Risk Factors for SARS-CoV-2 Infection and Illness in Cats and Dogs1.

We tested swab specimens from pets in households in Ontario, Canada, with human COVID-19 cases by quantitative PCR for SARS-CoV-2 and surveyed pet owners for risk factors associated with infection and seropositivity. We tested serum samples for spike protein IgG and IgM in household pets and also in animals from shelters and low-cost neuter clinics. Among household pets, 2% (1/49) of swab specimens from dogs and 7.7% (5/65) from cats were PCR positive, but 41% of dog serum samples and 52% of cat serum samples were positive for SARS-CoV-2 IgG or IgM. The likelihood of SARS-CoV-2 seropositivity in pet samples was higher for cats but not dogs that slept on owners' beds and for dogs and cats that contracted a new illness. Seropositivity in neuter-clinic samples was 16% (35/221); in shelter samples, 9.3% (7/75). Our findings indicate a high likelihood for pets in households of humans with COVID-19 to seroconvert and become ill.

Evaluating the utility of pest control sourced rats for zoonotic pathogen surveillance.

Norway rats (Rattus norvegicus) inhabit cities worldwide and live in close association with humans. Studies of urban rat zoonoses often rely on live-trapping, with fewer studies using rats sourced through lethal pest control interventions. Our objectives were to evaluate the utility of rats collected by pest control professionals for zoonotic pathogen surveillance and determine whether we could detect Leptospira interrogans and Streptobacillus moniliformis in pest control sourced rats. Rat carcasses were submitted from Windsor, Canada by pest control professionals between November 2018 and March 2020. Submissions were categorized by season and land use. Necropsies were performed to classify carcass quality, collect tissue samples, and record demographic data. The association between carcass quality and the ability to collect tissue samples for pathogen surveillance was assessed via an exact logistic regression model. Using PCR, a subset of kidney and spleen samples were tested for L. interrogans and S. moniliformis, respectively. Our sample of pest control sourced rats had similar sex and age distributions to those of live-trapping studies. Rats were primarily submitted from residential and industrial locations during fall, winter, and spring, which may reflect pest control service areas and peak business periods, rather than rat distribution. Of 124 submissions, 98 (79.0%) of rats showed only mild decomposition. The odds of collecting all tissue samples were reduced for fair compared to good-quality carcasses (OR: 0.029; 95% CI: 0-0.25; p = .0009) and for poor compared to fair-quality carcasses (OR: 0.048; 95% CI: 0.00085-0.53; p = .0065). Leptospira interrogans and S. moniliformis were detected in 9.1% (4/44) and 27.3% (15/55) of a subset of rats tested, respectively. Our results suggest that pest control sourced rats are suitable for surveillance for multiple zoonotic pathogens in urban environments. This method of rat collection may provide preliminary information to guide more detailed ecological studies.

Longitudinal study of the cutaneous microbiota of healthy horses.

BACKGROUND: Next-generation sequencing techniques have revealed that human and animal skin is colonised by a rich and diverse population of bacteria, and that microbial composition varies between different body sites and individuals. Very little is known about the normal microbiota of healthy equine skin. HYPOTHESIS/OBJECTIVES: To describe the taxonomic distributions of cutaneous bacterial microbiota in a population of healthy horses in Ontario, Canada, and to evaluate the effects of body site, individual and time of year on microbial diversity and community composition. ANIMALS: Samples were collected from four body sites (dorsum, ventral abdomen, pastern and groin) from 12 clinically healthy horses from the same farm. Samples were collected from all individuals at four time points (winter, spring, summer, autumn) within a calendar year. METHODS AND MATERIALS: Illumina sequencing of the V4 region of the 16S rRNA gene was performed following DNA extraction. Data were analysed using mothur software. RESULTS: Bacteria from 38 phyla and 1,665 genera were identified. Alpha diversity was higher in the winter and summer than spring and autumn although this was not statistically significant. Community membership and structure clustered more based on season than skin site. CONCLUSIONS AND CLINICAL IMPORTANCE: Healthy equine skin is inhabited by a marked diversity of microbiota. Individuals living in a similar environment share overlapping cutaneous microbial populations. These populations vary significantly over time and between body sites.

