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A variety of gram-positive bacteria carry mobile mef genes
1Department of Pathobiology, School of Public Health and Community Medicine, University of Washington, Seattle 98195-7238, USA.
Abstract:
The mefE gene codes for a membrane bound efflux protein, which confers resistance to macrolides, and has been identified in Streptococcus pneumoniae. A variety of gram-positive organisms were examined. Twenty-six isolates of S. pneumoniae carried mefE and were resistant to erythromycin (MIC of 2-16 mg/L). Two additional isolates of Emr S. pneumoniae carried both ermB and mefE(MIC of 16-128 mg/L). One Micrococcus luteus, one Corynebacterium jeikeium, three Corynebacterium spp., two viridans streptococci and seven Enterocccus spp. also carried mef genes. It was possible to move the mef gene from all 11 S. pneumoniae tested to susceptible S. pneumoniae and/or Enterococcus faecalis recipients. The addition of DNase (1 g/L) did not affect the gene transfer. It was also possible to move the mef gene from donor Enterococcus spp., viridans streptococci, M. luteus, C. jeikeium and Corynebacterium spp. to E. faecalis recipients. Transconjugant isolates were resistant to erythromycin (MIC = 16 mg/L). Hybridization with a labelled mef oligonucleotide probe against Southern blots and bacterial dot blots confirmed the presence of the mef genes. This is the first time that a mobile mef gene has been identified in four different genera, from three distinct geographical locations.
Insights
The mobile mefE gene confers macrolide resistance in bacteria. This study found the mobile mef gene in four genera across three locations, highlighting its widespread dissemination.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- The mefE gene encodes a membrane-bound efflux protein conferring macrolide resistance.
- MefE-mediated resistance is primarily observed in Streptococcus pneumoniae.
Purpose of the Study:
- To investigate the presence and mobility of the mefE gene in various Gram-positive bacteria.
- To determine the geographical distribution and inter-species transferability of the mefE gene.
Main Methods:
- Screening of Gram-positive bacterial isolates for mef genes using hybridization.
- Gene transfer experiments using conjugation assays with susceptible recipients.
- Confirmation of gene presence via Southern and dot blot hybridization.
Main Results:
- The mefE gene was identified in Streptococcus pneumoniae, Micrococcus luteus, Corynebacterium jeikeium, Corynebacterium spp., viridans streptococci, and Enterococcus spp.
- MefE-mediated erythromycin resistance (MIC 2-16 mg/L) was observed in S. pneumoniae.
- The mefE gene was successfully transferred between various bacterial genera, conferring erythromycin resistance (MIC = 16 mg/L) in transconjugants.
- The mefE gene was found in isolates from three distinct geographical locations.
Conclusions:
- The mefE gene is present and mobile in a diverse range of Gram-positive bacteria, including four different genera.
- This mobility facilitates the spread of macrolide resistance among clinically relevant bacteria.
- The identification of mobile mef genes across multiple geographical locations underscores a significant public health concern regarding antibiotic resistance.