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Date of Award
Bachelor of Science (BS)
Department of Biology
Methicillin-resistant Staphylococcus aureus (MRSA) gains resistance to β-lactam antibiotics through a mutated penicillin binding protein (PBP2a) encoded on the SCCmec element. In combination with the recombinase encoded by ccr, these two genes are used as markers of the mobile genetic element (SCCmec). Due to recent increases in community acquired MRSA infections, the mechanisms of antibiotic resistance gene transfer have gained attention. Transduction, a method of horizontal gene transfer mediated by bacteriophage, is believed to be responsible for the movement of the SCCmec element. Recent studies have shown the transduction of the SCCmec element in clinical isolates; however, this study is more concerned with transduction in the environment. The preliminary study presented here was based on two studies demonstrating the presence of the mecA gene in viral fractions from environmental sources by polymerase chain reaction (PCR). This study aimed to confirm the presence of the SCCmec element in environmental bacteriophage populations through PCR analysis and sequencing. Approximately 22% of the environmental samples collected contain mecA and/or ccr. One positive sample was sequenced, confirming the presence of the mecA gene and defining it as Type 1. Samples from non-fecal sources were more likely to contain one or both genes, and compost samples have the greatest percent (65%) positive. This preliminary study left many questions unanswered, spurring a second study with goals to determine the frequency of transduction and the allotype of the SCCmec element most frequently transduced. A number of bacterial isolates were collected and characterized. This works sets the stage for isolation of phages and transduction experiments in the future. The results of this work will lead to a better understanding of how antibiotic resistance genes are transferred in the environment, which could lead to preventative applications.
Sauder, Amber B., "Transduction as the method of horizontal gene transfer of the Staphylococcal Chromosomal Cassette mec (SCCmec)" (2015). Senior Honors Projects, 2010-current. 76.