Clostridioides (Clostridium) difficile in neonatal foals and mares at a referral hospital.

BACKGROUND: Understanding the epidemiology of Clostridium difficile is important for the development and assessment of infection prevention and control practices, as well as surveillance methods and interpretation of diagnostic testing results. OBJECTIVE: Our objective was to longitudinally evaluate C. difficile shedding in neonatal foals and mares admitted to a referral hospital neonatal intensive care unit. ANIMALS: Foals admitted to a neonatal intensive care unit, along with their dams. METHODS: Rectal swabs were collected from mares and foals at admission, and then approximately every 3 days, when possible. Selective culture for C. difficile was performed and isolates were characterized by toxin gene PCR and ribotyping. RESULTS: Clostridium difficile was isolated from 103/409 (25%) samples; 65/208 (31%) from foals and 38/201 (19%) from mares. Cumulatively, C. difficile was isolated from at least 1 sample from 50/113 (44%) foals and 30/97 (31%) mares. No association was found between hospitalization day and isolation of C. difficile (P = .13). Twenty-three different ribotypes were identified, with ribotype 078 predominating. Fifteen foals had 2 positive samples during hospitalization. In only 6/15 (40%) foals was the same strain identified both times (5 ribotype 078 and 1 ribotype 012). CONCLUSIONS AND CLINICAL IMPORTANCE: Clostridium difficile is an important pathogen in adult horses and foals, and our findings highlight the complexity surrounding the epidemiology of this opportunistic pathogen. It can be found commonly, transiently, and cluster within a facility in the absence of identifiable disease occurrences or clusters.

Feline conjunctival microbiota in a shelter: effects of time, upper respiratory disease and famciclovir administration.

OBJECTIVES: The aim of this study was to evaluate changes in the conjunctival microbiota of shelter-housed cats with time, upper respiratory disease (URD) and famciclovir administration. METHODS: Cats were assigned to treatment groups on shelter entry. Healthy cats or cats with URD received ~30 mg/kg or ~90 mg/kg of famciclovir or placebo PO q12h for 7 days, or were untreated. Swabs were collected from ventral conjunctival fornices prior to (day 1) and immediately after (day 8) the treatment period. Microbiota analysis was conducted on 124 randomly selected swabs from healthy (56 swabs) or URD-affected (68 swabs) cats. Following DNA extraction and amplification of the V4 region of the 16S rRNA gene, sequences were assembled into operational taxonomic units (OTUs). Over-represented OTUs (as determined by linear discriminate analysis effect size), alpha and beta diversity, and median relative abundance of known feline ocular surface pathogens were assessed for the entire population and in 10 clinically relevant subpopulations of cats. RESULTS: Bacteria from 33 phyla and 70 genera were identified. Considering all cats, median relative abundance of Mycoplasma increased from day 1 to day 8, while Proteobacteria decreased. Community membership and structure (beta diversity) differed between days 1 and 8 for all famciclovir-treated cats (regardless of health status or dose) and healthy or URD-affected cats (regardless of famciclovir dose). Differences in taxonomic diversity within a sample (alpha diversity) between day 1 and day 8 were not detected in any subpopulations. CONCLUSIONS AND RELEVANCE: Within 1 week of shelter entry, there were significant changes in community structure and membership of the feline conjunctival microbiota, with a shift towards over-representation of feline ocular surface pathogens. Although famciclovir may impact beta diversity of the feline conjunctival microbiota, absence of change in alpha diversity suggests minimal shift in individual cats.

Presence of Qac genes in clinical isolates of methicillin-resistant and methicillin-susceptible Staphylococcus pseudintermedius and their impact on chlorhexidine digluconate susceptibility.

