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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-

2012Staci M. MillerDepartment 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).

Perc

enta

ge o

f Coa

gula

se P

ositi

ve

Male0

5

10

15

20

25

30

35

401

Female

*

*

n=144

HC

2

NHCG

3

Coagulase

B-lactomase

NG

n=167

n=621

n=542

n=155

n=131

n=633

n=555

n=356

n=316

n=432

n=370

Fall 0

7

Sprin

g 08

Fall 0

8

Sprin

g 09

Fall 0

9

Sprin

g 10

Fall 1

0

Sprin

g 11

Fall 1

1

Sprin

g 12

0

10

20

30

40

50

60

70

Coagulase +β lactamase +

Perc

en

tag

e o

f P

osit

ive

Sam

ple

s 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 CitedCenter 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/.

AcknowledgmentsI 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.

ConclusionPrevalence 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).

B-Lactomase

Coagulase

0 5 10 15 20 25

Percent Positive

n= 788

n= 686

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).

Spring

Fall

26 26.5 27 27.5 28 28.5 29

Percentage of Coagulase Pos-itive

n= 280

ResultsMethods

Nose Samples Collected from Fall 2011 and Spring 2012

Cultured in Staphylococcus

enrichment broth

Mannitol Salt Agar Testing

Coagulase Testing

Beta-Lactamse Testing

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