Diagnosis of Renibacterium salmoninarum infection in harvested Atlantic salmon (Salmo salar L.) on the east coast of Canada: Clinical findings, sample collection methods and laboratory diagnostic tests.

Chronic subclinical infection with the aetiological agent of bacterial kidney disease (BKD), Renibacterium salmoninarum, presents challenges for the clinical management of disease in farmed salmonids and for prevalence estimation. Harvested salmon sampled at processing plants provide the opportunity to describe subclinical outcomes of BKD using gross necropsy observations and diagnostic test results in farmed Atlantic salmon (Salmo salar L.) populations that are apparently healthy (i.e. alive at harvest) but naturally exposed to R. salmoninarum infection. Sampling of farmed salmon (Population A, n = 124 and Population B, n = 160) was performed immediately post-slaughter as fish were being processed at a plant in New Brunswick, Canada. Populations were selected based on planned harvests from sites with histories of recent exposure events related to clinical BKD as evidenced by the site veterinarian's diagnosis of mortality attributable to BKD: One site (Pop A) had recently increasing mortalities attributed to BKD, and the other site (Pop B) had ongoing low-level mortalities with BKD pathology. As expected with the different exposure histories, Pop A had a higher percentage (57.2%) of R. salmoninarum culture-positive kidney samples compared with similar fish samples in Pop B (17.5%). Diagnosis of R. salmoninarum by gross granulomatous lesions in internal visceral organs, bacterial culture and identification by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) using different swab transport methods, and molecular detection methods (quantitative PCR, qPCR) were compared. Agreement of culture-positive percentages at the sample level was moderate (kappa: 0.61-0.75) among specimens collected using different kidney sampling methods in Pop A and Pop B. The highest proportion of R. salmoninarum-positive cultures occurred when kidney tissues were transported to the laboratory and inoculated directly onto agar using a swab (94% of cultures from Pop A and 82% from Pop B when fish were positive by any culture method). Fish with cumulative lesion scores (severity of granulomatous lesions in 3 different visceral organs) of >4 were all culture positive, and when compared with non-lesioned fish, had substantially higher odds of being culture positive: Pop A: odds ratio (OR) = 73, 95% confidence interval (CI) (7.91, 680.8); Pop B: OR = 66, 95% CI (6.12, 720.7). Our study found that onsite postmortem examinations with severity scores of gross granulomatous lesions were predictive of positive culture results for R. salmoninarum, and they were a useful proxy for assessing prevalence in apparently healthy populations with subclinical infection.

Comparison of chlorhexidine and alcohol-based antisepsis on the paralumbar fossa in cattle.

OBJECTIVE: To determine skin reaction, post-treatment reduction (immediate effect), and 1 hour post-treatment reduction (sustained effect) of aerobic bacterial colony forming units (CFU) following three antiseptic protocols in cattle. STUDY DESIGN: Prospective, randomized experimental study. ANIMALS: Eighteen cows. METHODS: Three sites in each paralumbar fossa were clipped and randomly assigned to one of three treatment groups: 5 minute 4% chlorhexidine gluconate scrub (CHG); 90 second 80% ethanol scrub (ET); 90 second 70% isopropyl alcohol scrub (IPA). All sites were monitored at all sampling time points and at 24 hours following treatment for adverse skin reaction. Samples were collected pre-, immediately post-, and 1 hour post-treatment and plated in duplicate. Bacterial counts were shifted to eliminate zeroes, log10 transformed, and averaged. ANOVA was used to compare differences in mean reduction in log10 CFU/ml between groups. RESULTS: Reduction in log10CFU/ml was more pronounced immediately after application of IPA (p = .001) and ET (p = .001) than CHG. This reduction was better sustained after preparation with CHG than ET (p = .005) but not IPA. Immediate and sustained reductions in bacterial loads did not differ after application of IPA or ET. No adverse skin reactions were noted. CONCLUSIONS: Skin preparation with alcohol-based antiseptics was well tolerated and improved immediate bacterial reduction compared to CHG. This reduction was better sustained 1 hour after application of CHG than ET, but no difference was detected between CHG and IPA. CLINICAL RELEVANCE: Lack of adverse skin reaction and performance provide evidence to support skin preparation with alcohol-based antiseptics in cattle.

Occurrence of extended-spectrum ß-lactamase and AmpC-producing Escherichia coli in retail meat products from the Maritime Provinces, Canada.

