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The aim of the study was to assess the suitability of multiplex PCR and culture for the detection of virulent R.equi in tracheobronchial aspirate (TBA) and feces of foals from enzootic farms. Fecal and TBA samples were taken randomly from a representative group of foals aged between 1 and 6 months. The solid selective medium NANAT was used for culture examination. Multiplex PCR reaction was performed with the use of two sets of primers complementary to the conservative gene fragment encoding the 16S subunit of ribosomal RNA of R.equi and the plasmid gene encoding virulence associated protein A (VapA), which determines bacterial virulence. During clinical observations three experimental groups (A, B, C), differing in the intensity of respiratory signs, were selected for further studies. In foals from group A, showing no clinical signs from the respiratory tract, the results of the examinations of TBA and fecal samples were negative irrespective of the method used. In group B, showing moderate respiratory signs, 15 TBA and fecal samples were examined. PCR results were positive for 7 TBA samples and 2 fecal samples, whereas culture examinations were positive for only 3 TBA samples from this group. In group C, consisting of 6 foals with severe respiratory signs, positive PCR and culture results were obtained for all TBA samples and for 3 fecal samples.
The aim of the study was to assess the prevalence of virulent and non-virulent R. equi strains in horse farms with enzootic and sporadic rhodococcosis. Based on the microbiological culture, a progressive growth of the number of bacteria in soil samples was found that was correlated with the air temperature growth and independent of the farm epizootic status. The number of virulence strains in the soil was dependent on the time of sample collection and type of stud. PCR is a useful method for classifying bacteria from the R. equi species and to detect the virulence marker. Comparison of microbiological culture and PCR suggests caution in interpreting culture results in terms of the identification of all bacterial colonies as belonging to Rhodococcus equi species
Rhodococcosis is known largely as an infectious disease of young foals that causes losses in the horse breeding industry. Besides in animals, the infection can also be a significant diagnostic, clinical and therapeutic problem in human medicine. The aim of the paper is to present the zoonotic aspect of rhodococcosis, including basic data about pathogen, epidemiology, pathogenesis, clinical picture, pathology, diagnosis and therapy of the disease. R. equi was isolated for the first time in 1923 by Magnusson in Sweden from a dead foal with the signs of pyogranulomatous pneumonia. The first case of human R. equi infection has been described in 1967 in a 29-year-old man subjected to immunosuppressive therapy. Hundreds of new cases of human rhodococcosis have been described since that time all over the world. The majority of human cases of R. equi infections concern patients immunodeppressed during the course of different diseases or treated with immunosuppressive drugs. However, 10-15% of cases concern fully immunocompetent patients. The role of farm animals as a primary source of infection to people has not been proved, but the importance of a contaminated environment seems to be evident. Molecular studies of human R. equi strains revealed that only 21% of isolates contained the typical for foal strains VapA plasmid. This suggests that the pathogenesis of the disease in humans may be different from that described in animals. Immunological investigations supporting the role of cell-mediated immunity in R. equi infections explain why AIDS patients with confirmed CD4+ lymphocytes deficiency and decreasing ability of INF gamma synthesis are more susceptible to infection in comparison to immunocompetent people. The clinical course of rhodococcosis in humans is varied, but in 80% of cases the process is localized in the respiratory tract. The mortality rate in immunosuppressed patients ranges between 20-55%. Diagnosis of rhodococcosis in humans is based on the isolation and identification of the pathogen in antemortem collected biological material. Radiology and CT may also be helpful. Myc. tuberculosis and Nocardia spp. infections should be included as a differential diagnosis. Treatment of rhodococcosis in humans, similarly to animals, usually requires a several-week course of a combination of 2-3 antibiotics. In practice intravenous application of vancomycin, carbapenem or aminoglycosides combined with oral administration of azithromycin and/or rifampin is used. In apparently cured individuals relapses occur frequently in which pathological changes are localized in primarily involved or in other tissues and organs.
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