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PubMed1997

Clinical evaluation of the serodiagnostic value of enzyme-linked immunosorbent assay for Rhodococcus equi infection in foals.

An enzyme-linked immunosorbent assay (ELISA) for detection of serum IgG antibodies against Tween 20-extracted antigen of strain ATCC 6939 was applied in Hidaka, Japan to a total of 752 sick foals showing a variety of signs of infectious disease. An optical density (OD) value of more than 0.3 was tentatively fixed to be positive on the basis of readings made of healthy horse sera in previous studies. During a 2 year study, 138 of the 752 sick foals showed an OD value of 0.3 or higher and were designated as 'suspected of R. equi infection'. Age distribution during the initial medical examination of the 138 seropositive foals was significant in that most (64%) foals were age 31-60 days, with a sharp decrease in subjects beyond that age. Of the 138 foals suspected of having R. equi infection, 34 foals (25%) showed OD values of over 0.9 at the initial medical examination, in addition to high blood leucocyte counts and serum fibrinogen and alpha-globulin values. The infectious foals had been treated with antibiotics just before and after serodiagnosis and 126 foals (91%) recovered from the disease. However, no clinical improvement was observed in 12 foals (9%). At necropsy, these foals revealed suppurative pneumonia and lymphadenitis of gut associated lymph nodes accompanied by abdominal abscesses. All isolates from the pulmonary and abdominal abscesses revealed R. equi. These results suggest that OD readings in the high range are associated with severe disseminated infection with R. equi.

Actinomycetales Infections↗
PubMedDate not supplied

[Rhodococcus equi pneumonia in patients with AIDS].

Rhodococus equi infection is frequent in animals, but rare in humans. It usually appears as an opportunistic infection, occurring in clinical settings where a compromise of cellular immunity exists, such as in leukemia, neoplastic or transplanted patients. It is currently considered, as another opportunistic AIDS infection. Sixty six cases of Rhodococus equi pneumonia have been published until March 1996. The differential diagnosis includes TB and Staphyloccocal Pneumonia and is generally an infection which is difficult to treat, often resistant to Betalactamic drugs. Therapeutic options include an association of intracellular active antibiotics. The authors report the first Rhodococus equi pneumonia diagnosed in their Hospital and discuss the main difficulties in the diagnostic and therapeutic approach.

AIDS-Related Opportunistic Infections↗
PubMed2006

Comparison of concentrations of Rhodococcus equi and virulent R. equi in air of stables and paddocks on horse breeding farms in a temperate climate.

REASONS FOR PERFORMING STUDY: Rhodococcoccus equi is a significant cause of bronchopneumonia in foals worldwide. Infection of the lungs is believed to result from inhalation of virulent R. equi in dust from contaminated environments. A measure of infectious risk in an environment is the level of airborne contamination. OBJECTIVES: To assess and compare the level of airborne virulent R. equi in paddocks and stables. METHODS: Air samples were collected sequentially over the 2003 foaling season from the paddocks and stables on 3 Irish horse breeding farms affected by R. equi pneumonia. Colony blotting and DNA hybridisation techniques allowed quantitation of virulent R. equi. RESULTS: The odds of detecting airborne virulent R. equi in stables were 173 times greater than in paddocks. The median airborne concentration of virulent R. equi was significantly higher (P < 0.001) in stables than in paddocks on all farms. These observations suggested that stables were high-risk areas for infection. CONCLUSIONS AND POTENTIAL RELEVANCE: Our results indicate that contaminated stables are a significant risk factor in the epidemiology of R. equi pneumonia on horse-breeding farms in a temperate climate, such as in Ireland. Management strategies that improve the air hygiene of stables, through better ventilation, use of less fragile bedding material and the use of fogging agents to reduce the airborne concentration of virulent R. equi, may reduce the incidence and severity of R. equi pneumonia on farms.

Actinomycetales Infections↗
PubMed1997

Immunity to Rhodococcus equi.

