RESUMO
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.