This study was conducted to determine the occurrence of antimicrobial resistance to the extended-spectrum cephalosporins (ESC) in Escherichia coli isolates. The isolates were collected from retail meat products collected in the Maritime Provinces of Canada. Our analyses involved the use of both selective and traditional culture methods; we also conducted genotype analyses using multiplex polymerase chain reactions. ESC-resistant (ESC-R) E. coli were detected in 33 of 559 samples (5.9%) using the traditional culture method, compared with 151 of 557 samples (27.1%) using the selective culture method. We recovered more isolates of ESC-R E. coli from poultry compared with beef and pork (P < 0.001). Multidrug resistance, extended-spectrum ß-lactamase (ESBL), and AmpC phenotypes were more common in chicken-derived isolates than other retail meat products (P < 0.001). From the 98 isolates examined, 76 isolates (77.6%) were positive for either ESBL and AmpC ß-lactamases or both. Among the 76 isolates, blaCMY-2 (78.9%), blaCTXM (46.1%), blaTEM (21.1%), and blaSHV (1.3%) genes were detected. Among the blaCTXM-producing isolates, blaCTXM-1, blaCTXM-2, and blaCTXM-9 phylogenetic groups were detected. ß-lactamase genes were more commonly detected in chicken-derived isolates compared with other meat types (P < 0.01). This study demonstrates the occurrence of ESBL- and AmpC-resistance genes in retail meat products in the Maritime Provinces of Canada. We found that selective culture significantly improved the recovery of ESC-R E. coli isolates from retail meat samples.

Short communication: Whole-genome sequence analysis of 4 fecal blaCMY-2-producing Escherichia coli isolates from Holstein dairy calves.

This study was carried out to determine the antimicrobial resistance (AMR) genes and mobile genetic elements of 4 fecal blaCMY-2-producing Escherichia coli isolated from Holstein dairy calves on the same farm using whole-genome sequencing. Genomic analysis revealed that 3 of the 4 isolates shared similar genetic features, including sequence type (ST), serotype, plasmid characteristics, insertion ST, and virulence genes. In addition to genes encoding for complex multidrug resistance efflux systems, all 4 isolates were carriers of genes conferring resistance to ß-lactams (blaCMY-2, blaTEM-1B), tetracyclines (tetA, tetB, tetD), aminoglycosides [aadA1, aph(3")-lb, aph(6)-ld], sulfonamides (sul2), and trimethoprim (dfrA1). We also detected 4 incompatibility plasmid groups: Inc.F, Inc.N, Inc.I, and Inc.Q. A novel ST showing a new purA and mdh allelic combination was found. The 4 isolates were likely enterotoxigenic pathotypes of E. coli, based on serotype and presence of the plasmid Inc.FII(pCoo). This study provides information for comparative genomic analysis of AMR genes and mobile genetic elements. This analysis could give some explanation to the multidrug resistance characteristics of bacteria colonizing the intestinal tract of dairy calves in the first few weeks of life.

Determination of antimicrobial resistance to extended-spectrum cephalosporin, quinolones, and vancomycin in selected human enteric pathogens from Prince Edward Island, Canada.

The aim of this study was to determine the frequency of fecal carriage of vancomycin-resistant Enterococcus spp. and Escherichia coli with reduced susceptibilities to extended-spectrum cephalosporins (ESCs) and quinolones in humans on Prince Edward Island, Canada. Convenience fecal samples from individuals on Prince Edward Island were screened phenotypically using selective culture and genotypically using multiplex polymerase chain reactions to detect E. coli and Enterococcus spp. resistant to critically important antimicrobials. Twenty-six (5.3%) of 489 individuals had E. coli with reduced susceptibility to ESCs. Twenty-five (96.2%) of the 26 isolates harbored blaTEM, 18 (69.2%) harbored blaCMY-2, 16 (61.5%) harbored blaCTX-M groups, 2 (7.7%) harbored blaSHV genes. None of the ESC-resistant E. coli was positive for carbapenem resistance. Twenty-one (8.3%) of 253 individuals had E. coli isolates with reduced quinolone susceptibility. All 21 isolates were positive for at least 1 qnr gene, with 3 (14.3%) isolates positive for qnrB, 5 (23.8%) positive for qnrS, and 13 (61.9%) positive for both qnrB and qnrS genes. All the enterococci isolates were vancomycin-susceptible. Higher susceptibility to the critically important antimicrobials was found in this study. This study can serve as a baseline for future antimicrobial resistance surveillance within this region.

