A One Health Genomic Investigation of Gentamicin Resistance in Escherichia coli from Human and Chicken Sources in Canada, 2014 to 2017.

We investigated whether gentamicin resistance (Genr) in Escherichia coli isolates from human infections was related to Genr E. coli in chicken and whether resistance may be due to coselection from use of lincomycin-spectinomycin in chickens on farms. Whole-genome sequencing was performed on 483 Genr E. coli isolates isolated between 2014 and 2017. These included 205 human-source isolates collected by the Canadian Ward (CANWARD) program and 278 chicken-source isolates: 167 from live/recently slaughtered chickens (animals) and 111 from retail chicken meat collected by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). The predominant Genr gene was different in human and chicken sources; however, both sources carried aac(3)-IId, aac(3)-VIa, and aac(3)-IVa. Forty-one percent of human clinical isolates of Genr E. coli contained a blaCTX-M extended-spectrum beta-lactamase (ESBL) gene (84/205), and 53% of these were sequence type 131 (ST131). Phylogenomic analysis revealed a high diversity of Genr isolates; however, there were three small clusters of closely related isolates from human and chicken sources. Genr and spectinomycin resistance (Specr) genes were colocated in 148/167 (89%) chicken animal isolates, 94/111 (85%) chicken retail meat isolates, and 137/205 (67%) human-source isolates. Long-read sequencing of 23 isolates showed linkage of the Genr and Specr genes on the same plasmid in 14/15 (93%) isolates from chicken(s) and 6/8 (75%) isolates from humans. The use of lincomycin-spectinomycin on farms may be coselecting for gentamicin-resistant plasmids in E. coli in broiler chickens; however, Genr isolates and plasmids were mostly different in chickens and humans.

Pandemic fatigue or enduring precautionary behaviours? Canadians' long-term response to COVID-19 public health measures.

The long-term dynamics of COVID-19 disease incidence and public health measures may impact individuals' precautionary behaviours as well as support for measures. The objectives of this study were to assess longitudinal changes in precautionary behaviours and support for public health measures. Survey data were collected online from 1030 Canadians in each of 5 cycles in 2020: June 15-July 13; July 22-Aug 8; Sept 7-15; Oct 14-21; and Nov 12-17. Precautionary behaviour increased over the study period in the context of increasing disease incidence. When controlling for the stringency of public health measures and disease incidence, mixed effects logistic regression models showed these behaviours did not significantly change over time. Odds ratios for avoiding contact with family and friends ranged from 0.84 (95% CI 0.59-1.20) in September to 1.25 (95% CI 0.66-2.37) in November compared with July 2020. Odds ratios for attending an indoor gathering ranged from 0.86 (95% CI 0.62-1.20) in August to 1.71 (95% CI 0.95-3.09) in October compared with July 2020. Support for non-essential business closures increased over time with 2.33 (95% CI 1.14-4.75) times higher odds of support in November compared to July 2020. Support for school closures declined over time with lower odds of support in September (OR 0.66 [95% CI 0.45-0.96]), October (OR 0.48 [95% CI 0.26-0.87]), and November (OR 0.39 [95% CI 0.19-0.81]) compared with July 2020. In summary, respondents' behaviour mirrored government guidance between July and November 2020 and supported individual precautionary behaviour and limitations on non-essential businesses over school closures.

One Health Genomic Analysis of Extended-Spectrum ß-Lactamase‒Producing Salmonella enterica, Canada, 2012‒2016.

Extended-spectrum ß-lactamases (ESBLs) confer resistance to extended-spectrum cephalosporins, a major class of clinical antimicrobial drugs. We used genomic analysis to investigate whether domestic food animals, retail meat, and pets were reservoirs of ESBL-producing Salmonella for human infection in Canada. Of 30,303 Salmonella isolates tested during 2012-2016, we detected 95 ESBL producers. ESBL serotypes and alleles were mostly different between humans (n = 54) and animals/meat (n = 41). Two exceptions were blaSHV-2 and blaCTX-M-1 IncI1 plasmids, which were found in both sources. A subclade of S. enterica serovar Heidelberg isolates carrying the same IncI1-blaSHV-2 plasmid differed by only 1-7 single nucleotide variants. The most common ESBL producer in humans was Salmonella Infantis carrying blaCTX-M-65, which has since emerged in poultry in other countries. There were few instances of similar isolates and plasmids, suggesting that domestic animals and retail meat might have been minor reservoirs of ESBL-producing Salmonella for human infection.

