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Transfusing foals with Rhodococcus equi hyperimmune plasma (REHIP) is a standard practice at many horse-breeding farms to help prevent R. equi pneumonia. At many large breeding farms, pneumonia is most commonly recognized as subclinical based on thoracic ultrasonography findings. The efficacy of REHIP transfusion and the impact of the volume of plasma transfused for reducing the cumulative incidence of subclinical R. equi pneumonia are unknown. A retrospective cohort study was conducted among foals born and residing through weaning at a large breeding farm. Foals were transfused with either 0 L (n = 2 foals), 1 L (n = 85 foals), or 2 L (n = 62 foals) of REHIP within 36 hours of birth. Volume transfused was principally based on intended use of the foals. All foals at the ranch were routinely screened using thoracic ultrasonography at 5, 7, and 9 weeks of age to detect subclinical pneumonia attributed to R. equi based on farm history. The proportion of the foals receiving < 1 L REHIP that developed subclinical pneumonia (32%; 26/82) was significantly (P = .0068; chi-squared test) greater than that among foals transfused with 2 L of REHIP (12%; 8/68). Despite the important limitations of this observational study, it provides evidence supporting the need for well-designed clinical trials to evaluate the impact of the use and dose of REHIP for preventing subclinical pneumonia. Reducing the incidence of subclinical pneumonia is important because reducing antibiotic treatment of subclinical cases will decrease selection pressure for antimicrobial resistance in R. equi.

A 550 kg Thoroughbred broodmare born in 2007 was evaluated repeatedly over five breeding seasons because of episodic seizures, which occurred only after vaccination. The mare had no health problems other than repetitive reactive, focal seizures that occurred over a 5-year period, in each case after vaccination with inactivated Rhodococcus equi, influenza or equine herpesvirus type 1 or 4 commercial vaccines. Each seizure episode occurred between 24 and 72 hours after vaccination and lasted no longer than 72 hours. No seizure activity was observed at any other time except after vaccination. During each reactive seizure, the mare was treated empirically with diazepam, dexamethasone, and flunixin meglumine. Altrenogest was administered to supplement placental production of progesterone until parturition, and butylscopolamine was administered to decrease suspected uterine contractions during seizure episodes. Each year after the seizure episodes, the mare gave birth prematurely to viable foals. In subsequent seasons, the mare was not vaccinated, resulting in no further seizure episodes. This is the first report of seizure-like activity after vaccination in a horse and suggests that vaccine components may trigger seizures in otherwise healthy animals. Because seizures recurred after each subsequent yearly vaccination and ceased when vaccinations were not administered, cessation of vaccination should be considered for horses thus affected.

The occurrence of Rhodococcus equi at farms varies, with disease occurring endemically at some farms, but only sporadically, or not at all at other farms. Only some foals residing on endemic farms develop clinical signs of disease. Limited evidence is available regarding foal-level risk factors for the development of R. equi pneumonia. The purpose of this study was to identify foal-level risk factors associated with the development of R. equi pneumonia among foals at a large breeding farm in Texas with a recurrent problem of R. equi pneumonia. A retrospective cohort study was conducted using data from foals born at the farm from January 2009 through December 2011 that met the criteria for inclusion. Dam-level, foal-level, and health-related data were collected from all foals. Independent variables were analyzed with logistic regression, controlling for the effect of year. Data from 787 foals born at the farm were included, of which 209 (27%) developed R. equi pneumonia. The cumulative incidence of disease at the farm varied significantly by year. Foals that were diagnosed with a prior morbidity besides R. equi were less likely to develop R. equi pneumonia.

A 2-month-old Andalusian colt in central Spain presented dyspnea, diarrhea, and depression. Despite the initial treatment for presumptive pneumonia caused by Rhodococcus equi, after 1 hour, the colt showed signs of shock and died. The necropsy revealed multiple abscesses in the lung, as well as enlarged mesenteric lymph nodes, and hemorrhagic peritonitis. Samples were taken from trachea, lung parenchyma, small intestine, and colon. All samples yielded a pure culture of Streptococcus equi spp. zooepidemicus, whereas R. equi was excluded by using a specific qPCR performed on all samples. Isolates from all samples were characterized by pulse-field gel electrophoresis and the representative strain was identified by MALDI-TOF and qPCR. Its genome was sequenced, assembled, and annotated; multilocus sequence typing data assigned the strain to sequence type 70 and genes related to adhesion, bacteriocins, invasion, antimicrobial resistance, toxins, and superantigens szeN and szeP were identified in the assembled genome. The strain was susceptible to all antimicrobials tested. Our findings support the inclusion of S. zooepidemicus on an endemic farm where R. equi has been ruled out via PCR testing. S. zooepidemicus can cause multiorgan disease in foals, similar to infection in humans. The presence of superantigens in this S. zooepidemicus strain may have contributed to the fatal outcome in this clinical case.

