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PubMedDate not supplied

Diagnostic contribution of thoracic ultrasonography in 17 foals with Rhodococcus equi pneumonia.

The aim of this retrospective study was to determine the clinical usefulness of thoracic ultrasonography compared to thoracic radiography in evaluation of Rhodococcus equi pneumonia. Criteria for patient inclusion in this study were: (1) isolation of R. equi from transtracheal aspirate, (2) radiographic evaluation of the pulmonary parenchyma, and (3) sonographic evaluation of the pulmonary parenchyma. Seventeen foals met this criteria and their medical records were reviewed. Pyogranulomatous pneumonia was identified radiographically in 13 foals. Severe consolidative pneumonia with no detectable abscessation was identified radiographically in three others. Both consolidation and abscessation were identified radiographically in one. In this foal only consolidation was ultrasonographically identified. Ultrasonographically, pulmonary abscessation was identified in 12 foals and pulmonary consolidation with no detectable abscessation was identified in three others. Sonographic examination allowed detection of only pleural irregularities in one foal, which was subsequently found to have pyogranulomatous pneumonia radiographically. Results indicate that ultrasonography may be an accurate alternative imaging modality for detection of pulmonary pathology attributed to R. equi pneumonia in foals when thoracic radiography is not available.

Actinomycetales Infections↗

PubMed2002

Pyogranulomatous skin disease and cellulitis in a cat caused by Rhodococcus equi.

This report describes a case of Rhodococcus equi infection causing pyogranulomatous skin disease and cellulitis in a two-year-old female domestic shorthaired cat. The case differed from previously reported cases in cats in its clinical presentation and in the locations of the lesions, which were similar to those seen in horses. The presence of an intracellular organism was confirmed by cytology and on histopathology. The aetiological diagnosis was confirmed by routine biochemical tests specific for R. equi on a pure isolate obtained from a biopsy specimen. The report also reviews the literature of the documented feline cases and discusses the common pitfalls in the diagnosis of such infections.

Actinomycetales Infections↗

PubMed1987

Studies of the pathogenesis of Rhodococcus equi infection in foals.

Pyogranulomatous pneumonia was induced in Thoroughbred foals by intranasal challenge with freeze-dried cultures of Rhodococcus equi (previously Corynebacterium equi). The incubation period was about 18 days and clinical signs were not seen for a further week. There were marked seasonal and individual foal differences in responses to infection. Elevations in serum caeruloplasmin oxidase activity and copper concentrations appeared to be sensitive indicators of infection. Serum zinc concentrations and serum alpha-mannosidase and alkaline phosphatase activities fell in the more severely infected foals. Use of trace elements and trace element-related parameters along with faecal culture for R. equi could prove useful for early diagnosis of field cases.

Actinomycetales Infections↗

PubMed1993

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.

Actinomycetales Infections↗

PubMed1995

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.

Actinomycetales Infections↗

PubMed1989

Rhodococcus equi foal pneumonia: protective effects of immune plasma in experimentally infected foals.

The immunoprophylactic capacity of specific immune plasma was evaluated in pony foals infected experimentally with Rhodococcus equi. Immune plasma, produced by repeated parenteral administration of viable R. equi to adult horses, was harvested and frozen. Group I (six control foals) and Group II (six principal foals) received lactated Ringers solution and immune plasma respectively at three and five days of age. R. equi were aerosolised into a caudal lung lobe of all foals at seven days of age. Clinical signs, haematological alterations, immune responses, thoracic radiographs and technetium99m pulmonary perfusion scans were monitored. All foals were destroyed and complete post mortem examinations performed. All foals developed pneumonia as evidenced by clinical, radiographic and perfusion alterations, but the survival rate of principal foals was significantly (P less than 0.01) greater than that of control foals. Five control foals developed terminal disease, whereas all principal foals recovered. There was no significant (P greater than 0.05) difference in temperature response, or peripheral blood leucocyte, neutrophil or fibrinogen concentrations between groups. ELISA values for R. equi antibody were significantly (P less than 0.001) greater in principal foals following treatment, but there was no significant (P greater than 0.05) difference in IgG or IgM concentrations between groups. Results of the haemolysis inhibition assay indicated that equi factor neutralising antibodies were transferred by immune plasma to the principal foals. Post mortem examinations of five control foals destroyed at approximately three weeks post infection because of terminal disease, revealed severe pyogranulomatous pneumonia. One control and all principal foals were either free of lesions or had resolving lesions and/or minimal scar formation at three months post infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Actinomycetales Infections↗

PubMed1996

Use of a virulence-associated protein based enzyme-linked immunosorbent assay for Rhodococcus equi serology in horses.

