raw FYM&S, while Cryptosporidium parvum and pathogenic E. coli showed high P_annual, and Listeria monocytogenes displayed moderate P_annual for raw FYM&S application. The use of AD reduces this risk; however, pasteurisation reduces the P_annual to an even greater extent posing a very low risk. An overall sensitivity analysis revealed that mesophilic-AD's inactivation effect is the most sensitive parameter of the QMRA, followed by storage and the decay on the field (all negatively correlated to risk estimate). The information generated from this model can help to inform guidelines for policymakers on the maximum permissible indicator or pathogen contamination levels in the digestate. The QMRA can also provide the AD industry with a safety assessment of pathogenic organisms resulting from the digestion of FYM&S.

Evaluation of pathogen concentration in anaerobic digestate using a predictive modelling approach (ADRISK)

Farmyard manure and slurry (FYM&S) is a valuable feedstock for anaerobic digestion (AD) plants. However, FYM&S may contain high concentrations of pathogens, and complete inactivation through the AD process is unlikely. Thus, following land application of digestate, pathogens may contaminate a range of environmental media posing a potential threat to public health. The present study aimed to combine primary laboratory data with literature-based secondary data to develop an Excel-based exposure assessment model (ADRISK) using a gamma generalised linear model to predict the final microorganism count in the digestate. This research examines the behaviour of a suite of pathogens (Cryptosporidium parvum, norovirus, Mycobacterium spp., Salmonella spp., Listeria monocytogenes, Clostridium spp., and pathogenic Escherichia coli) and indicators (total coliforms, E. coli, and enterococci) during mesophilic anaerobic digestion (M-AD) at 37 °C, pre/post-AD pasteurisation, and after a period of storage (with/without lime) for different feedstock proportions (slurry:food waste: 0:1, 1:3, 2:1, and 3:1). ADRISK tool simulations of faecal indicator bacteria levels across all scenarios show that the digestate can meet the EU standard without pasteurisation if the AD runs at 37 °C or a higher temperature with a higher C:N ratio (recipe 3) and a hydraulic retention time ≥ 7 days. The storage of digestate also reduced levels of microorganisms in the digestate. The Irish pasteurisation process (60 °C for 4 days), although more energy-intensive, is more effective than the EU pasteurisation (70 °C for 1 h) specification. Pre-AD pasteurisation was more effective for C. parvum, norovirus, Mycobacterium thermoresistibile. However, post-AD literature-based pasteurisation is most likely to assure the safety of the digestate. The information generated from this model can inform policy-makers regarding the optimal M-AD process parameters necessary to maximise the inactivation of microorganisms, ensuring adverse environmental impact is minimised, and public health is protected.

Quantitative microbial human exposure model for faecal indicator bacteria and risk assessment of pathogenic Escherichia coli in surface runoff following application of dairy cattle slurry and co-digestate to grassland

Animal waste contains high numbers of microorganisms and therefore can present a potential biological threat to human health. During episodic rainfall events resulting in runoff, microorganisms in the waste and soil may migrate into surface runoff, contaminating surface water resources. A probabilistic human exposure (HE) model was created to determine exposure to faecal indicator bacteria (FIB): total coliforms (TC), E. coli and enterococci following application of bio-based fertiliser (dairy cattle slurry, digestate) to grassland; using a combination of experimental field results and literature-based data. This step was followed by a quantitative microbial risk assessment (QMRA) model for pathogenic E. coli based on a literature-based dose-response model. The results showed that the maximum daily HE (HE_daily) is associated with E. coli for unprocessed slurry (treatment T1) on day 1, the worst-case scenario where the simulated mean HE_daily was calculated as 2.84 CFU day ^-1. The results indicate that the overall annual probability of risk (P_annual) of illness from E. coli is very low or low based on the WHO safe-limit of P_annual as 10 ^-6. In the worst-case scenario, a moderate risk was estimated with simulated mean P_annual as 1.0 × 10 ^-5. Unpasteurised digestate application showed low risk on day 1 and 2 (1.651 × 10 ^-6, 1.167 × 10 ^-6, respectively). Pasteurised digestate showed very low risk in all scenarios. These results support the restriction imposed on applying bio-based fertiliser if there is any rain forecast within 48 h from the application time. This study proposes a future extension of the probabilistic model to include time, intensity, discharge, and distance-dependant dilution factor. The information generated from this model can help policymakers ensure the safety of surface water sources through the quality monitoring of FIB levels in bio-based fertiliser.

Risk assessment of Escherichia coli in bioaerosols generated following land application of farmyard slurry

Transfer of Escherichia coli in bioaerosols to humans during and shortly after the land application of farmyard slurry may pose human health hazards, but it has not been extensively explored to date. The present study developed a quantitative risk assessment model for E. coli through the air exposure route. The probabilistic model assessed the predicted number of microorganisms in the air (PN_air) to which humans may be exposed. A Gaussian air dispersion model was used to calculate the concentration of E. coli transmitted through aerosols. Human exposure (HE) to E. coli was estimated using a Monte Carlo simulation approach. This research predicted the mean HE as 26 CFU day^-1 (95th percentile 263 CFU day^-1) and suggests the importance of keeping a distance of at least 100 m for the residential population from land spreading activities. However, the simulated mean daily or annual (once a year application) risk of 2.65 × 10^-7 person^-1 year^-1 due to land application of slurry indicates very low occupational risk for farmworkers not equipped with the personal protective equipment (PPE), who are potentially exposed to E. coli indirectly. The model found that the decay constant of E. coli in air, duration of decay, and bio-aerosolisation efficiency factor (top three) could influence HE to airborne E. coli. Furthermore, this research recommends an average time lag of at least 2.5 h following the application of farmyard slurry to the field before humans access the field again without PPE, allowing the airborne pathogen to decay, thereby ensuring occupational safety. The model suggested that the bio-aerosolisation efficiency factor (E) for other pathogens requires further investigation. The information generated from this model can help to assess likely exposure from bioaerosols triggered by land application of farmyard slurry.

