Staphylococcus Food Poisoning

Staphylococcus aureus is a serious and common foodborne pathogen – a bacterium widely found in the food supply chain (Tirado and Schmidt, 2001; Loir et al., 2003). There were nearly 350 cases of staphylococcal poisoning in Europe back in 2012 which represented 6.4% of the total number of outbreaks (EFSA, 2014). In the USA, it is reckoned to cause on an annual basis about 240,000 cases of poisoning with 1,064 of those going to hospital and about 6 deaths. It is reckoned that when all the food related illnesses are examined, of the 31 known pathogens involved, S. aureus ranks in 5^th spot for the most frequent cause in the USA, after norovirus, Salmonella species, Clostridium perfringens, and Campylobacter (FDA, 2012). It merits its own specific page on the CDC web-site in the USA which indicates just how serious the issue still is (see page).  Reports on annual occurrences indicate the number of cases of Staph. related food poisonings has not abated and is becoming ever more a global public threat (Kadariya et al., 2014).

Description Of The Bacterium

The bacterium is a Gram-positive spherical type that is widely distributed in the environment. It thrives especially in foods of low water activity (Aw = 0.84), is salt tolerant and also survives under anaerobic conditions (Belay and Rasooly 2002). It is dangerous because of a range of enterotoxins that are released on ingestion which are heat resistant and stable, and can persist in foods even after processing and rewarming (Balaban and Rasooly, 2000; Ortega et al., 2010).

Symptoms Of Staphylococcus Food Poisoning

Those of us suffering from Staph. aureas food poisoning will feel its effects after 1 to 6 hours following ingestion of the enterotoxin. In some cases, the symptoms appears within 30 minutes which seems extremely rapid but is not unusual given the type of bacteria.  The symptoms are nausea and vomiting, severe stomach cramps, diarrhoea with a mild fever. It lasts for 24 to 48 hours although a day is the average length of time. Thankfully, severe illness is uncommon. Also, the illness cannot be passed from person to person.

A wide range of foods both raw and processed are commonly affected:- fermented foods, vegetables, salads including coleslaw and potato types, sandwich fillings and bakery products. Milk and dairy products including eggs, fish, poultry, and meat and meat products are other sources (Jablonski and Bohach, 2001; FDA, 2012).

The bacteria is usually found on the skin and hair of all warm-bloodied animals and especially in the nostrils and throats of people. Even healthy people have a small amount of Staph. aureus as well as those suffering with a form of nose, throat or ear infection. It is estimated that between 30 to 50 % of all people are carriers of this bacteria including those who are healthy (Le Loir et al., 2003; CDC, 2006). One of the main issues about the bacteria is that not only is it involved in nosocomial infections, the bug is now developing resistance to antimicrobials. This makes it increasingly more difficult to treat, not only as an infection but in foods too. The greatest concern are the methicillin-resistant or MRSA strains (Ippolito et al., 2010; Doyle et al., 2012).

Food contamination usually occurs directly via the food handler route who touches themselves and then the food (CDC, 2006; Arguddin et al., 2010). Incorrect refrigeration and other forms of temperature abuse exacerbate the problem. Food surfaces are also another source for contamination especially when food is being prepared. The bacteria multiply rapidly at room temperature when the enterotoxin is released. Whilst the toxin can survive, the bacteria itself cannot survive cooking or pasteurisation. Staph. is also outcompeted by naturally occurring micro-organisms in food which is why continuous live fermentation is so successful in reducing the impact of this bacterium.

The Enterotoxin

To date, more than 20 staphyloccocal enterotoxins or related proteins are known to be the agents of the food poisoning (Hu & Nakane, 2014; Schelin et al., 2011). The classical toxin types are A to E. The type A (SEA) is the most widely known for producing such outbreaks.

Temperature is the most influential environmental factor in enterotoxin production along with pH, water activity and atmospheric conditions (Bergdoll, 1979).

It’s worth accessing the USA food safety web-site for further details on top of what is provided here for advice on treatment for the poisoning.

What Can Be Done To Prevent Staphylococcus Food Poisoning

As with most foods, it is best to prevent food from being held and stored at the unsafe temperature range of between 40 and 140 Fahrenheit for over 2 hours. This is the danger zone and none more so than for Staph. bacteria. The CDC web-page states the following food safety tips to be followed to minimise risk and they are:-

Use a food thermometer with cooked foods and ensure that food reaches the safe minimum temperature.

Try to keep hot foods hotter tan 140 °F or colder that 40 °F

When storing cooked foods, use wide, shallow containers and refrigerate within 2 hours. Keep to under 1 hour if the temperature is hotter than 90°F outside.

Regulations

(1) European Union

Currently, the presence or absence of staphyloccocal enterotoxins are tested for according to the European Regulations (2005). This applies to products over the course of their shelf-life. The products tested are cheese, milk powder and whey powder. The tests are looking for coagulase-positive staphyloccoccal enterotoxins. The method is a European screening method from the CRL specific for coagulase positive staph. 