OBJECTIVE: To evaluate the presence of quaternary ammonium compound (QAC) (resistance genes, qac A/B, smr, qacG, and qacJ, in clinical isolates of methicillin-susceptible Staphylococcus pseudintermedius (MSSP) and methicillin-resistant S pseudintermedius (MRSP) from dogs and the impact on in vitro chlorhexidine susceptibility. STUDY DESIGN: Experimental in vitro study. SAMPLE POPULATION: Seventy isolates from dogs colonized or infected with MRSP (n = 50) or MSSP (n = 20). METHODS: Agar dilution was used to determine the minimum inhibitory concentration (MIC) of chlorhexidine digluconate. Real-time polymerase chain reaction was used to detect the presence of QAC resistance genes, qacA/B, smr, qacG, and qacJ genes. RESULTS: One or more qac genes were identified in 52 of 70 (74%) isolates. Overall, there was no association between chlorhexidine MIC and the presence of one or more qac genes (P = .85) or the presence of qacA/B (P = .31), smr (P = .72) or qacJ (P = .93) individually. There was an association between qacG and MIC (P = .012), with a median MIC of 1.5 µg/mL for isolates possessing this gene and 1 µg/mL for those not possessing it. CONCLUSION: Quaternary ammonium compound resistance genes were present in MRSP and MSSP isolates. With the exception of qacG, the presence of these genes was not associated with increased MIC. All isolates exhibited MIC 5000 to 80 000 times lower than the concentration recommended for use. CLINICAL SIGNIFICANCE: Despite the presence of QAC genes, chlorhexidine digluconate should be effective against MRSP and MSSP if used correctly.

Clostridioides difficile on Ohio swine farms (2015): A comparison of swine and human environments and assessment of on-farm risk factors.

Swine are known reservoirs for Clostridioides difficile, formerly known as Clostridium difficile, and transmission from swine to human farm workers is strongly suggested by previous studies. This cross-sectional study evaluated the potential role of farm environmental surfaces, including those in worker breakrooms and swine housing areas, in the possible transmission of C. difficile from swine to farm workers. Environmental surfaces and piglet faeces at 13 Ohio swine farms were sampled in 2015. Typical culturing techniques were performed to isolate C. difficile from samples, and amplification of toxin genes (tcdA, tcdB and cdtB) and PCR-ribotyping were used to genetically characterize recovered isolates. In addition, sequencing of toxin regulatory gene, tcdC, was done to identify the length of identified deletions in some isolates. A survey collected farm-level management risk factor information. Clostridioides difficile was recovered from all farms, with 42% (188/445) of samples testing positive for C. difficile. Samples collected from all on-farm locations recovered C. difficile, including farrowing rooms (60%, 107/178), breakrooms (50%, 69/138) and nursery rooms (9%, 12/129). Three ribotypes recovered from both swine and human environments (078, 412 and 005) have been previously implicated in human disease. Samples taken from farrowing rooms and breakrooms were found to have greater odds of C. difficile recovery than those taken from nursery rooms (OR = 40.5, OR = 35.6, p < .001 respectively). Farms that weaned ≥23,500 pigs per year had lower odds of C. difficile recovery as compared to farms that weaned fewer pigs (OR = 0.4, p = .01) and weekly or more frequent cleaning of breakroom counters was associated with higher odds of C. difficile recovery (OR = 11.7, p < .001). This study provides important insights into the presence and characterization of C. difficile found in human environments on swine farms and highlights how these areas may be involved in transmission of C. difficile to swine farm workers and throughout the facility.

Clostridioides difficile in bat guano.

Bats are associated with the emergence of several mammalian diseases. Their sessional migration, and tendency to form large colonies in close proximity to human habitats enables effective intra- and inter-species transmission of pathogens. Clostridioides difficile is an important enteric pathogen in humans and animals; however, the source of its dissemination in the population is unknown. The purpose of this study was to determine the prevalence of C. difficile in bats, and to characterize C. difficile isolates. Feces (n = 93) was sampled from bats during their migration across Europe. Eighteen samples (19.4%) were positive for C. difficile; ribotypes 078, 056, and a new ribotype CDB3 were identified. Clostridioides difficile ribotypes 078 and 056 are associated with human and animal diseases. The C. difficile prevalence and ribotypes in this study do not necessarily identify bats as a significant source, but more likely as an indicator of C. difficile perpetuation in the environment.