A Bayesian inference approach to quantify average pathogen loads in farmyard manure and slurry using open-source Irish datasets

Farm-to-fork quantitative microbial risk assessments (QMRA) typically start with a preliminary estimate of initial concentration (C_initial) of microorganism loading at farm level, consisting of an initial estimate of prevalence (P) and the resulting pathogen levels in animal faeces. An average estimation of the initial concentration of pathogens can be achieved by combining P estimates in animal populations and the levels of pathogens in colonised animals' faeces and resulting cumulative levels in herd farmyard manure and slurry (FYM&S). In the present study, 14 years of data were collated and assessed using a Bayesian inference loop to assess the likely P of pathogens. In this regard, historical and current survey data exists on P estimates for a number of pathogens, including Cryptosporidium parvum, Mycobacterium avium subspecies paratuberculosis (MAP), Salmonella spp., Clostridium spp., Campylobacter spp., pathogenic E. coli, and Listeria monocytogenes in several species (cattle, pigs, and sheep) in Ireland. The results revealed that Cryptosporidium spp. has potentially the highest mean P (P_mean) (25.93%), followed by MAP (15.68%) and Campylobacter spp. (8.80%) for cattle. The P_mean of E. coli is highest (7.42%) in pigs, while the P_mean of Clostridium spp. in sheep was estimated to be 7.94%. C_initial for Cryptosporidium spp., MAP., Salmonella spp., Clostridium spp., and Campylobacter spp. in cattle faeces were derived with an average of 2.69, 4.38, 4.24, 3.46, and 3.84 log₁₀ MPN g ^-1, respectively. Average C_initial of Cryptosporidium spp., Salmonella spp., Clostridium spp., and E. coli in pig slurry was estimated as 1.27, 3.12, 3.02, and 4.48 log₁₀ MPN g ^-1, respectively. It was only possible to calculate the average C_initial of Listeria monocytogenes in sheep manure as 1.86 log₁₀ MPN g ^-1. This study creates a basis for future farm-to-fork risk assessment models to base initial pathogen loading values for animal faeces and enhance risk assessment efforts.

Toxigenic Corynebacterium ulcerans associated with upper respiratory infections in cats and dogs

OBJECTIVES

To describe infection in companion animals with the zoonotic pathogen Corynebacterium ulcerans and to determine its prevalence in clinically-affected and healthy animals.

MATERIALS AND METHODS

The clinical presentation and treatment of three cases of C. ulcerans infection is described. Two studies to determine C. ulcerans prevalence rates were undertaken: (a) a prospective study of nasal samples from healthy animals, 479 dogs and 72 cats; (b) a retrospective analysis of records of nasal samples collected over a 10-year period from 189 dogs and 64 cats affected by respiratory signs.

RESULTS

Toxigenic C. ulcerans was isolated from four cats with nasal discharge while concurrent C. ulcerans and mecC methicillin-resistant S. aureus infection was detected in a dog suffering from chronic nasal discharge. Clinical features were not distinctive and all cases recovered following antimicrobial treatment. Multilocus sequence typing supported a common source for isolates from the shelter cats. Carriage rates of C. ulcerans in healthy animals were 0.42% (2/479) in dogs and 0.00% (0/72) in cats whereas in animals with signs of upper respiratory tract infection prevalence rates were 0.53% (1/189) in dogs and 6.25% (4/64) in cats.

CLINICAL SIGNIFICANCE

Clinicians should be aware that dogs and cats can be infected with (or carriers of) toxigenic C. ulcerans Considering the potential zoonotic risk, assistance from medical and public health colleagues should be sought in confirmed cases.

Ranking hazards pertaining to human health concerns from land application of anaerobic digestate

Anaerobic digestion (AD) has been identified as one of the cleanest producers of green energy. AD typically uses organic materials as feedstock and, through a series of biological processes, produces methane. Farmyard manure and slurry (FYM&S) are important AD feedstock and are typically mixed with agricultural waste, grass and/or food wastes. The feedstock may contain many different pathogens which can survive the AD process and hence also possibly be present in the final digestate. In this study, a semi-quantitative screening tool was developed to rank pathogens of potential health concern emerging from AD digestate. A scoring system was used to categorise likely inactivation during AD, hazard pathways and finally, severity as determined from reported human mortality rates, number of global human-deaths and infections per 100,000 populations. Five different conditions including mesophilic and thermophilic AD and three different pasteurisation conditions were assessed in terms of specific pathogen inactivation. In addition, a number of scenarios were assessed to consider foodborne incidence data from Ireland and Europe and to investigate the impact of raw FYM&S application (without AD and pasteurisation). A sensitivity analysis revealed that the score for the mortality rate (S3) was the most sensitive parameter (rank coefficient 0.49) to influence the final score S; followed by thermal inactivation score (S1, 0.25) and potential contamination pathways (S2, 0.16). Across all the scenarios considered, the screening tool prioritised Cryptosporidium parvum, Salmonella spp., norovirus, Streptococcus pyogenes, enteropathogenic E. coli (EPEC), Mycobacterium spp., Salmonella typhi (followed by S. paratyphi), Clostridium spp., Listeria monocytogenes and Campylobacter coli as the highest-ranking pathogens of human health concern resulting from AD digestate in Ireland. This tool prioritises potentially harmful pathogens which can emerge from AD digestate and highlights where regulation and intervention may be required.

