First isolation and whole-genome sequencing of Trueperella abortisuis from a goat in Canada.

Objective: The present study reports the first isolation and whole-genome sequencing of a Trueperella abortisuis bacterium from a goat. Animals and sample: The T. abortisuis was isolated from the uterus of a goat following an abortion. Procedure: The T. abortisuis was identified by pure culture phenotype and MALDI-TOF analysis and further characterized by whole-genome sequencing. Results: This isolate was reliably identified as T. abortisuis and showed similar properties to type strain T. abortisuis DSM 19515T, which was recovered from a sow following an abortion. The assembled genome of this isolate was 2 564 866 bp long with a GC content of 63.9%. A total of 30 virulence-related genes were determined, suggesting the pathogenic potential of this organism. Conclusion and clinical relevance: This study details the first isolation of T. abortisuis from goats. The genotypic findings of this isolate will serve as a baseline description for any similar future studies.

Premier isolement et séquençage du génome entier de Trueperella abortisuis provenant d'une chèvre au Canada. Objectif: La présente étude rapporte le premier isolement et séquençage du génome entier d'un isolat de Trueperella abortisuis provenant d'une chèvre. Animaux et échantillon: Le T. abortisuis a été isolé de l'utérus d'une chèvre à la suite d'un avortement. Procédure: Le T. abortisuis a été identifié par un phénotype de culture pure et analyse par MALDI-TOF, puis caractérisé par séquençage du génome entier. Résultats: Cet isolat a été identifié de manière fiable comme étant T. abortisuis et a montré des propriétés similaires à la souche type T. abortisuis DSM 19515T, qui a été récupérée chez une truie après un avortement. Le génome assemblé de cet isolat mesurait 2 564 866 pb avec une teneur en GC de 63,9 %. Au total, 30 gènes liés à la virulence ont été déterminés, suggérant le potentiel pathogène de cet organisme. Conclusion et pertinence clinique: Cette étude détaille le premier isolement de T. abortisuis chez la chèvre. Les résultats génotypiques de cet isolat serviront de description de base pour toute étude future similaire.(Traduit par Dr Serge Messier).

Mycolyltransferase is important for biofilm formation and pathogenesis of Tsukamurella keratitis.

Tsukamurella, a group of multi-drug resistant, Gram-positive, aerobic, and partially acid-fast bacteria, are emerging causes of bacterial conjunctivitis and keratitis. However, the pathogenesis of Tsukamurella keratitis is largely unknown. To address this, we used New Zealand White rabbits to develop the first eye infection model and conducted in vitro tests to study the pathogenesis mechanisms of Tsukamurella. There is increasing evidence that biofilms play a significant role in ocular infections, leading us to hypothesize that biofilm formation is crucial for effective Tsukamurella infection. In order to look for potential candidate genes which are important in biofilm formation and Tsukamurella keratitis. We performed genome sequencing of two ocular isolates, T. pulmonis-PW1004 and T. tyrosinosolvens-PW899, to identify potential virulence factors. Through in vitro and in vivo studies, we characterized their biological roles in mediating Tsukamurella keratitis. Our findings confirmed that Tsukamurella is an ocular pathogen by fulfilling Koch's postulates, and using genome sequence data, we identified tmytC, encoding a mycolyltransferase, as a crucial gene in biofilm formation and causing Tsukamurella keratitis in the rabbit model. This is the first report demonstrating the novel role of mycolyltransferase in causing ocular infections. Overall, our findings contribute to a better understanding of Tsukamurella pathogenesis and provide a potential target for treatment. Specific inhibitors targeting TmytC could serve as an effective treatment option for Tsukamurella infections.

Experimental infection of goats with pVAPN-harboring Rhodococcus equi causes latent infection in the lymph nodes.