This study determined the antagonistic activity of a probiotic Bacillus subtilis strain PB6 (PB6) toward six bacterial pathogens of equine origin. Antimicrobial activity of PB6 was evaluated using two different in vitro methodologies. A streak line assay resulted in measurable zones of clearing between growth of PB6 and Clostridium difficile , Clostridium perfringens , Rhodococcus equi , and Streptococcus equi . A broth micro dilution assay using cell-free supernatant from PB6 culture demonstrated inhibition of Salmonella Typhimurium and R. equi growth. The results indicate the potential for PB6 to be a beneficial probiotic for use in the equine industry.

Pneumonia caused by the bacterium Rhodococcus equi (RE) is an important cause of disease and death in foals at breeding farms worldwide. The efficacy of transfusion with hyperimmune plasma (HIP) for preventing RE pneumonia remains ill-defined. The objective of this study was to determine whether the odds of pneumonia were decreased with higher antibody (Ab) concentrations against either the RE virulence-associated protein A (VapA) or the polysaccharide β-1→6-N-polyacetyl glucosamine (PNAG) among Quarter Horse foals from 2 large breeding farms transfused with either RE HIP or PNAG HIP, respectively. Foals were randomly and equally assigned to be transfused within 24 h of birth with 2 L of either PNAG HIP (n = 116) or RE HIP (n = 117). Serum was collected post-transfusion to test by ELISA for concentrations of Abs against PNAG and the RE virulence-associated protein A (VapA), and deposition of complement component 1q (C'1q) onto PNAG. Foals were then monitored through 6 mo of age. Foals at Farm A (n = 119) were monitored twice daily for clinical signs of pneumonia, and foals at Farm B (n = 114) were monitored by ultrasound for subclinical pneumonia. Study investigators were masked to the plasma identity until after analysis was completed. For data analysis, binary variables of Ab levels (higher or lower) were created using the median value of VapA Ab concentration for RE HIP-transfused foals and PNAG and C'1q Abs for PNAG HIP-transfused foals. Data were analyzed using logistic regression, with pneumonia as the binary outcome variable, and binary concentration for a given Ab level and farm as dependent variables. Our results indicated that among RE HIP-transfused foals, the odds of pneumonia were approximately 6-fold higher (P = 0.0005) among foals with lower (i.e., ≤ median) VapA concentrations, whereas among PNAG HIP-transfused foals the odds of pneumonia were approximately 3-fold (P = 0.0347) and 11-fold (P = 0.0034) higher for foals with lower concentrations for PNAG and C'1q deposition, respectively. These data indicated that Abs against VapA, and the PNAG antigen with C'1q deposition activity are important indicators of protection against both subclinical and clinical RE pneumonia. Additionally, concentrations of Abs with C'1q deposition activity were a stronger predictor of efficacy than PNAG Ab concentration alone among PNAG HIP-transfused foals.

Respiratory diseases are common in horses; however, there is a lack of information in the literature on respiratory disease affecting mule foals. The objective of this study was to investigate the presence of aerobic bacteria in tracheal wash samples from 20 mule foals up to 6 months of age, with and without clinical evidence of respiratory disease. Samples were collected via endoscopy in two separate occasions and sent for cytology, microbial culture, and PCR for detection of Rhodococcus equi. Based on clinical evidence, 32.5% (13/40) of the samples were obtained from mule foals displaying signs of a respiratory condition, whereas 50% (20/40) of the samples showed cytologic evidence of respiratory tract infection. One hundred percent of samples provided positive cultures with Escherichia coli (45%), Enterococcus (37.5%), and coagulase-negative Staphylococcus (30%) being the most common bacterial genera isolated. R. equi was not identified in any of the samples. The correlation between isolated bacterial agents and the presence of respiratory infection was not statistically significant. The microorganisms found in the samples may be naturally present in the soil, feces, and environment in which the animals live, presenting a risk of opportunistic respiratory infection.

