The distribution of cultivable oral anaerobic microbiota identified by MALDI-TOF MS in healthy subjects and in patients with periodontal disease.

In this study, we aimed to identify the cultivatable oral anaerobic bacterial distribution in oral cavity by MALDI-TOF Biotyper. The bacterial distribution of three groups, including subjects with/without periodontal disease, two clusters of age (60 years as the cutoff), and before/after treatment, were investigated in this study. There were 38 participants recruited in this study, involving 18 subjects with moderate to severe periodontal-infected patients and 20 healthy controls. Total number of 126 bacterial species were identified by MALDI-TOF MS. The relative abundance of Streptococcus gordonii and Streptococcus intermedius in periodontal patients is higher than healthy controls indicating potential biomarkers for periodontal disease. Participants with periodontal disease were subdivided in to two clusters of age (60 years as the cutoff), 11 and 7 participants were age <60 years and>60 years, respectively. Meanwhile, the incidence of Streptococcus pneumoniae and Streptococcus oralis infection were higher in the subjects above 60 years old than below. Moreover, the bacterial distribution between pre-treatment and post-treatment was similar indicating that basic treatment without the ability to redistribute the microbiota. In summary, the cultivable oral anaerobic bacteria were identified by MALDI-TOF MS and the bacterial distribution shifting was shown to be associated with the progress of periodontal disease to aging and basic treatment. This study provided information for diagnosis and treatment guidelines for oral healthcare.

A Glutamine Insertion at Codon 432 of RpoB Confers Rifampicin Resistance in Mycobacterium tuberculosis.

Tuberculosis (TB) is an infectious respiratory disease caused by Mycobacterium tuberculosis and one of the top 10 causes of death worldwide. Treating TB is challenging; successful treatment requires a long course of multiple antibiotics. Rifampicin (RIF) is a first-line drug for treating TB, and the development of RIF-resistant M. tuberculosis makes treatment even more difficult. To determine the mechanism of RIF resistance in these strains, we searched for novel mutations by sequencing. Four isolates, CDC-1, CDC-2, CDC-3, and CDC-4, had high-level RIF resistance and unique mutations encoding RpoB G158R, RpoB V168A, RpoB S188P, and RpoB Q432insQ, respectively. To evaluate their correlation with RIF resistance, plasmids carrying rpoB genes encoding these mutant proteins were transfected into the H37Rv reference strain. The plasmid complementation of RpoB indicated that G158R, V168A, and S188P did not affect the MIC of RIF. However, the MIC of RIF was increased in H37Rv carrying RpoB Q432insQ. To confirm the correlation between RIF resistance and Q432insQ, we cloned an rpoB fragment carrying the insertion (encoding RpoB Q432insQ) into H37Rv by homologous recombination using a suicide vector. All replacement mutants expressing RpoB Q432insQ were resistant to RIF (MIC > 1 mg/L). These results indicate that RpoB Q432insQ causes RIF resistance in M. tuberculosis.