Rhodococcus equi has recently been identified in various animals, including ruminants. Several studies have highlighted the emergence of pVAPN-harboring strains, isolated from multiple abscesses, in the liver and lungs of ruminants. Epidemiological evidence strongly suggests that pVAPN-harboring strains are pathogenic in ruminants. This study aims to replicate the disease in goats through experimental infection. Intravenous administration of the pVAPN-harboring strain (Yokkaichi), pVAPA-harboring strain (ATCC33701), and pVAPN-cured strain (Yokkaichi_P-), each at 1.0 × 107 CFU/head, was conducted in 24-month-old goats (n = 1 per group). During the observation period, goats treated with Yokkaichi or ATCC33701 exhibited transient increases in body temperature and white blood cell count, alongside a decrease in body weight from the administration day. Conversely, goats treated with Yokkaichi_P- displayed no significant changes in these values. The Yokkaichi-treated goat demonstrated a >10-fold increase in anti-VapN antibody titers from 11 to 14 days postadministration, whereas the other two goats exhibited no variation in anti-VapA and VapN antibody titers. Pathological autopsy analysis of organs harvested 28 days postadministration revealed no characteristic lesions on gross examination. However, the inoculated strain (vapN-positive R. equi) was exclusively recovered from the tracheobronchial lymph node in the Yokkaichi-treated goat. Immunohistochemistry detected a VapN-positive reaction in the tracheobronchial lymph node, confirming latent infection despite the absence of dramatic suppurative lesions seen in ruminants. Overall, this study highlights the latent infection in lymph nodes induced by the pVAPN-harboring strain, despite the absence of overt pathological manifestations.

Whole genome-based antimicrobial resistance, virulence, and phylogenetic characteristics of Trueperella pyogenes clinical isolates from humans and animals.

Trueperella pyogenes is an opportunistic zoonotic bacterial pathogen, whose antimicrobial resistance, virulence, and genetic relatedness between strains from animals and humans are barely studied. These characteristics were therefore analyzed for clinical T. pyogenes strains from 31 animals of 11 different species and 8 humans determining their complete circular genome sequence and antimicrobial susceptibility. The MICs of 19 antimicrobials including 3 antiseptics correlated to the resistance genes identified in silico within the genomes revealing a predominance of resistance to streptomycin (aadA9), sulfamethoxazole (sul1), and tetracycline (tet(33), tet(W/N/W)) among strains from humans and cattle. Additional resistance genes (erm(X), erm(56), cmx, drfA1, aadA1, aph(3'')-Ib (strA), aph(6)-Id (strB), aac(3)-IVa, aph(4)-Ia) were found only sporadically. The resistance genes were localized on genetic elements integrated into the chromosome. A cgMLST-based phylogenetic analysis revealed two major clusters each containing genetically diverse strains. The human strains showed the closest relatedness to strains from cattle. Virulence genes coding for fimbriae (fimA, fimC), neuroamidase (nanP, nanH), pyolysin (plo), and collagen binding protein (cbpA) were identified in strains from different hosts, but no correlation was observed between virulence factors and strain origin. The existence of resistance genes typically found in Gram-negative bacteria within the Gram-positive T. pyogenes indicates a wider capacity to adapt to antimicrobial selective pressure. Moreover, the presence of similar antimicrobial resistance profiles found in cattle and human strains as well as their closest relatedness suggests common zoonotic features and cattle as the potential source for human infections.

Monitoring of inflammatory blood biomarkers in foals with Rhodococcus Equi pneumonia during antimicrobial treatment.