Anaerobic digestion of agricultural manure and biomass - Critical indicators of risk and knowledge gaps

Anaerobic digestion (AD) has been identified as a potential green technology to treat food and municipal waste, agricultural residues, including farmyard manure and slurry (FYM&S), to produce biogas. FYM&S and digestate can act as soil conditioners and provide valuable nutrients to plants; however, it may also contain harmful pathogens. This study looks at the critical indicators in determining the microbial inactivation potential of AD and the possible implications for human and environmental health of spreading the resulting digestate on agricultural land. In addition, available strategies for risk assessment in the context of EU and Irish legislation are assessed. Storage time and process parameters (including temperature, pH, organic loading rate, hydraulic retention time), feedstock recipe (carbon-nitrogen ratio) to the AD plant (both mesophilic and thermophilic) were all assessed to significantly influence pathogen inactivation. However, complete inactivation of all pathogens is unlikely. There are limited studies evaluating risks from FYM&S as a feedstock in AD and the spreading of resulting digestate. The lack of process standardisation and varying feedstocks between AD farms means risk must be evaluated on a case by case basis and calls for a more unified risk assessment methodology. In addition, there is a need for the enhancement of AD farm-based modelling techniques and datasets to help in advancing knowledge in this area.

Investigation of in-feed organic acids as a low cost strategy to combat Salmonella in grower pigs

Salmonella carriage in pigs is a significant food safety issue. Dietary supplementation with organic acids has previously been shown to reduce shedding and transmission of Salmonella. Therefore, this study aimed to examine the effect of three commercially available organic acid-based products on Salmonella levels in grower pigs, using a model of experimental infection that closely mimics natural exposure to the organism. Seven week old trial pigs (n=40) with a mean weight of 14.7kg were placed in one of four pens with 10 pigs/pen. Pens had previously been contaminated with Salmonella Typhimurium 4,[5],12;i;- via seeder pigs. Trial pigs received one of four diets for 28days: 1, control diet; 2, sodium butyrate supplemented diet; 3, benzoic acid supplemented diet and 4, formic-citric acid supplemented diet. A further 10 pigs were placed in a Salmonella-free pen receiving the control diet. Pigs were weighed and blood sampled on days 0 and 28. Faeces was collected on day 0, 2, 3, 5, 7, 14, 21 and 28 and examined for Salmonella. On day 28, 5 pigs/group were euthanised and ileocaecal lymph nodes (ILN) and caecal contents sampled for culture. The remaining 5 pigs/pen were then fed the control diet and faeces were collected on days 35 and 42. On day 42 pigs were euthanised and ILN and caecal contents tested for Salmonella levels. The trial was repeated once. Within the first two days of exposure to the contaminated environment, 96% (77/80) of pigs became infected. Most pigs shed Salmonella at levels of between 10⁰-10³ CFU/g faeces for at least 7days post-exposure. A significant reduction in Salmonella faecal concentration was observed after supplementation with sodium butyrate (p=0.001) and a formic citric acid blend (p<0.0001). Average daily weight gain (ADWG) was significantly increased in all groups fed the supplemented feed when compared to the positive control group. The use of sodium butyrate or a blend of formic and citric acid in feed could be considered a cost-effective control measure to reduce Salmonella faecal shedding and improve ADWG in Salmonella infected herds.

Agricultural anaerobic digestion power plants in Ireland and Germany: policy and practice

The process of anaerobic digestion (AD) is valued as a carbon-neutral energy source, while simultaneously treating organic waste, making it safer for disposal or use as a fertilizer on agricultural land. The AD process in many European nations, such as Germany, has grown from use of small, localized digesters to the operation of large-scale treatment facilities, which contribute significantly to national renewable energy quotas. However, these large AD plants are costly to run and demand intensive farming of energy crops for feedstock. Current policy in Germany has transitioned to support funding for smaller digesters, while also limiting the use of energy crops. AD within Ireland, as a new technology, is affected by ambiguous governmental policies concerning waste and energy. A clear governmental strategy supporting on-site AD processing of agricultural waste will significantly reduce Ireland's carbon footprint, improve the safety and bioavailability of agricultural waste, and provide an indigenous renewable energy source. © 2016 Society of Chemical Industry.

Profiling oral and digital lesions in sheep in Ireland

BACKGROUND

During the FMD outbreak in Ireland and the UK in 2001, there was significant uncertainty amongstveterinary practitioners and government veterinary inspectors surrounding the clinical diagnosis of FMD insheep. This situation was complicated by reports of idiopathic oral ulcers that closely resembled FMD ongross appearance which at that time were referred to as ovine mouth and gum obscure disease.

