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PubMed2000

MICs of oxazolidinones for Rhodococcus equi strains isolated from humans and animals.

Eperezolid and linezolid are representatives of a new class of orally active, synthetic antimicrobial agents. The in vitro activity values (MICs) of linezolid, eperezolid, and comparator antibiotics against 102 strains of Rhodococcus equi isolated from humans and animals were determined. Linezolid was more active than eperezolid against the strains tested; premafloxacin was the most active comparator antibiotic.

Acetamides↗
PubMed1997

Chronic pneumonia caused by Rhodococcus equi in a patient without impaired immunity.

A 48 year old, human immunodeficiency virus (HIV)-negative, immunocompetent male patient had a chronic progressive pulmonary infiltrate, without radiological cavitation, in the middle lobe of the right lung produced by Rhodococcus equi. He reported direct contact with a diseased dog. The patient was diagnosed by thoracotomy and treated by lobectomy. After 16 months of follow-up, the patient was asymptomatic and had neither recurrence nor immunological disturbances.

Actinomycetales Infections↗
PubMed1998

[Rhodococcus equi pneumonia in AIDS: a case report]

We describe the first case, in Campania, of Rhodococcus equi pneumonia in an HIV positive subject. The clinical symptoms resolved after antibiotic therapy. The pulmonary lesion at 10 months of radiological follow up results just partially reduced in its diameters.

Journal Article↗
PubMed2006

Clinical evaluation of a peptide-ELISA based upon N-terminal B-cell epitope of the VapA protein for diagnosis of Rhodococcus equi pneumonia in foals.

A total of 227 field samples from naturally exposed foals aged between 3 weeks and 6 months were used in an evaluation of a peptide-based enzyme-linked immunosorbent assay (ELISA) for diagnosis of Rhodococcus equi infection. A biotinylated peptide derived from the virulence-associated protein A (VapA) of R. equi, a horse pathogen, was synthesized and designated as PN11-14. The peptide corresponds to the N-terminal B-cell epitope TSLNLQKDEPNGRASDTAGQ of the VapA protein. Based upon a serum immunoglobulin (Ig)G titre of 512 as a positive cut-off value for the R. equi infection, the ELISA provided the overall sensitivity of 47.62%, specificity of 69.67% and an accuracy of 59.47% with a positive predictive value of 57.47% for true R. equi pneumonia. The assay was improved by detecting VapA-specific IgGb antibodies against N-terminal B-cell epitope of the VapA protein rather than IgG antibodies. The VapA-IgGb ELISA showed the overall sensitivity of 70.47%, specificity of 72.13% and accuracy of 71.36% with a positive predictive value of 68.52%. Diagnosis of R. equi disease in 6-week-old foals showed that the VapA-IgGb ELISA provided an increasing trend (P=0.0572) in sensitivity of 82.4% in comparison with the VapA-IgG ELISA which showed the sensitivity of 58.8%. However, differences in specificity of both tests were statistically insignificant (P=0.357) as analysed by the McNemar test. These results indicated that detection of VapA-specific IgGb antibodies may be a better predictor of R. equi disease in foals.

Actinomycetales Infections↗
PubMed2001

Rhodococcus equi and cytomegalovirus pneumonia in a renal transplant patient: diagnosis by fine-needle aspiration biopsy.

Rhodococcus equi is a common cause of pneumonia in animals. Human infection is rare. Increasing number of cases are being reported in immunosuppressed individuals mostly associated with HIV infection, but also in solid organ transplant recipients and leukemia/lymphoma patients. We report on an adult male who developed pneumonia and gastroenteritis 4 mo after receiving a renal transplant. CT scan of the lungs showed a dominant 2.5-cm upper lobe lung mass and smaller bilateral nodules. He underwent a diagnostic bronchoscopy with fine-needle aspiration biopsy of the largest lung nodule. Smears showed histiocytic granulomatous inflammation, foamy macrophages, and acute inflammatory exudate. Scattered foamy macrophages displayed intracellular coccobacilli identifiable on Diff-Quik stain. A few cells with changes suggestive of viral inclusions were identified. Cytomegalovirus (CMV) immunostain was positive in the cell block sections. Lung cultures grew R. equi. To the best of our knowledge, this is the first report of coinfection with R. equi and CMV.

