Molecular characterization of mycobacterium tuberculosis complex strains from ruminants and evaluation of its purified protein derivative

Abstract

Bovine tuberculosis is one of the major disease affecting humans, bovines and wildlife, by virtue of its economic importance and public health significance. For early diagnosis of the disease, initial attempts were made to genomically characterize the Mycobacterium tuberculosis complex (MTBC) organisms causing disease in bovine or wildlife and to prepare a diagnostic reagent, purified protein derivative (PPD) from one of the more recent strains involved in the disease condition. newlinePurified protein derivative was prepared from one of our M. orygis isolates (TANUVAS_2) and tested in guinea pigs and cattle. The PPD-O prepared was not toxic and its potency was 98% to that of PPD-B (IVRI). The PPD-B (IVRI), PPD-O (TANUVAS), PPD-B (Prionics) and PPD-A (Prionics) were tested in 60 animals (51 cattle and 9 buffaloes), of which 20 animals were identified as positive by PPD-B (IVRI). PPD-O (TANUVAS) detected 32 animals as positive. However, PPD-B (Prionics) could detect 52 animals as positive. When PPD-B (IVRI) was considered as gold standard, our PPD-O (TANUVAS) had diagnostic sensitivity and specificity of 80% and 60% respectively. When PPD-B (Prionics) was considered as gold standard, PPD-O has diagnostic sensitivity and specificity of 59% and100%respectively. When the skin thickness produced by PPD-A was subtracted from the skin thickness readings produced by PPDs, the performance evaluation of the PPDs remained similar although lower in values. The quantitative correlation of skin thickness between PPD-O (TANUVAS), PPD-B (IVRI) and PPD-B (Prionics) varied from 0.19 to 0.50. However, more studies need to be performed in larger number of animals for further evaluation of the diagnostic potential of PPD-O. newlineKey words:Tuberculin skin test, Purified protein derivative, Tampon swab, MTBC, M. orygis and PPD-O. newline newline