Let’s know more about staphylococci!
Staphylococci are a genus of Gram-positive bacteria widely distributed in nature, in different environments, in animals and in humans. Some species are responsible for serious food and non-food infections and intoxications.

What are staphylococci?
Definition and microbiological characteristics
Staphylococci are round or oval Gram-positive bacteria with a diameter of 0.5 to 1.5 µm. They are aerobic or facultatively anaerobic, and have a thick peptidoglycan wall, giving them great resistance and flexibility in different environments.
Ubiquitous, they are naturally present on human and mammalian skin, and mucous membranes, as well as in the environment (objects, healthcare facilities or food). Their presence is often harmless, but certain strains can cause infections and intoxications, especially for those with weakened immune defenses.
Around 30% of the population are healthy carriers of Staphylococcus aureus, the most virulent of the Staphylococcus species. Staphylococcus contamination in the food industry often comes from an infected healthy carrier or staff member.
Apart from S. aureus, there are other staphylococcus species of varying pathogenicity, such as Staphylococcus saprophyticus, Staphylococcus epidermidis, Staphylococcus hyicus and Staphylococcus pseudintermedius.
Staphylococcus aureus is a coagulase-positive species, responsible for numerous infections and intoxications. Some coagulase-producing Staphylococcus species can also be pathogenic. These infections can range from mild to severe and even fatal, affecting different parts of the body, and vary according to strain and antibiotic resistance. Strains of methicillin-resistant Staphylococcus aureus (MRSA), one of the world’s leading causes of hospital-acquired infections, have been isolated from companion animals, production animals (pigs, cattle, poultry) and foodstuffs of animal origin.
Because of their ubiquitous nature, virulence and the large number of possible vectors, prevention and detection of coagulase-positive Staphylococcus are essential.
Methods for detection and identification of Staphylococcus in the laboratory
Culture and isolation techniques
The pathogenicity of coagulase-positive Staphylococcus is relative to the number of bacteria. The food and environmental standard are :
NF EN ISO 6888-1 : Microbiology of the food chain – Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) – Part 1: method using Baird-Parker agar medium
NF EN ISO 6888-2 : Microbiology of the food chain – Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) – Part 2 : method using rabbit plasma-fibrinogen agar medium
NF EN ISO 6888-3 : Microbiology of food and animal feeding stuffs – Horizontal method for the enumeration of coagulase-positive staphylococci (Staphylococcus aureus and other species) – Part 3 : Detection and MPN method for low numbers.
Typically, these methods take 2 days or more to obtain the result.
Biokar Diagnostics has developed EASY STAPH®, an alternative method for enumeration of coagulase-positive Staphylococci in food, feed and environmental products, including surface samples in the production environment. Validated by AFNOR Certification in accordance with standard 16140-2, EASY STAPH® is fast, simple and efficient, enabling the enumeration of pathogenic Staphylococcus from 22 hours without confirmation instead of 48 hours in standard methods, with 3 choices of inoculation : surface, deep and spiral.
Molecular identification techniques such as PCR are also available to detect specific genes, such as those coding for antibiotic resistance or specific toxins.
Implications for public health and food safety
Facts and figures
Staphylococcal food poisoning is due to the enterotoxin produced by the bacteria. Santé Publique France has estimated that there will be nearly 2,000 cases of CFTIs (collective food poisoning) reported in France in 2022. In Europe, staphylococci are responsible for at least 7.5% of reported CFTIs.
What are the symptoms and complications?
Symptoms appear 30 minutes to 8 hours after ingestion. Nausea followed by vomiting are the most characteristic; other symptoms include abdominal pain, diarrhea, dizziness, chills and general weakness, sometimes accompanied by a moderate fever. Toxic shock, although rare, can be fatal.
What are the sources of infection?
– Products from Staphylococcus-infected animals: cow’s, sheep’s or goat’s milk cheese or cream, meat and poultry products.
– Products contaminated by a sick person or healthy carrier during manufacture or cooking: cream, ice cream, pastries, pâté and salad.
– Contaminated production environment: staphylococci adhere strongly to surfaces and will not be completely eliminated if cleaning and disinfection of production materials and premises are not rigorous.
– Healthy carrier or infected personnel: the skin lesion and secretions from the nose or mouth of a healthy carrier or infected person can either directly contaminate the product, or contaminate the production environment.

Moreover, these bacteria are heat-sensitive, but their enterotoxins are thermostable. So, if a foodstuff is heavily contaminated prior to heat treatment, enterotoxins may persist and will not be eliminated by cooking or industrial sterilization.
Prevention
For food industry, the multiple sources of contamination from the environment and animals, as well as the high prevalence of healthy carriers, make it essential to prevent and control staphylococcal contamination throughout the production chain.
Every manufacturer must anticipate risks and implement a prevention plan adapted to industrial environment, including the installation, the manufacturing process, the materials, as well as the intermediate and finished products. This plan must include strict cleaning, disinfection protocols, and regular monitoring of equipment, processes, materials and products.
Given the large number of healthy carriers, it is very important that employees have good hygiene practices : rigorous hand washing, wearing a cap and mouth mask, and coverage of any skin lesions (by wearing suitable gloves, for example).
Respecting the cold chain from ingredients to finished products is also crucial to prevent bacterial growth and the production of enterotoxins. The latter are thermostable and cannot be eliminated by conventional sterilization and cooking techniques.