Resistance of Mycobacterium tuberculosis to Four First-line Anti-tuberculosis Drugs in a Referral Hospital in Northern Taiwan, 2002-2006

Introduction: The purpose of this retrospective study was to investigate the drug resistance of Mycobacterium tuberculosis to 4 first-line anti-tuberculosis (TB) drugs (isoniazid (INH), rifampin (RIF), ethambutol (EMB), streptomycin (SM)) at Taipei Medical University-Wan Fang Hospital from 2002 to 2006.
Methods: From 1 January 2002 through 31 December 2006, drug susceptibility testing for first-line anti-TB drugs, including INH, RIF, EMB, and SM, was performed using the indirect agar proportion method. A retrospective review of medical records to define the drug resistance of new, previously treated, and combined cases was conducted.
Results: Of the 436 M. tuberculosis isolates, 343 were recovered from new cases and 93 from previously treated cases. The combined drug resistance rate to at least 1 drug was 17.6%. The drug resistance rate to at least 1 drug among new cases was 11.7% and among previously treated cases was 39.8%. The combined drug resistance rate to individual drugs was 12.4% to INH, 7.1% to RIF, 3.2% to EMB, and 9.2% to SM. The rates of combined multidrug resistance (resistance to at least INH and RIF), among new cases, and previously treated cases were 5.7%, 1.5%, and 21.5%, respectively.
Conclusions: Drug resistance remains a serious problem in the treatment of TB in Taiwan. When treating a TB patient, drug resistance should be considered, especially in previously treated cases.