Category Archives: Staphylococcus aureus

Research – Staphylococcal (Staph) Food Poisoning


MRSA Staphylococcus KSW Food World

Staph food poisoning is a gastrointestinal illness caused by eating foods contaminated with toxins produced by the bacterium Staphylococcus aureus (Staph) bacteria.

About 25% of people and animals have Staph on their skin and in their nose. It usually does not cause illness in healthy people, but Staph has the ability to make toxins that can cause food poisoning.

People who carry Staph can contaminate food if they don’t wash their hands before touching it. If food is contaminated with Staph, the bacteria can multiply in the food and produce toxins that can make people ill. Staph bacteria are killed by cooking, but the toxins are not destroyed and will still be able to cause illness.

Foods that are not cooked after handling, such as sliced meats, puddings, pastries, and sandwiches, are especially risky if contaminated with Staph.

Food contaminated with Staph toxin may not smell bad or look spoiled.

What are the symptoms of Staph food poisoning?

  • Staph food poisoning is characterized by a sudden start of nausea, vomiting, and stomach cramps. Most people also have diarrhea.
  • Symptoms usually develop within 30 minutes to 8 hours after eating or drinking an item containing Staph toxin, and last no longer than 1 day. Severe illness is rare.
  • The illness cannot be passed from one person to another.

How do I know if I have Staph food poisoning?

You can suspect Staph food poisoning based on the type of symptoms and their fast resolution. Although laboratory tests can detect toxin-producing Staph in stool, vomit, and foods, these tests are usually not ordered except during an outbreak. If you think you might have Staph food poisoning and are experiencing severe symptoms, contact your health care provider.

USA – Maryland recalls cheeses due to Staphylococcus aureus (Staph) and E.coli

Food Poison Journal

The Maryland Department of Health (MDH) is warning consumers not to eat the following cheeses under the brand names La Cieba, La Colonia, and Selectos Latinos until further notice, as they may be contaminated with Staphylococcus aureus (Staph) and E.coli bacteria:

  • Cuajada el Terron
  • Queso Morolique con Chile
  • Queso Con Loroco
  • Queso Con Chile
  • Queso Frijolero
  • Queso Duro Blando Salvadoreno
  • Queso Salvadoreno
  • Queso Seco Salvadoreno

Marylanders are advised not to consume these products. If you have purchased one or more of these products, throw them away. If you consumed one or more of these products, watch for symptoms such as stomach cramps, diarrhea, vomiting, nausea, or fever. If symptoms occur, contact your healthcare provider.

Research – Can bacterial viruses improve the microbiological safety of raw milk cheeses?

Harper Adams

Harper Adams University research is exploring a biological control method to improve the safety of popular Egyptian cheeses produced from raw cows’ milk.

The work is being conducted by Sherif Kandil, a PhD student and scholar sponsored by the Newton Mosharafa Fund. Sherif is in the final year of a three-year study, directed by Dr Lynn McIntyre, Senior Lecturer in Food Safety in the Department of Food Technology and Innovation.

Dr McIntyre explained: “The project was prompted by a number of foodborne outbreaks and prevalence data showing high levels of Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in raw milk in Egypt.

“Cheeses made from raw cows’ milk, such as Karish, Domiatti and Ras, are popular in Egypt and Arab countries. Their strong flavour is produced by naturally occurring microorganisms in raw milk rather than the deliberate addition of starter culture organisms. However, their production also relies on smallholders in rural areas who make and store cheese under potentially uncontrolled hygiene and temperature conditions’’ Sherif added. Therefore, the growth of a variety of disease-causing (pathogenic) bacteria such as S. aureus and E. coli can be a real problem.

“These pathogens are also developing some resistance to antibiotics, but pasteurisation, normally used to kill pathogenic bacteria in raw milk, would also kill the desirable microorganisms and alter the flavours, which may be unacceptable to the consumer.”

Bacteriophages are highly specific viruses, which, unlike antibiotics, can selectively kill target bacterial species without affecting the desirable microorganisms. These could therefore have potential to target and control the disease-causing bacteria in raw cows’ milk cheeses, “an area that has not received much attention to date” according to Sherif.

For his study, Sherif collected 100 raw cows’ milk samples and processed them using a standard method to isolate and identify strains of S. aureus and E. coli in the Princess Margaret Laboratories, at Harper Adams University.

