日本および世界の薬剤耐性結核の現状

In 1994, the World Health Organization (WHO) and the International Union against Tuberculosis and Lung Disease (IUATLD) launched a global project on anti?tuberculosis drug resistance surveillance. The results from the first 4 years (1994-1997) and the second 4 years (1996-1999) of the projects were reported in 1998 and 2000, respectively. These surveillance results showed that resistance to anti-tuberculosis drugs is a global problem. The reports also showed that there were several hot spots around the world where prevalence of multidrug resistant tuberculosis (MDR-TB, defined as resistance to at least isoniazid and rifampin) was particularly high and could possibly threaten control programs.<BR>The Tuberculosis Research Committee of Japan (Ryoken) has conducted nationwide surveys for drug resistant tuberculosis at 2- or 5-yearly intervals since 1957. The 1997survey showed that among patients with no prior treatment, resistance to any of the four drugs was found in 10.3 %, and the prevalence of primary MDR was 0.8%. The prevalence of drug resistance in the previously treated cases was 42.4 % for any of the four drugs and 19.7 % for MDR, indicating a high prevalence rate compared with those reported in the global project. Compared with the previous survey in 1992, the current survey shows increased prevalence of drug resistance in both new and re-treatment cases. No significant differences in resistance rates by sex, age group, nationality, district, and/or accompanying diseases were observed in any of the new or re-treatment cases. Other factors associated with the high prevalence in re-treatment cases remain to be determined.<BR>A total of 78 hospitals in various districts of Japan participated the cooperative study. Each collaborating laboratory sent all the isolated mycobacterial cultures to the Research Institute of Tuberculosis (RIT). In the local laboratories, the absolute concentration method using 1 % Ogawa egg slant, its modified methods using a 48-well plate and a 16-well plate, combination of above 2 or 3 methods, and other method were used for drugsusceptibility testing, and the proportion method using 1 % Ogawa egg slant was used in the RIT. The results in the local laboratories were compared with those in the RIT. There was no significant difference in the concordance rates according to the test drugs among methods for drug susceptibility testing used in the local laboratories. Relatively lower concordance rates were seen in the laboratories using the Microtiter method related to high overestimation rates, compared with those in the laboratories using the standard method and Well—pack method. However, relatively lower concordance rates (less than 90%) were seen in the laboratories using any of the three methods, indicating that there are variations among facilities.