High-level antibiotic tolerance of a clinically-isolated Enterococcus faecalis strain.

High-level antibiotic tolerance of a clinically-isolated Enterococcus faecalis strain. Appl Environ Microbiol. 2020 Oct 23;: Authors: Gu H, Roy S, Zheng X, Gao T, Ma H, Soultan Z, Fortner C, Nangia S, Ren D Abstract Bacteria can survive antibiotic treatment both by acquiring antibiotic resistance genes, and through mechanisms of tolerance that are based on phenotypic changes and the formation of metabolically inactive cells. Here, we report an Enterococcus faecalis strain (E. faecalis UM001B) isolated from a cystic fibrosis patient that has no increase in resistance but extremely high-level tolerance to ampicillin, vancomycin, and tetracycline. Specifically, the percentage of cells that survive 3.5-h antibiotic treatment (at 100 μg ⋅mL-1) is 25.4 ± 4.3% and 51.9 ± 4.0% for ampicillin and tetracycline, respectively; and vancomycin does not exhibit any significant killing. Consistent with the change in antibiotic susceptibility, UM001B is found to have reduced penetration of ampicillin and vancomycin, and accumulation of tetracycline compared to the reference strain ATCC29212. Based on whole-genome sequencing (WGS), four amino acid variants are identified in one of the tetracycline efflux pump repressors (TetRs) compared to ATCC29212. Results of molecular simulations and experimental assays reveal that these mutations can lead to a higher level of tetracycline efflux activity. Consistently, replicating these mutations in Escherich...
Source: Applied and Environmental Microbiology - Category: Microbiology Authors: Tags: Appl Environ Microbiol Source Type: research