The Presence of Foodborne
Pathogens on Public Surfaces
Jennifer L. Stanley
Gabrielle F. Clodomir
Background
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Pathogenic microorganisms found normally in healthy animals used
for food can contaminate these products and be passed on to
humans.
Many bacteria have been found to survive from hours to weeks on
non-porous surfaces and inanimate objects have been found to play
a role in the transmission of human pathogens (Reynolds et al.
2005). Extremely pathogenic strains of E. coli have been found to
survive on stainless steel, a common surface material, for up to 28
days (Wilks et al., 2005).
The potential for contamination of public surfaces at the University
of Maryland is great. Hundreds if not thousands of people may come
in contact with a single door handle in a single day. Foodborne
pathogens have the potential to spread in dining halls and other
areas where food is prepared and/or eaten.
Background

The presence of S. aureus, Salmonella, and E. coli on several public
surfaces was tested.
– door handle, table top, and fork from a University of Maryland dining
hall
– keyboard and toilet lever found in the Microbiology building, and a
personal cell phone.

It was projected that the common food-borne pathogens
Escherichia coli, Salmonella, and Staphylococcus aureus will be
found on these surfaces, indicating that stricter precautions must be
followed to prevent contamination of these surfaces and to prevent
transmission of these organisms to humans.
Protocol
A door handle, table, and fork from the South Campus Dining
Hall, a keyboard and toilet lever in the Microbiology building, and
a personal cell phone were tested for the presence of three
bacterial organisms.
Two samples were taken from the same location on each surface.
A third sample was taken after the use of a disinfectant (Clorox
Disinfecting Wipes) on the location.
Selective media was used to determine the presence of S. aureus,
Salmonella, and E.coli each sample. The spread plate technique
was used. Samples were plated on TSA as well.
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–
–
–
MacConkey media: E. coli
Bismuth Sulfite: Salmonella
Chapman Agar: S. aureus
Protocol
1.
2.
3.
4.
5.
6.
7.
A sterile cotton swab was dipped in saline solution and used to
collect each sample.
The surface was swiped once with the cotton swab and placed in
a sterile container.
A second sample was taken with a new sterile cotton swab at the
exact same location as the first sample.
A third sample was taken using Clorox Disinfecting Wipes to clean
the surface prior to collection of the sample.
Each swabs was dipped in a tube containing 1 mL of saline and
vortexed. .1 ML of each sample was plated onto one TSA,
MacConkey, Bismuth Sulfite, and Chapman media plate.
All plates were incubated for 48 hours at 37 degrees Celsius
(MacConkey, Bismuth Sulfite, TSA) and 30 degrees Celsius
(Chapman)
After 48 hours, results were observed.
Results
Door handle
The TSA plate
contained two types
of white colored
colonies.
 No growth was found
on the MacConkey,
Bismuth Sulfite, or
Chapman Agar plates.

Sample 1 on TSA
Results
Fork
Two types of colonies
were found on the
TSA Plates.
 No growth was found
on the MacConkey,
Bismuth Sulfite, or
Chapman Agar plates.

Sample 1 on TSA
Results
Table
Sample 1 of the TSA
plate contained yellow
colonies. Sample 3
contained several
different types of
colonies.
 No growth was found
on the MacConkey,
Chapman, and
Bismuth Sulfite Agar
plates.

TSA Sample 1
Results
Keyboard
This section of the experiment was repeated after observing excessive
growth on sample 3 plates.
First Set of Samples
 The TSA plate for sample one
yield several yellow and white
colonies. Sample 2 and the control
contained a potential mold
contaminant.
 The Chapman plate for sample 2
contained several colonies. The
sample 3 plate contained many
yellow and white colonies.
 The first set of samples taken
produced no colony growth on
MacConkey or Bismuth Sulfite
plates.
Second Set of Samples
 The TSA plates for samples 1 and
2 contained several small colonies
 The sample 1 Chapman agar plate
contained several yellow colonies.
 No colonies were found on any of
the sample 3 plates.
 The second set of samples also
produced no growth on the
MacConkey and Bismuth Sulfite
plates, with the exception of a
very small white colony on the
Sample 1 MacConkey plate.
Results
Keyboard
TSA Plate Control
TSA Plate Sample 2
Sample Set 1
Sample Set 2
Results
Cell Phone
The TSA plate for
Sample 2 contained
large yellow colonies.
 No growth was found
on the MacConkey,
Bismuth Sulfite, or
Chapman Agar plates