Antimicrobial resistance in mastitis, respiratory and enteric bacteria isolated from ruminant animals from the Atlantic Provinces of Canada from 1994-2013.

Diagnostic laboratory antimicrobial susceptibility data for bacteria isolated from clinical samples of cattle, sheep, and goats from 1994 to 2013 were evaluated retrospectively. Among bacteria from bovine mastitis, Staphylococcus aureus and Streptococcus uberis were the most commonly isolated organisms. Pasteurella multocida, Mannheimia haemolytica, and Histophilus somni were commonly isolated from the respiratory tract, while Escherichia coli isolates were frequently recovered from the intestinal tract. Isolates from mastitis were generally highly susceptible to the antimicrobials tested, except neomycin and oxytetracycline. Respiratory tract isolates were highly susceptible to trimethoprim-sulfamethoxazole, penicillin, florfenicol, and ceftiofur, while enteric bacteria were frequently susceptible to ceftiofur. Antimicrobial resistance trends over the study period were generally stable for small ruminant and cattle isolates. Multi-drug resistance was more common among respiratory isolates from small ruminants compared to those from cattle but more common in enteric bacteria from cattle compared to those from small ruminants. This information may guide clinicians when they are choosing empirical therapies for the treatment of ruminant animals in Atlantic Canada.

Résistance antimicrobienne des bactéries respiratoires et entériques et de la mammite isolées des ruminants dans les provinces de l'Atlantique de 1994 à 2013. Les données de susceptibilité antimicrobienne des laboratoires diagnostiques, de 1994 à 2013, pour les bactéries isolées d'échantillons cliniques de bovins, de moutons et de chèvres, ont été évaluées rétrospectivement. Parmi les bactéries trouvées en lien avec la mammite bovine, Staphylococcus aureus et Streptococcus uberis ont été les organismes les plus communément isolés. Pasteurella multocida, Mannheimia haemolytica et Histophilus somni ont été communément isolés de l'appareil respiratoire, tandis que des isolats d'Escherichia coli étaient fréquemment récupérés du tractus intestinal. Les isolats de la mammite étaient généralement hautement susceptibles aux antimicrobiens testés, sauf pour la néomycine et l'oxytétracycline. Les isolats de l'appareil respiratoire étaient hautement susceptibles au triméthoprime-sulfaméthoxazole, à la pénicilline, au florfénicol et au ceftiofur, tandis que les bactéries entériques étaient fréquemment susceptibles au ceftiofur. Les tendances d'antibiorésistance pendant la période de l'étude étaient généralement stables pour les isolats des petits ruminants et des bovins. La multirésistance aux médicaments était plus commune pour les isolats respiratoires provenant des petits ruminants comparativement à ceux des bovins et plus commune dans les bactéries entériques des bovins par rapport à celles des petits ruminants. Ces données pourront guider les cliniciens qui choisissent des thérapies empiriques pour le traitement des ruminants dans les provinces de l'Atlantique.(Traduit par Isabelle Vallières).

Antimicrobial resistance in bacteria isolated from cats and dogs from the Atlantic Provinces, Canada from 1994-2013.

Antimicrobial susceptibility patterns and trends in bacteria isolated from cats and dogs were determined from diagnostic laboratory data from the Atlantic Veterinary College Diagnostic Services Bacteriology Laboratory over a 20-year period. Clinical samples were most commonly from the urinary tract and the ear. Staphylococcus spp. and Escherichia coli were the bacteria that were most frequently isolated. Increases in percentage resistant were seen with E. coli to cephalexin (57% to 61%), Pasteurella spp. to erythromycin (35% to 53%), and Pseudomonas aeruginosa (31% to 39%), and Streptococcus spp. (46% to 53%) to enrofloxacin. The frequency of resistance did not change significantly over the study period; however, increased enrofloxacin resistance was identified for canine isolates of Staphylococcus spp., Streptococcus spp., Enterococcus spp., E. coli, P. aeruginosa, and Proteus spp. Multidrug resistance was observed in 12% and 9% of the isolates from dogs and cats, respectively. Data from this study could be used to guide empirical antimicrobial selection in companion animal veterinary practices in Atlantic Canada.