METHODS

A field and abattoir study was carried out to determine the frequency, appearance and significance of oraland digital lesions in sheep in Ireland. A total of 3, 263 sheep were examined in 22 flocks, including 1, 969lambs and 1, 294 adults. A further 2,403 animals were examined by abattoir inspections. Animals bearing lesions of interest were identified, samples of the lesions were taken and subsequently examined by bacteriology, electron microscopy, serology, immunohistochemistry and histopathology.

RESULTS

Forty four oral and 20 digital lesions were identified and characterised. Oral lesions were recorded mostfrequently in lambs, where the most common cause was orf virus infection. The majority of the oral lesions recorded in the adults was idiopathic and consistent with a diagnosis of idiopathic oral ulceration. A variety of digital lesions was observed, consistent with scald, foot-rot and contagious ovine digital dermatitis (CODD). All of the animals with lesions were seronegative to FMD virus (FMDV).

CONCLUSIONS

There was no difficulty in differentiating these lesions from those caused by FMDV on the basis of flockhistory and careful clinical examination.

A longitudinal study of Staphylococcus aureus colonization in pigs in Ireland

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) in livestock has refocused attention on S. aureus colonization and transmission in pigs. This study investigated the effect of the S. aureus colonization status of a sow on the colonization status of her piglets, and whether pigs carry the same strain of S. aureus throughout production. Nasal swabs were collected from the piglets of six healthy sows two days after birth and two days before and two days after they were moved into each production stage. The average prevalence of S. aureus colonization varied between 26% and 73%. The odds of being S. aureus positive were almost 12 times higher for piglets born to nasal-positive sows than for those born to nasal-negative sows, and three times higher again for piglets born to sows that were both nasal- and vaginal-positive. Isolates recovered from piglets immediately after birth were indistinguishable from those of the dam as determined by phenotypic and molecular typing, including microarray analysis and optical mapping. All isolates belonged to clonal complex 9 and the majority exhibited a novel spa type, t10449. The findings show that the S. aureus colonization status of the sow influences the colonization status of her piglets in the early production stages but strains carried by pigs change over time. Multiresistant S. aureus was detected, in particular post-weaning. Results suggest that sow status and management practices, including mixing of pigs and antimicrobial usage at weaning, should be considered when implementing control measures for S. aureus on a farm.

Patterns of antimicrobial resistance in pathogenic Escherichia coli isolates from cases of calf enteritis during the spring-calving season

Neonatal enteritis is a common condition of young calves and can be caused by pathogenic strains of Escherichia coli. We hypothesised that on-farm antimicrobial use would result in an increased frequency of resistance in these strains during the calving season. We also sought to determine if the frequency of resistance reflected on-farm antimicrobial use. Faecal samples were collected from cases of calf enteritis on 14 spring-calving dairy farms during two 3 week periods: Period 1 - February 11th through March 2nd 2008 and Period 2 - April 14th through May 5th 2008. E. coli were cultured from these samples, pathogenic strains were identified and antimicrobial susceptibility testing was carried out on these pathogenic isolates. Antimicrobial prescribing data were collected from each farm for the previous 12 months as an indicator of antimicrobial use. The correlation between antimicrobial use and resistance was assessed using Spearman's correlation coefficient. Logistic regression analysis was used to investigate the relationship between resistance, sampling period and pathotype. Penicillins and aminopenicillins, streptomycin, and tetracyclines were the most frequently prescribed antimicrobials and the greatest frequencies of resistance were detected to these 3 antimicrobial classes. A strong correlation (ρ=0.879) was observed between overall antimicrobial use and frequencies of antimicrobial resistance on farms. Sampling period was significant in the regression model for ampicillin resistance while pathotype was significant in the models for streptomycin, tetracycline and trimethoprim/sulphamethoxazole resistance. The frequencies of resistance observed have implications for veterinary therapeutics and prudent antimicrobial use. Resistance did not increase during the calving season and factors other than antimicrobial use, such as calf age and bacterial pathotype, may influence the occurrence of resistance in pathogenic E. coli.

Influences on antimicrobial prescribing behaviour of veterinary practitioners in cattle practice in Ireland

Guidelines on prudent antimicrobial use in veterinary medicine have been developed to reduce inappropriate prescribing of antimicrobials. Such guidelines focus mainly on the clinical and pharmacological indications for prescribing. A questionnaire study of veterinary surgeons engaged in cattle practice was completed to determine if non-clinical issues influence the decision to prescribe antimicrobials, and to assess if pharmacological and non-pharmacological issues influence the choice of antimicrobial prescribed. Non-clinical issues, including issues related to professional stress, influenced the prescribing decision of the majority of respondents. However, the nature of the veterinarian-client relationship did not influence the prescribing behaviour of the majority of respondents. Pharmacological and non-pharmacological issues influenced the choice of antimicrobial prescribed. The veterinary surgeon's prior experience of a drug was considered 'often' or 'always' by 95.7 per cent of respondents when making this decision. The findings of this study have implications for the recognition and management of stress within the profession, and for the development of intervention strategies to reduce inappropriate antimicrobial prescribing.

