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First cases of animal diseases published since 2000. 4. Horses.

In this fourth article of a series of papers listing first case reports of animal diseases published since 2000, the following six cases of horse diseases are discussed: Disseminated metastatic intramedullary melanoma. Lipoma of the extensor tendon sheaths. Meningoencephalomyelitis in a neonatal foal due to Salmonella agona infection. Neuronal ceroid lipofuscinosis. Placentitis due to Rhodococcus equi infection. Right atrial diverticulum in a foal. After a short introduction, the bibliographical data, the abstract of the author(s), and some additional information derived from the article are given. The article will be regularly updated adding overlooked as well as new first reports.

Animals↗

Allogeneic bone marrow transplantation can restore CD4+ T-lymphocyte count and immune function in idiopathic CD4+ T-lymphocytopenia.

CD4+ T-lymphocytopenia in the absence of HIV infection is a heterogeneous disorder of unknown cause. Here we report a patient with idiopathic CD4+ T-lymphocytopenia, presenting with an opportunistic Rhodococcus equi infection. When aplastic anemia developed subsequently, allogeneic bone marrow transplantation was performed. Complete restoration of immune function was observed. We conclude that allogeneic bone marrow transplantation presents a potentially curative therapy for CD4+ T-lymphocytopenia.

Actinomycetales Infections↗

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 the 19 horses for which a follow up was available, 12 raced or performed the task for which they were intended. None of the indicators evaluated in this study could reliably predict the bacterial species involved or the outcome.

Actinomycetales Infections↗

In vitro activity and killing effect of uperin 3.6 against gram-positive cocci isolated from immunocompromised patients.

The in vitro activity of uperin 3.6, alone or combined with six antibiotics, against gram-positive cocci, including Rhodococcus equi, methicillin-resistant staphylococci, and vancomycin-resistant enterococci, was investigated. All isolates were inhibited at concentrations of 1 to 16 mg/liter. Synergy was demonstrated when uperin 3.6 was combined with clarithromycin and doxycycline.

Amphibian Proteins↗

TNF receptor p55 is required for elimination of inflammatory cells following control of intracellular pathogens.

The elimination of lymphocytes within inflammatory lesions is a critical component in the resolution of disease once pathogens have been cleared. We report here that signaling through the TNF receptor p55 (TNFRp55) is required to eliminate lymphocytes from lesions associated with intracellular pathogens. Thus, TNFRp55-/- mice, but not Fas-deficient mice, maintained inflammatory lesions associated with either Leishmania major or Rhodococcus equi infection, although they developed a Th1 response and controlled the pathogens. Inflammatory cells from either L. major- or R. equi-infected C57BL/6 mice were sensitive to TNF-induced apoptosis, and conversely the number of apoptotic cells in the lesions from TNFRp55-/- mice was dramatically reduced compared with wild-type mice. Furthermore, in vivo depletion of TNF in wild-type mice blocked lesion regression following R. equi infection. Taken together, our results suggest that signaling through the TNFRp55, but not Fas, is required to induce apoptosis of T cells within inflammatory lesions once pathogens are eliminated, and that in its absence lesions fail to regress.

Actinomycetales Infections↗

Polymorphisms in equine immune response genes and their associations with infections.

Polymorphic markers identified in the horse genes encoding the interleukin 12 p40 subunit, interferon gamma, tumor necrosis factor receptor 1, and inducible nitric oxide synthase were identified and tested, along with additional markers, for associations with two important horse infections: Rhodococcus equi and Lawsonia intracellularis. Eight immune response-related and 14 microsatellite loci covering 12 out of 31 equine autosomes were used for the association analysis. Markers located on horse Chromosomes Eca10 and 15 were significantly associated with the presence of high numbers of R. equi in transtracheal aspirates. Significant associations of markers located on Eca9, 15, and 21 with fecal shedding of Lawsonia intracellularis were found. Marginal associations with tumor necrosis factor alpha, interferon gamma, and other genes suggested that variations in immune response-related genes could underlie the phenotypic variation observed.