Résistance antimicrobienne des bactéries isolées chez des chats et des chiens des provinces de l'Atlantique, Canada, de 1994 à 2013. Les tendances de susceptibilité antimicrobienne des bactéries isolées chez des chats et des chiens ont été déterminées d'après les données des laboratoires de diagnostic du Diagnostic Services Bacteriology Laboratory de l'Atlantic Veterinary College pendant une période de 20 ans. Les échantillons cliniques provenaient le plus communément des voies urinaires et de l'oreille. Staphylococcus spp. et Escherichia coli étaient les bactéries les plus fréquemment isolées. Une hausse du pourcentage de la résistance a été observée pour E. coli à la céphalexine (de 57 % à 61 %), pour Pasteurella spp. à l'érythromycine (de 35 % à 53 %) ainsi que pour Pseudomonas aeruginosa (de 31 % à 39 %) et Streptococcus spp. (de 46 % à 53 %) à l'enrofloxacine. La fréquence de la résistance n'a pas changé significativement pendant la période de l'étude. Cependant, une résistance accrue à l'enrofloxacine a été identifiée pour les isolats canins de Staphylococcus spp., de Streptococcus spp., d'Enterococcus spp., d'E. coli, de P. aeruginosa, et de Proteus spp. La multirésistance aux médicaments a été observée dans 12 % et 9 % des isolats des chiens et des chats, respectivement. Les données de cette étude pourraient être utilisées pour guider le choix empirique des antimicrobiens dans les pratiques vétérinaires pour animaux de compagnie des provinces de l'Atlantique.(Traduit par Isabelle Vallières).

Antimicrobial resistance in bacteria isolated from horses from the Atlantic Provinces, Canada (1994 to 2013).

This study determined the antimicrobial susceptibility patterns and trends for selected bacteria isolated from horses using diagnostic data from the Atlantic Veterinary College Diagnostic Services Bacteriology Laboratory, Charlottetown, Prince Edward Island over a 20-year period. Streptococcus equi subsp. zooepidemicus and Escherichia coli were the most commonly isolated bacteria over the study period. Clinical samples were most frequently submitted from respiratory and reproductive systems. Most bacterial isolates were susceptible to ceftiofur. Resistance was most common in Gram-negative enteric bacteria, while streptococci were frequently susceptible to most of the antimicrobials tested including penicillin and trimethoprim-sulfamethoxazole. The antimicrobial resistance trends over the study period were relatively stable. Multi-drug resistance was observed in 9% of the bacterial isolates. Information provided in this study could be used to help guide rational, empirical antimicrobial treatment selection in equine practices in Atlantic Canada.

Résistance aux antimicrobiens dans les bactéries isolées des chevaux dans les provinces de l'Atlantique, au Canada, de 1994 à 2013. Cette étude a déterminé les modèles et les tendances de susceptibilité antimicrobienne pour certaines bactéries isolées des chevaux en s'appuyant sur des données diagnostiques du Laboratoire de bactériologie des services diagnostiques de l'Atlantic Veterinary College à Charlottetown, à l'Île-du-Prince-Édouard, pendant une période de 20 ans. Streptococcus equi ssp. zooepidemicus et Escherichia coli ont été les bactéries les plus communément isolées pendant la période à l'étude. Des échantillons cliniques des systèmes respiratoires et reproducteurs étaient les plus fréquemment soumis. La plupart des isolats bactériens étaient susceptibles au ceftiofur. La résistance était la plus courante chez les bactéries entériques à Gram négatif, tandis que les streptocoques étaient fréquemment susceptibles à la plupart des antimicrobiens testés incluant la pénicilline et le triméthoprime-sulfaméthoxazole. Les tendances de résistance aux antimicrobiens pendant la période à l'étude étaient relativement stables. Une multirésistance aux médicaments a été observée dans 9 % des isolats bactériens. Les renseignements fournis dans cette étude pourraient servir à guider un choix rationnel et empirique pour les traitements antimicrobiens dans les pratiques équines des provinces de l'Atlantique.(Traduit par Isabelle Vallières).

Retrospective study on the occurrence of Salmonella serotypes in veterinary specimens of Atlantic Canada (2012-2021).