Rhodococcus equi is an opportunistic, intracellular saprophyte that causes severe pyogranulomatous pneumonia in foals. The bacterium displays in vitro susceptibility to many antibiotics. The highest efficacy against R. equi in vitro and in vivo is achieved by using a combination of rifampicin and macrolide antibiotics. Recent years have seen an upward trend in the minimum inhibitory concentration (MIC) of rifampicin and erythromycin, suggesting increasing resistance of R. equi to these antibiotics. The aim of the study was to determine the antimicrobial activity of 24 selected antibiotics against R. equi strains isolated from dead foals and from the environment of horse breeding farms with and without endemic R. equi infections. Minimum inhibitory concentration gradient strips were used to determine the lowest concentration of the antibiotic that inhibited the growth of R. equi. Based on normal MIC distribution, an epidemiologic cutoff values (ECOFF) were assessed for particular antibiotics and R. equi strains. The results were compared with ECOFFs for S. aureus, according to the European Committee on Antimicrobial Susceptibility Testing data. The data indicate that the lowest MIC values were obtained for clarithromycin, rifampicin, imipenem, and vancomycin. The majority of R. equi strains can be classified as wild type in relation to the majority of antibiotics. A small percentage of strains presented non-WT (NWT) with the exception of SXT, for which 35% of strains were classified as NWT. The lack of interpretative criteria for R. equi creates a real problem in the assessment of antibiotic sensitivity both for clinical and scientific purposes.

Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) is used for bacterial identification by analyzing the spectra of isolates and comparing them against a database of reference spectra; it is known for its rapidity and accuracy. Although MALDI-TOF MS is used for identification of bacterial isolates from animals, not all animal pathogens are identified correctly. In this study, we used a commercial MALDI-TOF MS identification system to examine 3724 bacterial isolates from horses and their environments. Isolates that could not be identified with MALDI-TOF MS were identified by 16S rRNA gene sequence taxonomic analysis. MALDI-TOF MS could identify 86.2% of the isolates from horses to the species level, showing that this method could be successfully applied for bacterial identification in horses. However, some species known to be equine pathogenic agents including Taylorella equigenitalis and Rhodococcus equi were difficult to identify with MALDI-TOF MS, which might be the result of an inadequate reference database. Some Prevotella, Staphylococcus, and Streptococcus isolates, which could not be identified with either MALDI-TOF MS or 16S rRNA gene sequencing analysis, formed clusters in the 16S rRNA phylogenic tree, and might be unknown species isolated from horses. Adding the spectra of isolates identified in this study to an in-house database might make MALDI-TOF MS a more useful tool for identifying equine isolates.

Rhodococcus equi is a significant cause of pneumonia, resulting in disease and sometimes death of foals. It is believed that infection occurs by inhalation of dust contaminated with virulent Re qui. Although association between the airborne concentration of virulent R equi and the incidence of foal pneumonia at breeding farms has been documented, studies at the level of individual foals have not been reported. Thus, the objective of this study was to determine whether the magnitude of airborne virulent R equi was signifi- cantly associated with risk of Re quipneumonia for individual foals. The concentration of virulent R equi was significantly (P

Rhodococcus equi (R equi) pneumonia is an important cause of disease and death in foals. Feces from mares can contain R equi , including virulent R equi , and thus may act as a source of the bacteria at horse breeding farms. A previous report documented that every mare at a farm in central Kentucky shed virulent R equi in at least one of four fecal samples collected serially during the periparturient period. The objective of this study was to assess the extent to which this high prevalence of fecal shedding could be replicated at other horse breeding farms. The frequency of detection of R equi and virulent R equi in fecal samples was studied among 131 mares from 24 farms in central Kentucky. The proportions of fecal samples from mares containing R equi and virulent R equi were 95% and 76%, respectively. These findings indicate that R equi and virulent R equi may be isolated with high frequency from feces of mares at breeding farms in central Kentucky, and that mares are a source of virulent R equi for the environment of their foals.

Pneumonia caused by Rhodococcus equi is an insidious disease of young foals in which clinical signs may not be apparent until pathologic changes are well progressed. Thus, early and accurate diagnosis of foals with R. equi pneumonia is crucial. Thoracic ultrasound screening and polymerase chain reaction (PCR) from fecal and nasal swab samples were performed in 22 foals from 3 to 16 weeks of age from three endemic farms located in the south of Brazil to identify the occurrence of R. equi subclinical disease/pneumonia. The association of thoracic ultrasonography and fecal PCR detection of virulent R. equi provided a possibility of identification of critical points in disease control. Considering that 95.4% of the foals showed evidence of subclinical disease based on pulmonary abscessation or consolidation but none of them developed R. equi pneumonia, antibiotic treatment does not seem necessary in the population studied.

