oa Molecular Diagnosis and Vaccines - Direct differentiation between Mycobacterium bovis and Mycobacterium tuberculosis in sputum specimens from smear positive pulmonary tuberculosis cases
An oxyR allele-specific polymerase chain reaction (oxyR-PCR) was adopted for direct differentiation between Mycobacterium tuberculosis and Mycobacterium bovis in sputum from smear +ve pulmonary tuberculosis patients. The assay is based on one genetic polymorphism at the position 285 in the oxyR gene of both organisms. A ttal of 126 smear positive pulmonary tuberculosis-under treatment patients were studied. All of them were subjected to molecular diagnosis of tuberculosis (M-TB complex) using the IS6110-PCR. An internal control DNA fragment was sensitized and utilized in each reaction. Of the 116 culture positive cases, 111 (95.68%) were IS6110 +ve, 3 (2.58%) were IS6110 ve and 2 (1.72%) showed PCR inhibition, as indicated by the absence of amplification of the internal control DNA fragment. Of the 10 culture negative cases, 6 (60%) were IS6110-PCR positive, and 4 (40%) were negative. The specimens which showed no PCR inhibition in the IS6100-PCR were further subjected to oxyR PCR. All culture +ve/IS6110 +ve cases (n=111) were oxyR positive, and of them only one was identified as M. bovis (1/124=0.8%), and the remaining 110 were M. tuberculosis. On the other hand, 6 and 8 out of 10 culture negative cases were IS6110 and oxyR positive for M. tuberculosis respectively, denotying that oxyR PCR is more sensitive than the IS6110-PCR. In conclusion, oxyR PCR has the capacity to directly differentiate between M. bovis and M. tuberculosis in the sputum specimen. Pulmonary tuberculosis caused by M. bovis still occurs in Egypt and can easily be diagnosed by allele specific oxyR-PCR.
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