Rhodococcal pneumonia is an important, life threatening disease of foals and immunosuppressed humans. Increased knowledge of the mechanisms of protective immunity are required in order to develop an effective immunoprophylaxis strategy for horses and immunotherapeutic regiments for people. Both humoral and cellular components of the immune system may be involved in immune clearance of R. equi. The susceptibility of foals less than 4-6 months of age is postulated to reflect waning maternal antibody, and passive transfer of hyperimmune plasma can provide protection on endemic farms. However, effective clearance is likely to require appropriate cellular responses, including the secretion of cytokines. In murine models, both CD4+ and CD8+ T lymphocytes can reduce bacterial counts in the lung. CD4+ cells appear to be both required and sufficient, and IFN-gamma is a primary mediator. Clearance appears to be a type 1 immune response while type 2 responses may lead to a failure to clear and lesion development. It remains to be determined how the cellular immunity experiments reported in mice relate to horses and humans. Likewise, the role of specific R. equi antigens in protective immunity has not been determined.

Actinomycetales Infections↗
PubMed1999

Effect of prophylactic administration of hyperimmune plasma to prevent Rhodococcus equi infection on foals from endemically affected farms.

The effect on foals of prophylactic administration of hyperimmune plasma to prevent R. equi infection was investigated on three farms at which R. equi infection was endemic. Sixteen foals between 10 and 39 days of age were intravenously given 1-21 of hyperimmune plasma. ELISA antibody titres against R. equi were significantly increased and maintained at high levels for over 30 days in most of the recipient foals. The prevalence of R. equi infection was 6.3% (1/16) in the foals that received the immune plasma, and 26.3% (5/19) in the control foals not given the immune plasma on the three farms. For 2 years before and after this field trial on the three farms, 18 of 64 foals (28.1%) showed clinical signs of respiratory tract infection and four of them died of R. equi pneumonia. Heavy contamination of horses and their environment with virulent R. equi was detected by colony blotting, and plasmid profiles also suggested that foals on the three farms were constantly exposed to virulent R. equi. The results of this field trial support previous observations by some researchers that the administration of hyperimmune plasma to foals in the early days of life promotes prevention of R. equi infection on endemic farms; however, the mechanism of hyperimmune plasma protection remains unclear.

Actinomycetales Infections↗
PubMed1997

Protective effect against Rhodococcus equi infection in mice of IgG purified from horses vaccinated with virulence associated protein (VapA)-enriched antigens.

IgG was purified from horses immunized with repeated doses of virulence associated (VapA) enriched antigens extracted with Triton X-114 from the surface of a virulent strain of R. equi. This IgG were administered to mice immunosuppressed by prior treatment with indomethacin. Mice administered the higher dose were completely protected against intraperitoneal infection with R. equi; mice given the lower dose were partially protected. By contrast, mice administered concentrated nonimmune equine IgG were not protected. This study demonstrates that VapA may be an important antigen involved in humoral protective immunity in R. equi infections caused by foal virulent strains.

Actinomycetales Infections↗
PubMed1997

Antigenic analysis of Rhodococcus equi preparations using different horse sera.

An R. equi vaccine, prepared under conditions which induce the expression of many antigens, and which has given encouraging results in field trials, was analyzed by SDS-PAGE and immunoblots and compared with other R. equi preparations: a preparation made in with the same technique from a nonvirulent isolate (virulence associated protein negative, VapA-negative); a whole cell preparation of a VapA-positive R. equi, prepared as a standard bacterin; and a semipurified VapA preparation (APTX). The antigens in these preparations were analyzed using hyperimmune sera (from adult horses vaccinated with the R. equi vaccine), passively and actively immunized foals' sera, asymptomatic but serologically positive foals' sera sera from R. equi pneumonic foals, an equine APTX antiserum, and a VapA monoclonal antibody (Mab). The vaccine under study had many proteins in high concentrations. Hyperimmune sera reacted strongly with vaccine antigens in the high molecular weight regions. In the low molecular weight range, it reacted in the 14 and less kDa zone. Sera from passively immunized foals reacted similarly but not so strongly. Actively immunized foals gave very weak reactions. With the APTX extract, the Mab reacted with bands at 15-17, 44 and 66 kDa; it reacted weakly with the whole cell and not with the VapA-negative preparations. The APTX antiserum and the Mab reacted strongly with the vaccine at the 14 and less kDa zone, and also with bands at 21, 44 and 66 kDa and very tenuously at 18 kDa, but not in the expected 15-17 kDa zone, suggesting that the native form of VapA is altered but without loss of antigenicity in the vaccine preparation. Our results suggest that other higher molecular weight antigens, in addition to VapA, may be important in inducing antibodies that protect young foals from R. equi pneumonia. These antigens are in high concentrations and in an immunogenic form in the vaccine.

