Strain differentiation of Mycobacterium tuberculosis complex isolated from sputum of pulmonary tuberculosis patients

OBJECTIVE: This study represents an early attempt to determine the diversity of Mycobacterium tuberculosis in Egypt, particularly of drug-resistant strains. METHODS: We characterized 45 Mycobacterium tuberculosis complex isolates from sputum samples of Egyptian patients with pulmonary tuberculosis, in order to establish a database of strain types and antimicrobial susceptibility patterns. RESULTS: One Mycobacterium bovis and 44 Mycobacterium tuberculosis (MTB) isolates were identified by PCR-restriction fragment length polymorphism (RFLP) analysis of the oxyR gene. Twenty-five (56.8%) of the 44 MTB isolates were susceptible in vitro to all anti-tuberculosis drugs tested; five (11.4%) were mono-resistant to isoniazid or streptomycin (four were resistant to streptomycin and only one was resistant to isoniazid) and 14 (31.8%) were resistant to more than one drug (multidrug-resistant, MDR). Among the 44 MTB isolates tested by RFLP analysis in this study, 40 different RFLP patterns were obtained. The number of IS6110 copies ranged from 5 to 16. Studying the IS6110 RFLP patterns indicated that the 44 isolates did not cluster together but were generally scattered. None of the 14 MDR isolates were clustered. Twenty-two different spoligotypes were identified among the 44 MTB isolates, of which 13 were unique. The remaining 31 isolates were grouped into nine clusters of strains sharing identical spoligotypes. CONCLUSIONS: We have demonstrated evidence of diversity among the drug-susceptible and resistant MTB strains. Continued surveillance for strains of MTB involved in pulmonary tuberculosis in Egypt, and especially for drug-resistant strains, is warranted.