AIM: This study aimed to summarize the frequency and the antimicrobial susceptibility profiles of the Salmonella serotypes identified from the specimens of companion animals, livestock, avian, wildlife and exotic species within Atlantic Canada. MATERIALS AND METHODS: The retrospective electronic laboratory data of microbiological analyses of a selected subset of samples from 03 January 2012 to 29 December 2021 submitted from various animal species were retrieved. The frequency of Salmonella serotypes identified, and their antimicrobial susceptibility results obtained using the disk diffusion or broth method were analysed. The test results were interpreted according to the Clinical and Laboratory Standards Institute standard. The Salmonella serotypes were identified by slide agglutination (Kauffman-White-Le-Minor Scheme) and/or the Whole Genome Sequencing for the Salmonella in silico Serovar Typing Resource-based identification. RESULTS: Of the cases included in this study, 4.6% (n = 154) had at least one Salmonella isolate, corresponding to 55 different serovars. Salmonella isolation was highest from exotic animal species (n = 40, 1.20%), followed by porcine (n = 26, 0.78%), and canine (n = 23, 0.69%). Salmonella subsp. enterica serovar Typhimurium was predominant among exotic mammals, porcine and caprine samples, whereas S. Enteritidis was mostly identified in bovine and canine samples. S. Typhimurium of porcine origin was frequently resistant (>70.0%) to ampicillin. In contrast, S. Typhimurium isolates from porcine and caprine samples were susceptible (>70.0%) to florfenicol. S. Oranienburg from equine samples was susceptible to chloramphenicol, but frequently resistant (>90.0%) to azithromycin. In avian samples, S. Copenhagen was susceptible (>90.0%) to florfenicol, whereas Muenchen was frequently resistant (>90.0%) to florfenicol. S. subsp. diarizonae serovar IIIb:61:k:1,5 of ovine origin was resistant (50.0% isolates) to sulfadimethoxine. No significant changes were observed in the antibiotic resistance profiles across the study years. CONCLUSIONS: This report provides data for surveillance studies, distribution of Salmonella serotypes and their antimicrobial resistance among veterinary specimens of Atlantic Canada.

Genome Sequence Comparisons between Small and Large Colony Phenotypes of Equine Clinical Isolates of Arcanobacterium hippocoleae.

Arcanobacterium hippocoleae is a Gram-positive fastidious bacterium and is occasionally isolated from the reproductive tract of apparently healthy mares (Equus caballus) or from mares with reproductive tract abnormalities. Apart from a few 16S rRNA gene-based GenBank sequences and one recent report on complete genome assembly, detailed genomic sequence and clinical experimental data are not available on the bacterium. Recently, we observed an unusual increase in the detection of the organism from samples associated with mare reproductive failures in Atlantic Canada. Two colony morphotypes (i.e., small, and large) were detected in culture media, which were identified as A. hippocoleae by MALDI-TOF mass spectrometry and 16S rRNA gene sequencing. Here, we report the whole genome sequencing and characterization of the morphotype variants. The genome length of the large phenotypes was between 2.42 and 2.43, and the small phenotype was 1.99 Mbs. The orthologous nucleotide identity between the large colony phenotypes was ~99%, and the large and small colony phenotypes was between 77.86 and 78.52%, which may warrant the classification of the two morphotypes into different species. Phylogenetic analysis based on 16S rRNA genes or concatenated housekeeping genes grouped the small and large colony variants into two different genotypic clusters. The UvrA protein, which is part of the nucleotide excision repair (NER) system, and 3-isopropoylmalate dehydratase small subunit protein expressed by the leuD gene were identified as potential virulence factors in the large and small colony morphotypes, respectively. However, detailed functional studies will be required to determine the exact roles of these and other identified hypothetical proteins in the cellular metabolism and potential pathogenicity of A. hippocoleae in mares.

Occurrence and antimicrobial resistance of Salmonella species and potentially pathogenic Escherichia coli in free-living seals of Canadian Atlantic and eastern Arctic waters.