Animals↗
PubMed1998

Rhodococcus equi infection of monocytes/macrophages from human immunodeficiency virus (HIV)-infected patients and healthy individuals: evaluation of intracellular killing and nitric oxide production.

Monocytes/macrophages from human immunodeficiency virus (HIV)-infected patients had a defect in their ability to kill Rhodococeus equi in vitro, as compared with healthy HIV-seronegative individuals. Virulent and avirulent R. equi strains isolated from humans and horses showed no significant intracellular replicative differences within both HIV-positive and -negative monocytes/macrophages. Infection with R. equi induced the production of nitric oxide (NO) by monocytes/macrophages from healthy individuals, but not by cells from HIV-positive patients. The NO formation was significantly inhibited by L-NG-monomethyl arginine and arginase. However. neither competitive inhibition of NO synthesis from L-arginine with L-NMMA nor depletion of arginine with arginase altered the killing activity of human monocytes/macrophages against R. equi, thus suggesting that L-arginine:NO pathway is not required for the intracellular antirhodococcal mechanisms of human monocytes/macrophages.

AIDS-Related Opportunistic Infections↗
PubMed2004

Rhodococcus equi pneumonia in a renal transplant patient: a case report and review of literature.

Immunocompromised patients are susceptible to many pathogens, including those that are predominantly problems in veterinary medicine. We report a case of a 42-yr-old white male who presented 19 months post-cadaveric renal transplant (for IgA nephropathy) with a 5 d history of nausea, vomiting, abdominal cramping and diarrhea. Admission chest X-ray revealed a suspicious mass lesion in the left lower lobe. Computed tomography (CT) guided biopsy of the lesion showed a large zone of CD68 +ve histiocytes in a non-caseating granuloma. Gram stain revealed multiple gram-positive rods within the histiocytes, which were eventually identified as R. equi. After 4 months of therapy with fluoroquinolones (Avelox) and Azithromycin a repeat CT showed complete resolution of the lesion. We reviewed the literature with special focus on the clinical features, challenges in diagnosis, and treatment of this rare infection (especially in the transplant patients who are also on immunosuppressive therapy).

Actinomycetales Infections↗
PubMed1995

Pathogenesis of Rhodococcus equi infection in mice: roles of virulence plasmids and granulomagenic activity of bacteria.

Virulence of Rhocococcus equi ATCC 33701 and its plasmid-cured derivative ATCC 33701P- was compared in BALB/c and C3H/HeJ mice in terms of bacterial growth kinetics and histological changes in the liver, spleen and lungs, and humoral immune responses. Injection with a sublethal dose of 10(6) ATCC 33701 in mice resulted in microabscess formation after rapid multiplication in the liver and spleen by day 4, and then the bacteria were gradually eliminated with the formation of granuloma and the production of specific antibodies against 15- to 17-kDa antigens of the virulent bacteria. By contrast, ATCC 33701P- was avirulent as shown by early elimination of viable bacteria and no evidence of net multiplication in the organs. Histopathological changes consisted of only slight, transient infiltration of neutrophils and macrophages in the liver. Although live ATCC 33701P- did not evoke any humoral or histological responses in the mice, a large inoculum (10(8)) of killed ATCC 33701 and ATCC 33701P- resulted in the formation of granuloma in the liver and accelerated extramedullary hemopoiesis in the spleen. These results suggest that the pathogenesis of R. equi infection involves at least two important virulence determinants, both of which play critical roles in the disease: one is the virulence plasmid, which is required for R. equi to resist and grow within host cells; and the other is the granulomagenic activity that is related to the lipids and nature of the cell wall of the species, which induces the characteristic pathological changes.

Actinomycetales Infections↗
PubMed1992

Influence of inoculation route on virulence of Rhodococcus equi in mice.

Virulence of R. equi ATCC 33701 was compared by the intraperitoneal (i.p.) and intravenous (i.v.) routes in mice. Strain ATCC 33701 was more virulent by the i.v. than the i.p. route. The LD50 of strain ATCC 33701 by either route correlated with the initial number of bacteria in the liver and spleen at day 0.

Actinomycetales Infections↗
PubMed1997

Prevention of Rhodococcus equi pneumonia of foals using two different inactivated vaccines.

