A Comparison of Staphylococcus aureus Isolates from Laboratories LS 203 and LS 224 at York College of Pennsylvania Introduction Staphylococcus aureus causes a variety of human diseases ranging in severity from skin infections and food poisoning to more lethal diseases such as pneumonia and toxic-shock syndrome (Kuroda et al. 2001). S. aureus is one of the most pathogenic species of staphylococci and is a major cause of nosocomial infections. In addition, it is becoming increasingly associated with community-acquired diseases. Isolates of Staphylococcus aureus can be found most commonly in the nasal membranes, throat, and skin of some healthy individuals, which makes it easy to spread these illnesses in public places (Jacobs et al. 1961). b h gf ed LS 224 LS 203 Area Sampled LS 203 LS 224 DOORKNOB (back door) -- DOORKNOB (front door) +- GARBAGE CAN (front) +- CABINET HANDLE ++ CHAIR 1 ++ CHAIR 2 +- CHAIR 3 -- LIGHT SWITCH (front) -+ BACK BENCH -- MIDDLE BENCH -- INCUBATOR -- BALANCE -- MICROWAVE -- EQUIPMENT COUNTER -- SUPPLY COUNTER -- Total 53 Objectives ► To survey the frequency of Staphylococcus aureus in biology labs LS 224 and LS 203. ► To compare the number of areas in each lab that tested positive for Staphylococcus aureus. ► To observe and compare specific objects/sites found to contain S. aureus in both laboratories. Figure 1. Gram stained slides that contained S. aureus. Red circles indicate clusters of Staphylococcus aureus. a) front light switch b) cabinet handle c) chair d) chair e) front doorknob f) chair g) cabinet handle h) front garbage can Figure 1 Table 1. Each object sampled and whether it tested positive or negative for Staphylococcus aureus. Collection of Samples samples collected using sterile cotton swabs swabs were placed in sterile tubes containing staph broth Incubated 37°C for 72 hours Streak Plate Method all samples were plated on mannitol salt agar containing a phenol red indicator one sample on each plate Allowed bacteria to grow for 4 days Gram Stain Yellow colonies from plates Slide Agglutination Test All samples with yellow bacterial growth (test for coagulase)Methods a c Conclusions 1) No apparent difference in the amount of positive sites between the two labs. 2) No obvious difference between the specific objects containing S. aureus in each laboratory. Results 5 out of 15 samples (33%) in LS 203 were positive for S. aureus (Table 1). 3 out of 15 samples (20%) contained Staphylococcus aureus in LS 224 (Table 1). 3 samples in LS 203 were positive for S. aureus while the same 3 sites in LS 224 were negative. Only one sample in LS 224 was positive while the same object in LS 203 was negative. There was an insufficient sample size to conduct a sign test (Ostle 1963). Literature Cited Jacobs, S., Williamson, G., and Willis, A Nasal abnormality and the carrier rate of Staphyloccocus aureus. J. clinical Pathology Kuroda, M., Ohta, T., Uchiyama, I., Baba, T., Yuzawa, H., Kobayashi, I., Cui, L., Oguchi, A., Aoki, K., Nagai, Y., Lian, J., Ito, T., Kanamori, M., Matsumaru, H., Maruyama, A., Murakami, H., Hosoyama, A., Mizutani- Ui, Y., Takahashi, N., Sawano, T., Inoue, R., Kaito, C., Sekimizu, K., Hirakawa, H., Kuhara, S., Goto, S., Yabuzaki, J., Kanehisa, M., Yamashita, A., Oshima, K., Furuya, K., Yoshino, C., Shiba, T., Hattori, M., Ogasawara, N., Hayashi, H., Hiramatsu, K Whole genome sequencing of meticillin-resistant Staphylococcus aureus. The Lancet 357: Ostle, B Statistics in Research: basic concepts and techniques for research workers. 2 nd ed. The Iowa State University Press, Ames, Iowa. Jacqueline Boyle Department of Biological Sciences, York College of Pennsylvania Acknowledgements Dr. Carolyn Mathur, Research Mentor Dr. Karl Kleiner Mrs. Barbara Taylor Dr. Bruce Smith Discussion Only four out of the fifteen paired samples revealed contrasting results. All other results were the same for both labs. Although LS 203 had a slightly higher number of samples that tested positive for Staphylococcus aureus, the difference between the two labs was not evident. A larger sample size would have been necessary in order to carry out the sign test and show whether there was a significant difference between the two laboratories.Abstract The majority of infections caused by Staphylococcus aureus are acquired in hospitals, but it is becoming more common to contract these illnesses through public places in the community. The purpose of this experiment was to test two laboratories and compare the areas that test positive for Staphylococcus aureus in each location. Standard methods such as gram staining were used as well as a slide agglutination test. Data revealed 33% of the samples tested positive for S. aureus in LS 203 and 20% in LS 224. No substantial difference in the prevalence S. aureus could be confirmed between the two labs.