Salmonella, Campylobacter, Clostridium difficile, and anti-microbial resistant Escherichia coli in the faeces of sympatric meso-mammals in southern Ontario, Canada.

The role of free-ranging wildlife in the epidemiology of enteropathogens causing clinical illness in humans and domestic animals is unclear. Salmonella enterica and anti-microbial resistant bacteria have been detected in the faeces of raccoons (Procyon lotor), but little is known about the carriage of these bacteria in other sympatric meso-mammals. Our objectives were to: (a) report the prevalence of Salmonella and associated anti-microbial resistance, Campylobacter spp, Clostridium difficile, and anti-microbial resistant Escherichia coli in the faeces of striped skunks (Mephitis mephitis) and Virginia opossums (Didelphis virginiana) in southern Ontario; and (b) compare the prevalence of these bacteria in the faeces of these meso-mammal hosts with raccoons from a previously reported study. Faecal swabs were collected from striped skunks and Virginia opossums on five swine farms and five conservation areas from 2011 to 2013. Salmonella was detected in 41% (9/22) and 5% (5/95) of faecal swabs from Virginia opossums and striped skunks, respectively. None of the Salmonella serovars carried resistance to anti-microbials. The prevalence of Campylobacter spp., C. difficile, and anti-microbial resistant E. coli ranged from 6% to 22% in striped skunk and Virginia opossums. Using exact logistic regression, Salmonella was significantly more likely to be detected in faecal swabs of Virginia opossums than skunks and significantly less likely in faecal swabs from skunks than raccoons from a previously reported study. In addition, Campylobacter spp. was significantly more likely to be detected in raccoons than opossums. Salmonella Give was detected in 8/9 (89%) of Salmonella-positive Virginia opossum faecal swabs. Our results suggest that striped skunks and Virginia opossums have the potential to carry pathogenic enteric bacteria in their faeces. The high prevalence of Salmonella Give in Virginia opossum faecal swabs in this study as well as its common occurrence in other Virginia opossum studies throughout North America suggests Virginia opossums may be reservoirs of this serovar.

Characterization of the otic bacterial microbiota in dogs with otitis externa compared to healthy individuals.

BACKGROUND: Otitis externa is a common multifactorial disease in dogs. The diversity of the cutaneous microbiota in dogs appears to decrease in diseased states. However, little is known about the microbiota of the canine ear and how it is altered by disease. HYPOTHESIS/OBJECTIVES: To describe the otic bacterial microbiota in dogs with otitis externa compared to healthy dogs. ANIMALS: Samples were collected from 18 dogs with clinical and cytological evidence of otitis externa, and eight clinically normal dogs without cytological evidence of otitis externa. METHODS AND MATERIALS: DNA from each sample was isolated and Illumina® sequencing of the V4 hypervariable region of the 16S rRNA gene amplicons was performed. Sequences were processed using the bioinformatics software MOTHUR. RESULTS: Bacteria from 27 different phyla were identified. Affected ears had significantly decreased alpha diversity when compared to healthy ears. Community structure and membership also differed between the two groups. Linear discriminant analysis effect size analysis identified 153 operational taxonomic units (OTUs) that were differentially abundant. Eleven OTUs were over-represented in the affected ears, including Staphylococcus, Pseudomonas and Parvimonas. CONCLUSIONS: The otic bacterial microbiota is much more complex than has been identified with previous culture-based studies; otitis externa is accompanied by broad and complex differences in the microbiota.

Analysis of the otic mycobiota in dogs with otitis externa compared to healthy individuals.

