These "grapes" are free, but they can cost you your life!

In nature, there are many kinds of grapes that are very delicious. People also process them into raisins and wine. Therefore, grapes have become the main cash crop in the rich production areas, bringing considerable economic income to people. However, there is also a kind of small Gram-positive bacteria that can express golden pigment when artificially cultured. They are called Staphylococcus aureus, which can accumulate in the shape of grapes under the microscope after Gram staining. Humans can experience what is poisonous bacteria after contact. They are commonly known as pathogenic bacteria. Their toxicity is not only that they can cause food poisoning after ingestion, but also that they can invade wounds to cause suppuration, and even enter the blood to cause sepsis, and so on.

What is Staphylococcus aureus?

Staphylococcus aureus, also known as golden staphylococcus, is a common foodborne pathogen. The colony is spherical, and one of its most distinctive features is its appearance - it appears golden yellow on a blood plate and mostly piled up like grapes under a microscope, hence the name.

Staphylococcus aureus has a strong ability to survive and reproduce in a variety of environments. It is often found in foods such as dairy products, meat, and eggs that have not been thoroughly sterilized. In the process of processing and storing food in an environment with poor sanitation, it is very easy to contaminate food. Food contaminated by it can produce enterotoxins at 20-37℃ for 4-8 hours. However, these toxins cannot be easily removed even after heating, thus causing food poisoning.

Its cell wall is very strong, which allows it to withstand some adverse environmental conditions. It is highly resistant to heat and can be inactivated at 70°C for 1 hour. This also indicates that pasteurization (63°C, 30 minutes or 72°C, 15-20 seconds) of milk contaminated by it cannot completely kill it. This requires dairy production companies to isolate and treat dairy goats with mastitis in advance and stop milking to prevent contamination [1]. In addition, Staphylococcus aureus is highly salt-resistant and can survive and reproduce for a long time in a 10% NaCl solution. Since Staphylococcus aureus contains a large amount of lipopolysaccharides, which are easily dissolved by alcohol, 75% ethanol can quickly kill it within a few minutes.

What are the main foods contaminated by Staphylococcus aureus?

Milk and dairy products, starch (such as leftover rice, porridge, noodles, steamed buns, etc.), fish, eggs, etc.

What are the symptoms of Staphylococcus aureus food poisoning?

The incubation period is 2-5 hours. Symptoms include nausea, vomiting, cramping pain in the upper and middle abdomen, followed by diarrhea. Vomiting is the most prominent symptom.

How to prevent Staphylococcus aureus food poisoning?

1. Pay attention to personal hygiene. Keep your skin clean and wash your hands frequently, especially after handling food. Avoid touching your mouth, nose and eyes with your hands to reduce the chance of bacteria invading.

2. Rationally select food raw materials and ingredients. Use safe water and food raw materials, improve the sanitation of the processing environment and the personal hygiene habits of operators, and avoid Staphylococcus aureus contamination of food.

3. Strictly manage food hygiene to prevent food contamination. Food processing and storage processes must meet hygiene standards, cook food thoroughly, and keep raw and cooked food separate. Foods that are prone to breeding bacteria, such as dairy products and meat, must be properly stored and not left at room temperature for a long time.

In recent years, there have been numerous reports of food poisoning caused by Staphylococcus aureus, accounting for about 25% of foodborne microbial food poisoning incidents [2]. Staphylococcus aureus is the third most pathogenic bacterium after Salmonella and Vibrio parahaemolyticus. Pay attention to food safety, be vigilant against Staphylococcus aureus, and protect your health.

References

[1]Shalaby M, Reboud J, Forde T, Zadoks RN, Busin V. Distribution and prevalence of enterotoxigenic Staphylococcus aureus and staphylococcal enterotoxins in raw ruminants' milk: A systematic review. Food Microbiol. 2024 Apr;118:104405. doi: 10.1016/j.fm.2023.104405. Epub 2023 Oct 18. PMID: 38049264.

[2] Li Yanxing. Detection and comparison of methods for Staphylococcus aureus food poisoning pathogens[J]. Seeking Medical Advice (Academic Edition), 2011, (12): 507-507.

Source: Chongqing Science Writers Association

Written by: Xie Jinhua, chief technician of Zhongxian Center for Disease Control and Prevention, Luo Ningyu, laboratory technician, Yang Yuanyuan, laboratory technician, Tongliang District Center for Disease Control and Prevention, Xia Qing, chief technician, and Zou Jingbo, chief technician, Yongchuan District Center for Disease Control and Prevention

Audit expert: Li Hanbin

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