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The role of metabolic shifts and drug transporters in the response of M. avium to antibiotic stress

ABSTRACT: Background: Mycobacterium avium complex (MAC) bacteria cause opportunistic infections in humans. Treatment yields cure rates of 60% and is comprised of a macrolide, a rifamycin and ethambutol; and in severe cases amikacin. Mechanisms of antibiotic tolerance remain mostly unknown. To elucidate these mechanisms, we studied the transcriptomic response to antibiotics and investigated the contribution of efflux and amikacin modification to susceptibility. Methods: M. avium was subjected to subinhibitory concentrations of clarithromycin, amikacin, ethambutol and rifampicin followed by RNA sequencing. Based thereupon, we characterized M. avium efflux pumps and performed time-kill kinetic analysis using each antibiotic in combination with the efflux pump inhibitors (EPIs) berberine, verapamil and CCCP to study the role of efflux on susceptibility. Finally, we studied the modification of amikacin by M. avium using metabolomic analysis. Results: Changes in respiratory state and changes in ribosome binding and protein folding likely contribute to clarithromycin and amikacin tolerance, respectively. No clear drug-specific mechanisms of tolerance are found for ethambutol and rifampicin. Of the EPIs, only berberine increased the susceptibility to rifampicin and clarithromycin. Finally, we show that M. avium, in contrast to M. abscessus, is not able to modify amikacin. Conclusion: M. avium likely relies on a combination of drug-specific and generic mechanisms of antibiotic tolerance including changes in respiratory and metabolic state in addition to drug efflux and target modification. Efflux inhibition can increase susceptibility but this effect is EPI and antibiotic specific. Finally, the lack of amikacin modifying activity in M. avium is important for its activity.

ORGANISM(S): Mycobacterium avium subsp. hominissuis

PROVIDER: GSE213116 | GEO | 2024/01/01

REPOSITORIES: GEO

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Project description:Indole is ubiquitously synthesized by plants and bacteria and functions as an inter species signaling molecule to modulate a wide variety of cellular activities. However, it is not clear how the indole signal is perceived and responded by plant growth promoting rhizobacteria (PGPR) at the rhizosphere. Here, we demonstrated that indole enhanced antibiotic tolerance of Pseudomonas fluorescens 2P24, a PGPR well known for its biocontrol capacity. By conducting quantitative proteomic analysis, we showed that indole influences the expression of multiple genes including the emhABC operon encoding the major multidrug efflux pump in P. fluorescens 2P24. The indole-induced antibiotic tolerance was not related to bacterial dormancy or slow growth, but depended on the emhABC operon and the divergently transcribed TetR-like regulator emhR. By binding to the semi-palindromic operator sequence, EmhR repressed the expression of emhABC. It was further revealed that indole bound to EmhR and weakened the interaction between EmhR and the operator. This is consistent with our finding that indole-induced expression of the EmhABC efflux pump is dependent on EmhR. Using homology modeling and molecular dynamics simulation, we found that indole binding resulted in significantly decreased distance between the two DNA-recognizing α3 helices within the EmhR dimer, which would possibly account for its compromised DNA binding capacity. EmhR was further shown to globally influence protein expressions, especially transporters and proteins involved in the denitrification pathway. This EmhR-dependent, indole-induced antibiotic tolerance is likely to be prevalent in the Pseudomonas species, as the EmhR homologue in Pseudomonas syringae was also shown to be responsible for the indole-induced antibiotic tolerance. Taken together, our results revealed an indole-sensing transcription factor EmhR responsible for indole-induced antibiotic tolerance in Pseudomonas species and have important implications on the general mechanism for the indole sensing and responses in rhizobacteria.

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The role of metabolic shifts and drug transporters in the response of M. avium to antibiotic stress

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