Investigation of the persistence and transmission of MRSA CC 5 in pigs following intra-nasal inoculation

MRSA CC5 spa type t002 appears to have a broad host range, has been isolated from animals and in-contact humans in Ireland and could potentially become established in pigs in Ireland. The aims of this study were to determine if MRSA CC5 spa type t002 could persist in the tissues of the porcine upper respiratory tract following intra-nasal inoculation; to determine the relative importance of environmental and animal sources of the bacterium in the transmission cycle and to determine the importance of the pharynx as a carriage site of Staphylococcus aureus and MRSA. Twelve pigs were inoculated intra-nasally with MRSA CC5 t002. After 1 or 6 days, the inoculated pigs were removed from the contaminated environment, were washed in an antiseptic solution and placed in a clean house with a group of naive pigs (in-contact group). Another group of naive pigs was placed in the contaminated environment to assess transmission from the environment (environmental group). Nasal swabs, environmental swabs and tissue samples from the upper respiratory tract were taken for MRSA culture. Infection rates were calculated for each group of exposed pigs. MRSA persisted in the pharyngeal tissues of 6 inoculated pigs for at least 30 days and higher counts of S. aureus were found in pharyngeal tissues than in other sites. In this study we were able to demonstrate the establishment of colonisation by MRSA CC5 spa type t002 in commercially sourced pigs already colonised by S. aureus; however, colonisation was sporadic despite the inoculation of large doses. Onward transmission via pig-to-pig contact or environmental contamination was possible and a significant difference was found between the proportion of pigs infected in the environmental group and the proportion infected in the in-contact group during the first 5 days. However, no significant difference was detected in overall infection rates between the 2 groups. The tissues of the pharynx were found to carry greater numbers of S. aureus than other tissues of the upper respiratory tract; therefore, pharyngeal carriage of MRSA and S. aureus in pigs may be more significant than previously thought.

Application of quantitative real-time polymerase chain reaction for the diagnosis of toxoplasmosis and enzootic abortion of ewes

Toxoplasma gondii and Chlamydophila abortus are the 2 most common infectious causes of ovine abortion worldwide. These obligate intracellular pathogens are associated with severe placentitis leading to abortion or stillbirth in pregnant ewes, and resulting in significant economic losses. The objectives of the current study were the development, validation, and application of a duplex real-time polymerase chain reaction (PCR) assay capable of quantifying the burden of infection by T. gondii and C. abortus in material submitted for diagnostic purposes. The validation was carried out using samples from ewes experimentally infected with these organisms. Based on the numbers of genome copies detected, an arbitrary cutoff level was established to correlate with significant pathological changes sufficient to give rise to abortion. When the PCR assay was applied to samples from 66 Irish farms with naturally occurring outbreaks of ovine abortion, toxoplasmosis and enzootic abortion of ewes (EAE) accounted for 14% and 20% of the farms, respectively, while on 6% of the farms, there was evidence of dual infection. When standard diagnostic techniques including histopathological examination, serological analysis, chlamydial antigen detection, and bacteriological culture, were used on samples from the same farms, toxoplasmosis was diagnosed in 17% of farms, and EAE in 12%; dual infection was diagnosed on 3% of the farms. In general, good agreement was found between the PCR and the standard methods. The duplex real-time PCR assay developed in this study has proved to be a very sensitive and rapid tool that might provide a valuable addition to the methods currently available for routine diagnosis of ovine abortions.

Genetic variability of Chlamydophila abortus strains assessed by PCR-RFLP analysis of polymorphic membrane protein-encoding genes

This study used PCR-RFLP to investigate the genetic variability of pmp-encoding genes from fifty-two Chlamydophila abortus (C. abortus) strains originating from abortion cases from various geographical regions and host species. Six primer pairs were used to PCR-amplify DNA fragments encoding eighteen pmps. PCR products were digested using four restriction endonucleases and Bayesian methodologies were used to compare RFLP profiles and assign strains to a RFLP genotype. Strains could be assigned to 2 genotypes in the region encoding pmp18D, 3 genotypes in the regions encoding pmp1A-pmp2B, pmp3E-pmp6H and pmp11G-pmp15G, 4 genotypes in the region encoding pmp7G-pmp10G and 5 genotypes in the region encoding pmp16G-pmp17G. In all regions, the majority of strains (88.4-96.1%) had the same genotype as the reference strain S26/3. No correlation could be made between genotype, host species or geographical origin except for the two variant Greek strains, LLG and POS, which formed a discrete genotype in all pmp-encoding regions except pmp18D. Relative rates of evolution calculated for each pmp-encoding gene locus suggest that differing selective pressures and functional constraints may exist on C. abortus polymorphic membrane proteins. These findings suggest that although intraspecies heterogeneity of pmp-encoding genes in C. abortus is low, the sequence heterogeneity should be an important consideration when using pmps as the basis for novel diagnostics or vaccine development.

Monitoring clinical outcomes, pathological changes and shedding of Chlamydophila abortus following experimental challenge of periparturient ewes utilizing the natural route of infection

Enzootic abortion of ewes (EAE) caused by Chlamydophila abortus is an important disease resulting in significant lamb loss in most sheep producing countries. Ewes are considered to be naturally infected with C. abortus via the oral-nasal route and may become persistent carriers, shedding during subsequent oestrous cycles and at lambing. The aim of this study was to monitor the clinical outcomes, pathological changes and shedding of C. abortus in 18 periparturient orally infected sheep for two breeding seasons. In the first season, C. abortus was detected by real-time PCR (rt-PCR) in 13/18 conjunctival swabs at oestrus. Three out of the 15 pregnant ewes gave birth to 1 live and 1 dead lamb, and 2 of them aborted. Following parturition/abortion, C. abortus was detected in 12/15 vaginal swabs and in all the collected foetal membranes. However, only those membranes containing high copy numbers of the bacterium displayed the EAE typical lesions. In the second season, none of the 13 pregnant ewes aborted, and 5 of them gave birth to dead or weak lambs. C. abortus was not detected in conjunctival or vaginal swabs at oestrus or parturition. The bacterium was detected at low levels in 36% of the foetal membranes, but with no evidence of histopathological lesions. These results indicate that C. abortus can be detected in a large proportion of animals during the first pregnancy after oral infection. However, this proportion is reduced at the subsequent breeding season, confirming the occurrence of a chronic low level persistent infection in post-abortion/lambing ewes.

