The emergence of drug-resistant strains of Mycobacterium tuberculosis (Mtb), especially those that are multidrug resistant poses a serious threat to global tuberculosis control. However, the mechanism underlying the occurrence of drug resistance against more than one drug is poorly understood. Given that the Beijing/W strains are associated with outbreaks and multidrug resistance, they may harbor a genetic advantage and provide useful insight into the disease. One marker found in all Beijing/W Mtb strains is a deletion of RD105 region that results in a gene fusion, Rv0071/74, with a variable number (3–9 m) of VDP (V: Val, D: Asp; P: Pro) repeats (coded by gtggacccg repeat sequences) at the N-terminal. Here, we report that this variable number of VDP repeats in Rv0071/74 regulates the development of multidrug resistance. We collected and analyzed 1255 Beijing/W clinical strains. The results showed that the number of VDP repeats in Rv0071/74 was related to the development of multidrug resistance, and the deletion of Rv0071/74-9 m from Beijing/W clinical strain restored drug susceptibility. Rv0071/74-9 m also increased resistance to multiple drugs when transferred to different mycobacterial strains. Cell-free assays indicate that the domain carrying 4–9 VDP repeats (4–9 m) showed a variable binding affinity with peptidoglycan and Rv0071/74 cleaves peptidoglycan. Furthermore, Rv0071/74-9 m increased cell wall thickness and reduced the intracellular concentration of antibiotics. These findings not only identify Rv0071/74 with VDP repeats as a newly identified multidrug resistance gene but also provide a new model for the development of multiple drug resistance.

Aim: To characterize a novel macrolide ATP binding cassette efflux pump encoding gene Rv1473 which might be involved in antibiotic resistance. Methods: Mycobacterium smegmatis was used as a surrogate model for pathogenic mycobacteria, drug susceptibility assays and ethidium bromide accumulation assay were harnessed to verify drug resistance. The real-time quantitative PCR was used to evaluate the transcription levels of WhiB7 and Ms3140 upon exposure to macrolides. Results: Rv1473 contributes to macrolides resistance via efflux mechanisms, and was positively regulated by the transcription factor WhiB7 upon macrolides exposure. Conclusion: Rv1473 is a novel ATP binding cassette efflux pump involved in mycobacterium intrinsic antibiotics resistance via efflux mechanism. This finding will facilitate novel antibiotic discovery and the treatment of pathogen, especially for nontuberculous mycobacteria.

We established an aptamer fluorescence microscopy approach for rapid detection of MTB in clinical sputum samples. The use of aptamer probes was proven to significantly increase the sensitivity of sputum smear microscopy.