Sylvia Checkley

Invasion, establishment, and range expansion of two parasitic nematodes in the Canadian Arctic

Climate warming is occurring at an unprecedented rate in the Arctic and is having profound effects on host-parasite interactions, including range expansion. Recently, two species of protostrongylid nematodes have emerged for the first time in muskoxen and caribou on Victoria Island in the western Canadian Arctic Archipelago. Umingmakstrongylus pallikuukensis, the muskox lungworm, was detected for the first time in 2008 in muskoxen at a community hunt on the southwest corner of the island and by 2012, it was found several hundred kilometers east in commercially harvested muskoxen near the town of Ikaluktutiak. In 2010, Varestrongylus sp., a recently discovered lungworm of caribou and muskoxen was found in muskoxen near Ikaluktutiak and has been found annually in this area since then. Whereas invasion of the island by U. pallikuukensis appears to have been mediated by stochastic movement of muskoxen from the mainland to the southwest corner of the island, Varestrongylus has likely been introduced at several times and locations by the seasonal migration of caribou between the island and the mainland. A newly permissive climate, now suitable for completion of the parasite life cycles in a single summer, likely facilitated the initial establishment and now drives range expansion for both parasites.

Associations between reported on-farm antimicrobial use practices and observed antimicrobial resistance in generic fecal Escherichia coli isolated from Alberta finishing swine farms.

Multilevel random intercept logistic and Poisson regression were used to model associations between various antimicrobial use practices and resistance to individual and multiple antimicrobials among generic fecal Escherichia coli isolated from Alberta finishing swine. In-feed antimicrobial use in finishers was significantly associated with increased risk of resistance to ampicillin, chloramphenicol, streptomycin, and sulfisoxazole in generic E. coli isolates. Chlortetracycline use in grower rations was associated with ampicillin and tetracycline resistance. Use of in-feed antimicrobials in finishers was significantly associated with increased risk of resistance of generic E. coli to multiple antimicrobials. The study findings suggest that certain farm-level interventions related to antimicrobial use might be beneficial in reducing development and emergence of antimicrobial resistance in swine populations.

Phenotypic and genetic characterization of antimicrobial resistance in Salmonella serovars isolated from retail meats in Alberta, Canada

This study determined the prevalence of Salmonella serovars, antimicrobial resistance (AMR) and resistance genes in Salmonella isolated from retail meats purchased in Alberta, Canada. Samples were collected during one year period (May 2007-April 2008) on weekly basis from 19 census divisions in Alberta. A total of 564 samples including chicken (n = 206), turkey (n = 91), beef (n = 134) and pork (n = 133) were purchased. Salmonella were recovered from chicken (40%), turkey (27%) and pork (2%) samples and was not found in ground beef. A total of 21, 8, and 3 different serovars were recovered from chicken, turkey and pork meats, respectively. Salmonella Hadar was most common in chicken whereas S. Heidelberg was common in turkey meat. Overall 29% (32/110) of isolates were susceptible to tested antimicrobials and resistance to ciprofloxacin, amikacin and nalidixic acid was not found in any isolate. Multiresistance (≥2 antimicrobials) was found in 56% of isolates. Resistance to amoxicillin-clavulanic acid (AMC), ceftiofur (TIO), and ceftriaxone (CRO) was found in about 21% of chicken and 25% of turkey isolates. Resistance to either of tetracycline (TET), streptomycin (STR) or ampicillin (AMP) was unconditionally associated with S. Hadar but resistance to either of TET, AMP, AMC, TIO, CRO or cefoxitin was associated with S. Heidelberg. The strA/B (42% isolates), tet(A) (28% isolates), bla(CMY-2) (21% isolates) and bla(TEM) (17% isolates) were the most common resistance genes found. The bla(CMY-2) and bla(TEM) genes were unconditionally associated with S. Heidelberg; tet(A) and strA/B with S. Hadar and tet(B) gene with S. Kentucky. The strA/B genes were not associated with S. Heidelberg. Our data suggests that the prevalence of Salmonella serovars varied by the meat type and that AMR and resistance genes varied by the Salmonella serovars.