Actinomycetales Infections↗
PubMed2002

[Role of cytology in the diagnosis of Rhodococcus equi infection].

A 59-year-old HIV-positive man developed necrotizing right-lobe pneumonia with abscess formation. Bronchial aspirates and bronchoalveolar lavage showed numerous inflammatory cells, mainly histiocytes and neutrophils, and intracellular and extracellular Gram- and Ziehl-Nielsen-positive cocci and coccobacilli. Rhodococcus equi was identified. The patient died one week after diagnosis and necropsy confirmed the presence of R. equi nectrotizing pneumonia.

Actinomycetales Infections↗
PubMed1991

Lung abscess caused by Rhodococcus equi.

In the immunocompromised patient, early diagnosis of a lung cavity is essential for appropriate treatment. Rhodococcus equi (formerly Corynebacterium equi) is a variably acid-fast bacterium that can produce cavitary disease in an immunocompromised host. The two cases presented here demonstrate the clinical and radiographic features of R equi lung abscess. The first patient was on long-term corticosteroid therapy for rheumatoid arthritis. The second patient had AIDS. The correct diagnosis in both cases was delayed because acid-fast bacilli seen on smears of sputum were presumed to be Mycobacterium tuberculosis.

Actinomycetales Infections↗
PubMed1997

Rhodococcus equi pneumonia.

Corynebacterium equi is a pleomorphic gram-positive rod that was first isolated in 1923 by Magnusson, and is the cause of suppurative broncho-pneumonia in foals. The organism, now know as Rhodococcus equi, is ubiquitous in nature and is increasingly recognized as pathogenic, particularly in the immunocompromised population. Cavitary pneumonia clinically resembling Mycobacterium tuberculosis is the most common manifestation of R equi disease, but extrapulmonary infections are seen as well. Long term treatment with intracellularly active antimicrobial agents is required.

Actinomycetales Infections↗
PubMed2000

Detection of the 20-kDa virulence-associated antigen of Rhodococcus equi in malakoplakia-like lesion in pleural tissue obtained from an AIDS patient.

A malakoplakia-like lesion was detected in a pleural biopsy from an AIDS patient presenting clinical and radiologic features of pneumonia. Cultures of bronchoalveolar lavage and pleural fluid evidenced Rhodococcus equi as the causative agent of pleuro-pulmonary infection. Immunochemical characterization of the R. equi isolate showed the presence of a strain similar to the ATCC 33704 reference strain presenting the capsular antigen of serotype 4, and the intermediate virulence-associated antigen of 20-kDa. Histopathology of the patient's pleural biopsy showed plaques of macrophages interspersed with lymphocytes, and intracytoplasmic cocci and bacilli in macrophages, which were variably acid-fast positive. Immunohistochemistry of cocci, bacilli and their degradation products resulted strongly positive when stained with a mouse monoclonal antibody (MAb) produced against the 20-kDa antigen. This finding could have important implications for the pathogenicity of R. equi for human beings, since we do not know yet all the factors involved in the formation of malakoplakia. Indeed, the results obtained in the present study, taken together with the results obtained for pigs inoculated with R. equi strains of intermediate virulence (Madarame et al. 1998), raise the possibility that most strains presenting the 20-kDa antigen may be capable of inducing malakoplakia. If this hypothesis is confirmed by immunohistochemical analysis of human pulmonary malakoplakia cases due to R. equi, the detection of this antigen may be extremely helpful in the diagnosis and treatment of such patients. This is the first report of R. equi infection in human beings that suggests a relationship between pleural malakoplakia and the virulence-associated antigen of 20-kDa.

AIDS-Related Opportunistic Infections↗
PubMed2000

Pulmonary infection caused by Rhodococcus equi in HIV-infected patients: report of four patients from northern Thailand.