Rhodococcus equi (R. equi), a gram-positive facultative intracellular pathogen, is a common cause of pneumonia in foals and represents a major cause of disease and death. The aim of the present study was to investigate the time-depended changes in White Blood Cells (WBC), basophils (Baso), neutrophils (Neu), lymphocytes (Lymf), monocytes (Mon), eosinophils (Eos), platelet (PLT) counts, fibrinogen (Fbg) concentration, interferon (IFN-α, IFN-γ) and interleukins (IL-2 and IL-10) in foals with clinical R. equi pneumonia. The main treatment was with azithromycin-rifampicin for 14 days. Blood was sampled prior to, 7 and 14 days after starting therapy. Treatment was associated with significantly decreased counts of WBC, (25.6 ± 6.7 and 14.2 ± 2,7 × 103/ml), Neu (18.6 ±6.2 and 10.7 ± 3.1 × 103/ml), Mon (1.5 ± 0.5 and 0.9 ± 0.2 × 103/ml) and Fbg (539 ± 124 and 287 ± 26 g/dl) between day 0 and day 14. IL-2 and IL-10 concentrations were significantly increased (P = 0.028, P = 0.013, respectively) after treatment, whereas IFN-α and IFN-γ concentrations were not. The diagnostic potentials of INF-α, INF-γ, IL-2 and IL-10 per se seems not very high, however, the study suggests that the activity change of selected interleukins in the course of the disease may be associated with amelioration. We concluded that patterns of serum concentration changes of INF-α, INF-γ, IL-2 and IL-10 may help in the study of the innate immune response in foals during infection and treatment of R. equi pneumonia.

Isolation of vapB-positive Rhodococcus equi from submaxillary lymph nodes with or without granulomatous lesions in growing-finishing pigs in Japan.

To investigate the etiological role of vapB-positive Rhodococcus equi in pigs, R. equi was isolated from the submaxillary lymph nodes with or without macroscopically detectable lesions of apparently healthy growing-finishing pigs at a slaughterhouse in Toyama Prefecture, Japan. R. equi was isolated from 57 (24.6%) of 232 pigs with macroscopically detectable lymph node lesions, and 56 (98.2%) of the 57 isolates were vapB-positive. R. equi was isolated from 10 (2.4%) of 420 pigs without lymph node lesions, and six (60%) of the 10 isolates were vapB-positive. Plasmid DNA was isolated from the 62 vapB-positive isolates and digested with EcoRI and NsiI to obtain the plasmid profile. Fifty-two (83.9%), three (4.8%), and four (6.5%) isolates contained pVAPB subtypes 1, 2, and 3, respectively, while the remaining three isolates were of pVAPB subtypes 9, 13, and 14, respectively. Twelve specimens from lymph nodes with macroscopically detectable lesions were randomly selected for histopathological staining. Granulomatous lesions resembling tuberculosis were found in 11 of the 12 specimens, and the remaining specimen showed typical foci of malakoplakia in the lymph node. The isolation rates of R. equi and vapB-positive R. equi from lymph nodes with macroscopically detectable lesions were significantly higher (P<0.05) than those of lymph nodes without lesions, suggesting an etiologic association between vapB-positive R. equi and macroscopically detectable granulomatous lesions in porcine submaxillary lymph nodes. Previous reports on the prevalence of vapB-positive R. equi in pigs are reviewed and discussed.

Antimicrobial efficiency of bromhexine hydrochloride against endometritis-causing Escherichia coli and Trueperella pyogenes in bovines.

In this study, the main agents associated with endometritis in cows in the state of Santa Catarina, Brazil, were identified and the resistance profile and virulence mechanisms of the bacterial isolates were evaluated. Isolates of Escherichia coli and Trueperella pyogenes were tested for their biofilm forming ability and the antimicrobial action of bromhexine hydrochloride in combination with other antimicrobials. A total of 37 uterine lavage samples were collected from cows with endometritis. Of the 55 bacteria isolated, 25.4% were identified as T. pyogenes and 16.3% as E. coli. The bacterial isolates showed greater resistance to sulfamethoxazole + trimethoprim (58.2%) and tetracycline (56.3%). Among the species, E. coli showed the highest resistance rates, with 100% of isolates showing resistance to amoxicillin, streptomycin, and gentamicin. The results of the minimum inhibitory concentration for the T. pyogenes isolates showed that 91.6% of the isolates were resistant to enrofloxacin and tetracycline, and 75% were resistant to ceftiofur and sulfamethoxazole + trimethoprim. All E. coli and T. pyogenes isolates showed biofilm forming ability. The plo, fimA, and nanH genes were identified in 100% of T. pyogenes isolates. In parallel, 100% of E. coli isolates had the fimH gene, and 11.1% had the csgD gene. Bromhexine hydrochloride showed antimicrobial activity against 100% of E. coli isolates and 66.6% of T. pyogenes isolates. Furthermore, when associated with antimicrobials, bromhexine hydrochloride has a synergistic and additive effect, proving to be an option in the treatment of endometritis in cows and an alternative for reducing the use of antimicrobials.