Correlation between Phenotypic and In Silico Detection of Antimicrobial Resistance in Salmonella enterica in Canada Using Staramr.

Whole genome sequencing (WGS) of Salmonella supports both molecular typing and detection of antimicrobial resistance (AMR). Here, we evaluated the correlation between phenotypic antimicrobial susceptibility testing (AST) and in silico prediction of AMR from WGS in Salmonella enterica (n = 1321) isolated from human infections in Canada. Phenotypic AMR results from broth microdilution testing were used as the gold standard. To facilitate high-throughput prediction of AMR from genome assemblies, we created a tool called Staramr, which incorporates the ResFinder and PointFinder databases and a custom gene-drug key for antibiogram prediction. Overall, there was 99% concordance between phenotypic and genotypic detection of categorical resistance for 14 antimicrobials in 1321 isolates (18,305 of 18,494 results in agreement). We observed an average sensitivity of 91.2% (range 80.5-100%), a specificity of 99.7% (98.6-100%), a positive predictive value of 95.4% (68.2-100%), and a negative predictive value of 99.1% (95.6-100%). The positive predictive value of gentamicin was 68%, due to seven isolates that carried aac(3)-IVa, which conferred MICs just below the breakpoint of resistance. Genetic mechanisms of resistance in these 1321 isolates included 64 unique acquired alleles and mutations in three chromosomal genes. In general, in silico prediction of AMR in Salmonella was reliable compared to the gold standard of broth microdilution. WGS can provide higher-resolution data on the epidemiology of resistance mechanisms and the emergence of new resistance alleles.

Effectiveness of non-pharmaceutical interventions to reduce SARS-CoV-2 transmission in Canada and their association with COVID-19 hospitalization rates.

Background: Non-pharmaceutical interventions (NPIs) aim to reduce the incidence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections mostly by limiting contacts between people where virus transmission can occur. However, NPIs limit social interactions and have negative impacts on economic, physical, mental and social well-being. It is, therefore, important to assess the impact of NPIs on reducing the number of coronavirus disease 2019 (COVID-19) cases and hospitalizations to justify their use. Methods: Dynamic regression models accounting for autocorrelation in time series data were used with data from six Canadian provinces (British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, Québec) to assess 1) the effect of NPIs (measured using a stringency index) on SARS-CoV-2 transmission (measured by the effective reproduction number), and 2) the effect of the number of hospitalized COVID-19 patients on the stringency index. Results: Increasing stringency index was associated with a statistically significant decrease in the transmission of SARS-CoV-2 in Alberta, Saskatchewan, Manitoba, Ontario and Québec. The effect of stringency on transmission was time-lagged in all of these provinces except for Ontario. In all provinces except for Saskatchewan, increasing hospitalization rates were associated with a statistically significant increase in the stringency index. The effect of hospitalization on stringency was time-lagged. Conclusion: These results suggest that NPIs have been effective in Canadian provinces, and that their implementation has been, in part, a response to increasing hospitalization rates of COVID-19 patients.

A One-Health Genomic Investigation of Gentamicin Resistance in Salmonella from Human and Chicken Sources in Canada, 2014 to 2017.

