OBJECTIVETo explore the epidemic distribution of Mycobacterium tuberculosis isolates from Beijing, Guangdong and Ningxia, and to determine M. tuberculosis strains of the "Beijing Family".

METHODSTwo hundred and six IS6110 DNA fingerprinting patterns of M. tuberculosis strains from three provinces (city) were transferred to digital data, compared with the world M. tuberculosis DNA fingerprinting database, and then clustered by Gel compare 4.1 software. The clustering values in different patients with tuberculosis were compared by chi(2) test. Risk factors for recent transmission were calculated using odd ratios.

RESULTSNo M. tuberculosis strains were found the same as those of DNA fingerprint database. 56.8% (117/206) fingerprinting patterns of M. tuberculosis shared by least two-thirds of the IS6110 fragments and their Spoligotyping fingerprinting patterns were consistent with those of M.tuberculosis strains of the "Beijing Family". There were significant differences between female and male, different age groups (< 42 years old) and older (>or= 42 years old) (P < 0.05). Odd ratio was 5.06 in the group younger than 42 years old (95% CI: 1.00 - 34.34) and was 4.43 (95% CI: 0.94 - 28.76) in males.

CONCLUSIONM. tuberculosis strains of "Beijing Family" were popular in Beijing, Guangdong and Ningxia. Men and younger age group (< 42) were shown to be infected by identical strains more often than women and older aged which might play an important role in the recent transmission of tuberculosis in these areas. IS6110 DNA fingerprinting of M. tuberculosis could be used to trace the source of tuberculosis infection.