Update on emerging multidrug-resistant Rhodococcus equi.

Jose Vázquez-Boland, Jorge Val-Calvo and Mariela Scortti present a brief summary of the main aspects surrounding the recently identified multidrug-resistant Rhodococcus equi that emerged in the USA and the actions being taken to tackle the problem with support from the UK's Horserace Betting Levy Board.

First description of Rhodococcus equi infection in common bottlenose dolphin (Tursiops truncatus).

Rhodococcus equi is a terrestrial bacterium and a common pathogen in foals (Equus caballus), in which causes pneumonia. This report describes for the first time the infection caused by R. equi in a common bottlenose dolphin (Tursiops truncatus) stranded in the Calabrian coast, Italy. The post mortem examination of the animal revealed lesions in lung and colon. The animal was also positive to dolphin morbillivirus. The histological study showed lesions attributable to R. equi infection, such as pyogranulomatous bacterial pneumonia and chronic granulomatous colitis. Whole genome sequencing of the isolated strain confirmed its identification as R. equi.

The impact of age on vitamin D receptor expression, vitamin D metabolism and cytokine production in ex vivo Rhodococcus equi infection of equine alveolar macrophages.

Rhodococcus equi (R. equi), a pneumonia-causing intracellular bacterium, results in significant morbidity and mortality in young foals, while healthy adult horses rarely develop disease. Survival and replication within alveolar macrophages (AMφ) are the hallmarks of R. equi's pathogenicity. The vitamin D receptor (VDR) and its ligand, the active vitamin D metabolite 1,25(OH)2D, are important in immune responses to intracellular bacteria. The vitamin D/VDR pathway regulates the downstream production of cytokines in infected human AMφ. The immunomodulatory role of the vitamin D/VDR pathway in equine leukocytes is unknown. The objective of the current study was to determine the impact of R. equi infection and age on synthesis of 1,25(OH)2D, VDR expression, and cytokine production in an ex vivo model of R. equi infection in equine AMφ. AMφ were collected from ten healthy foals at 2-, 4- and 8-weeks old and from nine healthy adult horses once via bronchoalveolar lavage. AMφ were mock infected (CONTROL) or infected with a virulent laboratory strain of R. equi for 7 days (INFECTED). VDR expression was determined via RT-qPCR from cell lysates. 1,25(OH)2D and cytokines were measured in cell supernatant by immunoassays. VDR expression was impacted by age (P = 0.001) with higher expression in AMφ from 8-week-old foals than from 2-week-old foals and adults. There was no significant effect of infection in foal AMφ, but in adults, relative VDR expression was significantly lower in INFECTED AMφ compared to CONTROL AMφ (P = 0.002). There was no effect of age or infection on 1,25(OH)2D concentration (P > 0.37). Mean TNFα production was significantly higher from INFECTED compared to CONTROL AMφ from 4- and 8-week-old foals and adults (P < 0.005). Mean IFNγ production was significantly higher from AMφ from foals at 8-weeks-old compared to 2-weeks-old (P = 0.013) and higher from INFECTED AMφ than from CONTROL AMφ in foals at 4-weeks-old and in adults (P < 0.027). The proportion of samples producing IL-1ß and IL-10 was also significantly higher from INFECTED compared to CONTROL AMφ isolated from 4-week-old foals (P < 0.008). Similarly, in adult samples, IL-17 was produced from a greater proportion of INFECTED compared to CONTROL samples (P = 0.031). These data document age-associated changes in VDR expression and cytokine production in equine AMφ in response to R. equi infection. This preliminary investigation supports the need for further research to fully elucidate if the vitamin D pathway has an immunomodulatory role in the horse.