We report four human immunodeficiency virus (HIV)-infected patients (3 men and one woman, average age, 34.3 years) with pulmonary infection (two with pneumonia and two with lung abscess) caused by Rhodococcus equi. These patients, who presented with fever and productive cough, were admitted to Nakornping Hospital in northern Thailand. Chest roentgenograms showed pulmonary infiltration and/or cavitary lesions. Their conditions were poor because of severe anemia, and transfusion was necessary in three of the four patients. Before culture results were available, the etiologic microorganisms identified in sputum smears were gram-positive and acid-fast coccobacilli. One of the four patients had a mixed infection with R. equi and Salmonella enteritidis. The mean CD4 lymphocyte count in the three tested patients was 10/mm3 (CD4/CD8 ratio = 0.057). Four isolates of R. equi were sensitive to imipenem, minocycline, erythromycin, vancomycin, and ciprofloxacin (minimum inhibitory concentrations; MICs, 100 microg/ml) to rifampicin. Two patients were treated with erythromycin plus rifampicin, while the other two were treated with anti-tuberculous drugs. However, treatment was ineffective; three patients subsequently died because of respiratory failure, and one patient did not improve and was transferred to another hospital in her hometown.

AIDS-Related Opportunistic Infections↗
PubMed1985

Enzyme-linked immunosorbent assay for diagnosis of Corynebacterium (Rhodococcus) equi infection in foals.

An enzyme-linked immunosorbent assay (ELISA) was used to diagnose Corynebacterium (Rhodococcus) equi infection in foals. In tests done with different antigen-extraction procedures (sodium dodecyl sulfate, sodium deoxycholate, polyoxy-ethylene [9] p-tert-octylphenol, polyoxy-ethylene [9-10] p-tert-octylphenol, sonification, homogenization, and heat treatment at 121 C), Tween 20 was a satisfactory reactive antigen. Using hyperimmune rabbit sera or infected foal sera, we investigated the specificity and the sensitivity of the ELISA with the Tween 20 antigen of the different serotypes or of the isolates. Corynebacterium equi strain ATCC 6939 antigen had the best activity for detecting antibodies to C equi in foals. Sera from 218 healthy horses, 11 healthy foals, 17 healthy newborn foals, a foal with suspected C equi infection, and 5 infected foals were evaluated for antibodies to C equi, using ELISA. The optical density values of 206 healthy horses, 17 healthy newborn foals, and 9 healthy foals were less than 0.1. Infected foal sera, except from foal 3, and serum from a foal with suspected C equi infection had higher optical density values. Using ELISA, specific antibodies against C equi were detected in a naturally infected 6-week-old foal after the foal had a rapid increase in the number of bacteria in the feces and after the initial development of clinical signs of illness at 5 weeks of age. Therefore, ELISA was useful for the early diagnosis of C equi infection in foals.

Animals↗
PubMed2002

Cerebral infection with Rhodococcus equi in a heart transplant recipient.

Iatrogenic immunosuppression following organ transplantation leads to an increased number of opportunistic bacterial and viral infections. Similar to patients with human immunodeficiency virus (HIV) infection transplant recipients may suffer from rare infectious diseases. Herein we report on a patient presenting with a cerebral infection who had previously undergone orthotopic cardiac transplantation. Rhodococcus equi was isolated.

Actinomycetales Infections↗
PubMed2005

In vitro activity of citropin 1.1 alone and in combination with clinically used antimicrobial agents against Rhodococcus equi.

OBJECTIVES: The aim of this study was to investigate the in vitro activity of citropin 1.1, an antimicrobial peptide derived from the Australian tree frog Litoria citropa, alone and in combination with ampicillin, ceftriaxone, doxycycline, netilmicin, ciprofloxacin, rifampicin, linezolid, vancomycin, clarithromycin and imipenem against 12 nosocomial isolates of Rhodococcus equi. METHODS: Antimicrobial activity of citropin 1.1 was measured by MIC, MBC, time-kill studies and chequerboard titration method. RESULTS: All isolates were inhibited at concentrations of citropin 1.1 between 2 and 8 mg/L. Combination studies demonstrated synergy only when the peptide was combined with clarithromycin, doxycycline and rifampicin. CONCLUSIONS: Our findings show that citropin 1.1 is active against R. equi and that its activity could be enhanced when it is combined with hydrophobic antibiotics.

Actinomycetales Infections↗
PubMed1987

Experimental infection of mice with Rhodococcus equi: differences in virulence between strains.

