Transcript Staphylococcus aureus - York College of Pennsylvania

A Comparison of Staphylococcus aureus Isolates from
Laboratories LS 203 and LS 224 at York College of Pennsylvania
Jacqueline Boyle
Department of Biological Sciences, York College of Pennsylvania
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.
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).
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.
Discussion
Methods
Figure 1
LS 203
LS 224
Collection of Samples
• samples collected using
sterile cotton swabs
• swabs were placed in sterile
tubes containing staph broth
a
b
d
e
f
g
Incubated samples @
37°C for 72 hours
c
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.
Conclusions
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)
h
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
Table 1. Each object sampled and whether it tested positive
or negative for Staphylococcus aureus.
Area Sampled
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).
DOORKNOB (back door)
DOORKNOB (front door)
GARBAGE CAN (front)
CABINET HANDLE
CHAIR1
CHAIR2
CHAIR3
LIGHT SWITCH (front)
BACK BENCH
MIDDLE BENCH
INCUBATOR
BALANCE
MICROWAVE
EQUIPMENT COUNTER
SUPPLY COUNTER
Total
LS 203
LS 224
+
+
+
+
+
5
+
+
+
3
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.
Literature Cited
Jacobs, S., Williamson, G., and Willis, A. 1961. Nasal
abnormality and the carrier rate of Staphyloccocus
aureus. J. clinical Pathology 519-521.
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., MizutaniUi, 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. 2001.
Whole genome sequencing of meticillin-resistant
Staphylococcus aureus. The Lancet 357:1225-1238.
Ostle, B. 1963. Statistics in Research: basic concepts and
techniques for research workers. 2nd ed. The Iowa
State University Press, Ames, Iowa.
Acknowledgements
Dr. Carolyn Mathur, Research Mentor
Dr. Karl Kleiner
Mrs. Barbara Taylor
Dr. Bruce Smith