Characterization of antimicrobial resistance and virulence genes in Enterococcus spp. isolated from retail meats in Alberta, Canada

The objective of this study was to characterize antimicrobial resistance (AMR) and virulence genotypes of Enterococcus spp. particularly Enterococcus faecalis isolated from retail meats purchased (2007-2008) in Alberta, Canada. Unconditional statistical associations between AMR pheno- and genotypes and virulence genotypes were determined. A total of 532 enterococci comprising one isolate from each positive sample were analyzed for antimicrobial susceptibility. A customized enterococcal microarray was used for species identification and the detection of AMR and virulence genes. E. faecalis was found in >94% of poultry samples and in about 73% of beef and 86% of pork samples. Enterococcus faecium was not found in turkey meat and its prevalence was 2% in beef and pork and 4% in chicken samples. None of the enterococci isolates were resistant to the clinically important drugs ciprofloxacin, daptomycin, linezolid and vancomycin. Multiresistance (≥3 antimicrobials) was more common in E. faecalis (91%) isolated from chicken and turkey (91%) than those isolated from beef (14%) or pork (45%). Resistance to aminoglycosides was also noted at varying degrees. The most common resistance genes found in E. faecalis were aminoglycosides (aac, aphA3, aadE, sat4, aadA), macrolides (ermB, ermA), tetracyclines (tetM, tetL, tetO), streptogramin (vatE), bacitracin (bcrR) and lincosamide (linB). Virulence genes expressing aggregation substances (agg) and cytolysin (cylA, cylB, cylL, cylM) were found more frequently in poultry E. faecalis and were unconditionally associated with tetM, linB and bcrR resistance genes. Other virulence genes coding for adhesion (ace, efaAfs), gelatinase (gelE) were also found in the majority of E. faecalis. Significant statistical associations were found between resistance and virulence genotypes, suggesting their possible physical link on a common genetic element. This study underscores the importance of E. faecalis as a reservoir of resistance and virulence genes and their potential transfer to humans through consumption of contaminated undercooked meat.

Cortisol and corticosterone independence in cortisol-dominant wildlife

Species have traditionally been defined as cortisol-dominant or corticosterone-dominant, depending on the glucocorticoid that is reported. To assess the degree of covariance versus independence between cortisol and corticosterone, 245 serum samples belonging to 219 individuals from 18 cortisol-dominant, non-domesticated species (6 mammalian orders) were compared by mass spectrometry. In these samples, which were elevated above baseline, concentration ranges were overlapping for cortisol and corticosterone although cortisol was dominant in every sample except one of 17 bighorn sheep with a corticosterone-biased cortisol-to-corticosterone ratio of 0.17. As expected, cortisol and corticosterone were strongly associated among species (r(2)=0.8; species with high absolute cortisol tend to have high absolute corticosterone concentrations), with wide variation in the species-average cortisol-to-corticosterone ratio (range 7.5-49) and an even wider ratio range across individuals (0.2-341). However, only 9 out of 13 species with >7 individuals showed a positive association between cortisol and corticosterone among individuals, and repeated measures of the cortisol-to-corticosterone ratio within individuals were weakly associated (CV range 3-136%). We conclude that corticosterone, although at lower concentrations, has the potential to signal independently of cortisol, and should be included in integrated endocrine models of stress responses.

Managing Lead Exposure and Toxicity in Cow–Calf Herds to Minimize the Potential for Food Residues

Lead poisoning is commonly diagnosed in cattle. In this study, 3 groups of cattle from different herds accidentally exposed to discarded lead batteries on pasture were intensively studied to determine the extent and severity of exposure. The losses from acute death due to lead toxicity were substantial in all the 3 study groups at 12%, 17%, and 4%. Blood samples were taken from all cattle around the time of the first diagnosis and then later in 2 of the 3 herds to monitor the change in lead concentrations over time. Asymptomatic lead toxicosis was observed in these herds. In these 3 groups, between 4% and 12% of asymptomatic cattle had blood lead concentrations consistent with acute lead poisoning (>0.35 ppm), and between 7% and 40% of these asymptomatic animals were in the high-normal range (0.1–0.35 ppm). Because of the consistently high number of asymptomatic cattle with elevated lead levels, all cattle potentially exposed to a lead source should be tested before sale or slaughter to minimize the entry of lead into the food chain. The blood lead concentrations, which were monitored for months after the initial diagnosis, decreased slowly after the cattle were removed from the lead source. The prolonged retention of lead may be due to continued release and absorption of lead from metal particles in the reticulum or rumen. The mean reduction in the lead level was 0.046 ppm (95% CI, 0.017–0.075 ppm) every 30 days for these 2 herds. Using a single-component exponential model, the half-life of lead in the animals retested from Herds 1 and 2 was highly variable. The median half-life was 63 days (interquartile range, 34–107 days). One out of 8 pregnant heifers with high blood levels had a stillborn calf. There were no abortions or calf mortalities in this group. Blood samples were collected from the calves around the time of birth. The concentrations of lead in the blood of the calves exposed in utero were low (0.010–0.095 ppm).