Zoonotic transmission of Streptococcus equi subsp. zooepidemicus from a dog to a handler

This is, to the best of our knowledge, the first case report to describe the apparent transmission of Streptococcus equi subsp. zooepidemicus from an infected dog to a handler who subsequently developed severe systemic infection. Characterization of the haemolytic streptococci isolated from both the patient and the dog, by phenotypic and molecular analysis, confirmed the canine and human isolates were identical.

Meticillin-resistant Staphylococcus aureus in animals: A review

The objectives of this paper are to review published data on the prevalence and epidemiology of meticillin-resistant Staphylococcus aureus (MRSA) infection and colonization in animals and to provide suggestions for preventing and controlling the problem in veterinary practice. MRSA first emerged as a serious pathogen in human medicine during the late 1970s and has been increasingly reported in animals during the past 10 years. The prevalence of MRSA in human infections varies markedly between geographical areas, being as high as 60% in parts of the USA, 40% in southern Europe but <1% in northern Europe. Epidemiological evidence, including phenotypic and molecular typing data, suggests that MRSA isolates from dogs and cats are indistinguishable from human healthcare isolates, whereas strains of MRSA isolated from horses and associated personnel are different. There is evidence that transfer of MRSA strains can occur between animals and humans and vice versa. Guidelines for the control of MRSA in animals have been drawn up by individual institutions based on those available for human MRSA infection. Risk factors for MRSA infection in animals are currently under investigation and such data are essential for the preparation of specific guidelines for control of MRSA in veterinary practice.

Methicillin-resistant Staphylococcus aureus isolated from a veterinary surgeon and five dogs in one practice

Methicillin-resistant Staphylococcus aureus (MRSA) was isolated from five dogs with wound discharges after surgical procedures at a veterinary practice, and MRSA with similar molecular and phenotypic characteristics was isolated from the nares of one veterinary surgeon in the practice. The pulsed-field gel electrophoresis patterns of all the isolates were indistinguishable from each other and from the most common human isolates of MRSA in Ireland.

Comparison of Fetal and Maternal Inflammatory Responses in the Ovine Placenta after Experimental Infection with Chlamydophila abortus

Placentae from 13 pregnant ewes infected intravenously with Chlamydophila abortus, together with placentae from nine uninfected control ewes, were examined at 14, 21 or 28 days post-inoculation (p.i.). Chlamydial inclusions were present in the trophoblast at 14 days p.i. and were widespread by 21 days p.i. Chorioallantoic lesions (oedema, arteritis and thrombosis) were severe at 28 days p.i., the changes being particularly marked in the membrane surrounding placentomes. Lymphocytes constituted only a small proportion of the cellular infiltrate in the chorioallantois; neutrophil infiltration of the chorionic surface was evident where the trophoblast layer had sloughed, whereas macrophages represented the predominant cell type in the deeper stroma. In contrast, on the maternal side of the placenta, chlamydial inclusions were sparse at all timepoints, and even at 28 days p.i., lesions were restricted to focal endometritis at the placentomal limbus and occasional foci of septal necrosis. T lymphocytes were numerous within endometrial and septal lesions, the infiltrate consistently containing more CD8(+) than CD4(+) cells. The fetal response to chlamydial invasion of the placenta was innate in character, whereas the maternal response appeared to represent an acquired, chlamydia-specific immune response.

An aetiopathological study of chronic bronchopneumonia in lambs in Ireland

Chronic bronchopneumonia in lambs, also known as 'atypical' or 'chronic, non-progressive' pneumonia is a common, frequently sub-clinical disease affecting animals under 12-months-old in intensive production systems. Infection with both Mycoplasma ovipneumoniae and Mannheimia haemolytica have been implicated in the aetiology of this condition and a variety of pulmonary lesions can result. In this study, detailed laboratory examination of 30 abattoir-derived lungs with the characteristic gross features of atypical pneumonia (AP) was carried out with a view to refining and correlating the histopathological and microbiological criteria required for the diagnosis of this disease. For the first time a broad range of laboratory detection techniques including bacterial and virus isolation, fluorescent antibody tests and immunohistochemistry were used in parallel to identify potential causative pathogens such as M. ovipneumoniae, M. haemolytica, parainfluenza type-3 (PI3) virus and respiratory syncytial virus (RSV) in AP lesions. The most consistent finding was the association of gross AP lesions with M. ovipneumoniae, identified by either culture or immunohistochemistry in 27 (90%) of the 30 cases. However the presence M. ovipneumoniae organisms or antigen did not consistently correlate with particular histopathological changes. Furthermore, peri-airway lymphoid hyperplasia, intra-alveolar exudation and nodular 'hyaline scars', which are all previously reported microscopic lesions of AP, were not identified in 12 (40%) of the cases and isolation of M. haemolytica was over-represented in lungs exhibiting suppurative lesions. These findings illustrate the complex aetiopathogenesis of this disease and highlight the requirement to use a combination of diagnostic criteria in its laboratory diagnosis.

