Topic:Rhodococcus equi
Rhodococcus equi is a bacterial pathogen that primarily affects foals, leading to pneumonia and other systemic infections. It is a significant concern in equine health due to its impact on the respiratory system of young horses. The bacterium is found in soil and can be inhaled by foals, leading to infection. Clinical signs of Rhodococcus equi infection in foals include coughing, fever, and respiratory distress. Diagnosis is typically confirmed through bacterial culture or polymerase chain reaction (PCR) testing. Management of the disease involves antimicrobial therapy and supportive care. This page compiles peer-reviewed research studies and scholarly articles that explore the pathogenesis, diagnosis, treatment, and prevention of Rhodococcus equi infections in horses.
Identification of Rhodococcus equi using the polymerase chain reaction. Two regions in the gene coding for 16S rRNA in Rhodococcus equi were selected as species-specific primer sequences for the polymerase chain reaction (PCR). PCR using these primers was tested against 10 strains of R. equi (including the type strain) and gave positive results for all but was negative for all other tested species of Rhodococcus; representatives of the most closely related genera and a number of other bacterial species. This method could therefore be used to identify this species which can infect the lungs or other organs of horses, pigs, humans and other animals.
Serologic responses to Rhodococcus equi in individuals with and without human immunodeficiency virus infection. Thirty healthy blood donors, 15 workers from horse-breeding farms, 69 human immunodeficiency virus (HIV)-negative persons at risk for HIV infection, 125 HIV-infected subjects without Rhodococcus equi infection, and nine HIV-infected patients with Rhodococcus equi pneumonia were evaluated in order to detect serum antibodies to Rhodococcus equi precipitate-soluble antigen by an enzyme immunoassay (EIA). Whereas EIA values for healthy donors, horse farm workers, individuals at risk for HIV infection, and HIV-positive subjects without Rhodococcus equi infection were comparable, HIV-infected patien...
Equine herpesvirus type 2 (EHV-2) as a predisposing factor for Rhodococcus equi pneumonia in foals: prevention of the bifactorial disease with EHV-2 immunostimulating complexes. Equine herpesvirus type 2 (EHV-2), a member of the Gammaherpesvirinae subfamily, was studied in a two-phase respiratory disease complex of young foals as a predisposing factor for the secondary bacterial invasion of lungs with Rhodococcus equi (R. equi). Foals were immunized against EHV-2 on a farm where R. equi pneumonia regularly occurred during the last years. The immunizations were performed by using a subunit vaccine which selectively presents envelope glycoproteins of EHV-2 in a multimeric form of immunostimulating complexes (iscoms). The etiological role of EHV-2 was estimated by observ...
Immunohistochemical detection of virulence-associated antigens of Rhodococcus equi in pulmonary lesions of foals. Rhodococcus equi was isolated from the lungs of six foals with bronchopneumonia. All isolates expressed 15-17-kd antigens by immunoblot analysis and contained a virulence-associated plasmid of 85 or 90 kb. Immunohistochemically, R. equi from all pulmonary lesions showed the expression of 15-17-kd antigens mainly in the phagocytic cells. The specific monoclonal antibody to 15-17-kd antigens of R. equi (MAb 10G5) may be an aid in the diagnosis of R. equi-induced pneumonia.
Blastogenic response of lymphocytes from foals infected with Rhodococcus equi. The blastogenic response of lymphocytes from 16 newborn foals naturally infected with Rhodococcus equi was investigated, in order to evaluate the relationship between R. equi infection and depressed host response. Naturally infected foals showed evidence of R. equi infection at 5-6 weeks of age, as determined by clinical, haematological, bacteriological and serological methods. The blastogenic response of lymphocytes against phytohaemagglutinin was significantly depressed (stimulation index < 1.80; P < 0.01, P < 0.05) in R. equi-infected foals at 5-6 weeks of age compared with those o...
