David L. Pearl

Antimicrobial Resistance in Generic Escherichia coli Isolates from Wild Small Mammals Living in Swine Farm, Residential, Landfill, and Natural Environments in Southern Ontario, Canada

ABSTRACT To assess the impacts of different types of human activity on the development of resistant bacteria in the feces of wild small mammals, we compared the prevalences and patterns of antimicrobial resistance and resistance genes in generic Escherichia coli and Salmonella enterica isolates from fecal samples collected from wild small mammals living in four environments: swine farms, residential areas, landfills, and natural habitats. Resistance to antimicrobials was observed in E. coli isolates from animals in all environments: 25/52 (48%) animals trapped at swine farms, 6/69 (9%) animals trapped in residential areas, 3/20 (15%) animals trapped at landfills, and 1/22 (5%) animals trapped in natural habitats. Animals trapped on farms were significantly more likely to carry E. coli isolates with resistance to tetracycline, ampicillin, sulfisoxazole, and streptomycin than animals trapped in residential areas. The resistance genes sul2, aadA, and tet(A) were significantly more likely to be detected in E. coli isolates from animals trapped on farms than from those trapped in residential areas. Three S. enterica serotypes (Give, Typhimurium, and Newport) were recovered from the feces of 4/302 (1%) wild small mammals. All Salmonella isolates were pansusceptible. Our results show that swine farm origin is significantly associated with the presence of resistant bacteria and resistance genes in wild small mammals in southern Ontario, Canada. However, resistant fecal bacteria were found in small mammals living in all environments studied, indicating that environmental exposure to antimicrobials, antimicrobial residues, resistant bacteria, or resistance genes is widespread.

Methicillin-resistant and -susceptible Staphylococcus aureus infections in dogs.

Risk factors for MRSA include intravenous catheterization and receipt of certain antimicrobial drugs.

Evaluation of pet-related management factors and the risk of Salmonella spp. carriage in pet dogs from volunteer households in Ontario (2005-2006).

The purpose of this study was to determine pet‐related management factors that may be associated with the presence of Salmonella spp. in feces of pet dogs from volunteer households. From October 2005 until May 2006, 138 dogs from 84 households in Ontario were recruited to participate in a cross‐sectional study. Five consecutive daily fecal samples were collected from each dog and enrichment culture for Salmonella spp. was performed. A higher than expected number of the dogs (23.2%; 32/138) had at least one fecal sample positive for Salmonella, and 25% (21/84) of the households had at least one dog shedding Salmonella. Twelve serotypes of Salmonella enterica subsp. enterica were identified, with the predominant serotypes being Typhimurium (33.3%; 13/39), Kentucky (15.4%; 6/39), Brandenburg (15.4%; 6/39) and Heidelberg (12.8%; 5/39). Univariable logistic regression models were created with a random effect for household to account for clustering. Statistically significant risk factors for a dog testing positive included having contact with livestock, receiving a probiotic in the previous 30 days, feeding a commercial or homemade raw food diet, feeding raw meat and eggs, feeding a homemade cooked diet, and having more than one dog in the household. In two‐variable models that controlled for feeding raw food, the non‐dietary variables were no longer statistically significant. These results highlight the potential public health risk of including raw animal products in canine diets.

Avian bornavirus is present in many tissues of psittacine birds with histopathologic evidence of proventricular dilatation disease.

Proventricular dilatation disease (PDD) is a neurologic disease of psittacine birds suspected to be caused by a recently identified Avian bornavirus (ABV). In the current report, data supporting the causal association of ABV with PDD are presented. Immunohistochemistry (IHC) with rabbit polyclonal antiserum raised against ABV nucleocapsid protein was used to identify cell and organ distribution of viral antigen. The ABV antigen was most consistently detected in brain, spinal cord, adrenal gland, pancreas, and kidney. Histopathologic evaluation was correlated with ABV-specific polymerase chain reaction (PCR) and immunohistochemical tests in multiple tissues from 16 psittacine birds with and without PDD. Using histopathologic diagnosis as the gold standard, the sensitivity and specificity of IHC for ABV antigens were found to be 100% and 100%, respectively. Many more tissues were positive for ABV RNA by reverse transcription PCR than were positive for pathologic changes or viral antigens by IHC, indicating the presence of subclinical or asymptomatic infection at many sites.

The use of outbreak information in the interpretation of clustering of reported cases of Escherichia coli O157 in space and time in Alberta, Canada, 2000-2002

We obtained a list of all reported cases of Escherichia coli O157 in Alberta during the 2000-2002 period, and using scan statistics we identified yearly temporal and spatial clusters of reported cases of E. coli O157 during the summer and in southern Alberta. However, the location of the spatial cluster in the south was variable among years. The impact of using both outbreak and sporadic data or only sporadic data on the identification of spatial and temporal clusters was small when analysing individual years, but the difference between spatial clusters was pronounced when scanning the entire study period. We also identified space-time clusters that incorporated known outbreaks, and clusters that were suggestive of undetected outbreaks that we attempted to validate with molecular data. Our results suggest that scan statistics, based on a space-time permutation model, may have a role in outbreak investigation and surveillance programmes by identifying previously undetected outbreaks.