Antimicrobial Resistance and Resistance Genes in Escherichia coli Isolated from Retail Meat Purchased in Alberta, Canada

This study analyzed antimicrobial resistance (AMR) and resistance genes in generic Escherichia coli isolated from retail meat samples purchased (2007-2008) in Alberta, Canada, and determined potential associations between resistance phenotypes and resistance genes with relation to the meat types. A total of 422 E. coli isolates from retail chicken, turkey, beef, and pork meats were tested for antimicrobial susceptibility. Multiplex PCRs were used to detect major resistance genes for tetracyclines [tet(A), tet(B), tet(C)], sulfonamides (sul1, sul2, sul3), aminoglycosides (strA/B, aadA, aadB, aac(3)IV, aphA1, aphA2), and β-lactamase (bla(CMY-2), bla(TEM), bla(SHV), bla(PSE-1)). Resistance to ciprofloxacin was not found in any isolate. Overall resistances to clinically important antimicrobials amoxicillin-clavulanic acid (16.8% of isolates) and ceftriaxone (12.6% isolates) were observed. These resistances were observed more frequently (p<0.0001) in chicken-derived E. coli than those from the other meat types. Resistance to multiple antimicrobials (≥ 5) was found in more chicken derived E. coli (32%) than E. coli from other meat types. The β-lactamase genes of clinical importance, including bla(CMY-2) and bla(TEM), were found in about 18% of poultry-derived E. coli and in only 5% of ground beef. The bla(CMY-2) gene was more likely to be found in E. coli from chicken than turkey, beef, or pork meats. The tet(A) gene was associated with bla(CMY-2), whereas bla(CMY-2) and bla(TEM) genes were associated with strA/B genes. Resistance genes for tetracycline, sulfonamides, and aminoglycosides were associated with the phenotypic expression of resistance to unrelated classes of antimicrobials. These data suggest the prevalence of AMR and select resistance genes were higher in poultry-derived E. coli. The multiple associations found between AMR phenotypes and resistance genes suggest a complex nature of resistance in E. coli from retail meat, and hence the use of a single antimicrobial could result in the selection of resistant E. coli not only to the drug being used but to other unrelated classes of antimicrobials as well.

Ulcerative Colitis Patients With Clostridium difficile are at Increased Risk of Death, Colectomy, and Postoperative Complications: A Population-Based Inception Cohort Study

Objectives:Clostridium difficile (C. difficile) may worsen the prognosis of ulcerative colitis (UC). The objectives of this study were to: (i) validate the International Classification of Diseases-10 (ICD-10) code for C. difficile; (ii) determine the risk of C. difficile infection after diagnosis of UC; (iii) evaluate the effect of C. difficile infection on the risk of colectomy; and (iv) assess the association between C. difficile and postoperative complications.Methods:The sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated by comparing ICD-10 codes for C. difficile with stool toxin tests. A population-based surveillance cohort of newly diagnosed UC patients living in Alberta, Canada were identified from 2003 to 2009 (n=1,754). The effect of a C. difficile infection on colectomy was modeled using competing risk survival regression after adjusting for covariates. The effect of a C. difficile infection on postoperative complications was assessed using a mixed effects logistic regression model.Results:The sensitivity, specificity, PPV, and NPV of the ICD-10 code for C. difficile were 82.1%, 99.4%, 88.4%, and 99.1%, respectively. The risk of C. difficile infection within 5 years of diagnosis with UC was 3.4% (95% confidence interval (CI): 2.5–4.6%). The risk of colectomy was higher among UC patients diagnosed with C. difficile (sub-hazard ratio (sHR)=2.36; 95% CI: 1.47–3.80). C. difficile increased the risk of postoperative complications (odds ratio=4.84; 95% CI: 1.28–18.35). C. difficile was associated with mortality (sHR=2.56 times; 95% CI: 1.28–5.10).Conclusions:C. difficile diagnosis worsens the prognosis of newly diagnosed patients with UC by increasing the risk of colectomy, postoperative complications, and death.