We investigated whether the increased prevalence of gentamicin resistance in Salmonella from human infections was related to a similar increased prevalence in isolates from broiler chickens and whether this increase may have been due to coselection from use of lincomycin-spectinomycin in chickens on farms. Whole-genome sequencing was performed on gentamicin-resistant (Genr) Salmonella isolates from human and chicken sources collected from 2014 to 2017 by the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). We determined the genomic relatedness of strains and characterized resistance genes and plasmids. From 2014 to 2017, 247 isolates of Genr Salmonella were identified by CIPARS: 188 were from humans, and 59 were from chicken sources (26 from live animals on farm and 33 from retail meat). The five most common Genr serovars were Salmonella enterica serovars Heidelberg (n = 93; 31.5%), 4,[5],12:i:- (n = 42; 14.2%), Kentucky (n = 37; 12.5%), Infantis (n = 33; 11.2%), and Typhimurium (n = 23; 7.8%). Phylogenomic analysis revealed that for S. Heidelberg and S. Infantis, there were closely related isolates from human and chicken sources. In both sources, resistance to gentamicin and spectinomycin was most frequently conferred by aac(3)-VIa and ant(3'')-Ia, respectively. Plasmid closure confirmed linkages of gentamicin and spectinomycin resistance genes and revealed instances of similar plasmids from both sources. Gentamicin and spectinomycin resistance genes were linked on the same plasmids, and some plasmids and isolates from humans and chickens were genetically similar, suggesting that the use of lincomycin-spectinomycin in chickens may be selecting for gentamicin-resistant Salmonella in broiler chickens and that these resistant strains may be acquired by humans.

Genomic Epidemiology of Major Extraintestinal Pathogenic Escherichia coli Lineages Causing Urinary Tract Infections in Young Women Across Canada.

BACKGROUND: A few extraintestinal pathogenic Escherichia coli (ExPEC) multilocus sequence types (STs) cause the majority of community-acquired urinary tract infections (UTIs). We examine the genomic epidemiology of major ExPEC lineages, specifically factors associated with intestinal acquisition. METHODS: A total of 385 women with UTI caused by E. coli across Canada were asked about their diet, travel, and other exposures. Genome sequencing was used to determine both ST and genomic similarity. Logistic regression was used to identify factors associated with the acquisition of and infection with major ExPEC STs relative to minor ExPEC STs. RESULTS: ST131, ST69, ST73, ST127, and ST95 were responsible for 54% of all UTIs. Seven UTI clusters were identified, but genomes from the ST95, ST127, and ST420 clusters exhibited as few as 3 single nucleotide variations across the entire genome, suggesting recent acquisition. Furthermore, we identified a cluster of UTIs caused by 6 genetically-related ST1193 isolates carrying mutations in gyrA and parC. The acquisition of and infection with ST69, ST95, ST127, and ST131 were all associated with increased travel. The consumption of high-risk foods such as raw meat or vegetables, undercooked eggs, and seafood was associated with acquisition of and infection with ST69, ST127, and ST131, respectively. CONCLUSIONS: Reservoirs may aid in the dissemination of pandemic ExPEC lineages in the community. Identifying ExPEC reservoirs may help prevent future emergence and dissemination of high-risk lineages within the community setting.

Genomic Investigation of the Emergence of Invasive Multidrug-Resistant Salmonella enterica Serovar Dublin in Humans and Animals in Canada.

Salmonella enterica subsp. enterica serovar Dublin is a zoonotic pathogen that often leads to invasive bloodstream infections in humans that are multidrug resistant. Described here are the results of Canadian national surveillance of S Dublin from 2003 to 2015 in humans and bovines, principally collected through the Canadian Integrated Program for Antibiotic Resistance Surveillance (CIPARS). An increase in human infections due to multidrug-resistant (MDR) S Dublin was observed in 2010, many of which were bloodstream infections. Phylogenomic analysis of human and bovine isolates revealed a closely related network that differed by only 0 to 17 single nucleotide variants (SNVs), suggesting some potential transmission between humans and bovines. Phylogenomic comparison of global publicly available sequences of S Dublin showed that Canadian isolates clustered closely with those from the United States. A high correlation between phenotypic and genotypic antimicrobial susceptibility was observed in Canadian isolates. IS26 replication was widespread among U.S. and Canadian isolates and caused the truncation and inactivation of the resistance genes strA and blaTEM-1B A hybrid virulence and MDR plasmid (pN13-01125) isolated from a Canadian S Dublin isolate was searched against NCBI SRA data of bacteria. The pN13-01125 coding sequences were found in 13 Salmonella serovars, but S Dublin appears to be a specific reservoir. In summary, we have observed the rise of invasive MDR S Dublin in humans in Canada and found that they are closely related to bovine isolates and to American isolates in their mobile and chromosomal contents.