Seal populations in Canadian waters provide sustenance to coastal communities. There is potential for pathogenic and/or antimicrobial-resistant bacteria to transfer to humans through inadvertent faecal contamination of seal products. The objective of this study was to investigate the occurrence and potential antimicrobial resistance of Salmonella spp., Escherichia coli and Listeria monocytogenes in faecal samples collected from grey seals (Halichoerus grypus) in the Gulf of St. Lawrence and from ringed seals (Pusa hispida) in Frobisher Bay and Eclipse Sound, Nunavut, Canada. Grey seals were harvested during commercial hunts or during scientific sampling; ringed seals were collected by Inuit hunters during subsistence harvests. Virulence genes defining pathogenic E. coli were identified by PCR, and antimicrobial susceptibility testing was performed on recovered isolates. In grey seals, E. coli was detected in 34/44 (77%) samples, and pathogenic E. coli (extraintestinal E. coli [ExPEC], enteropathogenic E. coli [EPEC] or ExPEC/EPEC) was detected in 13/44 (29%) samples. Non-susceptibility to beta-lactams and quinolones was observed in isolates from 18 grey seals. In ringed seals from Frobisher Bay, E. coli was detected in 4/45 (9%) samples; neither virulence genes nor antimicrobial resistance was detected in these isolates. In ringed seals from Eclipse Sound, E. coli was detected in 8/50 (16%) samples and pathogenic E. coli (ExPEC and ExPEC/EPEC) in 5/50 (10%) samples. One seal from Eclipse Sound had an E. coli isolate resistant to beta-lactams. A monophasic Salmonella Typhimurium was recovered from 8/50 (16%) seals from Eclipse Sound. All Salmonella isolates were resistant to ampicillin, streptomycin, sulfisoxazole and tetracycline. L. monocytogenes was not detected in any sample. These findings suggest that seals may act as important sentinel species and as reservoirs or vectors for antimicrobial-resistant and virulent E. coli and Salmonella species. Further characterization of these isolates would provide additional insights into the source and spread of antimicrobial resistance and virulence genes in these populations of free-living seals.

Development and validation of main spectral profile for rapid identification of Yersinia ruckeri isolated from Atlantic salmon using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry.

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows rapid and reliable identification of microorganisms. The accuracy of bacterial identification using MALDI-TOF MS depends on main spectral profiles (MSPs) provided in a quality-assured commercial reference library, which requires ongoing improvement. This study aimed to develop and validate an in-house MALDI-TOF MS MSP to rapidly identify Yersinia ruckeri isolated from Atlantic salmon (Salmo salar). The novel MSP was prepared using an isolate of Y. ruckeri recovered from Atlantic salmon and confirmed by 16S rRNA gene sequencing. Subsequently, a validation set which comprises 29 isolates of Y. ruckeri were examined from three fishes: Atlantic salmon (Salmo salar) (n = 26), American eel (Anguilla rostrata) (n = 1), and Atlantic cod (Gadus morhua) (n = 2). These isolates were randomly selected from the Atlantic Veterinary College, Aquatic Diagnostic Services Bacteriology Laboratory's culture collection to validate the novel MSP. Analytical sensitivity of MALDI-TOF MS using the novel MSP to identify the validation set was 86.2%. Repeatability was assessed by acquiring spectra from 30 different spots of a randomly-selected isolate of Y. ruckeri, and analyzed spectra from each spot were compared against the novel MSP. The coefficient of variation was 3.3%. The novel MSP clustered with Bruker MSPs (n = 3) of Y. ruckeri in the reference library and did not falsely identify any closely related bacteria to Y. ruckeri. This study reports the development of a novel MSP of high analytical sensitivity and specificity for rapid identification of Y. ruckeri using MALDI-TOF MS.

Antimicrobial Susceptibility Profiles of Bacteria Commonly Isolated from Farmed Salmonids in Atlantic Canada (2000-2021).

Bacterial infection and antimicrobial resistance are important constraints in the production and sustainability of farmed salmonids. This retrospective study aimed to describe the frequency of bacterial isolates and antimicrobial resistance profiles in salmonid aquaculture in Atlantic Canada. Bacterial isolates and antimicrobial susceptibility testing (AST) results assessed by disk diffusion testing were summarized for 18,776 Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss) samples from 2291 unique cases submitted to the Atlantic Veterinary College, Aquatic Diagnostic Services Bacteriology Laboratory from 2000 to 2021. Kidney was the most commonly submitted tissue (60.29%, n = 11,320), and these specimens were mostly submitted as swabs (63.68%, n = 11,957). The most prevalent pathogens detected in these cases were Yersinia ruckeri type 1 (5.54%, n = 127), Renibacterium salmoninarum (2.10%, n = 48), Aeromonas salmonicida (atypical) (1.66%, n = 38), and Pseudomonas fluorescens (1.22%, n = 28). Most bacterial isolates tested (n = 918) showed resistance to florfenicol, oxytetracycline, ormetoprim-sulfadimethoxine, and trimethoprim-sulfamethoxazole, but not to enrofloxacin. This report provides baseline data for antimicrobial surveillance programs that investigate emerging antimicrobial resistance trends in salmonid aquaculture in Atlantic Canada.

Comparison of chlorhexidine and alcohol-based antisepsis of the distal limbs of horses.

