Factors influencing Staphylococcus aureus Nasal Carriage Rate and
Antibiotic Resistance Prevalence among College Students: 2007-2012
Joshua E. Fabie* & Carolyn F. Mathur
Department of Biological Sciences, York College of Pennsylvania 17403
Methods
Cultured in
Staphylococcus
enrichment broth
Nasal samples
collected
Abstract
n=57*
A
Percent Positive
30
16S ribosomal DNA
extraction and
amplification for
sequencing
Individual positive
colonies grown in
slants
B
C
n=105
n=173
25
n=157*
n=109
n=41
20
15
% coag
% β-lac
*
n=27
n=23
10
n=55
*
n=75
n=71
n=43
5
0
Male
Female
HC
NHC
G
NG
Figure 1. The prevalence of CPSA (2007 to 2012) and β-lactamase positive CPSA
(2008-2012) nasal samples are isolated by gender (Male vs. Female); healthcare
exposure (HC vs. NHC); and gym participation (G vs. NG). Prevalence was
compared with a Fisher’s exact two-tailed test. A) Prevalence of CPSA was
greater in males than females (p = 0.0148*), while there was no difference
between genders when measuring β-lactamase in the isolates (p = 0.3558).
B) When comparing healthcare exposure, there was no difference for CPSA (p =
0.5615), but the prevalence of β-lactamase was higher in the HC samples
compared to NHC (p = 0.0051*). C) Differences were not relevant between G
and NG samples for the CPSA or β-lactamase tests (p = 0.2376 and p = 0.0743).
n= 35
Spring
Figure 2. Comparison of
the prevalence of CPSA
and β-lactamase positive
% β-lac CPSA by season. No
% Coag difference was determined
between spring and fall for
CPSA or β-lactamase (p =
0.5009 and p = 0.5650).
n= 72
n= 63
Fall
n= 142
0
Objectives
5
10
15
20
Percent Positive
50
25
30
n= 55
45
Percent Coagulase Positive
• To determine the prevalence of CPSA and
β-lactamase in nasal samples collected
biannually from college students from
2007 through 2012
• To determine if gender, healthcare
exposure, or gym participation relates to
prevalence rates of CPSA and β-lactamase
in the aforementioned samples
• To determine if the prevalence of CPSA and
β-lactamase in the above samples varies
annually or seasonally (fall vs. spring)
β-lactamase
testing
35
Introduction
• Staphylococcus aureus (SA) is an established facultative
anaerobic Gram positive coccal bacterium due to a
combination of high carriage rates and its immunoevasive strategies.
• Coagulase production is a known virulence factor; the
enzyme protease converts fibrinogen to fibrin providing
resistance from phagocytosis (Wan et al 2013).
• The blaZ gene allows for production of β-lactamase
which affords SA resistance to antibiotics containing a
β-lactam ring (Pitkälä et al 2007).
• A new SA strain, Community-acquired coagulase
positive SA (CA-CPSA), is infecting young, healthy
individuals, and it is infiltrating hospitals replacing less
aggressive nosocomial SA strands (D'Agata et al 2009).
• CA-CPSA most often subsists on the soft mucosal
membranes of the nose and is capable of spreading
rapidly in areas where carriers gather (Munckhof et al
2009).
Mannitol salt agar
streak plates
Results
uwsscience.wordpress.com/tag/mrsa/
Potentially pathogenic Staphylococcus aureus (Sa) is important in clinical
medicine due to its ability to persist within the human respiratory tract and
on the skin under certain conditions. In order to understand more about
this interaction, an ongoing study of the nasal carriage rates of Sa and
antibiotic resistance prevalence in college students has been underway since
2007. This report is an update covering data from 2007 through 2012. Nasal
swabs were cultured in staphylococcus enrichment broth, and further tested
for positive, yellow growth on mannitol-salt agar, and for the presence of
coagulase (CPSa if positive) and β- lactamase( in CPSa samples only).