An enzyme-linked immunosorbent assay (ELISA) was developed against Rhodococcus equi using Triton X-114 detergent extracted whole cell material, in which the virulence associated protein (VapA) predominated. Enzymelinked immunosorbent assay titres corresponded to antibody reacting with VapA on Western blots. There was considerable variation in antibody titres of nonimmunised mares and in the time when the colostrally derived antibody of their foals had declined to low or undetectable titres. In general, antibodies in foals declined to their lowest levels at age 4-8 weeks. Seroconversion occurred in foals age 8-10 weeks, but the precise time depended on maternal titre and the month in which the foal was born. Foals reaching age 8 weeks in late summer showed more marked seroconversion than foals born earlier. The ELISA was used to follow the response to immunisation with the same Triton X-114 extracted material. Six mares immunised before parturition with the antigen in aluminium hydroxide adjuvant developed high titres, up to > 102,400 and transferred them to their foals through colostrum. Their foals responded to immunisation with 0.5-1.0 mg antigen 3, 5, 7 and 9 weeks after birth. Antibody titres following immunisation with similar dosage reached up to > 102,400 in a separate group of foals of nonimmunised mares. Nonvaccinated control foals seroconverted at age 6-8 weeks. The VapA based ELISA is useful to follow the course of natural infection with R. equi or immunisation with VapA based antigen.

Actinomycetales Infections↗

PubMed1998

Clostridium difficile associated with acute colitis in mares when their foals are treated with erythromycin and rifampicin for Rhodococcus equi pneumonia.

In Sweden, mares sometimes develop acute, often fatal, colitis when their foals are treated orally with erythromycin and rifampicin for Rhodococcus (R.) equi infection. Clostridium (C.) difficile, or its cytotoxin, was demonstrated in faecal samples from 5 of 11 (45%) mares with diarrhoea. By contrast C. difficile was not found in the faecal flora of 12 healthy mares with foals treated for R. equi infection or in 56 healthy mares with healthy untreated foals. No other enteric pathogen was isolated from any diarrhoeic mare. Of 7 investigated treated foals, 4 had a high (1651.0, 1468.3, 273.0 and 88.8 microg/g) faecal concentration of erythromycin. The dams of those 4 foals developed acute colitis, whereas the dams of 3 foals with a lower (26.3, 4.6 and 3.7 microg/g) faecal erythromycin concentration remained healthy, indicating that there might have been an accidental intake of erythromycin by mares. The foals treated with antibiotics were regarded as asymptomatic carriers and potential reservoirs, as C. difficile was found in 7 of 16 foals investigated, while 56 untreated foals proved negative. The isolated C. difficile strains proved resistant to both erythromycin (MIC>256 mg/l) and rifampicin (MIC>32 mg/l), a fact that may have favoured the growth of C. difficile in the foal intestine. All mares found positive for C. difficile were, or had recently been, hospitalised together with their foals, indicating that C. difficile may be a nosocomial infection, in horses. The results emphasise that routine testing for C. difficile and its cytotoxin is recommended when acute colitis occurs in mares when their foals are treated with erythromycin and rifampicin. Preventive measures in order to avoid accidental ingestion of erythromycin by mares from the treatment of their foals are suggested.

Actinomycetales Infections↗

PubMed2002

Gas exchange during intense exercise in Standardbreds with earlier Rhodococcus equi pneumonia.

It is not known if pulmonary function and gas exchange during exercise are altered after pyogranulomatous pneumonia caused by Rhodococcus equi infection in the foal. The aim was to evaluate whether pulmonary gas exchange during high intensity exercise was altered in mature Standardbreds with a history of R. equi pneumonia as foals. In 7 foals, R. equi pneumonia was confirmed and treated. At age 3 years, when these horses were subjected to professional training, an inclined treadmill exercise test including 4 speeds was performed. Samples were collected when a steady state in VO2 was obtained. Red cell volume, heart rate, respiratory rate, and systemic and pulmonary mean arterial pressures were measured and cardiac output calculated. Oxygen and carbon dioxide tensions in arterial and mixed venous blood were analysed. The alveolar ventilation and the alveolar-arterial oxygen tension difference were determined. Pulmonary gas exchange was assessed and the ventilation-perfusion distribution, VA/Q, was estimated by the multiple inert gas elimination technique. Ventilation-perfusion mismatch and shunt were determined and diffusion limitation calculated. The gas exchange in Standardbred trotters previously infected with R. equi and successfully treated was not compromised during intense treadmill exercise compared with reference values for healthy, fit Standardbreds. We conclude that adult Standardbreds trotters with diagnosed R. equi pneumonia as foals, can achieve an adequate gas exchange at a workload close to VO2peak.