Karish, Domiatti and Ras cheeses have been successfully produced from raw cows’ milk on a small-lab-scale using traditional production methods, and their properties characterised during manufacture and storage.

A range of conditions, based on these data, has also been tested to understand how the bacteriophages behave under conditions they will be exposed to during cheese production. The last phase this year will evaluate how effective these phages are at controlling S. aureus and E. coli in milk and during further lab-scale cheese manufacture and storage.

“There is increasing interest in controlling pathogenic bacteria in food using natural non-thermal approaches without compromising the manufacturing process and product quality,” Dr McIntyre added. “We are not immune to these food safety challenges in the UK, and much of what we’ve been investigating in this project could also be applied to raw milk cheese production here.”

Research – Persistence of Foodborne Pathogens on Farmers Market Fomites

Journal of Food Protection

The number of farmers markets registered by the U. S. Department of Agriculture (USDA) has seen a significant increase, jumping from 1,755 in 1994 to 8,771 in 2019. Microbial studies have found evidence that produce sold at farmers can yield higher microbial counts than their retail counterparts; however, no previous literature explored the efficacy of microbial (bacteria and virus) persistence on a variety of different farmers market fomites over a 2-month period. The objectives of the current study were to conduct observations to determine the most commonly used food contact surface fomites at farmers markets and to investigate the persistence of key foodborne pathogens ( Escherichia coli O157:H7, Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and MS2 bacteriophage) on these fomites. A repeated-measures analysis of variance was used to compare the persistence rates of foodborne pathogens on cardboard, plastic, tablecloth, molded pulp fiber, and wicker baskets used to store, transport, and display produce at farmers markets. In general, molded pulp fiber, plastic and wicker surface materials supported the persistence of foodborne pathogens the most, with S. aureus demonstrating the highest log concentrations over the longest period of time. Additionally, Salmonella and E. coli strains also persisted for a significant period of time (approximately 32-days) on all fomites with the exception of tablecloth. The results suggest that foodborne pathogens on these fomites pose a high-risk of cross-contamination particularly if the fomites cannot be washed, rinsed, and sanitized effectively (e.g. cardboard). The results highlight the need avoid using porous, single-use storage containers such as cardboard, molded pulp fiber and wicker containers for extended periods of time and suggest the use of easily cleanable materials such as plastic containers.

USA – Researchers describe outbreaks in Brazil, Pakistan and Malaysia

Food Safety News

Abstracts from a cancelled event have been issued on outbreaks in Brazil, Pakistan and Malaysia.

The conference abstracts were scheduled to be presented at the International Congress on Infectious Diseases in September 2020 in Kuala Lumpur, Malaysia, but the gathering was called off because of the coronavirus pandemic.

Studies in the International Journal of Infectious Diseases supplement involve E. coli O157, Staphylococcus aureus and Brucella.

The first study involves a deadly Shiga toxin-producing E. coli (STEC) O157:H7 outbreak with hemolytic uremic syndrome (HUS) cases in Brazil.

RASFF Alert – Staphylococcus aureus – Chilled Black Ham

European Food Alerts


coagulase-positive Staphylococcus (500 CFU/g) in chilled black ham from Germany in Austria

Research – Animal petting zoos as sources of Shiga toxin‐producing Escherichia coli, Salmonella and extended‐spectrum β‐lactamase (ESBL)‐producing Enterobacteriaceae