BACKGROUND: An alcohol-based rub has been confirmed effective at reducing bacterial counts on equine skin. Skin sites with expected high bacterial burden have not been tested or has a comparison to a common protocol been performed. OBJECTIVES: To determine if ethanol-based antisepsis reduces bacterial counts on the equine distal limb comparable to a current chlorhexidine scrub method and determine the most effective application technique for the product. STUDY DESIGN: Randomised trial. METHODS: Forty-one horses were used in the study. By horse, each limb was randomly assigned to a treatment group: 5min scrub using 4% chlorhexidine gluconate to a clipped site (CHG); 90s scrub using 80% ethanol to a clipped site (ETC); 90s contact with 80% ethanol applied as a spray to a clipped site (ETS) and 90s scrub using 80% ethanol to an unclipped site (ETUC). Samples were collected pre- and post-treatment and plated in duplicate. Bacterial counts were log10 transformed and averaged between duplicates. A linear mixed model was used to compare mean log10 CFU/mL reduction between groups. A cost-benefit analysis was performed. RESULTS: There was no significant difference in mean log10 CFU/mL reduction between CHG and ETC in either fore- or hindlimbs. In forelimbs, there was no significant difference in mean log10 CFU/mL reduction between any groups. In hindlimbs, CHG had significantly greater mean log10 CFU/mL reduction than ETUC and ETS. No significant difference in cost-benefit was found between CHG and ETC. Significant differences were noted between CHG and both ETUC and ETS. MAIN LIMITATIONS: Researchers were not blinded to treatment group during sample collection. CONCLUSIONS: This study showed no significant difference in reduction in bacterial counts on the distal limb of horses between CHG and ethonol (ET) when applied as a scrub to a clipped site and there was no significant difference in cost-benefit between these treatments.

Genomics accurately predicts antimicrobial resistance in Staphylococcus pseudintermedius collected as part of Vet-LIRN resistance monitoring.

Whole-genome sequencing (WGS) has changed our understanding of bacterial pathogens, aiding outbreak investigations and advancing our knowledge of their genetic features. However, there has been limited use of genomics to understand antimicrobial resistance of veterinary pathogens, which would help identify emerging resistance mechanisms and track their spread. The objectives of this study were to evaluate the correlation between resistance genotypes and phenotypes for Staphylococcus pseudintermedius, a major pathogen of companion animals, by comparing broth microdilution antimicrobial susceptibility testing and WGS. From 2017-2019, we conducted antimicrobial susceptibility testing and WGS on S. pseudintermedius isolates collected from dogs in the United States as a part of the Veterinary Laboratory Investigation and Response Network (Vet-LIRN) antimicrobial resistance monitoring program. Across thirteen antimicrobials in nine classes, resistance genotypes correlated with clinical resistance phenotypes 98.4 % of the time among a collection of 592 isolates. Our findings represent isolates from diverse lineages based on phylogenetic analyses, and these strong correlations are comparable to those from studies of several human pathogens such as Staphylococcus aureus and Salmonella enterica. We uncovered some important findings, including that 32.3 % of isolates had the mecA gene, which correlated with oxacillin resistance 97.0 % of the time. We also identified a novel rpoB mutation likely encoding rifampin resistance. These results show the value in using WGS to assess antimicrobial resistance in veterinary pathogens and to reveal putative new mechanisms of resistance.

Equine Skin Antisepsis Using an Alcohol-Based Rub.

Alcohol-based antisepsis has been extensively studied in human health care, but only little information is available regarding efficacy and tolerance in other species. The purpose of this study was to determine if an alcohol-based antiseptic is effective at reducing bacterial counts on equine skin and the appropriate contact time to do so, without causing any adverse skin reactions. Samples were collected before and after preparation from clipped sites over both jugular veins of horses and were plated on 3M Petrifilm Aerobic Count Plates in duplicate. Trial 1 tested an alcohol-based product (ET-80% ethanol) against a control of sterile saline at a contact time of 180-second. Trial 2 tested two different contact times of ET-90 and 180 seconds. All samples were assessed for colony-forming unit counts using an automated 3M Petrifilm reader. Data were analyzed by Kruskal-Wallis test, and the significance was set at P < .05. The results determined that ET had a mean 2.95 log10 reduction from prepreparation to postpreparation colony-forming unit counts. A significant difference in log reduction between ET and control (P = .0033) was observed. There was no difference in log10 reduction between the two contact times (P = .75). Mild urticaria was the only skin reaction observed and was often present in both ET and control groups. These findings demonstrate that ET is effective at reducing bacterial counts on equine skin at a contact time of 90 seconds without producing significant adverse skin reaction.