Changes in antimicrobial resistance levels among Escherichia coli, Salmonella, and Campylobacter in Ontario broiler chickens between 2003 and 2015.

Poultry has been identified as a reservoir of foodborne enteric pathogens and antimicrobial resistant bacteria. The objective of this study was to describe and compare antimicrobial resistant isolates from an Ontario broiler chicken farm-level baseline project (2003 to 2004) to the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS) Ontario abattoir and retail surveillance data from 2003, and to the most recent (2015) CIPARS Ontario chicken surveillance data in order to assess the impact of an industry-wide policy change in antimicrobial use. Ceftiofur resistance (TIO-R) prevalence in Salmonella decreased by 7% on farm between 2003 and 2004 and 2015. During the same timeframe, TIO-R E. coli prevalence decreased significantly by 16%, 11%, and 8% in farm, abattoir, and retail samples, respectively. Gentamicin resistant (GEN-R) E. coli, however, increased by 10% in farm and 15% in retail-derived isolates, and trimethoprim-sulfamethoxazole resistant (TMSm-R) E. coli increased significantly by 20%, 18%, and 5% in farm, abattoir, and retail isolates, respectively. Similarly, ciprofloxacin-resistant (CIP-R) Campylobacter spp. significantly increased in retail isolates by 11% and increased in farm (33%) and abattoir isolates (7%). The decrease in TIO-R Salmonella/E. coli in recent years is consistent with the timing of an industry-led intervention eliminating the preventive use of ceftiofur, a third generation cephalosporin and class of antimicrobials deemed critically important to human medicine. The rise in GEN-R and TMSm-R prevalence is indicative of recent shifts in antimicrobial use. Our study highlights the importance of integrated surveillance in detecting emerging trends and determining the efficacy of interventions to improve food safety.

La volaille a été identifiée comme étant un réservoir d'agents pathogènes entériques d'origine alimentaire et de bactéries résistantes aux antimicrobiens. L'objectif de la présente étude était de décrire et comparer des isolats résistants aux antimicrobiens provenant d'une ferme ontarienne de poulets à griller obtenus dans le cadre d'un projet de base (2003 à 2004) aux données de surveillance de 2003 du Programme intégré canadien de surveillance de la résistance aux antimicrobiens (PICRA) d'abattoir et de ventes au détail en Ontario, et aux plus récentes données de surveillance (2015) du PICRA Ontario pour la volaille afin d'évaluer l'impact d'un changement à l'ensemble de l'industrie dans l'utilisation des antimicrobiens. La prévalence de la résistance au cefiofur (TIO-R) de Salmonella a diminué de 7 % sur la ferme entre 2003 à 2004 et 2015. Durant ce même intervalle de temps, la prévalence de TIO-R de E. coli diminua de manière significative de 16 %, 11 %, et 8 % dans les échantillons provenant de la ferme, de l'abattoir et de la vente au détail, respectivement. Toutefois, les E. coli résistant à la gentamicine (GEN-R) ont augmenté de 10 % et 15 % dans les échantillons pris à la ferme et de la vente au détail, respectivement. Les E. coli résistants au trimethoprime-sulfaméthoxazole (TMSm-R) ont augmenté de manière significative par 20 %, 18 %, et 5 % dans les isolats de la ferme, de l'abattoir et de la vente au détail, respectivement. Les isolats de Campylobacter spp. résistants au ciprofloxacin (CIP-R) augmentèrent de manière significative dans les échantillons de vente au détail (11 %), ceux de la ferme (33 %) ainsi que ceux de l'abattoir (7 %). La diminution de la TIO-R chez Salmonella/E. coli au cours des dernières années concorde avec une intervention menée par l'industrie d'éliminer l'utilisation en prévention du ceftiofur, une céphalosporine de troisième génération qui est une classe d'antimicrobiens considérée d'importance critique en médecine humaine. L'augmentation de la prévalence de GEN-R et de TMSm-R est indicative d'un changement récent dans l'utilisation des antimicrobiens. Notre étude fait ressortir l'importance d'un programme intégré de surveillance pour détecter les tendances émergentes et déterminer l'efficacité des interventions pour améliorer la salubrité alimentaire.(Traduit par Docteur Serge Messier).

