[Mycobacterium tuberculosis L forms in patients with pulmonary silicotuberculosis and silicosis].

OBJECTIVE: To evaluate significance of Mycobacterium tuberculosis L forms in pathogenesis of silicotuberculosis and silicosis.

METHODS: Sputum culture for Mycobacterium tuberculosis and its L forms was conducted from both silicotuberculosis and silicosis groups, and the results were compared.

RESULTS: Among 60 silicotuberculosis patients, 6 (10%) were sputum Mycobacterium tuberculosis culture positive, of which 5 (83%) were Mycobacterium tuberculosis L forms culture positive; 28 were sputum Mycobacterium tuberculosis L forms culture positive (positive rates in the patients with silicosis stage I, stage II, stage III were 33%, 67%, 100% respectively), with a positive rate of 47%, and a significant difference was found comparing with the frequency of detecting Mycobacterium tuberculosis (P < 0.01). All of the 30 cases with silicosis were Mycobacterium tuberculosis culture negative, however, 3 of them were sputum Mycobacterium tuberculosis L forms culture positive, accounting for 10 percent.

CONCLUSIONS: Sputum culture for Mycobacterium tuberculosis L forms is a convenient and rapid way to improve the detection rate of Mycobacterium tuberculosis, with a positive value in early diagnosis of silicotuberculosis by reducing misdiagnosis and underdiagnosis of this disease. Detection rate of Mycobacterium tuberculosis L forms significantly increases with deterioration of silicosis.