The growth kinetics in outbred mice of clinical and environmental isolates of Rhodococcus equi were followed by serial bacterial enumeration of organ homogenates. Clinical isolates multiplied until Day 4 before being progressively cleared, but could still be recovered from the liver at 3-4 weeks post-infection. Intravenous inoculation of clinical strains was associated with histopathological responses very similar to those elicited by intravenous infection with various facultative intracellular parasites. Whereas lesions in mice and foals at 7-9 days following respiratory infection are those of severe bronchopneumonia with massive consolidation, a week later the patterns of host response have diverged as the murine lesions resolve. The type strain, NCTC 1621 and 4-6 environmental isolates were eliminated without prior multiplication and these strains caused negligible lesions. The two environmental strains which behaved as the clinical strains were recovered from a stud with an R. equi problem. No association of colonial morphology of R. equi with virulence was apparent.

Actinomycetales Infections↗
PubMed1996

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 observing the occurrence of the respiratory disease complex in groups of foals immunized against the virus, in comparison to non-immunized controls. The immunization trials of young animals revealed that the iscom subunit vaccine formulation is able to overcome the interference of maternal antibodies. Active immunization of foals with a single dose of the iscoms provided a certain degree of protection, while two injections of iscoms yielded complete protection against the disease complex in the majority of the treated animals, by preventing the manifestation of R. equi pneumonia. The present findings strongly support the hypothesis that EHV-2 is a predisposing factor for the R. equi invasion of the respiratory tract. The EHV-2 iscom formulation provides highly specific and effective means to prevent the disease complex.

Actinomycetales Infections↗
PubMed1995

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 resolved completely. Two years after discharge, the horse remained neurologically normal and did not have apparent effects as a result of its previous disorder.

Abscess↗
PubMed1987

Diagnosis of Rhodococcus equi infection in foals by the agar gel diffusion test with protein antigen.

A protein antigen that reacted in the agar gel diffusion (AGD) test and which had equi factor(s) activity, was partially purified from the culture supernatant of Rhodococcus equi by successive column chromatography on diethylaminoethyl cellulose and Sepharose 4B. Employing a standard foal serum, the concentration of this antigen was adjusted for the AGD test. Optimal dilutions of the antigen reacted in the AGD test with sera from foals naturally infected with serologically different R. equi. The antigen prepared was considered suitable for use in field surveys of R. equi infection. Accordingly, four groups of sera were tested: those from 18 foals diagnosed as being infected with R. equi, those from 54 control foals with culture-negative R. equi pneumonia, arthritis or cellulitis, those from 46 diseased foals suspected of having R. equi infection and those from 51 clinically normal foals. A positive precipitation reaction was observed with sera from 100% of the first group, 69.5% of the third group and 17.7% of the fourth group. A negative reaction was obtained with sera from 100% of the second group.

Actinomycetales Infections↗
PubMed2005

Septic pleuritis and abdominal abscess formation caused by Rhodococcus equi in a foal.

A 3-month-old female Arabian horse was evaluated because of fever, respiratory distress, lethargy, and decreased appetite of 5 days' duration. Pleural effusion was diagnosed on the basis of ultrasonographic and radiographic examinations. Cytologic examination of pleural fluid collected via thoracocentesis revealed septic inflammation; bacteriologic culture of a sample of that fluid yielded Rhodococcus equi. A large intra-abdominal mass adjacent to the body wall was identified ultrasonographically. A specimen of the mass was collected via aspiration; the specimen was identified cytologically as purulent exudate that contained large numbers of rod-shaped bacteria, which confirmed abdominal abscess formation. Bacteriologic culture of a sample of the exudate also yielded R. equi. The foal was treated with azithromycin (10 mg/kg [4.5 mg/lb], PO, q 24 h for 5 days then q 48 h) and rifampin (5 mg/kg [2.3 mg/lb], PO, q 12 h) for 8 weeks and metronidazole (15 mg/kg [6.8 mg/lb], PO, q 8 h) for 3 weeks. Clinically, the foal responded to antimicrobial treatment within 2 weeks. At 8 weeks after the initial evaluation, ultrasonographic examination of the foal revealed resolution of the pleural effusion and abdominal abscess. In foals, R. equi infection typically results in pyogranulomatous pneumonia, and pleural effusion is an uncommon clinical sign. The combination of azithromycin and rifampin appears to be an effective treatment for R. equi infection in foals.

Abdominal Abscess↗