Wiley Online

Animal petting zoos and farm fairs provide the opportunity for children and adults to interact with animals, but contact with animals carries a risk of exposure to zoonotic pathogens and antimicrobial‐resistant bacteria. The aim of this study was to assess the occurrence of Shiga toxin‐producing Escherichia coli (STEC), Salmonella, extended‐spectrum β‐lactamase (ESBL)‐producing Enterobacteriaceae and methicillin‐resistant Staphylococcus aureus (MRSA) in animal faeces from six animal petting zoos and one farm fair in Switzerland. Furthermore, hygiene facilities on the venues were evaluated. Of 163 faecal samples, 75 contained stx1, stx2 or stx1/stx2 genes, indicating the presence of STEC. Samples included faeces from sika deer (100%), sheep (92%), goats (88%), mouflons (80%), camels (62%), llamas (50%), yaks (50%), pigs (29%) and donkeys (6%), whereas no stx genes were isolated from faeces of calves, guinea pigs, hens, ostriches, ponies, zebras or zebus. Salmonella enterica subsp. enterica serovar Stourbridge (S. Stourbridge) was detected in faecal samples from camels. A total of four ESBL‐producing E. coli strains were isolated from faeces of goats, camels and pigs. PCR and sequencing identified the presence of blaCTX‐M‐15 in three and blaCTX‐M‐65 in one Ecoli. Antimicrobial resistance profiling using the disk diffusion method revealed two multidrug‐resistant (MDR) E. coli with resistance to ciprofloxacin, gentamicin and azithromycin, all of which are critically important drugs for human medicine. Multilocus sequence typing identified E. coli ST162, E. coli ST2179, extraintestinal high‐risk E. coli ST410 and E. coli ST4553, which belongs to the emerging extraintestinal clonal complex (CC) 648. No MRSA was detected. On all animal petting venues, there were inadequacies with regard to access to hygiene information and handwashing hygiene facilities. This study provides data that underscore the importance of hygiene measures to minimize the risk of transmission of zoonotic pathogens and MDR, ESBL‐producing E. coli to visitors of animal petting venues.

RASFF Alert – Staph Enterotoxin – Chilled Cured Sheep Cheese

European Food Alerts


Staphylococcal enterotoxin (presence /25g) in chilled cured sheep cheese from Portugal in Portugal

Research – Investigation and Follow-Up of a Staphylococcal Food Poisoning Outbreak Linked to the Consumption of Traditional Hand-Crafted Alm Cheese



Image CDC

Staphylococcal food poisoning (SFP) is one of the most important foodborne diseases. This work describes a SFP event linked to the consumption of alm cheese and involved three people belonging to the same family. Leftovers of the consumed cheese, samples from the grocery store and the producing alm were collected and tested for Coagulase positive staphylococci (CPS) enumeration and for the presence of staphylococcal enterotoxins (SEs). Isolates were typed with MLST, spa typing, and tested for SEs and methicillin resistance genes. An in vitro test evaluated SEs production in relation to bacterial growth. The presence of CPS and SEs was detected in all cheese samples and all isolates belonged to the same methicillin sensitive ST8/t13296 strain harbouring sedser and sej genes. The in vitro test showed the production of enterotoxins started from 105 CFU/mL. The farmer was prescribed with corrective actions that led to eradication of the contaminating strain. View Full-Text

Research – Biofilm-Forming Ability of Pathogenic Bacteria Isolated from Retail Food in Poland

Journal of Food Protection


Biofilms have a significant impact on food safety in the food industry. Many foodborne outbreaks have been associated with pathogenic bacterial strains that can form a biofilm. The present study was conducted under the Official Control and Monitoring Program in Poland to examine the ability of pathogenic bacteria collected from retail food samples to form biofilms. Biofilm formation was assessed by qualitative detection of extracellular polymeric substances on Congo red agar, by adherence to glass with the tube method, by the crystal violet biofilm (CV) assay, and by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay. A total of 40 isolates from food samples (10 strains each of Listeria monocytogenes, Staphylococcus aureus, Escherichia coli, and Bacillus cereus) were examined. The strains were classified as adherent, slightly adherent, or nonadherent; biofilm production was classified as weak (WBP), moderate (MBP), or strong (SBP); and metabolic activity was classified as weak (WMA), moderate (MMA), or high (HMA). The incubation conditions and time influenced the amount of biofilm formed as well as did the growth medium. In the test tubes with Luria-Bertani broth (LBB), 22.5% of the strains were adherent and 77.5% were slightly adherent. Stronger adhesion was obtained in brain heart infusion (BHI) with 2% sucrose; 60% of the isolates were classified as adherent. With the CV assay with LBB, SBP was noted for 7.5% of the strains after 24 h of incubation and for 37.5% of the strains after 48 h. In BHI plus 2% sucrose, SBP was noted for 42.5 and 37.6% of the strains after 24 and 48 h, respectively. With the MTT assay with LBB, HMA was found for 15% of the strains after 24 h of incubation and for 25% of the strains after 48 h. In BHI plus 2% sucrose, 70 and 85% of the incubated strains were classified as HMA after 24 and 48 h, respectively.

  • All tested bacterial pathogens isolated from food formed biofilms.
  • Biofilm formation was dependent on environmental conditions and the assay used.
  • Culture in BHI plus 2% sucrose produced more biofilm with higher metabolic activity.