Animals↗

Hemolytic interactions of Dermatophilus congolensis.

The strains of Dermatophilus congolensis grew on blood agar with washed sheep erythrocytes with marked total hemolysis. In testing for hemolytic interactions they gave a significant synergistic effect of a characteristic shape with Rhodococcus equi and Streptococcus agalactiae, whereas with Staphylococcus aureus producing beta hemolysin and with Staphylococcus aureus producing delta hemolysin a simultaneous synergistic as well as antagonistic effect were observed. First of all a conspicuous inhibition of in the beta hemolysin zone began and then the hemolytic effect of D. congolensis was enhanced. A similar double reaction was also observed with Listeria ivanovii. With delta hemolysin there was an inhibition of the hemolytic effect of D. congolensis and at the same time a synergistic effect could be observed. Also D. congolensis gave a weak synergistic effect with Micrococcus lylae and Listeria monocytogenes, and a further weak antagonistic effect with alpha hemolysin of Staphylococcus aureus, Staphylococcus hyicus, Staphylococcus chromogenes and Micrococcus luteus. No interaction of D. congolensis was established with Corynebacterium pseudotuberculosis.

Actinomycetales↗

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 foals with uncomplicated bacterial pneumonia. Foals with PCP tended to be more tachypnoeic than the control foals and 4 of the 5 PCP+ foals appeared dyspnoeic before death. The ante-mortem recognition of PCP may be expedited by bronchoalveolar lavage and successful treatment of foals with PCP may require the administration of adequate levels of potentiated sulphonamides.

Actinomycetales Infections↗

Isolation of a bacterium that degrades urethane compounds and characterization of its urethane hydrolase.

A bacterium which degrades urethane compounds was isolated and identified as Rhodococcus equi strain TB-60. Strain TB-60 degraded toluene-2,4-dicarbamic acid dibutyl ester (TDCB) and accumulated toluene diamine as the degradation product. The enzyme which cleaves urethane bond in TDCB was strongly induced by acetanilide. The purified enzyme (urethane hydrolase) was found to be homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The molecular weight was estimated to be 55 kDa. The optimal temperature and pH were 45 degrees C and 5.5, respectively. The enzyme hydrolyzed aliphatic urethane compound as well as aromatic ones. The activity was inhibited by HgCl(2), p-chrolomercuribenzoic acid, and phenylmethylsulfonyl fluoride, suggesting that cysteine and/or serine residues play an important role in the activity. The enzyme catalyzed the hydrolysis of anilides, amides, and esters as well as TDCB. It was characterized as a novel amidase/esterase, differing in some properties from other known amidases/esterases.

Amidohydrolases↗

The association of erythromycin ethylsuccinate with acute colitis in horses in Sweden.

In Sweden there are several reports of mares developing acute colitis while their foals were being treated orally for Rhodococcus equi pneumonia with the combination of erythromycin and rifampicin. In this study 6 adult horses were given low oral dosages of these antibiotics, singly or in combination. Within 3 days post administration of erythromycin, in one case in combination with rifampicin, 2 horses developed severe colitis (one fatal). Clostridium difficile was isolated from one of the horses, whereas no specific pathogens were isolated from the other. Both horses had typical changes in blood parameters seen in acute colitis. Clostridium difficile was also isolated from the faeces of a third horse given an even lower dosage of erythromycin in combination with rifampicin. This horse developed very mild clinical symptoms and recovered spontaneously. In the fourth horse given erythromycin only, very high numbers of Clostridium perfringens were isolated. The horses given rifampicin only did not develop any clinical symptoms and there were no major changes in their faecal flora. In conclusion, it has been demonstrated that low dosages of erythromycin ethylsuccinate can induce severe colitis in horses associated with major changes of the intestinal microflora. Clostridium difficile has been demonstrated as a potential aetiological agent in antibiotic-induced acute colitis.