A Whole-Genome Sequencing Approach To Study Cefoxitin-Resistant Salmonella enterica Serovar Heidelberg Isolates from Various Sources.

This study characterized cefoxitin-resistant and -susceptible Salmonella enterica serovar Heidelberg strains from humans, abattoir poultry, and retail poultry to assess the molecular relationships of isolates from these sources in Québec in 2012. Isolates were collected as part of the Canadian Integrated Program for Antimicrobial Resistance Surveillance (CIPARS). All isolates were subjected to antimicrobial susceptibility testing, PCR for CMY-2, pulsed-field gel electrophoresis (PFGE), and whole-genome sequencing (WGS). A total of 113 S Heidelberg isolates from humans (n = 51), abattoir poultry (n = 18), and retail poultry (n = 44) were studied. All cefoxitin-resistant isolates (n = 65) were also resistant to amoxicillin-clavulanic acid, ampicillin, ceftiofur, and ceftriaxone, and all contained the CMY-2 gene. PFGE analysis showed that 111/113 (98.2%) isolates clustered together with ≥90% similarity. Core genome analysis using WGS identified 13 small clusters of isolates with 0 to 4 single nucleotide variations (SNVs), consisting of cefoxitin-resistant and -susceptible human, abattoir poultry, and retail poultry isolates. CMY-2 plasmids from cefoxitin-resistant isolates all belonged to incompatibility group I1. Analysis of IncI1 plasmid sequences revealed high identity (95 to 99%) to a previously described plasmid (pCVM29188_101) found in Salmonella Kentucky. When compared to pCVM29188_101, all sequenced cefoxitin-resistant isolates were found to carry 1 of 10 possible variant plasmids. Transmission of S Heidelberg may be occurring between human, abattoir poultry, and retail poultry sources, and transmission of a common CMY-2 plasmid may be occurring among S Heidelberg strains with variable genetic backgrounds.

Prevalence and antimicrobial resistance of Salmonella isolated from two pork processing plants in Alberta, Canada.

This study investigated the frequency of Salmonella serovars on pig carcasses at various processing steps in two commercial pork processing plants in Alberta, Canada and characterized phenotypic and genotypic antimicrobial resistance (AMR) and PFGE patterns of the Salmonella isolates. Over a one year period, 1000 swab samples were collected from randomly selected pigs at two slaughter plants. Sampling points were: carcass swabs after bleeding (CSAB), carcass swabs after de-hairing (CSAD, plant A) or skinning (CSASk, plant B), carcass swabs after evisceration (CSAE), carcass swabs after pasteurization (CSAP, plant A) or washing (CSAW, plants B) and retail pork (RP). For plant A, 87% of CSAB and 8% of CSAE were positive for Salmonella while at plant B, Salmonella was recovered from 94% of CSAB and 10% of CSAE. Salmonella was not recovered from the RP samples at either plant, indicating that the plants used effective control measures. Salmonella enterica serovar Derby was the most common serotype (23%, 29/127) recovered in plant A and plant B (61%, 76/124). For plant A, 35% (45/127) of isolates were resistant to at least one antimicrobial. Five isolates (3.9%), 4 serovar Ohio strains and one serovar I:Rough-O:I,v:-, strain were simultaneously resistant to antimicrobials of very high (Category I), high (Category II), and medium (Category III) importance to human medicine. The 4 S. Ohio isolates were recovered from 3 different steps of pork processing on the same sampling day and displayed resistance to 5-7 antimicrobials, with all of them displaying resistance to ceftiofur and ceftriaxone (Category I). An I:Rough-O:l,v:- isolate, recovered on a different sampling day, was resistant to 7 antimicrobials that included resistance to ampicillin/clavulanic acid, ceftiofur and ceftriaxone (Category I). Salmonella strains isolated from plant A harbored 12 different AMR genes. The most prevalent genes were sul1, sul2, tet(A), tet(B), aadA, strA/strB, aac(3)IV and aphA1. For Salmonella isolates from plant B, 7 resistance genes were identified alone or in combination where tet(B) was found in 77 (62.3%) of the isolates. For plant A, 19 different PFGE subtypes of Salmonella isolates that displayed phenotypic and/or genotypic resistance were observed while 13 different PFGE subtypes were observed for plant B. The lack of detection of Salmonella on the surfaces of RP suggests that current pork processing practices can dramatically reduce Salmonella. Salmonella isolates from pig carcasses at various steps displayed multidrug resistance, including to those of very high importance in human medicine, which represent a public health concern.