Methodological comparisons for antimicrobial resistance surveillance in feedlot cattle

BackgroundThe purpose of this study was to objectively compare methodological approaches that might be utilized in designing an antimicrobial resistance (AMR) surveillance program in beef feedlot cattle. Specifically, four separate comparisons were made to investigate their potential impact on estimates for prevalence of AMR. These included investigating potential differences between 2 different susceptibility testing methods (broth microdilution and disc diffusion), between 2 different target bacteria (non-type-specific E. coli [NTSEC] and Mannheimia haemolytica), between 2 strategies for sampling feces (individual samples collected per rectum and pooled samples collected from the pen floor), and between 2 strategies for determining which cattle to sample (cattle that were culture-positive for Mannheimia haemolytica and those that were culture-negative).ResultsComparing two susceptibility testing methods demonstrated differences in the likelihood of detecting resistance between automated disk diffusion (BioMIC®) and broth microdilution (Sensititre®) for both E. coli and M. haemolytica. Differences were also detected when comparing resistance between two bacterial organisms within the same cattle; there was a higher likelihood of detecting resistance in E. coli than in M. haemolytica. Differences in resistance prevalence were not detected when using individual animal or composite pen sampling strategies. No differences in resistance prevalences were detected in E. coli recovered from cattle that were culture-positive for M. haemolytica compared to those that were culture-negative, suggesting that sampling strategies which targeted recovery of E. coli from M. haemolytica-positive cattle would not provide biased results.ConclusionsWe found that for general purposes, the susceptibility test selected for AMR surveillance must be carefully chosen considering the purpose of the surveillance since the ability to detect resistance appears to vary between these tests depending upon the population where they are applied. Continued surveillance of AMR in M. haemolytica recovered by nasopharyngeal swab is recommended if monitoring an animal health pathogen is an objective of the surveillance program as results of surveillance using fecal E. coli cannot be extrapolated to this important respiratory pathogen. If surveillance of E. coli was pursued in the same population, study populations could target animals that were culture-positive for M. haemolytica without biasing estimates for AMR in E. coli. Composite pen-floor sampling or sampling of individuals per-rectum could possibly be used interchangeably for monitoring resistance in E. coli.

Antimicrobial Resistance in Escherichia coli Recovered from Feedlot Cattle and Associations with Antimicrobial Use

The objectives of this study were to estimate the prevalence of antimicrobial resistance (AMR) and to investigate the associations between exposures to antimicrobial drugs (AMDs) and AMR in fecal non-type specific Escherichia coli (NTSEC) recovered from a large population of feedlot cattle. Two-stage random sampling was used to select individually identified cattle for enrollment, which were sampled at arrival and then a second time later in the feeding period. Advanced regression techniques were used to estimate resistance prevalences, and to investigate associations between AMD exposures in enrolled cattle and penmates and AMR identified in NTSEC recovered from the second sample set. Resistance was most commonly detected to tetracycline, streptomycin, and sulfisoxazole, and was rarely identified for critically important AMDs. All cattle were exposed to AMDs in feed, and 45% were treated parenterally. While resistance prevalence generally increased during the feeding period, most AMD exposures were not significantly associated with AMR outcomes. Exposures of enrolled cattle to tetracycline were associated with increased resistance to tetracycline and trimethoprim sulfa, while beta-lactam exposures were associated with decreased likelihood of detecting streptomycin resistance. Pen-level AMD exposure measures were not associated with resistance outcomes. These findings suggest that tetracycline treatment of feedlot cattle can be associated with modest increases in risk for recovery of resistant NTSEC, but the numerous treatments with an advanced macrolide (tulathromycin) were not associated with detectable increases in resistance in NTSEC. All cattle were exposed to in-feed treatments of tetracycline and this could limit the ability to identify the full impact of these exposures, but these exposures varied for enrolled cattle varied, providing an opportunity to evaluate a dose response. While AMD exposures were not associated with detectably increased risks for resistance to critically important AMDs, rare resistance outcomes and infrequent exposure to other important AMDs (e.g., cephalosporins) limited our ability to rigorously investigate questions regarding factors that can influence resistance to these important AMDs.