Intramuscular but not nebulized administration of a mRNA vaccine against Rhodococcus equi stimulated humoral immune responses in neonatal foals.

OBJECTIVE: Design and evaluate immune responses of neonatal foals to a mRNA vaccine expressing the virulence-associated protein A (VapA) of Rhodococcus equi. ANIMALS: Cultured primary equine respiratory tract cells; Serum, bronchoalveolar lavage fluid (BALF), and peripheral blood mononuclear cells (PBMCs) from 30 healthy Quarter Horse foals. METHODS: VapA expression was evaluated by western immunoblot in cultured equine bronchial cells transfected with 4 mRNA constructs encoding VapA. The mRNA construct with greatest expression was used to immunize foals at ages 2 and 21 days in 5 groups: (1) 300 µg nebulized mRNA (n = 6); (2) 600 µg nebulized mRNA (n = 4); (3) 300 µg mRNA administered intramuscularly (IM) (n = 5); (4) 300 µg VapA IM (positive controls; n = 6); or (5) nebulized water (negative controls; n = 6). Serum, BALF, and PBMCs were collected at ages 3, 22, and 35 days and tested for relative anti-VapA IgG1, IgG4/7, and IgA activities using ELISA and cell-mediated immunity by ELISpot. RESULTS: As formulated, nebulized mRNA was not immunogenic. However, a significant increase in anti-VapA IgG4/7 activity (P < .05) was noted exclusively in foals immunized IM with VapA mRNA by age 35 days. The proportion of foals with anti-VapA IgG1 activity > 30% of positive control differed significantly (P = .0441) between negative controls (50%; 3/6), IM mRNA foals (100%; 5/5), and IM VapA (100%; 6/6) groups. Natural exposure to virulent R equi was immunogenic in some negative control foals. CLINICAL RELEVANCE: Further evaluation of the immunogenicity and efficacy of IM mRNA encoding VapA in foals is warranted.

Short review: Geographical distribution of equine-associated pVAPA plasmids in Rhodococcus equi in the world.

Virulent Rhodococcus equi strains expressing virulence-associated 15-17 kDa protein (VapA) and having a large virulence plasmid (pVAPA) of 85-90 kb containing vapA gene are pathogenic for horses. In the last two decades, following pVAPA, two host-associated virulence plasmid types of R. equi have been discovered: a circular plasmid, pVAPB, associated with porcine isolates in 1995, and a recently detected linear plasmid, pVAPN, related to bovine and caprine isolates. Molecular epidemiological studies of R. equi infection in foals on horse-breeding farms in Japan and many countries around the world have been conducted in the last three decades, and the epidemiological studies using restriction enzyme digestion patterns of plasmid DNAs from virulent isolates have shown 14 distinct pVAPA subtypes and their geographical preference. This short review summarizes previous reports regarding equine-associated pVAPA subtypes in the world and discusses their geographic distribution from the standpoint of horse movements.

Evaluation of oxidative stress in foals with Rhodococcus equi infection-induced pneumonia for the judgment of therapeutic effect.

Forty-five foals with Rhodococcus equi infection and pneumonia symptoms were classified into a surviving group and a dead group. Using serum samples, the oxidative stress index (OSI) was determined at the first visit and the follow-up visit. The OSI of the surviving group was significantly lower at the follow-up than that at the first visit. No significant difference was observed between the OSI of the dead group at the first and follow-up visits. In the surviving group, treatment at the first visit mitigated inflammation and reduced OSI. However, in the dead group, poor response to the treatment provided at the first visit led to continued inflammation, and no change was observed the OSI.