Actinomycetales Infections↗

Effect of a mixed culture on co-oxidation during the degradation of saturated hydrocarbon mixture.

Two bacterial strains, Pseudomonas aeruginosa K1 and Rhodococcus equi P1, were used to degrade cyclo-alkanes (such as decalin) by a co-oxidation mechanism. Both strains possessed the capacity to degrade a broad range of n-alkane mixtures (C7 to C28) within 24 h of incubation. Strain P1 rapidly degraded 10 gl-1 pristane within 24 h of incubation (mu = 0.36 h-1 and Yx/s = 0.6). The addition of hexadecane as a growth substrate (above 0.5%, v/v) resulted in complete degradation of 1% (v/v) decalin by strain P1 via a co-oxidation mechanism. Co-oxidation to degrade decalin or pristane by strain K1 proved unsuccessful. Strain P1 was able to degrade decalin totally in a saturated hydrocarbon mixture. Strain K1 was only able to degrade hexadecane from the hydrocarbon mixture, but its degradation rate was higher than that of strain P1. Therefore, there was competition for the hexadecane needed to co-oxidize decalin. As a result, degradation of the hydrocarbon mixture, especially decalin, was incomplete in a mixed culture of strain P1 and K1. Serial addition of hexadecane (twice) allowed complete degradation of the remaining decalin by strain P1. Also, the biodegradation rate of the hydrocarbon mixture by a microbial population from gasoline-contaminated soil was delayed by addition of strain K1 to the population, while the addition of strain P1 resulted in an increase in the biodegradation rate.

Alkanes↗

A chemoenzymatic route to mannosamine derivatives bearing different N-acyl groups.

The chemoenzymatic route to 2-deoxy-2-propionamido-D-mannose (1b), 2-butyramido-2-deoxy-D-mannose (2b) and 2-deoxy-2-phenylacetamido-D-mannose (3b) involved N-acylation of 2-amino-2-deoxy-D-glucose followed by alkaline C-2 epimerization and selective microbial removal of the epimers with gluco-configuration. The latter step employed whole cells of Rhodococcus equi A4 able to degrade 2-deoxy-2-propionamido-D-glucose (1a), 2-butyramido-2-deoxy-D-glucose (2a) and 2-deoxy-2-phenylacetamido-D-glucose (3a) but inactive towards the corresponding manno-isomers. The metabolism of the gluco-isomers probably involved phosphorylation and subsequent deacylation. 2-Acetamido-2-deoxy-6-O-phospho-D-glucose amidohydrolase [EC 3.5.1.25] but not 2-acetamido-2-deoxy-D-glucose amidohydrolase was detected in the cell extract, the former enzyme being partially purified (15.8-fold with an overall yield of 18.1% and a specific activity of 0.95 units mg-1 protein). According to SDS-PAGE electrophoresis, gel filtration and mass spectrometry, the enzyme was a monomer with an apparent molecular mass of approximately 42 kDa. The optimum temperature and pH of the enzyme were 60 degrees C and 8.0-9.0, respectively. 2-Acetamido-2-deoxy-6-O-phospho-D-glucose and 2-acetamido-2-deoxy-6-O-sulfo-D-glucose but not 2-acetamido-2-deoxy-1-O-phospho-D-glucose or 2-acetamido-2-deoxy-D-glucose were substrates of the enzyme. Its activity was slightly inhibited by the addition of 1 mM Al3+, Ca2+, Co2+, Cu2+, Mn2+ or Zn2+ and activated by 1 mM Mg2+. The concentrated enzyme is highly stable at 4 degrees C in the presence of 0.1 M ammonium sulfate.

Acylation↗

Evaluation of the applicability of amplified rDNA-restriction analysis (ARDRA) to identification of species of the genus Corynebacterium.