Attempts to find phenotypic markers of the virulence plasmid of Rhodococcus equi. Four isolates of Rhodococcus equi, from pneumonic foals, and containing the 85 kb virulence plasmid, a porcine isolate containing an 80 kb plasmid, and their plasmid cured derivatives, were examined for 239 phenotypic properties in an attempt to find characters other than the virulence-associated protein (VapA) which might be encoded by the virulence plasmid in organisms grown at 37 degrees C. Tests chosen included those which have previously given variable results for R. equi isolates, since such variability might be attributed to plasmid curing, and characteristics which have been described ...
Pharmacokinetics and therapeutic potential for repeated oral doses of trimethoprim/sulphachlorpyridazine in horses. The pharmacokinetic parameters of a powder formulation of trimethoprim/sulphachlorpyridazine were studied in eight healthy horses which received 5 mg/kg trimethoprim and 25 mg/kg sulphachlorpyridazine 12-hourly with concentrate for five days. The intake of the medicated concentrate by the horses was variable during the first two days, but after they became accustomed to the taste the intake by all the horses during the last three days was good. Faecal samples taken before and on the last day of the drug administrations were negative when cultured for salmonella. Compared with the results of a ...
Failure of hyperimmune plasma to prevent pneumonia caused by Rhodococcus equi in foals. A trial was conducted on a Thoroughbred stud to determine whether or not the administration of anti-Rhodococcus equi hyperimmune plasma would reduce the prevalence of R equi pneumonia (rattles) in foals born in the 1992 horse breeding season. Hyperimmune plasma was administered to 34 foals; another 57 foals were untreated. There was no significant difference in the number of transfused foals developing R equi pneumonia compared with the untreated foals. The time required for recovery from pneumonia between the 2 groups was not significantly different.
Cytokine modulation alters pulmonary clearance of Rhodococcus equi and development of granulomatous pneumonia. Rhodococcus equi, a facultative intracellular bacterium, causes chronic, often fatal granulomatous pneumonia in young horses and in humans with AIDS. The inability of host alveolar macrophages to kill intracellular R. equi results in the development of granulomas and progressive loss of pulmonary parenchyma. Clearance of the organism from the lung requires functional CD4+ T cells. The purpose of this study was to identify the cytokine effector mechanisms that mediate clearance of R. equi from the lung. Mice were treated with monoclonal antibodies (MAbs) to either gamma interferon (IFN-gamma) o...
[Susceptibility of bacterial isolates from the equine respiratory tract to trimethoprim, sulfadoxine, sulfadimethoxine and combinations of these compounds]. Using a broth microdilution technique, the in vitro susceptibility of bacterial isolates from the equine respiratory tract to trimethoprim, sulfadoxine, sulfadimethoxine, and combinations of these compounds was determined. The bacterial strains (n = 88) isolated recently from horses with respiratory symptoms belonged to the following species: Streptococcus equi subsp. zooepidemicus (n = 34), Streptococcus equi subsp. equi (n = 22), Staphylococcus aureus (n = 9), Klebsiella pneumoniae (n = 7), Rhodococcus equi (n = 4), Pseudomonas spp. (n = 3) and Escherichia coli (n = 3). In addition, two isol...
Cauda equina syndrome, diskospondylitis, and a paravertebral abscess caused by Rhodococcus equi in a foal. A 4-month-old male Quarter Horse was referred for evaluation of urinary incontinence. Physical examination revealed clinical signs consistent with cauda equina syndrome. Radiography revealed diskospondylitis of S2 through S4. Infected bone was surgically curretted, and drainage was established for an associated paravertebral abscess. Rhodococcus equi was isolated from specimens of bone and from fluid samples obtained from the paravertebral abscess. Bethanechol was administered to stimulate urination. Erythromycin and rifampin were administered for 120 days. The foal's neurologic dysfunction re...
