IMPORTANCE OF CATALASE ENZYME IN VIRULENCE OF ISONIAZID RESISTANT ST RAINS OF MYCOBACTERIUM TUBERCULOSIS IN GUINEAPIGS

In this study, twenty-five strains of Mycobacterium tuberculosis resistant to isoniazid (INH) were isolated from patients with tuberculosis (TB). Nine strains (36%) were found to be virulent in guinea-pigs [root index virulence (RIV» 1 ]. The remaining sixteen strains (64%) were non-virulent (RIV <1). Of the nine strains resistant to INH as well as virulent to guinea-pigs, eight of them were found to be catalase positive and only one strain was catalase negative, whereas the remaining sixteen INH resistant strains were catalase negative. A strong association was observed between INH resistance and catalase positivity and virulence (p<0.0001 chi-square test). This study supports the hypothesis that catalase has an important role in the virulence of INH-resistant strains of M tuberculosis.