Methicillin-resistant Staphylococcus aureus (MRSA) isolated from animals and veterinary personnel in Ireland

Reports of methicillin-resistant Staphylococcus aureus (MRSA) in animals have become more frequent in recent years. This paper documents the recovery of MRSA from animals with respiratory, urinary tract or wound infection and from animals subjected to surgical procedures following treatment in one veterinary hospital and 16 private veterinary clinics in different geographical locations throughout Ireland. MRSA was recovered from 25 animals comprising 14 dogs, eight horses, one cat, one rabbit and a seal, and also from 10 attendant veterinary personnel. Clinical susceptibility testing suggested that the 35 isolates fell into two different groups. One group of isolates (Group 1) was resistant to one or more of the following classes of antimicrobials: macrolides, lincosamines, tetracyclines and/or fluoroquinolones. The second group (Group 2) was resistant to macrolides, aminoglycosides, tetracyclines and trimethoprim/sulphamethoxazole and variably resistant to fluoroquinolones, lincosamines and rifampicin. One isolate in Group 2 was susceptible to trimethoprim. Epidemiological typing by antibiogram-resistogram (AR) typing, biotyping and by chromosomal DNA restriction fragment length polymorphism analysis using SmaI digestion followed by pulsed field gel electrophoresis (PFGE), confirmed these two major clusters. PFGE analysis showed that most isolates from non-equine animals were indistinguishable from each other and from the isolates from personnel caring for these animals. MRSA was isolated from eight horses which attended six different veterinary practices before referral to an equine veterinary hospital. Isolates from the eight horses and from their attendant personnel had PFGE patterns that were indistinguishable and were unlike the patterns obtained from the other isolates. Comparison of PFGE patterns of isolates from veterinary sources with patterns from MRSA recovered in human hospitals showed that the most frequently occurring pattern of MRSA from non-equine animals was indistinguishable from the predominant pattern obtained from the most prevalent MRSA strain in the human population in Ireland. However, the patterns of the isolates from horses were unlike any patterns previously reported in Irish studies of human isolates. This study shows that transmission of two strains of MRSA is occurring in veterinary practices in Ireland and that one strain may have arisen from human hospitals. The source of the second strain remains to be determined.

Rechallenge of previously-infected pregnant ewes with Chlamydophila abortus

In an attempt to ascertain the means whereby previous exposure to Chlamydophila (C.) abortus can protect against the re-occurrence of enzootic abortion of ewes (EAE), ten previously-exposed ewes were intravenously rechallenged with a large infective dose of C. abortus during pregnancy. The patterns of development of chlamydial placentitis and its sequelae closely resembled that observed following first-time challenge of previously-naïve ewes, although placentitis appeared to develop more slowly following rechallenge infection and none of the rechallenged ewes aborted. Chorioallantoic and foetal pathology and foetal immune responses were qualitatively similar whilst the local maternal response to C. abortus infection of the endometrium did not appear to differ in rechallenged and first-time challenged sheep. This demonstrates that if C. abortus reaches the foetal side of the placenta, a stereotypical response is elicited, regardless of the status of maternal immunity. Therefore it appears that in natural circumstances, acquired immunity of the dam protects against the re-occurrence of EAE by preventing the causative agent from reaching the susceptible foetal trophoblast.

Prevalence and number of Salmonella in irish retail pork sausages

A national Salmonella control program in the pork industry was enacted in Ireland in August 2002. This study was undertaken as part of a larger project investigating the role of pork as a source of human salmonellosis in Ireland. The objective of this survey was to assess the prevalence of Salmonella in Irish pork sausage at retail level. Samples, comprising branded prepacked sausages and loose sausages from supermarket meat counters and butcher shops, were collected from selected retail sites in four cities from October to December 2001 and from June to August 2002. A three-tube most-probable-number method was used to enumerate Salmonella in a selected number of samples that were positive by enrichment. Salmonella serotypes were detected in 4.4 and 1.7% of samples at each of the respective sampling periods, a level similar to those reported in other U.S. and U.K. studies. Isolates were characterized by serotype, phage type, and antimicrobial susceptibility. Eighteen (70%) were resistant to at least one antimicrobial, and 15 (58%) were resistant to four or more antimicrobials. Most of the isolates exhibited resistance to tetracycline. Five different phage types were detected. DT104 was the predominant phage type among Salmonella Typhimurium isolates. This study revealed that multidrug-resistant salmonellae are present in a proportion of Irish sausages and that further risk analysis work is necessary in order to quantify the risk posed to public health.

A study of greyhounds with tonsillar enlargement and a history of poor racing performance

Fifteen greyhounds with tonsillar enlargement were subjected to detailed investigation. Affected greyhounds exhibited coughing, poor racing performance and tonsillar lymphoid hyperplasia over a period of months. Each of the 15 affected animals had evidence of respiratory tract disease. Twelve had non-specific respiratory tract disease, two had pneumonia and one had pulmonary infiltration with eosinophils (PIE). Histopathological examination of the tonsils from affected dogs revealed that greyhounds with tonsillar enlargement are more likely to have tonsillar lymphoid hyperplasia than tonsillitis. As a result, lymphoid hyperplasia would be a suitable term to describe this tonsillar condition. Respiratory tract diseases, rather than tonsillar hyperplasia, was the more likely cause of the poor racing performance of affected dogs. The aetiological relationship, if any, between respiratory disease and tonsillar enlargement is unclear from this study and requires further investigation.