Rhodococcal abortion and pneumonia in an equine fetus. No abstract available
Survival and replication of Rhodococcus equi in macrophages. Rhodococcus equi is a facultative intracellular bacterium of macrophages that can cause serious pneumonia in both young horses and immunocompromised people. Essential to understanding rhodococcus pathogenesis is a quantitative documentation of the intracellular events that follow macrophage phagocytosis of the organism. By using a bacterial immunofluorescence staining assay, we verified the intracellular survival and replicative potential of R. equi in both murine peritoneal macrophages and equine alveolar macrophages in vitro. Following an initial lag period of 6 to 12 h, the intracellular nu...
Review of 40 cases of lung abscesses in foals and adult horses. A retrospective study of 40 horses with primary lung abscesses without pleuropneumonia showed that lung abscesses occurred predominantly in young horses, usually in foals aged < or = 6 months. Hyperfibrinogenaemia was present in all but 2 horses, and other common clinical and haematological findings were hyperthermia, tachycardia, polypnoea, and neutrophilic leucocytosis. The most common bacterial species isolated from transtracheal aspirates were Streptococcus zooepidemicus (20/34) and Rhodococcus equi (13/34). Most horses (23/27) discharged from the hospital were long term survivors. Of t...
Evaluation of a monoclonal antibody-based colony blot test for rapid identification of virulent Rhodococcus equi. We recently generated a monoclonal antibody immunoglobulin G1 (MAb 10G5), which can recognize 15- to 17-kDa antigens, virulence-associated antigens of Rhodococcus equi, and developed a colony blot enzyme-linked immunosorbent assay with MAb 10G5 for the rapid identification of virulent R. equi. In this epidemiologic study, we evaluated the results of the colony blot test in the identification of virulent isolates of R. equi from feces of horses and soil and compared them with those from a conventional procedure (plasmid profiles of isolates by agarose gel electrophoresis). Environmental isolate...
Comparison of oral erythromycin formulations in the horse using pharmacokinetic profiles. The pharmacokinetic properties of four erythromycin formulations were compared in six adult horses after administration of single and multiple oral doses. Formulations of erythromycin administered were estolate and phosphate given 37.5 mg/kg every 12 h and 25 mg/kg every 8 h, and stearate and ethylsuccinate given 25 mg/kg every 8 h. Areas under the curve (AUC) and maximum plasma erythromycin concentrations (Cmax) were equal or greater (P > or = 0.05) following administration of erythromycin phosphate and stearate compared with those values following administration of erythromycin estolate or e...
Lack of residual lung damage in horses in which Rhodococcus equi-induced pneumonia had been diagnosed. The effect of prior Rhodococcus equi-induced pneumonia on pulmonary health was investigated in 5 horses (< 24 months old) using endoscopy, radiography, hematologic and bronchoalveolar lavage analyses, and pulmonary function testing. Rhodococcus equi-induced pneumonia had been diagnosed in principal horses when they were foals. Diagnosis was based on positive results of transtracheal aspiration and thoracic radiography at the time of initial clinical examination. Results of reevaluation of the respiratory system of these horses (R+) were compared with those of 5 age-matched healthy horses (R...
Association of microbiologic flora with clinical, endoscopic, and pulmonary cytologic findings in foals with distal respiratory tract infection. Undifferentiated distal respiratory tract disease (nasal discharge, cough, pneumonia) in foals (1 to 8 months old) is a burdensome economic problem on breeding farms; yet, the infective agents associated with these episodes have not been well described. Possible causes of these episodes of illness were investigated by culturing specimens of proximal and distal airways of clinically diseased foals (n = 101), prior to any treatment, for aerobic and anaerobic bacteria and viruses (rhinoviruses, equine arteritis virus, equine herpesvirus subtype 1 [EHV-1], influenza virus, and adenovirus). Pairs o...
