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Staphylococcus aureus

What is Staphylococcus aureus?

  Staphylococcus aureus or “Staph” for short, are spherical bacteria carried mainly on human skin and nose. They are found among 25-30% of population but do not cause infection unless they find a way inside the skin through a cut for example. Staphylococcus aureus can also cause foodborne illness if it is transferred to food.   When transferred to food, S. aureus can quickly produce a toxin that is extremely heat resistant and, if consumed, will cause foodborne illness. Staphylococcal infections can produce very serious complications including: wound infections, bloodstream infections, pneumonia and meningitis.   What is MRSA? Methicillin-resistant Staphylococcus aureus (MRSA) is a type of staphylococcal bacteria that is resistant to most antibiotics used to treat infections. It is a growing concern in many hospitals and health care facilities.     Where is Staph. aureus found?   Human skin and nose are the main reservoirs for S. aureus; however, it has also been found on some animals (chicken and pig) and in the environment including places that are hard to clean such as ventilation systems.  

 

What kind of environmental conditions can it survive?   Staphylococcus aureus can grow in a wide range of temperatures (6 to 48°C) but grows best at 37°C. It can also grow at pH levels of 4.2 to 9.3 but grows best at pH levels of 7-7.5.Staphylococcus aureus can grow in salt concentrations of about 7-25%. While S. aureusprefers to grow in the presence of oxygen they are also capable of growing without it.   Staphylococcus aureus do not compete well with other bacteria and is, therefore rarely the cause of foodborne illness in raw foods. The bacterial cells are destroyed by heat but the toxin that they leave behind in the food they have contaminated is extremely heat resistant.Staphylococcus aureus can also survive drying.     What foods are involved?  
  Foods that are cooked, salty, and high in protein are most commonly implicated in foodborne illness caused by S. aureus, such foods include:  
  • Meat and meat products
  • Pasta
  • Milk and dairy products
  • Cream fillings and pies
  • Chocolate
 
     
      What is the duration and onset of illness?   The onset of illness can occur rapidly depending on the overall health of the individual and the amount of toxin consumed. Symptoms generally appear within 30 minutes to 7 hours (mean 2-4 hours) of eating toxin-contaminated food. People generally recover from staphylococcal infections within 2 to 3 days.   Places where individuals are in close proximity to one another such as hospitals, athletic teams, prisons and the military, provide a greater opportunity for MRSA infections and are often called community-associated MRSA (CA-MRSA).     What are the symptoms of illness?   Symptoms of foodborne illness caused by S. aureus include:
  • Nausea
  • Vomiting
  • Abdominal cramps
  • Diarrhea.
  The manifestations of skin infections caused by MRSA include:
  • Pimples
  • Boils
  • Pus
  • Areas that are red, painful and swollen.
Symptoms of severe infections caused by S. aureus include:
  • Headaches
  • Sweating heavily
  • Fever.
    What can you do to control or prevent Staphylococcus aureusinfections?   Prevention of staphylococcal infections is mainly achieved through good personal hygiene practices including: ·   Keep hands clean by washing thoroughly with soap and water or using an alcohol-based hand sanitizer. ·   Keep cuts and scrapes clean and covered with a bandage until healed. ·   Avoid contact with other people’s wounds or bandages. ·   Do not share personal items such as towels or razors. ·   Keep kitchens and food-serving areas clean and sanitized. ·   Keep hot foods hot (over 60°C, 140°F) and cold foods cold (4°C, 40°F or under), especially when foods are stored longer than two hours.     Information Sources   Centers for Disease Control and Prevention (2008). Community-Associated MRSA. Retrieved from http://www.cdc.gov/ncidod/dhqp/ar_mrsa_ca_public.html#1   Centers for Disease Control and Prevention. (2006). Staphylococcal food poisoning. Retrieved from www.cdc.gov/ncidod/dbmd/diseaseinfo/staphylococcus_food_g.htm
  New Zealand Food Safety Authority. (2001). Microbial Pathogen Data Sheets: Staphylococcus aureus. Retrieved from www.nzfsa.govt.nz/science/data-sheets/staphylococcus-aureus.pdf                      

Public Health Agency of Canada. (2001). Staphylococcus aureus. Retrieved from www.phac-aspc.gc.ca/msds-ftss/msds143e-eng.php

 

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