Staphylococcal food intoxication were discussed, including major sources of s.aureus in food, the intrinsic and extrinsic parameters needed, common food association and clinical symptoms associated with it.

1. HAWASSA UNIVERSITY
School of Graduate Studies
Faculty of Biological Sciences
Department of applied microbiology
Food microbiology (Biol.543)
Individual assignment I
Tittle:- Staphylococcus aureus
By. ID.No.
Wakwayya Amsale ---------------GpApMiR/0009/15
May, 2023
Hawassa Ethiopia
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2. INTRODUCTION
 The term food intoxication involves toxins produced by microorganisms in
food substances and causes illness when it is consumed.
 Although S. aureus usually acts as a commensal of the human micro biota, it
can also become an opportunisticpathogen, can cause
 skin infections including abscesses,
 respiratory infections such as sinusitis,
 Acute endocarditis, Septicemia
 food intoxification.
 The staphylococcal food-poisoning or food-intoxication syndrome was first
studied in 1894 by J. Denys
 later in 1914 by M.A. Barber, who produced in himself the signs and
symptoms of the disease by consuming milk that had been contaminated
with a cultureof Staphylococcusaureus.
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3.  Gram-positive, clusters of cells.
 Grapes like clusters arrangement.
 1 um in diameter
 Spherical colonies in clusters in two planes.
 Cell wall- very thick peptidoglycan layer
 Non-Flagellated, Non-Motile
 Non-Spore forming
 They are capsulated.
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4.  Aerobic or microaerophilic, grow
rapidly at 37 OC
 Round,smooth, raised, glistening and
forms gray to deep golden yellow
colonies.
 Mannitol SaltAgar: circular (2-3 mm),
smooth, shiny surface; coloniesappear
opaqueand are often pigmented golden
yellow.
 Tryptic SoyAgar: circular, convex, and
entire margin.
 BloodAgar: beta-hemolysis.
Cultural characteristics
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5. Biochemical characteristics
Positive
+
 Catalase
 Coagulase
 Methylred
 Voges- proskauer (VP)
 Nitratereduction
 Gelatin hydrolysis
 Citrate
 Urease
Negative
-
 Oxidase
 Hydrogen sulfide
 Indole
 Motility
 PYR
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6. Sources of S.aureus in food
 Boils and wounds might be
source of infection
 Nasal passage of humans
have abundant amount of
staphylococcipresent, which
cause sinus infection
 Human Skin (food workers
who do not wash properly
before touching food) or
animal sources.
 animals harbor S. aureus
and if milk from infected
cows is consumed or used
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7. Food association
 The bacteria can multiplyand producetoxins in foods that are rich in protein.
 food which is undercooked or left at room temperature. Despite contamination,
many foods have a normal taste and odor.
 Typical contaminated foods include poultry and cooked meat products such as ham
or corned beef, milk and milk products, canned food, bakery products custard,
cream-filled pastry, and fish.
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8. Parameters of S. aureus in foods
 Different parameters are involved in toxin production such as type of
food and its medium such as liquid or solid consistency, temperature,
pH, and.
 Generally, the temperature range is about 4- 46 0C, which actually
depends on food for e.g., in condensed milk and custard the minimal
temperature is 6.7-7.8 0C,
 minimal pH for aerobic condition is 4.8, and for anaerobic it is 5.5 pH.
 The minimal water activity aw Under aerobic conditions is 0.86 &
anaerobic conditions is 0.90.
 Ready-to-eat food should be below 103 cfu/g of S.aureus. If it is
>104 cfu/g, the food is unsatisfactory and potentially hazardous for
health and unfit for human consumption.
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9. Clinical symptoms of staphylococcal food intoxication
 Incubation period of Staphylococcus food
intoxication, is short up to 2-4 hrs also may
range between 1-7 hr.
 Symptoms may vary in individual, in some
people symptoms are minor , in others it can
make them really ill.
 Some common symptoms includes:
 Nausea
 Vomiting
 Diarrhea
 Abdominal cramps
 Secondary symptoms like chills, sweating,
headache, weak pulse, and may be shallow
respiration. Mortalityrate is low.
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10. S.aureus enterotoxin(SEs)
 Staphylococcal toxins are enteric toxins and cause gastroenteritis.
 SEs stimulate the vagus nerve in the abdominal viscera, which transmits the signal
to the vomiting center in the brain.
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S.aureus enterotoxin(SEs)

12. Identification Methods
 Food or vomit samples are analyzed for the presence of high levels of
enterotoxigenic S.aureus cells and enterotoxins.
 Enumeration technique in one or more selective, differential agar media to
determine the load of viable cells of Sta. aureus.(large manitol fermenting
colonies in MSA)
 followed by several biochemical tests, such as Catalase, coagulase,
reactions.
 Serological or molecular identification (PCR) means to associate them with
the outbreak.
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13. Prevention of Staphylococcal Food intoxication
 Preventive measures one can take to help prevent the spread of the
disease include :-
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 washing hands thoroughly with soap
and water before preparing food.
 Stay away from any food if ill, and
wear gloves if any open wounds occur
on hands or wrists while preparing
food.
 If storing food for longer than 2
hours, keep the food below 4.4 or
above 60 °C.

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Recent S.aureus outbreaks

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Recent S.aureus outbreaks

16. References
• Jay, J.M., Loessner, M.J. and Golden, D.A., 2008. Modern food
microbiology. Springer Science & Business Media.
• Ray, B. and Bhunia, A., 2005. Fundamental food microbiology. CRC
press.
• Argudín, M.Á., Mendoza, M.C. and Rodicio, M.R., 2010. Food
poisoning and Staphylococcus aureus enterotoxins. Toxins, 2(7),
pp.1751-1773.
• https://www.researchgate.net/publication/321957191_Food_Poisonin
g_Caused_by_Bacteria_Food_Toxins
• https://academic.oup.com/femsre/article/36/4/815/520403
• https:// www.foodsafetynews.com/S.aureus
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