BACKGROUND: Otitis externa is a common multifactorial disease with a prevalence in dogs as high as 10-20%. In humans, the diversity of the cutaneous mycobiota appears to increase in diseased states, whereas one canine study identified a decrease in diversity of the cutaneous mycobiota in atopic dogs compared to healthy individuals. HYPOTHESIS/OBJECTIVES: To describe the otic mycobiota in dogs with otitis externa compared to healthy dogs. ANIMALS: Samples were collected from six dogs with clinical and cytological evidence of otitis externa and five clinically normal dogs. METHODS AND MATERIALS: Swabs were collected from the ears of six dogs with fungal otitis externa. DNA from each sample was isolated and Illumina sequencing was performed targeting the internal transcribed spacer region. Sequences were processed using the bioinformatics software MOTHUR. RESULTS: Fungi from ten different phyla were identified. The mycobiota of all affected ears was dominated by the genera Malassezia, which accounted for 55.7-98.4% of sequences (median 96.8%). Affected ears had significantly decreased observed richness, estimated richness and inverse Simpson's diversity index compared to controls (P = 0.008). Linear discriminant analysis effect size (LEfSe) analysis identified 42 operational taxonomic units (OTUs) that were differentially abundant (P < 0.05). Three OTUs were over-represented in the affected ears, including M. pachydermatis, whereas 39 OTUs were over-represented in healthy ears. CONCLUSIONS: Reduced fungal richness and diversity was present in affected ears, with markedly higher relative abundances of Malassezia. The otic fungal mycobiota is much more complex than has been identified with culture-based studies.

Livestock-associated methicillin-resistant Staphylococcus aureus and Clostridium difficile in wild Norway rats (Rattus norvegicus) from Ontario swine farms.

Methicillin-resistant Staphylococcus aureus (MRSA) and Clostridium difficile are important human pathogens that are also carried by animals. The role of wild mammals on farms in their maintenance and transmission, however, is poorly understood. To determine if Norway rats (Rattus norvegicus) are potential carriers of these bacteria on Canadian farms, we tested 21 rats from swine farms in Ontario. The MRSA spa type t034 was isolated from 1 (4.8%) rat. This livestock-associated strain often colonizes pigs and pig farmers, suggesting that transmission among rats and pigs or environmental transmission is possible on pig farms. Clostridium difficile ribotype 078 was isolated from 1 rat from a different farm. This strain is associated with infection in piglets, calves, and humans. The identification of MRSA and C. difficile in Norway rats on farms in Canada adds to the growing knowledge about the role of rats in the ecology of these pathogens. Further studies are required to determine if rats play a part in the epidemiology of these pathogens on farms.

Les bactéries Staphylococcus aureus résistants à la méthicilline (SARM) et Clostridium difficile sont des agents pathogènes importants chez l'humain et sont également retrouvées chez des animaux. Le rôle des animaux sauvages sur les fermes en lien avec leur maintenance et transmission est toutefois peu compris. Afin de déterminer si les rats (Rattus norvegicus) sont des porteurs potentiels de ces bactéries sur les fermes canadiennes, nous avons testé 21 rats provenant de fermes porcines en Ontario. Du SARM spa type t034 fut isolé à partir de un rat (4,8 %). Cette souche associée au bétail colonise souvent les porcs et les éleveurs de porcs, suggérant ainsi que la transmission entre les rats et les rats ou la transmission environnementale est possible sur les fermes porcines. Le ribotype 078 de Clostridium difficile fut isolé de un rat sur une ferme différente. Cette souche est associée à l'infection chez des porcelets, des veaux, et les humains. L'identification de SARM et de C. difficile chez des rats sur des fermes au Canada accroit les connaissances sur le rôle des rats dans l'écologie de ces agents pathogènes. Des études supplémentaires sont requises afin de déterminer si les rats jouent un rôle dans l'épidémiologie de ces agents pathogènes sur les fermes.(Traduit par Docteur Serge Messier).

Microbiota of field-collected Ixodes scapularis and Dermacentor variabilis from eastern and southern Ontario, Canada.