Bronchointerstitial pneumonia and respiratory distress in young horses: clinical, clinicopathologic, radiographic, and pathological findings in 23 cases (1984-1989). Twenty-three foals, between 1 and 7 months old, with signs of acute respiratory distress, were examined at the Veterinary Medical Teaching Hospital (VMTH), University of California, Davis, between 1984 and 1989. Characteristic features included sudden onset of severe respiratory distress and tachypnea, cyanosis unresponsive to nasal oxygen, pyrexia, hypoxemia, hypercapneic respiratory acidosis, poor response to treatment, and histopathologic lesions of bronchiolitis and bronchointerstitial pneumonia. Seven of the 23 foals were normal before the onset of respiratory distress, 3 foals were found...
Rhodococcus equi. This article summarizes recent advances in understanding of the epidemiology, pathogenesis, clinical and laboratory diagnosis, immunology, treatment, and control of Rhodococcus equi infections in foals. Our understanding of these aspects currently is sufficient to ensure control of this problem on affected farms and in infected foals. More information, however, is needed on factors predisposing foals to R. equi pneumonia, in particular, the nature of the naturally occurring cellular immunodeficiency in foals of 2 to 4 months of age, which also predisposes them to severe respiratory infection w...
Rhodococcus equi-associated osteomyelitis in foals. Two cases of Rhodococcus equi infection in foals are described, in which osteomyelitis was a feature. Because rhodococcal infection is usually low grade and chronic, and because the signs of early metaphysitis can be subtle, any articular or periarticular swelling in a foal from a farm with a history of rhodococcosis should be strongly suspected to be associated with R equi until proven otherwise.
Recognition of Pneumocystis carinii in foals with respiratory distress. Five 3-month-old foals presenting with fever and respiratory disease were found to have pulmonary abscesses with patchy to diffuse alveolar and interstitial pneumonia on post-mortem examination. All affected foals had evidence of Rhodococcus equi infection and had few to abundant Pneumocystis carinii cysts in the sections of affected lung. Of the 5 foals examined radiographically, 3 had a distinct reticulonodular (miliary) pattern which may aid in the ante-mortem diagnosis of P. carinii pneumonia (PCP). Leukocyte counts of foals with PCP were significantly greater than in the control group of ...
Rhodococcus equi infection in foals: a report of an outbreak on a thoroughbred stud in Zimbabwe. Twenty-four foals were confirmed to be infected with Rhodococcus equi on a private stud in Zimbabwe over a two-year period. Six mares had foals which were affected in each of the two years. All the foals were febrile and early cases were detected by this pyrexia. Bronchopneumonia was only clinically detectable in advanced cases. In spite of energetic hygiene measures relating to pasture and housing management, the incidence was higher in the second year (23 per cent of foals born) than in the first (15 per cent of foals born). The mean age of the foals was significantly greater in the second y...
Serological survey of Rhodococcus equi infection in horses in Hokkaido. Serological survey of Rhodococcus equi infection in horses in Hokkaido was performed using ELISA. Of 2,879 horse sera, 318 (11.0%) gave antibody-positive (OD greater than or equal to 0.3) reactions. The antibody-positive rate of female was significantly higher (p less than 0.01) than that of male, and no statistical difference between Anglo-Arab and thoroughbred was detected in the antibody-positive rate. The maximum antibody-positive rate (27.1%) was shown at 14 years of age. The antibody-positive rates on the 160 farms were found to vary widely from 0 to 78.9%. A significant difference (p le...
Immunohistochemical observations on pneumonic lesions caused by Rhodococcus equi in foals. An immunohistochemical analysis of Rhodococcus equi-induced pneumonia in 10 foals was performed by biotin-streptavidin system. The detection of R. equi was more sensitive in immuno-stain using anti-R. equi serum than in Gram's stain. This bacteria also reacted to anti-BCG serum. Lysozyme and alpha 1-antitrypsin were detectable in macrophages. A particularly intense staining was observed in association with intracellular bacteria. Though a degree of reaction for alpha 1-antichymotrypsin was very low in comparison with lysozyme and alpha 1-antitrypsin, it was also demonstrated in macrophages ing...