The 16S rRNA genes (rDNA) of 50 strains belonging to 26 different coryneform bacterial species and genomospecies and of the type strain of Rhodococcus equi were enzymatically amplified. Amplified rDNA restriction analysis (ARDRA) with the enzymes AluI, CfoI and RsaI was carried out. The combination of the ARDRA patterns obtained after restriction with these three different enzymes enabled the differentiation between the following species: Corynebacterium accolens (number of strains = 2), C. afermentans subsp. afermentans (2), C. afermentans subsp. lipophilum (2), C. amycolatum (3), CDC coryneform group ANF-1-like (1), CDC coryneform group ANF-3-like (1), C. cystitidis (1), C. diphtheriae (4), C. jeikeium (3), C. macginleyi (2), C. minutissimum (1), C. pilosum (1), C. pseudotuberculosis (2), C. renale (2), C. striatum (2), C. urealyticum (3), C. xerosis (1), CDC coryneform groups B-1 (2), B-3 (2), F-1, genomospecies 1 and 2 (6), G, genomospecies 1 (1) and G, genomospecies 2 (2). The following strains or species could not be differentiated from each other: C. pseudodiphtheriticum (2) from C. propinquum (former CDC coryneform group ANF-3) (2), CDC coryneform group F-1, genomospecies 1 (4) from genomospecies 2 (2) and C. jeikeium genomospecies A (1) from genomospecies C (2). ARDRA may represent a possible alternative for identification of coryneforms, since this technique enabled the identification of most coryneforms tested and since DNA extraction (i.e. cell lysis by boiling), amplification, restriction and electrophoresis can be carried out within 8 hours. This might allow quick identification of C. diphtheriae and other possible pathogens of the genus Corynebacterium.

Corynebacterium↗

Detection of equine herpesvirus type 1 using a real-time polymerase chain reaction.

Equid herpesvirus 1 (EHV1) is a major disease of equids worldwide causing considerable losses to the horse industry. A variety of techniques, including PCR have been used to diagnose EHV1. Some of these PCRs were used in combination with other techniques such as restriction enzyme analysis (REA) or hybridisation, making them cumbersome for routine diagnostic testing and increasing the chances of cross-contamination. Furthermore, they involve the use of suspected carcinogens such as ethidium bromide and ultraviolet light. In this paper, we describe a real-time PCR, which uses minor groove-binding probe (MGB) technology for the diagnosis of EHV1. This technique does not require post-PCR manipulations thereby reducing the risk of cross-contamination. Most importantly, the technique is specific; it was able to differentiate EHV1 from the closely related member of the Alphaherpesvirinae, equid herpesvirus 4 (EHV4). It was not reactive with common opportunistic pathogens such as Escherichia coli, Klebsiella oxytoca, Pseudomonas aeruginosa and Enterobacter agglomerans often involved in abortion. Similarly, it did not react with equine pathogens such as Streptococcus equi, Streptococcus equisimilis, Streptococcus zooepidemicus, Taylorella equigenitalis and Rhodococcus equi, which also cause abortion. The results obtained with this technique agreed with results from published PCR methods. The assay was sensitive enough to detect EHV1 sequences in paraffin-embedded tissues and clinical samples. When compared to virus isolation, the test was more sensitive. This test will be useful for the routine diagnosis of EHV1 based on its specificity, sensitivity, ease of performance and rapidity.

Animals↗

Survey of the large-animal diplomates of the American College of Veterinary Internal Medicine regarding knowledge and clinical use of polymerase chain reaction: implications for veterinary education.