Comparison of culture methodology for the detection of methicillin-resistant Staphylococcus pseudintermedius in clinical specimens collected from dogs.

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) has emerged as a major pathogen in dogs and has been implicated as a hospital-acquired pathogen in veterinary hospitals. We attempted to determine if selective culture methods will detect more MRSP when compared to the traditional culture methods in clinical samples from dogs in Atlantic Canada with a high risk for MRSP infection. Each sample was tested using 4 culture methods: traditional culture; mannitol salt agar with 2 µg/mL of oxacillin (MSAox); enrichment broth (EB) with MSAox; and EB with traditional culture. Detection of penicillin-binding protein 2', via latex agglutination, was used as a confirmatory test for oxacillin resistance. We analyzed 741 samples from 556 dogs between February 2013 and April 2014. The prevalence of MRSP in samples detected by any method was estimated at 13.4% (95% CI: 11.1-16.0%). When the prevalence of MRSP was determined according to culture method, EB with MSAox detected the highest prevalence (11.2% [9.1-13.7%]), followed by EB with traditional (10.8% [8.8-13.2%]), traditional (10.1% [8.1-12.5%]), and MSAox (8.9% [7.1-11.2%]). The prevalence using the traditional culture method did not differ significantly from any of the 3 selective culture methods. Culture with MSAox detected significantly fewer MRSP than either of the EB methods. The addition of EB to current methodology is recommended, particularly for patients considered at high risk for MRSP infection.

Direct repeat unit (dru) typing and antimicrobial resistance of methicillin-resistant Staphylococcus pseudintermedius isolated from dogs in Atlantic Canada.

There are few reports investigating the characterization of methicillin-resistant Staphylococcus pseudintermedius (MRSP) in dogs in Canada and none from Atlantic Canada. The objectives of this study were to strain type MRSP isolates cultured at a regional diagnostic laboratory using direct repeat unit (dru) typing and to describe their antimicrobial resistance profiles. Ninety-four isolates recovered from dogs between 2010 and 2012 had dru typing, cluster analysis, and antimicrobial susceptibility testing done. The majority of isolates belonged to type dt11a (30.9%), dt10h (24.5%), dt9a (18.1%), and dt11af (10.6%) with the remaining 15.9% of isolates distributed among 13 dru types. The predominant dru types identified were similar in Ontario; however, cluster 9a appears to be less common in Atlantic Canada. A significant difference in the distribution of clusters among Atlantic provinces was detected (P = 0.01). Resistance to ≥ 2 non-ß-lactam antimicrobials was observed in 71.4% of the isolates. The MRSP isolates from this study were notably less resistant than those reported in the literature. A more comprehensive study of the MRSP dru types could help further elucidate the distribution of this pathogen in Canada.

Il y a peu de publications rapportant la caractérisation des isolats de Staphylococcus pseudintermedius résistant à la méticilline (SPRM) chez les chiens au Canada et aucun ne provenant des provinces maritimes. Les objectifs de la présente étude était de typer les isolats de SPRM cultivés à un laboratoire de diagnostic régional en utilisant le typage direct des unités répétées (dur) et de décrire les profils de résistance antimicrobienne. Quatre-vingt-quatorze isolats canins obtenus entre 2010 et 2012 furent soumis au typage du dur, une analyse de regroupement, et un antibiogramme. La majorité des isolats appartenait au type dt11a (30,9 %), dt10h (24,5 %), dt9a (18,1 %), et dt11af (10,6 %) et le 15,9 % des isolats restant étaient distribués parmi 13 types dur. Les types prédominants de dur identifiés étaient similaires à ceux de l'Ontario, Canada, bien que le regroupement 9a semble moins fréquent dans les provinces maritimes. Une différence significative dans la distribution des regroupements entre les provinces maritimes a été détectée (P = 0,01). Une résistance à ≥ 2 antimicrobiens n'appartenant pas à la classe des ß-lactames fut observée chez 71,4 % des isolats. Les isolats de SPRM de la présente étude était sensiblement moins résistant que ceux rapportés dans la littérature. Une étude plus complète des types dur des SPRM pourrait aider à élucider un peu plus la distribution de cet agent pathogène au Canada.(Traduit par Docteur Serge Messier).