Development of monoclonal antibodies against Rhodococcus equi virulence-associated protein N and their application to pathological diagnosis.

IMPORTANCE: Rhodococcus equi can cause infection in ruminants, and its pathogenicity is suggested to be associated with VapN. Despite its wide distribution, no immunological diagnostic method has been developed for VapN-producing R. equi. Against this background, we attempted to develop monoclonal antibodies targeting VapN and assess their application in immunostaining. In the study, mice were immunized with recombinant VapN, and cell fusion and cloning by limiting dilution permitted the generation of three antibody-producing hybridomas. The utility of the antibodies produced from the hybridomas in immunostaining was demonstrated using an infected mouse model, and the antibodies were further applied to previously reported cases of R. equi infection in goats and cattle. Although the 4H4 antibody induced the strongest reactions, the reactivity of two other antibodies was improved by antigen retrieval. Our monoclonal antibodies will be utilized to support the definitive diagnosis of suspected R. equi infection, including cases that were previously missed.

Rhodococcus Equi: Challenges to Treat Infections and to Mitigate Antimicrobial Resistance.

Rhodococcus equi, a gram-positive facultative intracellular pathogen and a soil saprophyte, is one of the most common causes of pneumonia in young foals. It poses a threat to the economy in endemic horse-breeding farms and to animal welfare annually. Many farms use thoracic ultrasonographic screening and antimicrobial treatment of subclinically affected foals as a preventive measure against severe R. equi infections. The wide use antimicrobials to treat subclinically affected foals has contributed to the emergence of multidrug resistant (MDR)-R. equi in both clinical isolates from sick foals and in the environment of horse-breeding farms. Alternatives to treat foals infected with MDR-R. equi are scarce and the impact of the emergence of MDR-R. equi in the environment of farms is still unknown. The aim of this review is to discuss the emergence of MDR-R. equi in the United States and the challenges faced to guide antimicrobial use practices. Reduction of antimicrobial use at horse-breeding farms is essential for the preservation of antimicrobial efficacy and, ultimately, human, animal, and environmental health.

Rhodococcus equi-What is New This Decade?

Foals become infected shortly after birth; most develop subclinical pneumonia and 20% to 30% develop clinical pneumonia that requires treatment. It is now well established that the combination of screening programs based on thoracic ultrasonography and treatment of subclinical foals with antimicrobials has led to the development of resistant Rhodococcus equi strains. Thus, targeted treatment programs are needed. Administration of R equi-specific hyperimmune plasma shortly after birth is beneficial as foals develop less severe pneumonia but does not seem to prevent infection. This article provides a summary of clinically relevant research published during this past decade.

Transfusion of hyperimmune plasma for protecting foals against Rhodococcus equi pneumonia.

The bacterium Rhodococcus equi causes pneumonia in foals that is prevalent at breeding farms worldwide. In the absence of an effective vaccine, transfusion of commercial plasma from donor horses hyperimmunised against R. equi is used by many farms to reduce the incidence of pneumonia among foals at farms where the disease is endemic. The effectiveness of hyperimmune plasma for controlling R. equi pneumonia in foals has varied considerably among reports. The purposes of this narrative review are: (1) to review early studies that provided a foundational basis for the practice of transfusion of hyperimmune plasma that is widespread in the United States and in many other countries; (2) to summarise current knowledge of hyperimmune plasma for preventing R. equi pneumonia; (3) to provide an interpretive summary of probable explanations for the variable results among studies evaluating the effectiveness of transfusion of hyperimmune plasma for reducing the incidence of R. equi pneumonia; (4) to review mechanisms by which hyperimmune plasma might mediate protection; and (5) to consider risks of transfusing foals with hyperimmune plasma. Although the weight of evidence supports the practice of transfusing foals with hyperimmune plasma to prevent R. equi pneumonia, many important gaps in our knowledge of this topic remain including the volume/dose of hyperimmune plasma to be transfused, the timing(s) of transfusion, and the mechanism(s) by which hyperimmune plasma mediates protection. Transfusing foals with hyperimmune plasma is expensive, labour-intensive, and carries risks for foals; therefore, alternative approaches for passive and active immunisation to prevent R. equi pneumonia are greatly needed.