The frequencies of neurologic diseases and various corresponding causes were analyzed in 4,319 Norman horses examined by autopsy between 1986 and 2006. Five hundred forty-three cases of nervous system disorders were detected, or a total prevalence of 12.6%. One hundred eighty-seven of the 543 horses (34.4%) exhibited lesions of a traumatic origin affecting the skull or the vertebral column at different levels. Their frequency was less in foals younger than 1 month of age and higher in horses aged 6 months to 2 years. Eighty-three cases of cervical vertebral compressive myelopathy (CVCM) (15.3%) were identified. Males and geldings were more often affected than females. CVCM was diagnosed mostly in animals aged 6 months to 2 years. Horses affected with lesions in the mid-cervical region (region C3–C5) were significantly younger than those exhibiting more caudal lesions (region C5–C7). Neonatal maladjustment syndrome was diagnosed in 62 foals younger than 3.5 days (4.8% of the causes of death between birth and 1 month) by using clinical or lesional criteria. The prevalence was higher in Thoroughbreds as well as in the miscellaneous breed category and less in French Standardbreds. Bacterial meningoencephalomyelitis and meningitis represented 9.6% of nervous system disorders (52 cases) and most often affected foals aged 1 to 6 months. The main bacteria identified were beta-hemolytic Streptococci , Escherichia coli, Listeria monocytogenes, Staphylococcus aureus, and Actinobacillus sp. The other causes diagnosed were, in decreasing order of frequency: grass sickness or equine dysautonomia (6.3% of neurologic diseases), hepatic encephalopathy syndrome (5.2%), septic vertebral arthritis or osteitis mainly caused by Rhodococcus equi (2.6%), congenital defects of the nervous system (2.4%), equine herpesvirus 1 myeloencephalopathy (2.2%), botulism (2.2%), malformations of the vertebral column other than CVCM (2%), and neighboring polyneuritis associated with guttural pouch mycosis (1.5%).

A relative immunodeficiency of young foals is considered to account for the increased susceptibility of foals to infectious diseases, including pneumonia caused by Rhodococcus equi . In this report, peripheral blood mononuclear cells (PBMCs) from healthy foals at 14 and 56 days of age, or from their dams, were incubated with three stimulatory and one nonstimulatory (control) synthetic cytosine-phosphate-guanosine oligodeoxynucleotides (CpG-ODNs), and mRNA expression of tumor necrosis factor alpha (TNF-α), interferon gamma (IFN-γ), interleukin (IL) -6, IL-8, IL12-p35, and IL-12p40 were determined. Results indicated that synthetic CpG-ODNs can induce strong, rapid cytokine responses in healthy foals and adult horses. B-class CpG-ODNs 2135 and 2142 induced greater messenger RNA (mRNA) expression of IFN-γ, IL-6, and IL-12p40 than the C-class CpG-ODN 2395 in foal PBMCs. In foals, B-class CpG-ODNs induced IFN-γ, IL-6, and IL-12P40 mRNA expression that was similar to or higher in magnitude than that observed in adult horses. These observations indicate that CpG-ODNs might be useful as immunomodulators or as potential adjuvants for vaccines to aid in preventing R. equi pneumonia and other bacterial diseases of foals.

The objective of this study was to assess the ability of prophylactically administered gallium maltolate (GaM) to inhibit growth or kill Rhodococcus equi within murine macrophage-like (J774A.1) cells. Cells were treated with three different doses of GaM or a single dose of maltol (equivalent to the concentration present in the highest dose of GaM studied); they were then infected with virulent R. equi and incubated. Quantitative cultures of R. equi from lysed macrophages were obtained at 0, 24, 48, and 72 hours. All GaM dosages resulted in significant reductions of intracellular R. equi compared with untreated control cells, and a dose‐response effect was evident. Maltol treatment alone had no significant effect on intracellular R. equi concentrations compared with untreated control cells. Results suggest the potential usefulness of gallium maltolate for the prevention or control of R. equi infections.