Actinomycetales Infections↗

PubMed1992

Therapy of Rhodococcus equi disseminated infections in nude mice.

Rhodococcus equi is a facultative, intracellular, gram-positive coccobacillus increasingly reported as an opportunistic pathogen in human immunodeficiency virus-positive patients. However, the optimal drug regimen for treating R. equi pulmonary or systemic infections is not yet known. Therefore, a model of intravenously infected nude mice with disseminated infection was created to study the efficacy of antibiotics alone or in combination as determined by the reduction of bacterial CFU per gram in the lungs and spleen after 4 and 11 days of treatment. The studied antibiotics possessing low MICs against R. equi strains were amikacin, ciprofloxacin, erythromycin, imipenem, minocycline, rifampin, and vancomycin. Vancomycin, imipenem, and rifampin were the most effective agents in monotherapy. On the other hand, amikacin, ciprofloxacin, erythromycin, and minocycline alone were not active in this model. The most active drug combinations were those including vancomycin. No antibiotic-resistant mutants were selected in vivo with treatment involving any drugs used alone or in combination. Although the treatment recommended until now for R. equi infections is rifampin plus erythromycin, this study suggests that antibiotic combinations which include vancomycin may be the most effective in vivo.

Actinomycetales Infections↗

PubMed1993

Penicillin-binding proteins of Rhodococcus equi: potential role in resistance to imipenem.

Rhodococcus equi is a gram-positive coccobacillus which, like other members of the order Actinomycetales, is increasingly reported as an opportunistic pathogen in patients with AIDS. The use of combinations of antibiotics that include imipenem (IMP) has been suggested for the treatment of patients infected with R. equi. An antagonism between IMP, meropenem, cefoxitin, ceftriaxone, moxalactam, and oxacillin and other beta-lactams, such as penicillin, amoxicillin, cephalothin, and ticarcillin, was detected in vitro both on Mueller-Hinton agar and in broth for all 10 IMP-susceptible R. equi strains examined. To study the mechanism of the antagonism between beta-lactams, a mutant with decreased susceptibility to IMP (isolate IpR) was selected in vitro from a susceptible clinical isolate of R. equi (isolate IpS). IpR exhibited decreased susceptibility to IMP, meropenem, cefoxitin, ceftriaxone, moxalactam, and oxacillin but not to penicillin, amoxicillin, cephalothin, or ticarcillin. No beta-lactamase was found in IpS, IpS cultured with antagonistic beta-lactams, or IpR strains. Labeling of penicillin-binding proteins (PBPs) revealed four PBPs with molecular masses of ca. 59, 56, 43, and 26 kDa in IpS. In IpR, PBP 3 disappeared and was replaced by PBP 3a of 40 kDa. The 50% saturation of PBP 3 and PBP 3a by the carbapenems correlated with the MICs of these antibiotics, respectively, for IpS and IpR strains. However, PBP 3a was not detected in IpS when IpS was cultured in the presence of beta-lactams, with which antagonism was observed. The present work describes the PBPs of R. equi and reports that IMP resistance in R. equi is related to an altered PBP pattern.

Anti-Bacterial Agents↗

PubMed1997

Monooxygenase-like sequence of a Rhodococcus equi gene conferring increased resistance to rifampin by inactivating this antibiotic.

A DNA clone from Rhodococcus equi conferring low-level rifampin resistance through the ability to inactivate this antibiotic via its decomposition was identified. The iri (inactivation of rifampin) gene consisted of an open reading frame of 1,437 bp encoding a 479-amino-acid sequence strongly resembling those of monooxygenases acting upon phenolic compounds or involved in polyketide antibiotic synthesis. When expressed in Escherichia coli, the gene conferred resistance to a > 50-micrograms/ml concentration of the drug.

Amino Acid Sequence↗

PubMed1999

In vitro activities of polycationic peptides alone and in combination with clinically used antimicrobial agents against Rhodococcus equi.

The in vitro activities of magainin II, nisin, and ranalexin alone and in combination with other antimicrobial agents against six clinical isolates of Rhodococcus equi were investigated by MIC and time-kill studies. All isolates were more susceptible to nisin. A positive interaction was observed when the peptides were combined with ampicillin, ceftriaxone, rifabutin, rifampin, azithromycin, clarithromycin, and vancomycin.

