CATALASE EXPRESSION, KATG, AND MIC OF ISONIAZID FOR MYCOBACTERIUM-TUBERCULOSIS ISOLATES FROM SAO-PAULO, BRAZIL

The MIC of isoniazid, peroxidase-catalase expression, and the presence of the katG gene for 102 Mycobacterium tuberculosis isolates from pat ients in Sao Paulo were compared. Fifty-three isoniazid-resistant and 49 isoniazid-sensitive isolates were analyzed by polymerase chain reac tion (PCR) for the presence of katG sequences. All isoniazid-sensitive and 43 (81%) isoniazid-resistant isolates expressed catalase (P = .00 1). None of isoniazid-sensitive and 4 (7%) of 53 isoniazid-resistant i solates lacked katG sequences. Among 6 isolates with MICs >50 mu g/mL, 5 (83%) did not express catalase and 2 lacked katG sequences; only 1 had complete gene deletion shown by Southern blot analysis. These find ings indicate a correlation between loss of catalase and isoniazid res istance among highly resistant isolates, but these isolates were a sma ll proportion of resistant clinical M. tuberculosis isolates from Sao Paulo.