[A study on the drug resistance to p-nitrobenzoic acid in Mycobacterium tuberculosis].

OBJECTIVE: To investigate the resistance of Mycobacterium tuberculosis (MTB) to p-nitrobenzoic acid (PNB), in order to provide the scientific basis for reliable identification of laboratory strains of mycobacterium. METHODS: Strains of mycobacterium grown in PNB media were identified with additional traditional biochemical tests, according to the standard protocols of laboratory diagnostics for tuberculosis by the Chinese Antituberculosis Association. For mycobacteria grown in the PNB media but highly suspected as MTB by traditional biochemical tests, MPB64 monoclonal antibody was used for the differentiation between MTB and non-tuberculosis mycobacteria group (NTM). Minimal inhibitory concentrations (MIC) of PNB was further determined for culture-confirmed MTB, 10 strains of clinically isolated MTB (control), H(37)Rv standard strain, mycobacterium avium standard strain, and 5 strains of clinically isolated NTM. RESULTS: A total of 1114 strains of MTB were confirmed, among which 58 PNB manifested resistance. The rate of resistance was 5.21% (58/1114), with an MIC ranging for 1.0 - 1.5 g/L. The MICs of control MTB and H(37)Rv standard strain were 0.25 - 0.5 g/L and 0.25 g/L, respectively. Both mycobacterium avium standard strain and clinically isolated NTM showed an MIC of > 2.0 g/L. Differences between groups were statistically significant (t = 4.87, 5.09, 6.68, respectively, P < 0.01). CONCLUSION: In order to avoid laboratory misdiagnosis, for primary screening with NTB with PNB culture, the presence of MTB characteristics, including cream-colored broccoli-like colony morphologies, as well as clinical response to first-line anti-tuberculosis medications, despite PNB tolerance, warrants further investigations of traditional biochemical tests, differentiation with MPB64 monoclonal antibodies, or simply by the use of temperature manipulation or drug-sensitivity test results.

[Analysis on the current situation of Mycobacteria other than tuberculosis during 1994-2003 in the old city area of Guangzhou].

OBJECTIVE: To analyze the current situation and trend of Mycobacteria other than tuberculosis (MOTT) in the old city area of Guangzhou and to provide information for diagnosis, treatment and policy on tuberculosis (TB) control in the city. METHODS: Relevant data regarding Mycobacteria culture, species identification and drug-resistance from out-patients under suspicion of having pulmonary tuberculosis seen at our TB and Pulmonary Tumor Control Institute, was analyzed retrospectively during 1994-2003. RESULTS: A total number of 12,634 strains of Mycobacteria were isolated and 794 strains were identified as MOTT which accounted for 6.28% of the isolated strains during the ten years. The annual isolation rates of MOTT were between 3.51% and 10.06%. When compared with 1994, the rates of isolation on MOTT had increased 73.15% in 2003, i.e. from 5.81% in 1994 to 10.06% in 2003. 512 strains were not susceptible at least to rifampin and isoniazid out of 613 MOTT strains tested for drug susceptibility to isoniazid, rifampin, streptomycin sulfate and ethambutol. The average rate of multi-drugs resistance of these strains was 83.5%, and the annual rates were between 71.4% and 93.9%. Based on the results of species identification on 136 strains of MOTT in 2003, most of them belonged to pathogenic/opportunistic species of Mycobacteria. All together, 30 strains of M. abscessus, 26 of M. intracellulare, 17 of M. smegmatis, 14 of M. scrofulaceum, 11 of M. avium, 5 of M. kansasii and M. chelonae and M. fortuitum respectively, 4 of M. nonchromogenicum, 2 of M. triviale and 1 of M. aurum were identified. People at 45 years of age or older, with 55-65 the most, were more susceptible to MOTT than other age groups. Sex ratio was 3.36 to 1. CONCLUSION: Based on information from the Third National Tuberculosis Epidemiology Survey in 1990 and the Fourth one in 2000, the current situation and trend of MOTT were nearly the same in the old city area of Guangzhou during 1994-2003. However, the rising tendency of rate of isolation, mainly consisted of opportunistic pathogens and the surprisingly high rate of multi-drugs resistance to MOTT all call for special attention. Studies regarding the epidemiology of MOTT should be posed and implemented in the National TB Control Program.