Culturing Stools To Detect Mycobacterium tuberculosis

The Enterococcus secretome inhibits the growth of Mycobacterium tuberculosis complex mycobacteria

Enterococcus mundtii , a commensal intestinal bacterium, was demonstrated to inhibit the growth of some Mycobacterium tuberculosis complex (MTC) species that cause tuberculosis in humans and mammals. To further explore this preliminary observation, we cross-investigated five E. mundtii strains and seven MTC strains representative of four MTC species using a standardized quantitative agar well diffusion assay. All five E. mundtii strains, calibrated at 10 MacFarland, inhibited the growth of all M. tuberculosis strains with various susceptibility profiles, but no inhibition was observed with lower inoculums. Further, eight E. mundtii freeze-dried cell-free culture supernatants (CFCS) inhibited the growth of M. tuberculosis , Mycobacterium africanum, Mycobacterium bovis and Mycobacterium canettii, the most susceptible MTC species (inhibition diameter 25±1 mm), proportionally to CFCS protein concentrations. The data reported here indicate that the E. mundtii secretome inhibited growth of all MTC species of medical interest, which broadens previously reported data. In the gut, the E. mundtii secretome may modulate the expression of tuberculosis, exhibiting an anti-tuberculosis effect, with some protective roles in human and animal health.

Study on the value of molecular biology combined with liquid MGIT culture method in clinical examination of mycobacterium tuberculosis

OBJECTIVE

To investigate the clinical value of molecular biology (xpert MTB/RIF) combined with a liquid mycobacterium culture tube (MGIT) in the clinical examination of Mycobacterium tuberculosis (MTB).

METHODS

A total of 782 patients with suspected pulmonary tuberculosis who came to our hospital from February 2018 to February 2020 were selected as the research subjects. Sputum samples of all patients were taken in the morning, and BACTEC MGIT culture and xpert MTB/RIF, Lowenstein-Jenden (L-J) culture and acid fast staining microscopy were used respectively to detect the sputum samples. The positive samples were cultured, and the bacteria identification and liquid drug sensitivity test were carried out. We also analyzed the value of xpert MTB/RIF combined with MGIT culture method in the clinical testing of MTB.

RESULTS

(1) Among the 782 suspected patients, 405 cases were diagnosed with pulmonary tuberculosis and 377 cases were non tuberculosis patients. The sensitivity of smear microscopy was 17.28% (70/405), the specificity was 98.94% (373/377), and the average time was 3.05 h. The sensitivity of L-J culture test was 20.49% (83/405), the specificity was 97.61% (368/377), and the average time was 28.58 h. The sensitivity of MGIT culture test was 38.02% (154/405), the specificity was 96.82% (365/377), and the average time was 11.23 h. The sensitivity of xpert MTB/RIF test was 36.54% (148/405), the specificity was 99.46% (375/377), and the average time was 2.03 h. The sensitivity of MTB/RIF + MGIT test was 42.47% (172/405), the specificity was 96.02% (362/377), and the average time was 11.29 h. The sensitivity of MTB/RIF combined with MGIT culture was significantly higher than that of smear microscopy and L-J culture (χ²=61.31, 45.33, P<0.001). (2) The average culture time of 13 smear negative xpert MTB/RIF negative specimens was 17.02 days. The average culture time of 82 smear negative xpert MTB/RIF positive samples was 14.12 days. The average culture time of 77 smear positive xpert MTB/RIF positive samples was 7.45 days. (3) The sensitivity of Xpert MTB/RIF test for rifampicin resistance is 100% (11/11), and the specificity is 91.14% (144/158).

CONCLUSION

The method of molecular biology combined with MGIT has a high sensitivity and specificity for clinical diagnosis of MTB.

Fecal Excretion of Mycobacterium leprae, Burkina Faso

Mycobacterium leprae was detected by optical microscopy, fluorescent in situ hybridization, and molecular detection in feces collected for the diagnosis of Entamoeba coli enteritis in a leprosy patient in Burkina Faso. This observation raises questions about the role of fecal excretion of M. leprae in the natural history and diagnosis of leprosy.

Culturomics Discloses Anti-Tubercular Enterococci Exclusive of Pulmonary Tuberculosis: A Preliminary Report

Mycobacterium tuberculosis causes pulmonary tuberculosis, a deadly infection of which the clinical expression and prognosis are not fully understood at the individual level, apart from genetic susceptibility traits. We investigated whether individual gut microbiota may correlate with pulmonary tuberculosis status. Culturomics investigations of gut microbiota in two pulmonary tuberculosis patients and two controls in Burkina Faso found 60 different bacterial species in patients and 97 in controls, including 45 in common. Further analysis of the results at the individual level indicated seven bacteria, including Enterococcus mundtii and Enterococcus casseliflavus, which were exclusively cultured in controls. Blind quantitative PCR-based exploration of faeces samples in two cohorts in Burkina Faso and in France confirmed a nonsignificant association of E. mundtii and E. casseliflavus with controls. Further in vitro explorations found four E. mundtii and E. casseliflavus strains inhibiting the growth of M. tuberculosis strains representative of four different lineages as well as Mycobacterium africanum, Mycobacterium canettii, and Mycobacterium bovis, in an inoculum-dependent manner. Heat-killed E. mundtii or E. casseliflavus were ineffective. These unprecedented observations of direct interactions between gut E. mundtii and E. casseliflavus with M. tuberculosis complex mycobacteria suggest that gut microbiota may modulate the expression of pulmonary tuberculosis.