Factors associated with whole carcass condemnation rates in provincially-inspected abattoirs in Ontario 2001-2007: implications for food animal syndromic surveillance

BackgroundOntario provincial abattoirs have the potential to be important sources of syndromic surveillance data for emerging diseases of concern to animal health, public health and food safety. The objectives of this study were to: (1) describe provincially inspected abattoirs processing cattle in Ontario in terms of the number of abattoirs, the number of weeks abattoirs process cattle, geographical distribution, types of whole carcass condemnations reported, and the distance animals are shipped for slaughter; and (2) identify various seasonal, secular, disease and non-disease factors that might bias the results of quantitative methods, such as cluster detection methods, used for food animal syndromic surveillance.ResultsData were collected from the Ontario Ministry of Agriculture, Food and Rural Affairs and the Ontario Cattlemens Association regarding whole carcass condemnation rates for cattle animal classes, abattoir compliance ratings, and the monthly sales-yard price for various cattle classes from 2001-2007. To analyze the association between condemnation rates and potential explanatory variables including abattoir characteristics, season, year and commodity price, as well as animal class, negative binomial regression models were fit using generalized estimating equations (GEE) to account for autocorrelation among observations from the same abattoir. Results of the fitted model found animal class, year, season, price, and audit rating are associated with condemnation rates in Ontario abattoirs. In addition, a subset of data was used to estimate the average distance cattle are shipped to Ontario provincial abattoirs. The median distance from the farm to the abattoir was approximately 82 km, and 75% of cattle were shipped less than 100 km.ConclusionsThe results suggest that secular and seasonal trends, as well as some non-disease factors will need to be corrected for when applying quantitative methods for syndromic surveillance involving these data. This study also demonstrated that animals shipped to Ontario provincial abattoirs come from relatively local farms, which is important when considering the use of spatial surveillance methods for these data.

Distribution of Sulfonamide Resistance Genes in Escherichia coli and Salmonella Isolates from Swine and Chickens at Abattoirs in Ontario and Québec, Canada

ABSTRACT Sulfonamide-resistant Escherichia coli and Salmonella isolates from pigs and chickens in Ontario and Québec were screened for sul1, sul2, and sul3 by PCR. Each sul gene was distributed differently across populations, with a significant difference between distribution in commensal E. coli and Salmonella isolates and sul3 restricted mainly to porcine E. coli isolates.

Association of wild bird density and farm management factors with the prevalence of E. coli O157 in dairy herds in Ohio (2007-2009).

Our objective was to determine the role that European starlings (Sturnus vulgaris) play in the epidemiology of Escherichia coli O157:H7 in dairy cattle. We visited 150 dairy farms in Ohio twice during summer and fall months from 2007 to 2009. Fresh faecal pats from 30 lactating cows were collected during each visit. Information on farm management and environmental variables was gathered through a questionnaire administered to the farm owner. The number of starlings observed on the farm was also recorded. Approximately 1% of dairy cattle and 24% of farms were positive for E. coli O157. Risk factors associated with the presence of E. coli O157 in faecal pats included contact between adult cattle and calves, types or number of ventilation and manure management systems and number of birds per milking cow.

Epidemiology of Clostridium difficile on a veal farm: prevalence, molecular characterization and tetracycline resistance.

Concern has been raised about the potential for Clostridium difficile to be a bovine and foodborne pathogen, yet limited study has been performed in cattle, and none in veal calves. This study evaluated the epidemiology and microbiology of C. difficile on one veal farm. Rectal swabs were obtained from calves within 48 h of arrival and at one, 17 and 21 weeks later. Selective culture for C. difficile was performed. Isolates were characterized by PCR ribotyping and PCR for tcdA, tcdB and cdtA. Tetracycline resistance and resistance genes were investigated. Multivariable logistic regression models were constructed to determine the relationship between shedding of the bacterium and specific ribotypes and the independent variables: time of sampling and area of housing. Calves were twice more likely to test positive 1 week after arrival (51%) when compared to initial results (32%). Shedding at 17 and 21 weeks was significantly lower (2% at both samplings). Ribotype 078 was the most common. Twelve different ribotypes were present initially with only three ribotypes found subsequently. Seventy-six percent (40/53) of isolates initially recovered were tetracycline resistant compared to 93% (81/87) from 2nd sampling. Tetracycline resistance genes were detected in 24% (13/53) of isolates during 1st and in 55% (50/91) during 2nd sampling. The high prevalence of pathogenic C. difficile in veal calves could be of zoonotic concern. The low prevalence before slaughter may be of importance for the evaluation of foodborne risks. Oxytetracycline administration to calves may have an impact on prevalence of C. difficile colonization.

Multiple-locus variable-nucleotide tandem repeat subtype analysis implicates European starlings as biological vectors for Escherichia coli O157:H7 in Ohio, USA

Aims:  To provide molecular epidemiological evidence of avian transmission of Escherichia coli O157:H7 between dairy farms in Ohio, this study was designed to identify genetic relatedness between isolates originating from bovine faecal samples and intestinal contents of European starlings captured on these farms.