Ciprofloxacin-resistant Campylobacter spp. in retail chicken, western Canada.

During 2005-2010, the Canadian Integrated Program for Antimicrobial Resistance Surveillance identified increased prevalence of ciprofloxacin (a fluororquinolone) resistance among Campylobacter isolates from retail chicken in British Columbia (4%-17%) and Saskatchewan (6%-11%), Canada. Fluoroquinolones are critically important to human medicine and are not labeled for use in poultry in Canada.

Antimicrobial resistance in fecal generic Escherichia coli and Salmonella spp. obtained from Ontario sheep flocks and associations between antimicrobial use and resistance.

The purpose of this study was to examine the prevalence and patterns of antimicrobial resistance (AMR) in enteric bacteria obtained from Ontario sheep flocks, and associations between antimicrobial use (AMU) and AMR. Forty-nine sheep producers participated for a 1-year interval between 2006 and 2008. Two-hundred and eighty-three pooled fecal samples were collected from the flocks during initial and final visits. Up to 3 isolates of Salmonella spp. and generic E. coli per pooled fecal sample were tested for susceptibility to 15 antimicrobials. Resistance was infrequent among Salmonella (0%, n = 7 isolates) and low among E. coli (13.1%; n = 849) isolates. A small number of isolates were resistant to antimicrobials classified as being of very high importance to human health. Tetracycline resistance was most frequently observed (12.0%). Logistic regression was used to model potential AMU (qualitative and quantitative) risk factors for tetracycline resistance in generic E. coli from final visits. Qualitative analysis indicated that the use of injectable sulfonamides [including trimethoprim-sulfonamide combinations (TMS)] and tetracycline in the feed and water were significantly associated with tetracycline resistance (OR = 2.6, P = 0.01; and OR = 4.8, P ≤ 0.01, respectively). Quantitative analysis also indicated that TMS exposure rate was significantly associated with tetracycline resistance, which varied depending on the exposure rate. The exposure rate of tetracycline in the feed and water was only significant after the removal of one influential flock, warranting further research examining flocks with higher tetracycline exposure rates. Although the prevalence of AMR in participating flocks was relatively low, risk factors for resistance were identified.

Rates and determinants of antimicrobial use, including extra-label, on Ontario sheep farms.

Few antimicrobials are licensed for use in sheep in Canada, and the range of indications is narrow. Treatment in an "extra-label" manner may be ineffective. In addition, potentially harmful drug residues in food-animal products and antimicrobial resistance in bacteria may be associated with extra-label drug use (ELDU). No data had been documented on drug use, specifically antimicrobial use (AMU), in Ontario sheep, although it was thought that much use was extra-label. This study investigated AMU and ELDU on 49 lamb-producing Ontario sheep farms. Data were prospectively collected over 12 months from the participating farms, and farm-level practices were ascertained with a questionnaire. Treatment-level and farm-level variables were investigated for associations with rates of AMU by means of Poisson rate regression models fit with a generalized estimating equation to control for clustering at the farm level. Antimicrobials with high mean exposure rates included chlortetracycline (in feed), penicillins, and oxytetracycline. The exposure rate in lambs was significantly lower (P < 0.01) with antimicrobial treatment of systemic signs, respiratory disease, or wound or injury than with treatment of other reported diseases or conditions; it was also significantly lower with 3 or more lambing periods per year (α = 0.05). The exposure rate in adult sheep was significantly lower with treatment of 5 of the 6 most prevalent diseases or conditions (α = 0.05) and significantly higher with producer decision to treat and producer experience of 20 y or greater. Rates of using antimicrobials not licensed for use in sheep were high, as was extra-label use of licensed antimicrobials. Diseases reportedly treated most often with antimicrobials (e.g., systemic signs, mastitis) were significantly associated with lower rates of ELDU (α = 0.05). Compared with the rates in adult sheep, the mean rate of use of nonlicensed antimicrobials was similar in the lambs, whereas the mean rate of extra-label use of licensed antimicrobials was lower among the lambs. The results are useful in determining if public health concerns about antimicrobial use in Ontario sheep are warranted and in creating drug use and licensure strategies for the Canadian sheep industry.