The microbiota of hard ticks has been an area of growing interest due to the potential role that the broader microbial community may play in pathogen carriage and transmission. In the last two decades, Ontario, Canada has experienced rapid changes in the risk of tick-borne disease, primarily due to the range expansion of Ixodes scapularis. Another human-biter, Dermacentor variabilis, is a longstanding resident of the province, but currently poses minimal risk of pathogen transmission. To examine the microbiota of these two species, we collected adult and nymphal I. scapularis and D. variabilis from the eastern and southern regions of the province via tick dragging, and conducted next generation sequencing of 19 samples (composed of 45 ticks) via Illumina MiSeq. A total of 1400469 sequences were detected (median 69118/sample; range 23350-155227). The most abundant families of bacteria were unclassified Clostridiales and Ruminococcaceae for both I. scapularis and D. variabilis. No significant differences in the relative abundances of any phylum, class, order, family or genus were detected between locations (east vs south), sex, life stage or tick species. There were no differences in community membership or structure based on unifrac and AMOVA analyses. Female and male ticks had lower microbial diversity when compared to nymphs, based on the Simpson's index and Shannon evenness index. The findings of our study differ from previous studies of these tick species conducted in other geographic areas, and highlight the potential role geography and related ecological factors may have in shaping the tick microbiota.

Comparison of methicillin-resistant Staphylococcus pseudintermedius adherence to 2 canine limb salvage endoprosthesis implants.

The objective of our study was to compare adhesion of methicillin-resistant Staphylococcus pseudintermedius (MRSP) to stainless steel (SS) and to tantalum (TA) canine limb salvage endoprosthesis implants in an in vitro experimental study. The median of the mean log10 colony forming units/mL for adherent MRSP was 4.96 (range: 4.63 to 6.33) for the TA endoprosthesis and 4.31 (range: 3.86 to 5.05) for the SS endoprosthesis (P = 0.009). Although the trabecular and porous design of the TA endoprosthesis provides mechanical benefits over the SS endoprosthesis, it may increase the risk of developing infection due to higher levels of bacterial adherence.

Comparaison de l'adhérence deStaphylococcus pseudintermediusrésistant à la méthicilline à deux implants d'endoprothèse pour sauver des membres canins. L'objectif de notre étude consistait à comparer l'adhésion de Staphylococcus pseudintermedius résistant à la méthicilline (MRSP) à des implants d'endoprothèse en acier inoxydable (AI) et en tantale (TA) pour sauver des membres canins lors d'une étude expérimentale in vitro. La médiane des moyennes en log10 des unités formatrices de colonies/mL pour le MRSP adhérent était de 4,96 (écart : de 4,63 à 6,33) pour l'endoprothèse TA et 4,31 (écart : de 3,86 à 5,05) pour l'endoprothèse d'AI (P = 0,009). Même si la conception trabéculaire et poreuse de l'endoprothèse de TA offre des avantages mécaniques par rapport à l'endoprothèse d'AI, elle peut accroître le risque de développer une infection en raison des taux supérieurs d'adhérence bactérienne.(Traduit par Isabelle Vallières).

Dermatophyte surveillance in cats in three animal shelters in Ontario, Canada.

Objectives The aim of the study was to determine the prevalence of dermatophyte shedding in cats admitted to three Ontario animal shelters from February to May 2013. Methods Four hundred cats were sampled within 48 h of admission, using a standard toothbrush sampling technique. Dermatophyte culture was performed. Results Dermatophytes were not identified in any of the 400 cats (0-0.9% one-sided exact 97.5% confidence interval). Conclusions and relevance These results imply that dermatophyte shedding is rare in cats admitted to Ontario animal shelters. Consequently, identification of infected animals, particularly multiple animals, represents an unusual occurrence that may justify prompt and intensive control measures.

Evaluation of the Impact of Methicillin-Resistant Staphylococcus pseudintermedius Biofilm Formation on Antimicrobial Susceptibility.

