Detection of Mycobacterium tuberculosis DNA in blood or sputum cultures by fluorescence quantitative PCR

Abstract

Objective To evaluate if fluorescence quantitative PCR (FQ-PCR) detection for Mycobacterium tuberculosis in blood or sputum culture can help tuberculosis (TB) diagnosis. Methods A total of 81 patients with a clinical diagnosis of tuberculosis but sputum negative were enrolled, 40 were tuberculosis group and 41 coexisting HIV were HIV-TB group. Blood and sputum were cultured for bacilli or L-forms of Mycobacterium tuberculosis, and FQ-PCR was used to detected bacilli DNA. Results For pulmonary tuberculosis group, 54.1 %(20/37) were positive for bacilli or Informs of Mycobacterium tuberculosis in sputum by FQ-PCR, 27.5% (11/40) were positive in blood culture, 22.5%(9/40) were positive in blood by FQ-PCR, and the total positive rate of blood was 42.5% (17/40). But for HIV-TB group, only 2 positive cultures were found in 10 sputum, the positive rate of blood culture was 7.3% (3/41), and the positive rate of blood was 17.1%(7/41) by FQ-PCR. There was no significant difference between two groups in the positive rate of Mycobacterium tuberculosis by FQ-PCR after blood cultures (P > 0.05). The total positive rates detected by FQ-PCR of sputum or blood cultures were 65.0% (26/40) and 22.0% (9/41) respectively, and there was significant difference between two groups( χ2 = 15.305, P < 0.01). Conclusions FQ-PCR for blood or sputum culture detection appears to be a useful method to diagnose TB in persons with or without HIV infection. The use of FQ-PCR significantly enhance the efficiency of the etiological diagnosis of sputum negative pulmonary tuberculosis. Key words: Tuberculosis, pulmonary; Mycobacterium tuberculosis; Fluorescence quantitative PCR; HTV; Bacteremia