Indoor Dust Microbes Contain Mobile Antibiotic Resistance Genes

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In indoor environments, bacteria face selective pressure to carry antibiotic resistant genes (ARGs) from antimicrobial substances used in furniture, building materials, and personal care products. Humans rely on antibiotics to clear bacterial infections, so understanding the way in which these genes are transferred, i.e., on mobile genetic elements, is critical. To investigate this phenomenon, dust samples were collected from over 100 collection sites in over 40 different athletic facilities. DNA from these samples was sequenced to assemble a metagenomic database, which was analyzed to locate ARGs in mobile genetic elements. In parallel, bacteria were cultured from these samples and exposed to antibiotics to screen for resistance phenotypes, and plasmid DNA was extracted from resistant species. From the metagenomics data, the ARG gidB was found only on plasmids, a common method of horizontal gene transfer. This gene codes for resistance to streptomycin, an antibiotic used to treat tuberculosis. Seven strains of streptomycin-resistant bacteria were identified from the culture isolates. To confirm the presence of gidB on plasmids in resistant bacteria, PCR primers were developed by dividing known sequences of gidB genes into categories based on their phylogenetic tree. This gene evolves quickly, so creating more than one specific primer was necessary. Optimization is ongoing to uniquely amplify this gene. Once gidB is identified in plasmid DNA, future experimentation will determine if this gene can be passed to other species of bacteria through conjugation. These results will direct future recommendations for antibiotic development and indoor environment design.

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  • 06/13/2018
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