Infection with Rhodococcus equi is a common cause of pneumonia in foals. Extrapulmonary manifestations occur, including gastrointestinal disease such as enterocolitis, musculoskeletal disease such as osteomyelitis, as well as other aberrant regions of abscess. Osteomyelitis predominately occurs in the metaphyseal or epiphyseal regions of long bones because of low-pressure blood flow through the sinusoids of these regions of the bone. In this report, a case of cortical, diaphyseal osteitis of the humerus caused by Rhodococcus equi and subsequent medical and surgical management is described.

presence of erm(46) as detected by PCR in 124 isolates of R. equi. Expression of erm(46) in a macrolide-susceptible strain of R. equi induced high level resistance to macrolides, lincosamides, and streptogramins B, but not to other classes of antimicrobial agents. Transfer of erm(46) from resistant to susceptible strains of R. equi was confirmed and occurred at a transfer frequency of up to 2 10-3. This is the first molecular characterization of macrolide, lincosamides and streptogramins B resistance in R. equi. Resistance is caused by a novel erm gene, erm(46), which is transferrable likely by conjugation.

isolated 3 strains with different colonies sizes on the blood agar plate, UBA8Ch (0.5mm), UBA8Md (2mm) andUBA8Gd (4 mm). Expression of capsule was observed by negative staining with India ink solution and with electron microscopywith fosfotungstic acid.Diskdiffusion testwereusedas recommended by Clinical and Laboratory Standards Institute (CLSI). The antibiotic tested were: erithromycin (ERY), penicillin (PEN), ciprofloxacine (CIP), enrofloxacin (ENR), tetracycline (TET) trimethoprim-sulfamethoxazole (TMS), cefotaxime (CTX) and florfenicol (FFC). Results were categorized by using the guidelines recommended by the CLSI 2008, 2010 [3]. The capsule was observed in the 3 strains with optical microscope and with electron microscope. The strains expressed different levels of capsule, UBA8Ch: small sized, UBA8Md:medium sized andUBA8Gd: high sized. The UBA8Ch and UBA8Gd strains were susceptible for all the antimicrobials tested. The UBA8Md strain was intermedia susceptibility for ERY, ENR and TMS. The immune status of the host and the guttural pouch environment could influence in the phenotypic characteristics variation of the strains. Itwas isolated three strains froma same sample that expressed different levels of capsule, different colonies sizes on the blood agar plate and antibiotic sensibility. This suggests the presence of different clones of See in carriers.

Rhodococcus equi causes pyogranulomatous bronchopneumonia (rattles) and gastrointestinal abscessation of foals. Early diagnosis is essential for minimising the impact of this disease on the horse industry. Current best clinical practice involves ultrasonographic (U/S) thoracic screening to detect small abscesses and initiate treatment before serious clinical abnormalities are obvious. Ecological and epidemiological studies in Australia have demonstrated that foals shed virulent R. equi from the respiratory tract and that high airborne levels of virulent R. equi are associated with high disease prevalence. The role of the foal as a contributor to environmental contamination remains an important practical area of R. equi research. Two studies were conducted. Samples from the breathing zone were collected from 53 foals as neonates and again at 6 weeks of age. These samples were cultured on selective bacteriological media. Samples were also collected from 80 mares and foals. Serum samples were collected from foals at 12 hours, 3 weeks and 6 weeks of age. Faecal and breath samples were collected at 3 weeks and 6 weeks of age. Colostrum samples were collected from mares at parturition. Serum and colostrum samples were tested using a VapA ELISA that detects antibody to the major R. equi virulence factor (the VapA protein). Faecal samples were cultured on selective media. There was strong correlation between anti-VapA IgG level in serum samples from newborn foals and maternal colostrum. However, foal VapA antibody concentration at 12 hours was not related to the likelihood of subsequent R. equi abscessation. Virulent R. equi was detected in breathing zone samples from 19% of neonatal foals and from 45% of 6 week old foals. The concentration of virulent R. equi in these samples was greater in the older foals. Antibody to VapA declined from 12 hours to 3 weeks of age as maternal antibody waned, but increased significantly between 3 and 6 weeks of age. Foals with ultrasonographic evidence of rattles had higher levels of antibody than non-diseased foals. Although >90% of 6 week old foals had virulent R. equi in faeces, foals with U/S evidence of rattles had a greater proportion. However, the concentration of virulent R. equi in faeces was not statistically greater than in foals with no U/S lesions. Six week old foals are a significant source of environmental contamination with virulent R. equi. These foals shed higher amounts of virulent R. equi from both faeces and breath compared to younger foals. This has significant implications for management and reinforces the current practice of separation of mares and foals based on age. These results also support collection of faeces from high traffic areas such as yards. Importantly, neither samples from the breathing zone, nor maternally derived antibody levels, were useful predictors of subsequent development of rattles. Perinatal airborne exposure to Rhodococcus equi is associated with increased risk of pneumonia caused by R equi in foals