A questionnaire was developed to document the knowledge base of large-animal diplomates of the American College of Veterinary Internal Medicine (ACVIM) regarding polymerase chain reaction (PCR) technology and to identify the common use of this technology in equine practice. Ninety-three of the 278 mailed questionnaires were returned, for an overall response rate of 33.4%. Ninety respondents (99%) reported being familiar with the general principles of nucleic acid probe technology; however, only 52 (57%) knew the difference between conventional (traditional) and real-time (second-generation) PCR. The majority of the respondents (88%) emphasized the need for continuing education on molecular diagnostics. Eighty-four (92%) of the respondents regularly use PCR (conventional and/or real-time) for the detection of equine pathogens, and 80 (88%) commonly submit their samples to university/state veterinary laboratories. Blood, nasal swabs, and feces are the three equine specimens most commonly submitted for PCR analysis of Streptococcus equi, Lawsonia intracellularis, Neorickettsia risticii, equine herpesvirus 1/4, Rhodococcus equi, Sarcocystis neurona, and equine influenza virus. Diplomates reported costs associated with molecular diagnostics and unreliability of PCR as the most common limitations of PCR. Didactic training in veterinary curricula and during continuing-education opportunities continues to be necessary to produce veterinarians who have an understanding of the clinical applications of molecular diagnostics.

Animals↗

Identification and epidemiological typing of clinical and environmental isolates of the genus Rhodococcus with use of a digoxigenin-labeled rDNA gene probe.

Rhodococcus species are ubiquitous in the environment, and several species have been reported to have pathogenic potential for humans. Rhodococcus equi, in particular, has been reported to cause infections in patients with AIDS. However, the identification of Rhodococcus species with use of conventional biochemical tests is problematic, and no simple and reproducible method exists for their rapid identification and differentiation. We found that the type strains of the 20 recognized species in the genus Rhodococcus could be clearly distinguished with use of a combination of the Pvu II and Pst I rRNA gene restriction endonuclease patterns and a digoxigenin-labeled Escherichia coli rDNA probe. Analysis of four clinical or environmental isolates confirmed as Rhodococcus bronchialis showed no interstrain variation of rRNA gene bands. Analysis of 15 isolates confirmed as R. equi from 13 patients showed 11 different rRNA gene patterns. No discernible difference was observed in the ribotype patterns between R. equi isolates from patients for whom AIDS had been diagnosed and those from patients who did not have AIDS, and there was no evidence of geographic clustering of R. equi ribotype patterns. Three of five Rhodococcus species isolates that could not be differentiated with use of conventional biochemical methods were identified with use of ribotype analysis. Therefore, ribotype analysis may provide an important adjunct to current biochemical identification of environmental and clinical isolates of Rhodococcus species.

Acquired Immunodeficiency Syndrome↗

High-performance liquid chromatography analysis of mycolic acids as an aid in laboratory identification of Rhodococcus and Nocardia species.

High-performance liquid chromatography analysis of the p-bromophenacyl esters of mycolic acids from whole organisms gave chromatographic patterns that were useful in differentiation of Rhodococcus and Nocardia species. Rhodococcus equi, R. erythropolis, and R. rhodochrous contained more-polar mycolic acids and were easily separated from the less-polar mycolic acid-containing species of R. sputi, R. bronchialis, R. corallinus, R. rubropertinctus, and R. terrae. The less-polar mycolic acid-containing Rhodococcus species showed chromatographic patterns that partially overlapped (in elution times) the patterns of Nocardia asteroides, N. otitidiscaviarum, and N. brasiliensis, but the larger number of peaks in the last species made separation between the genera possible. Distinct chromatographic patterns were found for most species, except for R. equi strains that showed two different patterns. Strains of R. rubropertinctus and R. terrae appeared identical. N. asteroides and N. otitidiscaviarum showed similar mycolic acid patterns.

Actinomycetales↗

Identification of Rhodococcus, Gordona and Dietzia species using carbon source utilization tests ("Biotype-100" strips).

The "Biotype-100" identification system (BioMérieux, La Balme-Ies-Grottes, France) based on carbon source utilization was evaluated for its ability to discriminate among 10 species of Rhodococcus, 7 species of Gordona and one species of Dietzia. The type strains of three species of Tsukamurella and 8 species of Nocardia were also included in the study. Results were compared with chemotaxonomic and conventional data. Carbon source utilization was shown to be reliable, rapid and easy to use when compared with standard identification methods. The 29 species tested were unambiguously separated by carbon source utilization tests. Rhodococcus equi was found to be heterogenous.

Bacterial Typing Techniques↗