OBJECTIVE: To compare the minimum inhibitory concentration (MIC) of four antimicrobials in planktonic vs. biofilm-associated Staphylococcus pseudintermedius. STUDY DESIGN: In vitro study. SAMPLE POPULATION: 78 isolates from dogs colonized or infected with methicillin-resistant S. pseudintermedius (MRSP, n=39) or methicillin-susceptible S. pseudintermedius (MSSP, n=39). METHODS: Agar dilution was used to determine the MIC of amikacin, cefazolin, enrofloxacin, and gentamicin for planktonic bacteria. A modified broth microdilution assay was used to assess the MIC of biofilm-associated bacteria. RESULTS: MIC were significantly higher in biofilm-associated vs. planktonic bacteria for all antimicrobials; amikacin (median MIC: biofilm >2,000 µg/mL vs. planktonic 3 µg/mL, P<.0001), cefazolin (>1,000 vs. 0.5 µg/mL, P<.0001), enrofloxacin (>1,000 vs. 0.25 µg/mL, P<.0001), and gentamicin (>1,000 vs. 0.3 µg/mL, P<.001). For all antimicrobials, there were significant differences in planktonic MIC for MRSP and MSSP (all P<.0001) but no differences between biofilm MIC for MRSP and MSSP (P=.08-1.0). CONCLUSION: The MIC for biofilm-associated S. pseudintermedius are significantly higher than for planktonic bacteria. Standard methods for determining MIC are not appropriate for biofilm-associated infections. This must be considered when determining treatment regimens for infections that potentially involve biofilms, and further study of methods to control biofilm-associated infections is needed.

False Negative Results in Clostridium difficile Testing.

BACKGROUND: Accurate diagnosis of Clostridium difficile infection (CDI) is paramount for patient management. The wrong diagnosis places patients at risk, delays treatment, and/ or contributes to transmission of infection in the healthcare setting. Although amplification of the toxin B gene by polymerase chain reaction (PCR) is a sensitive method for detecting toxigenic C. difficile, false negative results still occur and could impact the diagnosis and treatment of this infection. METHODS: This study investigated 48 patients that tested negative for toxigenic C. difficile via GeneXpert C. difficile epi test, while simultaneously testing positive for toxigenic C. difficile via stool culture. Fifty discrepant samples were collected over a 15-month period and all C. difficile isolates were characterized by ribotype. Patient charts were reviewed to assess whether discrepant results impacted the treatment course or clinical outcome of affected patients. RESULTS: Fifty samples of a total of 2308 samples tested in an acute healthcare facility over a 15-month period had negative PCR and positive stool culture for toxigenic C. difficile. C. difficile isolated from the discrepant samples resulted in diverse ribotyping patterns suggesting they were derived from different strains. The samples belonged to patients who were distributed evenly between age groups and wards in the hospital. In the majority of cases, the false negative C. difficile test results did not seem to impact the clinical outcome in these patients. CONCLUSIONS: The PCR limit of detection may impact the results of molecular methods for C. difficile detection. Both clinical and analytical sensitivity of C. difficile tests should be considered when deciding which diagnostic assay to use, and clinical correlates should be examined carefully before excluding CDI as a cause of disease.

Adherence of methicillin-resistant Staphylococcus pseudintermedius to suture materials commonly used in small animal surgery.

OBJECTIVE: To evaluate adherence of methicillin-resistant Staphylococcus pseudintermedius (MRSP) to 5 suture materials commonly used in small animal surgery. SAMPLE: 10 epidemiologically unrelated MRSP isolates (obtained from dogs with clinical infections) that had strong biofilm-forming ability and 5 types of suture. PROCEDURES: The 5 types of suture evaluated were monofilament polyglecaprone 25, monofilament polydioxanone, triclosan-coated (TC)-monofilament polydioxanone, braided polyglactin 910, and barbed monofilament polydioxanone. Suture segments were incubated in standard suspensions of MRSP for 2 minutes. Segments were then placed in tryptone soy broth and incubated overnight. After incubation, segments were rinsed with PBS solution and sonicated to dislodge adherent bacteria. Resulting suspensions were used to create serial dilutions that were plated, incubated overnight, and counted the following day. Bacterial adherence to 1 segment of each suture type was assessed by use of scanning electron microscopy. RESULTS: There was significantly less adherence of MSRP to TC-monofilament polydioxanone than to polyglecaprone 25, polyglactin 910, barbed monofilament polydioxanone, and monofilament polydioxanone. There was significantly less adherence of MSRP to polyglecaprone than to polyglactin 910. CONCLUSIONS AND CLINICAL RELEVANCE: Barbed suture had a bacterial adherence profile comparable to that for monofilament suture. Adherence of MRSP was greatest for braided polyglactin 910. Use of TC-monofilament polydioxanone can be considered for patients that are at high risk of developing surgical site infections and for which a surgeon chooses a multifilament suture.