Two different, inactivated, aluminium salt adsorbed vaccines, one containing a R. equi strain (serotype 1, 10(9) CFU/ml and equine herpesvirus 2 (EHV-2) (1.5 x 10(7) PFU/ml) and another containing R. equi only were used on three studfarms to determine whether the disease can be prevented by vaccination of both pregnant mares and their foals. Pregnant mares received two 3 ml doses of vaccine intramuscularly 6 and 2 weeks before parturition and their foals were vaccinated on two or three occasions at 3, 5 or 7 weeks of age. The efficacy of the vaccines was evaluated on the basis of the clinical signs, serological response (indirect haemagglutination and virus neutralisation tests) and culture of R. equi from sick or dead foals. On studs A and B where the bivalent vaccine was used, 24 and 14 foals were born respectively to the vaccinated mares but no clinical case or death occurred due to R. equi pneumonia, while out of the 10 nonvaccinated control foals (stud B) two succumbed to R. equi pneumonia and 4 other foals had to be treated with antibiotics because of fever, coughing and dyspnea. In stud C, where the vaccine containing R. equi strain alone was used, all 15 vaccinated foals remained healthy but one of the 11 control foals died of suppurative R. equi pneumonia and one foal had to be treated due to R. equi pneumonia. R. equi strains (serotype 1) were isolated from the lungs of all dead foals. The serological response was very weak to both R. equi and the EHV-2 strain. Antibody titres in the colostrum of the vaccinated mares against R. equi (in studs A and B, geometric mean 3.79 +/- 1.63 and 4.14 +/- 1.46, respectively) were practically not higher than titres in the controls (in stud B geometric mean 2.12 +/- 1.96). More antibody was present in the colostrum samples against EHV-2 (geometric mean 6.1 + 1.4 compared to 2.5 +/- 1.2). In all foals antibody levels were hardly detectable against both R. equi and EHV-2 until five weeks of age. From the fifth week, antibody levels gradually increased and by the ninth week their reached a titre of 5.5 +/- 1.8 (2.7 +/- 1.2 in the control foals) against R. equi and 5.2 +/- 1.4 against EHV-2. The favorable clinical results and the low antibody titres in the sera of the vaccinated foals during the first week of life suggest that protection probably was due to repeated vaccination of young foals rather than to vaccination of mares.

Actinomycetales Infections↗
PubMed1993

Cholesterol side-chain cleavage by immobilized cells of Rhodococcus equi DSM 89-133.

Side-chain cleavage of sterol and extracellular cholesterol oxidase activity were investigated using viable cells of R. equi DSM 89-133 immobilized in polyacrylamide gel. In batch culture, immobilized cells were active in side-chain cleavage of cholesterol for more than 30 days. Free or immobilized cells were incapable of side-chain cleavage in the absence of 2,2' dipyridyl; cholesterol oxidase was, however, produced in both the cases. Maximal activity of the immobilized cells was 60 to 70% of the free cells.

2,2'-Dipyridyl↗
PubMed2004

Foal IgG and opsonizing anti-Rhodococcus equi antibodies after immunization of pregnant mares with a protective VapA candidate vaccine.

The aim of this study was to evaluate serum IgG antibody levels and opsonizing activity in foals from pregnant mares immunized with either proteins from an R. equi strain containing virulence-associated protein A (VapA), an immunodominant surface-expressed lipoprotein encoded by a virulence plasmid crucial for virulence in foals, or a whole killed virulent R. equi preparation. Forty-eight pregnant mares were distributed into three groups, i.e. 24 immunized with R. equi VapA protein antigen associated with a water-based nanoparticle adjuvant (Montanide IMS 3012), 8 immunized with whole killed R. equi, and 16 non-immunized as control. Serum IgG and opsonizing capacity were evaluated during pregnancy in mares, and up to day 45 post-delivery in foals in which R. equi infections were recorded in the first 6 months of life. Pregnant mares immunized with virulent R. equi proteins developed higher serum IgG and opsonic activity which were transferred to the foals than either in the whole R. equi immunized or the control group. Four foals developed pneumonia in the control group while none in immunized groups. Results support further evaluation of VapA protein antigen associated with a water-based nanoparticle adjuvant as a candidate vaccine for immunization of pregnant mares resulting in passive antibody-mediated protection of foals.

Actinomycetales Infections↗