Clostridium difficile in seafood and fish.

The objective of this study was to determine the prevalence of Clostridium difficile contamination in retail seafood and fish from Canadian grocery stores. C. difficile was found in 4.8% (5/119) of the samples. This study, combined with studies of other food sources, suggests that widespread contamination of food is common.

Prevalence of Clostridium difficile in retail pork.

Clostridium difficile was isolated from 1.8% (7/393) of retail pork samples obtained from 4 Canadian provinces. Five ribotypes and 3 toxinotypes were identified. Three isolates were indistinguishable from the international outbreak strain ribotype 027 and were toxinotype III. Although the implications for food safety practices remain elusive, the frequency of toxigenic isolates and isolates indistinguishable from known human pathogenic strains suggests contaminated pork may be a source of C. difficile in humans.

Characteristics of drug use on sheep farms in Ontario, Canada.

This study examined characteristics of the use of drugs, especially antimicrobials, on Ontario sheep farms. Forty-nine sheep farms participated in a 12-month prospective study. Producers documented treatment events during the study period and drug use data from the records were summarized. The most frequently used drugs of the 15 drug categories used by producers belonged to the following categories: antimicrobial (40.7%, n=2710), vitamin/mineral (12.0%), and biological (11.1%). Short-acting penicillin (27.2%, n=1103), long-acting oxytetracycline (22.9%), and long-acting penicillin (21.9%) were the most frequently used antimicrobials. The drugs that were used most frequently on sheep farms were antimicrobials, of which 93% of treatments were extra-label. Extensive extra-label drug use may be the result of the limited number of drugs that are approved in Canada for use in sheep.

Detection and enumeration of Clostridium difficile spores in retail beef and pork.

Recent studies have identified Clostridium difficile in food animals and retail meat, and concern has been raised about the potential for food to act as a source of C. difficile infection in humans. Previous studies of retail meat have relied on enrichment culture alone, thereby preventing any assessment of the level of contamination in meat. This study evaluated the prevalence of C. difficile contamination of retail ground beef and ground pork in Canada. Ground beef and ground pork were purchased from retail outlets in four Canadian provinces. Quantitative and enrichment culture was performed. Clostridium difficile was isolated from 28/230 (12%) samples overall: 14/115 (12%) ground beef samples and 14/115 (12%) ground pork samples (P = 1.0). For ground beef, 10/14 samples (71%) were positive by enrichment culture only. Of the 4 ground beef samples that were positive by direct culture, 20 spores/g were present in 2 while 120 and 240 spores/g were present in 1 each. For ground pork, 10/14 (71%) samples were positive by enrichment culture only. Of the 4 ground pork samples that were positive by direct culture, 20 spores/g were present in 3 while 60 spores/g were present in 1. Ribotype 078 predominated, consistent with some previous studies of C. difficile in food animals. Ribotype 027/North American pulsotype 1 was also identified in both retail beef and pork. This study has identified relatively common contamination of retail ground beef and pork with C. difficile spores; however, the levels of contamination were very low.

Possible seasonality of Clostridium difficile in retail meat, Canada.

We previously reported Clostridium difficile in 20% of retail meat in Canada, which raised concerns about potential foodborne transmissibility. Here, we studied the genetic diversity of C. difficile in retail meats, using a broad Canadian sampling infrastructure and 3 culture methods. We found 6.1% prevalence and indications of possible seasonality (highest prevalence in winter).