Diagnosis of ovine enzootic abortion, using a competitive ELISA based on monoclonal antibodies against variable segments 1 and 2 of the major outer membrane protein of Chlamydia psittaci serotype 1

OBJECTIVE

To develop and evaluate a competitive ELISA (cELISA) specific for detection of antibodies to abortion strains of Chlamydia psittaci and C pecorum that is based on monoclonal antibodies against the 2 segments. PROCEDURA: Monoclonal antibodies were screened for binding to ELISA plates coated with elementary bodies, and were selected on the basis of positive competition with experimentally produced sera against C psittaci and lack of competition with anti-C pecorum sera. The cELISA was evaluated with field sera, and the results were compared with those obtained by complement-fixation testing and by an ELISA containing solubilized outer membrane complexes (A-ELISA).

RESULTS

The cELISA detected 9 of 10 C psittaci-infected flocks (57/125 sera, 45.6%), and in 6 of 10 flocks (27.3% of the sera), it specified correctly the infecting chlamydial species. Regarding test sensitivity, the complement-fixation test detected 6 of 10 test-positive (19.2% of the sera) flocks, whereas 7 of 10 test-positive (48.8% of the sera) flocks were detected by use of the A-ELISA. The specificity of the test was satisfactory (100%), compared with the A-ELISA (72.2%).

CONCLUSIONS

The new cELISA is a sensitive and specific assay for antibodies against C psittaci abortion strains. It is rapid and easy to perform and does not require serum dilutions. The new cELISA is, therefore, suitable as a routine test for chlamydial diagnosis and seroepidemiologic studies.

Morbidity and mortality in a large Irish feedlot; microbiological and serological findings in cattle with acute respiratory disease

A survey of morbidity and mortality was undertaken in a slatted unit containing 6399 beef cattle over a 6 month period. The mortality rate was 0.78% and the morbidity rate was 12.7%. The interval from arrival to morbidity was 25.5 days +/- 0.9. Significantly more sick cattle were identified on either Mondays or Tuesdays than were seen on Saturdays or Sundays (P < 0.005). The mean interval to mortality (all diseases) was 48.5 days +/- 7.4. Respiratory disease was the most frequently recorded disease and was responsible for 62% of morbidity and 58% of mortality. Samples from 133 cattle, taken as they presented with acute onset respiratory disease, contained antibodies to Bovine Herpes Virus -1(BHV-1) (14.3%), Bovine Viral Diarrhoea Virus (BVDV) (78%), Bovine Respiratory Syncytial Virus (BRSV) (94%) and Parainfluenza type 1 Virus (P13V) (99%). When the same cattle were resampled 4 to 6 weeks later antibodies were found for BHV-1 (93.2%), BVDV (99.2%), BRSV (100%) and P13V (100%). Eleven of 27 bronchoalveolar lavage samples taken from the above group of cattle exhibited positive fluorescence for BHV-1 but all 27 samples were negative for BVDV, BRSV and P13V. Pasteurella multocida was isolated from eight of the 27 lavage samples and Pasteurella haemolytica from one sample.

Comparison of serological tests for the diagnosis of Chlamydia psittaci infection of sheep

An enzyme-linked immunosorbent assay (ELISA) was developed and compared with the complement fixation test (CFT) and the indirect immunofluorescence antibody test (IIFAT) for the detection of antibodies to C. psittaci in sheep. Field sera and experimental sera from aborting ewes, subclinically infected sheep and vaccinated sheep were used. The ELISA and IIFAT were much more sensitive than the CFT. Agreement between the CFT and ELISA varied between 50% and 98%, while agreement between the IIFAT and ELISA varied between 70.5% and 94.3%. The specificity of IIFAT and ELISA with regard to the identification of animals which may be a source of ovine abortion strains of C. psittaci was critically assessed, using antigen preparations derived from an abortion isolate and from a non-abortion isolate of C. psittaci. Indirect immunofluorescence was shown to be the more discerning test.

Comparison of ovine abortion and non-abortion isolates of Chlamydia psittaci using inclusion morphology, polyacrylamide gel electrophoresis, restriction endonuclease analysis and reactivity with monoclonal antibodies

Twelve reference and four Northern Ireland ovine Chlamydia psittaci isolates including ovine abortion, faecal, conjunctivitis and arthritis isolates were compared. Inclusion morphology was shown to provide a useful means of differentiating the abortion and the non-abortion isolates studied. Identical SDS-PAGE polypeptide profiles were produced by the ovine abortion isolates. The polypeptide profiles of the non-abortion isolates were similar to one another and clearly distinct from the abortion isolate profiles. The restriction endonuclease profiles of the abortion isolates were remarkably similar whereas different profiles were produced by most of the non-abortion isolates. Monoclonal antibodies were prepared and characterized. A number of these reacted with all the isolates of chlamydia tested. Three mAbs reacted exclusively with the ovine abortion isolates while four mAbs reacted exclusively with a number of the faecal isolates.