References

Argudin, M.A., Mendoza, M.C., Rodicio, M.R. (2010) Food poisoning and Staphylococcus aureus enterotoxins. Toxins 2 pp. 1715–1173.

Balaban, N., Rasooly, A. (2000) Staphylococcal enterotoxins. Int. J. Food Microbiol. 61 pp. 1–10.

Belay, N., Rasooly, A. (2002) Staphylococcus aureus growth and enterotoxin A production in an anaerobic environment. J. Food Prot. 65(1) pp. 199–204.

 Bergdoll, M. S. (1979). Staphylococcal intoxication. In H. Riemann & L. Bryan (Eds.), Food‐borne infections and intoxications (2nd ed, pp. 444–494). New York: Academic Press. 

[CDC] Centers for Disease Control and Prevention (U.S.). (2006). Staphylococcal food poisoning. Available from: https://www.cdc.gov/ncidod/dbmd/diseaseinfo/staphylococcus_food_g.htm. Accessed 2015 December 21st. No longer available 30th April 2019.

CDC (2016). Staphylococcal food poisoning. Retrieved from http://www.cdc.gov/foodsafety/diseases/staphylococcal.html 

Czop, J. K., & Bergdoll, M. S. (1974). Staphylococcal enterotoxin synthesis during the exponential, transitional, and stationary growth phases. Infection and Immunity, 9, pp. 229–235 https://www.ncbi.nlm.nih.gov/pubmed/4205941?dopt=Abstract .

Doyle, M.E., Hartmann, F.A., Lee Wong, A.C. (2012) Methicillin-resistant staphylococci: implications for our food supply? Anim. Health Res. Revs. 13 pp. 157–180.

EFSA. (2014) The European Union Summary Report on Trends and Sources of Zoonoses, Zoonotic Agents and Food-borne Outbreaks in 2012. EFSA J. 12 pp. 3547

European Commission. (2005). EC European Commission Regulation No. 2073/2005 of 15 November 2005 on microbiological criteria for foodstuffs. Off. J. Eur. Union, L338, 1e26. Available from: http://faolex.fao.org/docs/pdf/eur61603.pdf. 

[FDA] Food and Drug Administration (U.S.). (2012). Bad Bug Book, Foodborne Pathogenic Microorganisms and Natural Toxins. Second Edition. Available from: https://www.fda.gov/downloads/Food/FoodborneIllnessContaminants/UCM297627.pdf. Accessed 2015 December 20th. 

Fujikawa H., & Igarashi, H. (1988). Rapid latex agglutination test for detection of staphylococcal enterotoxins A to E that uses high‐density latex particles. Applied and Environmental Microbiology, 54, pp. 2345–2348.  https://www.ncbi.nlm.nih.gov/pubmed/3202627?dopt=Abstract.

Hu, D.‐L., & Nakane, A. (2014). Mechanisms of staphylococcal enterotoxin‐induced emesis. European Journal of Pharmacology, 722, pp. 95–107 https://doi.org/10.1016/j.ejphar.2013.08.050 .

Ippolito, G., Leone, S., Lauria, F.N., Nicastri, E.,Wenzel, R.P. (2010) Methicillin-resistant Staphylococcus aureus: the superbug. Int. J. Infect. Dis. 14 (Suppl. 4) S7-11.

Kadariya, J., Smith, T.C., Thapaliya, D. (2014) Staphylococcus aureus and Staphylococcal Food-Borne Disease: an ongoing challenge in public health. BioMed. Research Intl. Volume 2014, Article ID 827965, 9 pages. http://dx.doi.org/10.1155/2014/827965. Accessed 2015 December 2nd.

Loir, Le Y., Baron, F., Gautier, M. (2003) Staphylococcus aureus and food poisoning. Genet. Mol. Res. 2 pp. 63–76.

Ortega, E., Abriouel, H., Lucas, R., Gálvez, A. (2010) Multiple roles of Staphylococcus aureus enterotoxins: pathogenicity, superantigenic activity, and correlation to antibiotic resistance. Toxins 2 pp. 2117–2131.

Scallan, E.S., Hoekstra, R.M., Angulo, F.J., Tauxe, R.V., Widdowson, M., Roy, S.L., Jones, J.L., Griffin, P.M. (2011) Foodborne illness acquired in the United States – major Pathogens. Emerg. Infect. Diseases 17 pp. 7–15

Schelin, J., Wallin‐Carlquist, N., Cohn, M. T., Lindqvist, R., Barker, G. C., & Rådström, P. (2011). The formation of Staphylococcus aureus enterotoxin in food environments and advances in risk assessment. Virulence, 2, pp. 580–592. https://doi.org/10.4161/viru.2.6.18122  .

Tirado, C., Schmidt, K. (2001) WHO surveillance programme for control of foodborne infections and intoxications: preliminary results and trends across greater Europe. J. Infect. 43 pp. 80–84.

http://www.foodsafety.gov/poisoning/causes/bacteriaviruses/staphylococcus

Revised 22nd December 2015 following a review of new evidence on food poisoning cases.