1. commons.wikimedia.org Introduction  Staphylococcus aureus (SA) is a gram- positive cocci bacterium. The Methicillin- resistant SA (MRSA) is a strain resistant to B-Lactam antibiotics such as methicillin, penicillin, and amoxicillin (CDC 2013).  SA emerged in the mid 1940’s and the first CA (community associated)-MRSA case in the United States was reported in 1980 (DeLeo and Chambers 2009).  The most common site of SA carriage is in the nose (Munckhof et al 2008).  Hospital associated MRSA (HA-MRSA) and Community associated MRSA (CA-MRSA) are the two forms of SA infection. HA-MRSA is when patients have risk factors such as recent hospital stay, catheters, or dialysis. CA-MRSA would not have these risk factors (Naimi et al 2003).  Skin and soft tissue infections are the most common symptoms of CA-MRSA, which is the most frequent cause of skin and soft tissue infection in the emergency room (Klevens et al 2007) (DeLeo and Henry 2009).  CA-MRSA has been identified among numerous populations such as high schools, athletic team facilities, and child daycare centers (DeLeo and Henry 2009) (Stevens et al 2010 ). Objectives  To determine if gender, attendance at a gym, or working in healthcare affect the prevalence of CA-MRSA.  To determine the prevalence of CA-MRSA in nasal samples collected biannually from York College students from 2007-2012.  To determine if the prevalence of CA-MRSA varies annually or seasonally (spring vs. fall ). Prevalence of Staphylococcus aureus among York College Students: 2007-2012 Staci M. Miller Department of Biological Sciences, York College of Pennsylvania Figure 3. The prevalence of coagulase positive SA (2007-2012) and B-Lactamase positive SA (2008-2012) nasal samples for the following categories: gender (Male vs. Female); work in healthcare (HC vs. NHC); and participation in a gym (G vs. NG). Prevalence was compared with a Fisher's Exact two-tailed test. 1) Prevalence of coagulase positive SA was greater in males than in females (p=0.0401) and there was no difference between genders when measuring B- Lactamase (p= 0.3668). 2) Comparing HC with NHC there was no difference for coagulase positive SA (p= 0.3395) and no difference for prevalence of B-Lactamase samples (p=0.1609). 3) There was no difference between G and NG samples for coagulase positive SA and B-Lactamase tests (p=0.1247 and p=0.1127 respectively). Percentage of Coagulase Positive n=167 n=621 n=542 n=155 n=131 n=633 n=555 n=356 n=316 n=432 n=370 Figure 4. Prevalence of coagulase positive SA and B- Lactamase nasal samples from 2007-2012. The data looks to be following a natural wave of bacterial infection over time. Literature Cited Center for Disease Control and Prevention. 2010. Definition of MRSA. Retrieved March 20, 2013 from http://www.cdc.gov/mrsa/definition/index.html. DeLeo, F. and Chambers, F. 2009. Reemergence of antibiotic-resistant Staphylococcus aureus in the genomics era. The Journal of Clinical Investigation. 119: 2464- 2474. Klevnes, M., Morrison, M., Nadle, J., Petit, S., Gershman, K., Ray, S., Harrison, L., Lynfield, R., Dumyati, G., Townes, J., Craig, A., Zell, E., Fosheim, G., McDougal, L., Carey, R. and Fridkin, S. 2007. Invasive Methicillin-Resistant Staphylococcus aureus infections in the United States. The Journal of the American Medical Association. 298: 1763-1771. Munckhof, W.J., Nimmo, G.R., Schooneveldt, J.M., Schlebusch, S., Stephens, A.J., Williams, G., Huygens, F. and Giffard, P. 2008. Nasal carriage of Staphylococcus aureus, including community-associated methicillin-resistatnt strains, in Queensland adults. European Society of Clinical Microbiology and Infectious Diseases. 15: 149-155. Naimi, T., LeDell, K., Como-Sabetti, K., Borchardt, S., Boxrud, D., Etienne, J., Johnson, S., Vandenesch, F., Fridkin, S., O’Boyle, C., Danila, R. and Lynfield, R. 2003. Comparison of Community and Health Care-Associated Methicillin-Resistant Staphylococcus aureus infection. The Journal of the American Medical Association. 290: 2976-2984. Stevens, M., Hennessy, T., Baggett, H., Bruden, D., Parks, D. and Klejka, J. 2010. Methicillin-Resistant Staphylococcus aureus Carriage and Risk Factors for Skin Infections, Southwestern Alaska, USA. Emerging Infectious Diseases. 15: 797- 803/. Acknowledgments I would like to thank Dr. Mathur for all her help throughout my senior thesis experiences. She has helped me learn a lot and improve as a student. I would also like to thank previous students for providing SA data, since 2007, that contributed to the depth of my study. Conclusion  Prevalence of coagulase positive SA was higher in males than females (p=0.0401). The difference could be due to hygiene differences between males and females (Stevens et al 2010).  The prevalence of coagulase positive SA and B-Lactamase was not affected by the gym or healthcare workers. Healthcare workers may be more likely to be exposed to drug-resistant pathogens, but was not significantly different in this study.  Coagulase positive SA samples were not affected by season (Spring and Fall) (p=0.6771).  Comparing coagulase positive samples to the B-Lactamase samples 40.54% of the time the coagulase positive SA samples were also positive for B-Lactamase, which is an antibiotic resistant strain of SA. A study done in 2003 showed about 25% of all SA infections were MRSA, which is lower than the average at York College (Naimi et al 2003). Figure 2. Prevalence of coagulase positive and B- Lactamase positive nasal samples from 2007- 2012. About forty-one percent of coagulase positive samples were B-Lactamase positive. n= 508 Figure 1. Seasonal comparison showing coagulase positive nasal sample prevalence from 2007-2012. There was no difference in prevalence between fall and spring (p=0.6771 ). Results Methods Nose Samples Collected from Fall 2011 and Spring 2012 Cultured in Staphylococcus enrichment broth Mannitol Salt Agar Testing Coagulase Testing Beta-Lactamse Testing www.flickr.com