Plasma metabolome of healthy and Rhodococcus equi-infected foals over time.

BACKGROUND: Foals that develop pulmonary ultrasonographic lesions on Rhodococcus equi (R. equi) endemic farms are treated with antibiotics because those at risk of developing clinical pneumonia (~20%) cannot be recognised early. Candidate biomarkers identified using metabolomics may aid targeted treatment strategies against R. equi. OBJECTIVES: (1) To describe how foal ageing affects their plasma metabolome (birth to 8 weeks) and (2) to establish the effects that experimental infection with Rhodococcus equi (R. equi) has on foal metabolome. STUDY DESIGN: Experimental study. METHODS: Nine healthy newborn foals were experimentally infected with R. equi as described in a previous study. Foals were treated with oral antibiotics if they developed clinical pneumonia (n = 4, clinical group) or remained untreated if they showed no signs of disease (n = 5, subclinical group). A group of unchallenged foals (n = 4) was also included in the study. By the end of the study period (8 weeks), all foals were free of disease. This status was confirmed with transtracheal wash fluid evaluation and culture as well as thoracic ultrasonography. Plasma metabolomics was determined by GC-MS weekly for the study duration (8 weeks). RESULTS: Foals' plasma metabolome was altered by ageing (birth to 8 weeks) and experimental infection with R. equi as demonstrated using multivariate statistical analysis. The intensities of 25 and 28 metabolites were altered by ageing and infection (p < 0.05) respectively. Furthermore, 20 metabolites changed by more than 2-fold between clinical and subclinical groups. MAIN LIMITATIONS: The number of foals is limited. Foals were experimentally infected with R. equi. CONCLUSIONS: Ageing and R. equi infection induced changes in the plasma metabolome of foals. These results provide an initial description of foal's plasma metabolome and serve as background for future identification of R. equi pneumonia biomarkers.

INTRODUCTION/CONTEXTE: Les poulains qui développent des lésions pulmonaires échographiques dans les fermes d'élevage où Rhodococcus equi (R. equi) est endémique sont traités avec antibiotiques car ceux à risque de développer des lésions cliniques (~20%) ne peuvent être identifiés précocement. Certains biomarqueurs identifiés par le biais de la métabolomique pourraient aider à orienter les stratégies de traitement pour R. equi. OBJECTIFS: (1) Décrire les changements de métabolome plasmatique qui surviennent chez les poulains en lien avec l'âge (naissance jusqu'à 8 semaines d'âge) et (2) Établir les effets d'une infection expérimentale à Rhodococcus Equi sur le métabolome des poulains. TYPE D'ÉTUDE: Étude expérimentale. MÉTHODES: Neufs poulains nouveaux-nés en santé ont été infectés de façon expérimentale par R. equi tel que décrit précédemment. Ils ont été traités avec des antibiotiques s'ils ont développé une pneumonie clinique (n = 4, groupe clinique) ou ont simplement été suivi dans le temps s'ils n'ont pas montré de signes de la maladie (n = 5, groupe sous-clinique). Un groupe de poulains sains (n = 4) était aussi inclus dans l'étude. À la fin de l'étude (8 semaines), tous les poulains étaient sains tel que confirmé par l'évaluation et la culture de leur fluide de lavage transtrachéal de même qu'à l'échographie thoracique. Les métabolomiques plasmastiques ont été déterminées par GC-MS de façon hebdomadaire pour la durée de l'étude (8 semaines). RÉSULTATS: À la fois l'âge et l'infection expérimentale ont altéré le métabolome plasmatique des poulains tel que démontré par l'analyse statistique multivariée. L'âge a altéré l'intensité de 25 métabolites et l'infection a modifié l'intensité de 28 métabolites (p < 0.05). De plus, 20 métabolites ont changé de plus de 2 fois leur valeur initiale, entre les groupes cliniques et sous-cliniques. LIMITES PRINCIPALES: Le nombre de poulains reste limité. Les poulains ont été infecté par R. equi de façon expérimentale. CONCLUSIONS: Le vieillissement et l'infection par R. equi induisent des changements dans le métabolome plasmatique des poulains. Ces résultats représentent une description initiale du métabolome plasmatique chez le poulain et peuvent servir de base pour l'identification future de biomarqueurs pour la détection de pneumonie à Rhodococcus equi.

