[Comparison of P-nitrobenzoic acid and hydroxylamine hydrochloride for the primary screening of mycobacterial species].

OBJECTIVES: To examine the screening methods for mycobacteria recommended by the China Anti-tuberculosis Association, in order to increase laboratory diagnostic accuracy for mycobacterial screening. METHODS: Using P-nitrobenzoic acid (PNB 0.5 g/L) as the control group, and hydroxylamine hydrochloride (HA, in 125, 150 and 175 mg/L concentrations) as the study group, laboratory preserved strains of H37Rv M.tuberculosis, and standard and clinically isolated strains of M.nontuberculosis (NTM) from Guangzhou Chest Hospital were tested for both PNB and HA sensitivity. Differences between groups were analyzed by χ(2) test. RESULTS: Among the 2529 MTB strains, the resistance rate to PNB was 3.0% (76/2529), to HA was 12.2% (308/2529), 4.8% (121/2529), and 0.9% (23/2529), respectively, corresponding to the aforementioned 3 different concentrations of HA. Among the 1766 NTM strains, the sensitive rate to PNB was 8.3% (147/1766), to HA was 0.1% (2/1766), 0.5% (9/1766), and 0.9% (16/1766), respectively, corresponding to the aforementioned 3 different concentrations of HA. There was significant difference (χ(2) = 5.44-83.50, P < 0.05). CONCLUSION: HA at 175 mg/L concentration was the optimal condition for laboratory tuberculosis preliminary screening.

[Analysis of the changes in bacterial types and drug sensitivity profiles of mycobacterial strains in Guangzhou over the last twelve years].

OBJECTIVE: To improve evidence-based care in the management of tuberculosis, we retrospectively analyzed the bacterial types and drug sensitivity test results of mycobacteria in Guangzhou over the past twelve years (from July 1998 to March 2010). METHODS: Over these twelve years, a total of 14 095 mycobacterial strains isolated from different samples were subjected to type identification and drug sensitivity tests according to the Standard Protocols of Laboratory Diagnostics for Tuberculosis by the Chinese Antituberculosis Association. Chi-square test was performed for statistical analyses for comparisons between groups. RESULTS: Of 14 095 strains of mycobacteria isolated, 10 844 strains (76.84%) were MTB, and 3251 strains (23.16%) were non-tuberculosis mycobacteria (NTM). Compared with the result of the fourth national survey of tuberculosis epidemiology, which showed 11.1% of NTM, the one of our study was significantly different (χ(2) = 69.79, P < 0.001). Drug sensitivity tests of MTB showed tolerance rates of 28.99% (2729/9413), 21.75% (2047/9413), 17.45% (1643/9413) and 11.53% (1085/9413) against isoniazid, rifampin, streptomycin and ethambutol, respectively. CONCLUSION: An increasing trend was observed in MTB drug tolerance against streptomycin, rifampin and isoniazid, whereas more and more NTM strains were isolated in recent years. These findings are worthy of note for clinicians.