Overall, 214/881 (24%) of samples taken were coagulase -positive Sa (CPSa),
which agrees the prevalence reported in other studies and with our previous
reports. Forty-six percent of CPSa carriers were also positive for βlactamase, indicating high levels antibiotic resistance among these
individuals. Males had a higher prevalence of CPSa compared to females,
(p=0.0148, Fisher exact two-tailed test). CPSa carriers who had regular
contact with a health-care environment had higher β-lactamase prevalence
compared to non-health care individuals (p = 0.0051). However, the actual
CPSa carriage rate did not differ in these 2 groups (p = 0.5614). In addition,
no differences were found comparing gym and non-gym users for CPSa (p =
0.2376) and β-lactamase activity (p = 0.0743). No seasonal (spring vs. fall)
differences in CPSa prevalence (p=0.5650) or β-lactamase activity (p =
0.5650) were detected.
Coagulase
testing
40
35
30
n= 103
n= 93
n= 124
n= 57
n= 102
25
n= 80
n= 89
n= 90
n= 37
n= 57
S. aureus 1000x
Conclusion
• Overall nasal carriage of CPSA was 24.3%, which
is slightly less than the carriage rates of 25 to
30% reported by the CDC (2013). Out of the
CPSA samples, 45.8% were β-lactamase positive,
which is high compared to similar studies (Talan
et al 2011). This could be because carriage
rates peak in young adult populations and
progressively decline with increasing age
(Munckhof et al 2009).
• The higher prevalence of nasal CPSA for males
(31.5%) over females (22.4%) was paralleled in
other studies; Munckhof et. al. (2009) found
carriage rates of 24.6% for females and 34.8%
for males. However, further research is
necessary to determine the mechanism for
gender differences in carriage in young
populations (Kupfer et al. 2010).
• The prevalence of CPSA resistant to β-lactam
antibiotics was higher in students exposed to
health care settings (p = 0.0051). Although
there was no difference in the CPSA levels alone,
students involved in health care may have a
higher risk of exposure to resistant strains of Sa.
• Sequencing were not obtained due to ineffective
extraction most likely due to complications
caused by G+ cell wall.
Literature Cited
Centers for Disease Control and Prevention. (2013). Definition of MRSA. Retrieved
February 12, 2013 from http://www.cdc.gov/mrsa/definition/index.html
D'Agata, Erica M. C.; Webb, Glenn F.; Horn, Mary Ann; Moellering Jr., Robert C., &
Shigui Ruan. 2009. Modeling the Invasion of Community-Acquired MethicillinResistant Staphylococcus aureus into Hospitals. Clinical Infectious Diseases.
48(3), 274-284.
Kupfer, M., Jatzwauk, L., Monecke, S., Möbius, J., & Weusten, A. 2010. MRSA in a
large German University Hospital: Male gender is a significant risk factor for
MRSA acquisition. GMS Krankenhaushygiene Interdisziplinär, 5(1), 1-8.
Munckhof, W. J., Nimmo, G. R., Schooneveldt, J. M ., Schlebusch, S. S., Stephens,
A. J., Williams, G. G., & Giffard, P. P. 2009. Nasal carriage of Staphylococcus
aureus, including community-associated methicillin-resistant strains, in
Queensland adults. Clinical Microbiology & Infection, 15(2), 149-155.
Pitkälä, L. Salmikivi, P. Bredbacka, A.-L. Myllyniemi1, & M. T. Koskinen. 2007.
Comparison of Tests for Detection of β-Lactamase-Producing Staphylococci.
Journal of Clinical Microbiology. 2031-2033.
Talan, D. A., Krishnadasan, A., Gorwitz, R. J., Fosheim, G. E., Limbago, B., Albrecht,
V., & Moran, G. J. 2011. Comparison of staphylococcus aureus From Skin and
Soft-Tissue Infections in US Emergency Department Patients, 2004 and 2008.
Clinical Infectious Diseases, 53(2), 144-149.
Wan, M., Lauderdale, T., & Chou, C. (2013). Characteristics and virulence factors of
livestock associated ST9 methicillin-resistant Staphylococcus aureus with a
novel recombinant staphylocoagulase type. Veterinary Microbiology, 162(2-4),
779-784.
20
Acknowledgments
15
10
5
0
Fall 07
Spring 08
Fall 08
Spring 09
Fall 09
Spring 10
Fall 10
Spring 11
Fall 11
Spring 12
Figure 3. Semester trends in prevalence of CPSA nasal samples from 2007 to 2012
Fall 12
I would like to thank C. Taylor, A. Newson, R. Cheng, S.
Giordano, M. Branche, C. Cusick, and S. Miller for
providing SA data since 2007 that contributes to the
depth of my data set.