Antimicrobial susceptibility, virulence genes and genomic characterization of Trueperella pyogenes isolated from abscesses in dairy cattle.

Trueperella pyogenes is an opportunistic animal pathogen mainly associated with various suppurative infections in wild and domestic animals. Limited studies have investigated the pathogenesis of diseases caused by this pathogen. The main objective of the current study was to investigate the prevalence, phenotypic properties, virulence genotypes, antimicrobial susceptibility and genetic characterization of T. pyogenes isolated from abscess lesions in different tissues of on-farm dairy cattle. The study was performed on 150 postpartum cattle with clinical abscess symptoms on 22 farms around Tehran, Iran. Classical and disk diffusion methods are used for phenotypic characterization and antibiotic susceptibility. Detection of virulence factor encoding genes and genomic characterization of the isolates also are carried out by conventional PCR and BOX-PCR assays, respectively. Sixty-eight T. pyogenes strains (45.3%) were isolated, 12 were identified as pure cultures and the other 56 strains were isolated from mixed cultures. Seven distinct biotypes were identified among the T. pyogenes isolates. The isolates were mostly resistance to trimethoprim-sulfamethoxazole (70.6%), erythromycin (36.7%), tetracycline (26.5%) and tylosin (23.5%) antibiotics. Also, the genes plo, nanH, nanP and fimA were detected in all isolates. Forty-two isolates (61.7%) carried all virulence factor genes detected in this study. Three isolates only carried plo, nanH, nanP and fimA genes were identified as the least frequent genotype. All sixty-eight isolates and the reference strain were categorized into seven main clusters (A-G). A strong association was observed between virulence factor encoding genes, pathogenicity and biochemical biotypes in some specific clonal relationships.

Evaluation of serum concentration of acute-phase proteins (haptoglobin and serum amyloid A) in the affected Arabian foals with rhodococcosis.

BACKGROUND: Early detection of Rhodococcus equi pneumonia in foals is essential for horse health and for veterinarians. OBJECTIVES: This study aimed to demonstrate the usefulness of assessing the serum concentration of acute-phase proteins (APPs) in the early diagnosis of pneumonia. METHODS: The study evaluated APPs in 19 Arabian foals with R. equi pneumonia and compared them with 18 normal Arabian foals in equestrian clubs in Tabriz, Iran. Affected foals were identified through history, clinical findings and bacterial culture of tracheal washing. Biochemical methods and polymerase chain reaction tests were performed by examining the 16S rRNA and vapA genes to confirm the diagnosis of bacterial isolates. Blood samples were taken from all sick and healthy horses, and their serum was isolated. APPs in the serum were measured in all the samples. RESULTS: Rhodococcosis increased the serum concentration of haptoglobin (Hp) and serum amyloid A (SAA) (p < 0.001). The relationship between SAA and Hp was meaningful in the infected group (r = 0.933) but not in the healthy group. In cases where there are clinical findings of R. equi pneumonia, the concentration of SAA and Hp can help the effectiveness of treatment. - CONCLUSIONS: Serum concentration analysis of APPs can be helpful in early diagnosis and successfully treating foals with R. equi pneumonia.