Anti-Bacterial Agents↗

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↗

PubMed2003

Pathogenic Nocardia, Rhodococcus, and related organisms are highly susceptible to imidazole antifungals.

Rhodococcus equi and species of Nocardia and Gordonia may be human opportunistic pathogens. We find that these, as well as several isolates from closely related genera, are highly susceptible to the imidazoles bifonazole, clotrimazole, econazole, and miconazole, whose MICs are </=1 micro g/ml. In liquid cultures 1 micro g of the drug/ml was bacteriostatic and 10 micro g/ml was bactericidal. On solid media at 10 micro g of azole/ml no resistant mutants could be isolated. An MIC of 1 to 15 micro g/ml was observed with ketoconazole, whereas none of these organisms was inhibited by the triazoles fluconazole and voriconazole (100 micro g/ml). Imidazoles may offer the prospect of treatment of nocardioform mycetomas and may provide the basis for the development of additional antimicrobial agents to combat these pathogens.

Antifungal Agents↗

PubMed2003

In vitro susceptibilities of Rhodococcus equi and other common equine pathogens to azithromycin, clarithromycin, and 20 other antimicrobials.

The objective of this study was to determine in vitro activities of azithromycin (AZM), clarithromycin (CLR), and 20 other antimicrobial agents against Rhodococcus equi and other common equine bacterial pathogens. A total of 201 bacterial isolates from various equine clinical samples were examined. CLR was more active than AZM against R. equi, with MICs at which 90% of the isolates were inhibited of 0.12 and 1.0 micro g/ml, respectively. Other antimicrobial agents highly active against at least 90% of R. equi isolates in vitro included rifampin, gentamicin, and imipenem. Both AZM and CLR showed good activity against beta-hemolytic streptococci and Staphylococcus spp. AZM was more active than other macrolides against Pasteurella spp. and Salmonella enterica.

Animals↗

PubMed2004

Members of the genera Paenibacillus and Rhodococcus harbor genes homologous to enterococcal glycopeptide resistance genes vanA and vanB.

Genes homologous to enterococcal glycopeptide resistance genes vanA and vanB were found in glycopeptide-resistant Paenibacillus and Rhodococcus strains from soil. The putative D-Ala:D-Lac ligase genes in Paenibacillus thiaminolyticus PT-2B1 and Paenibacillus apiarius PA-B2B were closely related to vanA (92 and 87%) and flanked by genes homologous to vanH and vanX in vanA operons.

Bacteria↗

PubMed2006

Multiple-subunit genes of the aromatic-ring-hydroxylating dioxygenase play an active role in biphenyl and polychlorinated biphenyl degradation in Rhodococcus sp. strain RHA1.

A gram-positive strong polychlorinated biphenyl (PCB) degrader, Rhodococcus sp. strain RHA1, can degrade PCBs by cometabolism with biphenyl or ethylbenzene. In RHA1, three sets of aromatic-ring-hydroxylating dioxygenase genes are induced by biphenyl. The large and small subunits of their terminal dioxygenase components are encoded by bphA1 and bphA2, etbA1 and etbA2, and ebdA1 and ebdA2, respectively, and the deduced amino acid sequences of etbA1 and etbA2 are identical to those of ebdA1 and ebdA2, respectively. In this study, we examined the involvement of the respective subunit genes in biphenyl/PCB degradation by RHA1. Reverse transcription-PCR and two-dimensional polyacrylamide gel electrophoresis analyses indicated the induction of RNA and protein products of etbA1 and ebdA1 by biphenyl. Single- and double-disruption mutants of etbA1, ebdA1, and bphA1 were constructed by insertional inactivation. The 4-chlorobiphenyl (4-CB) degradation activities of all the mutants were lower than that of RHA1. The results indicated that all of these genes are involved in biphenyl/PCB degradation. Furthermore, we constructed disruption mutants of ebdA3 and bphA3, encoding ferredoxin, and etbA4, encoding ferredoxin reductase components. The 4-CB degradation activities of these mutants were also lower than that of RHA1, suggesting that all of these genes play a role in biphenyl/PCB degradation. The substrate preferences of etbA1A2/ebdA1A2- and bphA1A2-encoded dioxygenases for PCB congeners were examined using the corresponding mutants. The results indicated that these dioxygenase isozymes have different substrate preferences and that the etbA1A2/ebdA1A2-encoded isozyme is more active on highly chlorinated congeners than the bphA1A2-encoded one.

Bacterial Proteins↗