BACKGROUND: It is not known with certainty whether patients with persistently positive sputum smear results who have also had negative sputum culture results require prolongation of treatment for tuberculosis in order to avoid an increased risk of eventual relapse. The purpose of the present study was to retrospectively describe the treatment characteristics and evaluate the appropriate duration of treatment in these patients. METHODS: Sixty of 69 patients with sputum smear positive and culture negative tests at 5 months after first line anti-tuberculous chemotherapy from 2002 to 2003 were retrospectively analyzed. Exclusion criteria included incomplete treatment or resistance to rifampicin or two additional antibiotics, as determined by a drug susceptibility test (DST). RESULTS: Smear conversion of the study subjects was observed after 8.3+/-2.3 months treatment, and the patients were culture negative after 2.0+/-0.8 months. The relapse rates of the study subjects were 3.8, 10.0, and 25.8% after 1, 2, and 5 years of anti-tuberculosis chemotherapy, respectively. The relapse rates were not significantly affected by a series of risk factors such as age, sex, presence of diabetes, a sputum culture examination after 2 months treatment, previous treatment history, chest radiograph, and duration of the treatment (p>0.05). CONCLUSION: Regimen change is not required for patients with persistent smear positive but culture negative tests in the fifth month for first line antituberculous treatment. However, a further study will be needed to clarify the high relapse rate in this specific group of patients.
Anti-Bacterial Agents ; Drug Therapy* ; Humans ; Radiography, Thoracic ; Recurrence ; Retrospective Studies ; Rifampin ; Risk Factors ; Sputum* ; Tuberculosis ; Tuberculosis, Pulmonary

BACKGROUND: The emergence of multidrug-resistant strains of Mycobacterium tuberculosis presents a significant challange to the treatment and control of tuberculosis, and there is an urgent need to understand the mechanisms by which strains acquire multidrug resistance. Recent advances in molecular methods for the detection of M. tuberculosis genetic targets have approached the sensitivity of culture Furthermore the prospect of determining resistance in mycobacteria at the nucleic acid level particulary to first-line drugs like rifampin, isoniazid has provided a glimps of the next generation of sensitivity test for M. tuberculosis. Previous studies in RMP resistant M. tuberculosis have shown that mutation in beta subunit of RNA polymerase is main mechanism of resistance. METHOD: In this study, rpoB gene for the ~3 subunit of RNA polymerase from M. tuberculosis of 42 cultured samples (32 were RMP resistant and 10 were sensitive cases) were isolated and characterised the mutations. Direct sequencing data were compared with the results of INNO-LiPA Line Probe Assay (LiPA, Innogenetics, Belgium), commercial RMP resistance detecting kit using reverse hybridization method. RESULTS: All of the RMP resistant samples were revealed the presence of mutation by LiPA. In 22 samples (68.8%) out of 32 RMP resistant cases, the mutation types were confirmed by the positive signal at one of 4 mutation bands in the strip. The most frequent type was R5 (S53 IL) which were 17 cases (77.3%). Results of direct sequencing were identified the exact characteristics of 8 mutations which were not comfirmed by LiPA. S522W type point mutation and 9 base pair deletion at codon 513-515 were new identified mutations for the first time. CONCLUSION: Mutations in rpoB gene is the main mechanism of RMP resistance in M. tuberculosis and LiPA is a very useful diagnostic tool for the early diagnosis of RMP resistance in M. tuberculosis.
Base Pairing ; Codon ; DNA-Directed RNA Polymerases ; Drug Resistance, Multiple ; Early Diagnosis ; Isoniazid ; Mycobacterium tuberculosis ; Point Mutation ; Rifampin ; RNA Polymerase I ; Tuberculosis*