Biochemical and molecular identification of coagulase negative staphylococcal strains from university students and the genetic transfer mechanisms of antibiotic resistance

The appearance of methicillin resistant staphylococcal strains has been cause for concern in clinical and community settings. The mechanism for methicillin resistance is conferred by the mecA cassette which encodes for the penicillin binding protein 2A. Nasal and pharyngeal swabs were obtained from 478 students attending Texas A&M University Kingsville. Samples collected from students were then streaked on mannitol salt agar, a selective and differential medium used to isolate and distinguish staphylococcal species based on the organisms’ ability to ferment mannitol. Staphylococcal strains were identified at the biochemical level using antibiotic disc diffusion, enzymatic activity, and differential carbohydrate fermentation. In order to identify staphylococcal species at the molecular level, the RNA polymerase subunit B gene was amplified using polymerase chain reaction methodology and the resulting product was sequenced. Amplification of mecA by polymerase chain reaction confirms that antibiotic resistance in methicillin resistant staphylococci is due to PBP 2a rather than a β-lactamase activity. Samples identified through this process were then used for bacterial mating procedures to identify the possible genetic transfer mechanisms of antibiotic resistance between antibiotic resistant and non-antibiotic resistant bacterial species. Culture mating was carried out using an oxacillin resistant coagulase negative staphylococcal species as the donor and an oxacillinsensitive Staphylococcus aureus. This aim of this study is to identify oxacillin resistant coagulase negative staphylococcal species found in university students and confirm the presence of mecA. Staphylococcal species carrying the mecA cassette may act as reservoirs for transformation of pathogenic Staphylococcus aureus into antibiotic resistant strains that are very difficult to treat and may lead to serious health issues or possibly death for these students