Sample 2 on TSA
Results
Toilet

No growth was found on any of the plates for
the toilet samples.
Sample 1 on TSA
Discussion
Staphylococcus aureus
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Gram-positive, nonmotile, nonspore-forming facultative anaerobe
in pairs, short chains, or bunched, grape-like clusters
Common bacterium found on skin and in the nose of 25% of healthy people
Produces seven different toxins that are responsible for food poisoning
Most commonly food contaminated by food workers who carry the bacteria
or through contaminated milk
Staphylococci exist in air, dust, sewage, water, milk, and food or on food
equipment, environmental surfaces, humans, and animals
Presence indicates poor sanitation
Staphylococcal toxins could be used as a biological agent either by
contamination of food/water or by aerosolization and inhalation. Breathing
in low doses of staphylococcal enterotoxin B may cause fever, cough,
difficulty breathing, headache, and some vomiting and nausea. High doses
of the toxin have a much more serious effect
Staphylococcal food poisoning
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true incidence of staphylococcal food poisoning is unknown because of poor
responses from victims during interviews with health officials; misdiagnosis,
inadequate collection of samples for laboratory analyses; improper
laboratory examination; not contagious
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Disease Process: Gastrointestinal illness-via preformed enterotoxins
Symptoms: fast acting, sometimes causing illness in as little as 30 minutes,
symptoms usually develop within one to six hours. Patients typically
experience several of the following: nausea, vomiting, stomach cramps, and
diarrhea.
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Treatment: rest, plenty of fluids, and medicines to calm their stomachs;
antibiotics not effective against enterotoxins; Recovery after 1-3 days

Prevention: wash hands and under fingernails vigorously with soap and
water before handling and preparing food, keep kitchens and food-serving
areas clean and sanitized, food is to be stored longer than two hours, keep
hot foods hot (over 140°F) and cold foods cold (40°F or under)
Salmonella
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Salmonella serotype Typhimurium and Salmonella
serotype Enteritidis are the most common in the United
States
gram negative
rod-shaped, motile bacterium -- nonmotile exceptions S.
gallinarum and S. pullorum, nonsporeforming
Onset time -- 6-48 hours.
Infective dose -- As few as 15-20 cells; depends upon
age and health of host, and strain differences among the
members of the genus.
estimated that from 2 to 4 million cases of salmonellosis
occur in the U.S. annually; 40,000 cases of salmonellosis
are reported in the United States
Salmonellosis
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Disease Process: Infection of the intestines
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Symptoms: Acute symptoms -- Nausea, vomiting, abdominal cramps, minal
diarrhea, fever, and headache. Chronic consequences -- arthritic symptoms
may follow 3-4 weeks after onset of acute symptoms
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Treatment: usually resolve in 5-7 days and often do not require treatment
unless the patient becomes severely dehydrated or the infection spreads
from the intestines. Antibiotics are not usually necessary unless the
infection spreads from the intestines, then it can be treated with ampicillin,
gentamicin, trimethoprim/sulfamethoxazole, or ciprofloxacin.
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Prevention: Poultry and meat, including hamburgers, should be wellcooked. Avoid consumption raw or unpasteurized milk or other dairy
products. Produce should be thoroughly washed before consuming; People
should wash their hands after contact with animal feces
E. coli
Facultative gram negative rod
 An estimated 73,000 cases of infection and 61 deaths occur in the United
States each year
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E. coli is a normal inhabitant of the intestines of all animals and humans.
When aerobic culture methods are used, E. coli is the dominant species
found in feces.
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Normally E. coli serves a useful function in the body by suppressing the
growth of harmful bacterial species and by synthesizing appreciable
amounts of vitamins. A minority of E. coli strains are capable of causing
human illness by several different mechanisms.
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E. coli serotype O157:H7- rare variety of E. coli that produces large
quantities of one or more related, potent toxins that cause severe damage
to the lining of the intestine; emerging cause of foodborne illness
E. coli O157:H7:
Hemorrhagic colitis
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Most illness has been associated with eating undercooked, contaminated ground
beef. Person-to-person contact is also an important mode of transmission
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Disease process: organism can be found on a small number of cattle farms and can
live in the intestines of healthy cattle; Bacteria in diarrheal stools of infected persons
can be passed from one person to another if hygiene or handwashing habits are
inadequate.
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Symptoms: severe bloody diarrhea and abdominal cramps; sometimes the infection
causes no symptoms. Usually little or no fever is present.
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Treatment: Most persons recover without antibiotics or other specific treatment in 510 days. There is no evidence that antibiotics improve the course of disease,
treatment with some antibiotics may precipitate kidney complications
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Prevention: Cook all ground beef and hamburger thoroughly. Wash hands, counters,
and utensils with hot soapy water after they touch raw meat. Persons with diarrhea
should wash their hands carefully with soap, and that persons wash hands after
changing soiled diapers. Anyone with a diarrheal illness should avoid swimming in
public pools or lakes, sharing baths with others, and preparing food for others.
Discussion
Comments
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More research and adjustment of sample 3 procedures.
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The results indicate that, while some potential
pathogens may be present on public surfaces, the
danger perceived by the public is often exaggerated.

This project reinforces the importance of basic hygiene
and cleaning methods in dining areas and home
surfaces.
References
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“Center for Food Safety and Applied Nutrition”, FDA.
http://www.cfsan.fda.gov/list.html
“Foodborne Illness”, CDC.
http://www.cdc.gov/ncidod/dbmd/diseaseinfo/foodbornei
nfections_g.htm
Reynolds, Kelly A et al. “Occurrence of bacteria and
biochemical markers on public surfaces”. International
Journal of Environmental Health Research. Jun 2005.
Wilks, S. A. et al. “The survival of Escherichia coli O157
on a range of metal surfaces”. International Journal of
Food Microbiology. Dec 2005.