Association between methicillin-resistant Staphylococcus pseudintermedius carriage and the development of surgical site infections following tibial plateau leveling osteotomy in dogs.

OBJECTIVE: To evaluate the association between preoperative carriage of methicillin-resistant Staphylococcus pseudintermedius (MRSP) and the development of surgical site infections (SSIs) following tibial plateau leveling osteotomy (TPLO) in dogs. DESIGN: Prospective multicenter study. ANIMALS: 549 dogs. PROCEDURES: At 7 veterinary hospitals, swab specimens were obtained from the pharynx, nares, rectum, and skin of dogs admitted for TPLO. Specimens were submitted for culture of MRSP. For each dog, information regarding preoperative and postoperative antimicrobial administration, comorbidities, contact with other dogs, and whether the dog developed an SSI was obtained. Univariable and multivariable analyses were performed to identify variables associated with preoperative and postoperative MRSP colonization and the development of an SSI. RESULTS: Of the 549 study dogs, 24 (4.4%) were identified as MRSP carriers before TPLO and 37 (6.7%) developed an SSI after TPLO. Bacteriologic culture was performed on specimens obtained from 32 of the 37 SSIs, and MRSP was isolated from 11 (34%). Carriers of MRSP (OR, 6.72; 95% confidence interval [CI], 2.12 to 21.4) and Bulldogs (OR, 11.1; 95% CI, 2.07 to 59.3) were at risk for development of an SSI after TPLO, whereas postoperative administration of antimicrobials (OR, 0.36; 95% CI, 0.15 to 0.91) appeared to protect against development of an SSI. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that carriage of MRSP were a risk factor for development of an SSI after TPLO and measures to rapidly identify and treat MRSP carriers are warranted. Postoperative administration of antimicrobials protected against development of an SSI after TPLO.

Impact of polymethylmethacrylate additives on methicillin-resistant Staphylococcus pseudintermedius biofilm formation in vitro.

OBJECTIVE: To evaluate the impact of gentamicin, silver, or both additives in polymethylmethacrylate (PMMA) beads on methicillin-resistant Staphylococcus pseudintermedius (MRSP) biofilm formation in vitro. SAMPLE: 4 preparations of PMMA beads (formed with no additive [control], gentamicin, silver, and gentamicin and silver). PROCEDURES: Beads from each group were exposed to 10 MRSP isolates known to be strong biofilm formers. Following incubation, the beads were rinsed to remove planktonic bacteria, then sonicated to dislodge biofilm-associated bacteria. Resulting suspensions were serially diluted, plated on blood agar, and incubated overnight; CFUs were counted. Variance of mean CFU counts following log10 transformation was analyzed among PMMA groups. RESULTS: None of the PMMA additives tested completely inhibited MRSP biofilm formation. There was a significant effect of gentamicin and gentamicin plus silver on this variable, compared with controls, but not of silver alone. There was no difference between gentamicin and gentamicin plus silver. When only isolates not susceptible to gentamicin were evaluated, there were no significant differences among PMMA additive groups. Within gentamicin-susceptible isolates, there was an impact of gentamicin and gentamicin plus silver, but no impact of silver alone and no difference between gentamicin and gentamicin plus silver. CONCLUSIONS AND CLINICAL RELEVANCE: Gentamicin-impregnated PMMA was effective at reducing biofilm formation of gentamicin-susceptible MRSP isolates but had no effect on isolates not susceptible to gentamicin. Silver-impregnated PMMA had no effect on MRSP biofilm formation. Results suggested that gentamicin-impregnated PMMA may not be effective in vivo against MRSP isolates not susceptible to gentamicin. Antibacterial efficacy of silver should not be assumed without proper testing of the target bacteria and specific silver compound.