Staphylococcus aureus in food

Staphylococcus aureus is one of the most successful human pathogens, with global distribution and the potential to cause, potentially fatal disease.

Staphylococcus aureus may be present in virtually any food because it can reproduce within wide ranges of temperature, acidity and salt content.

The organism is well-arm with potent virulence factors, survival fitness, and antimicrobial resistance determinants. The largest numbers tend to be found near openings to the body surface such as the anterior nares, axillae and the inguinal and perineal areas. It has tremendous capacity to cause harm when an opportunity such as wound or weakened immune system presents itself.

In addition, Staphylococcus aureus produces a wide range of virulence factors – proteins that help the bacteria sustain an infection and damage human host cells.

The main sources of staphylococcal contamination are food handlers and contamination typically occurs after heat treatment of the food. The two most important causes to foods are nasal carriers and individuals whose hands and arms are inflicted with boils and carbuncles, who are permitted to handle foods.

Commonly identified sources of Staphylococcus aureus foodborne illness include red meats and sausages; cheeses; cream-filled pastries; milk; dairy product; and salads made with chicken, mayonnaise, pasta with tomato sauce, egg, tuna and macaroni.

Staphylococcus aureus can be transferred from the mouth to food via the spoon. If the spoon is left for some time at a warm temperature the bacteria will grow, multiply and produce toxin.
Staphylococcus aureus in food

Bread mouldiness

Mold is a term used to commonly describe the wooly growth that occurs on damp or decaying organic matter caused from the growth of fungi. The mold growth may result in several kinds of food spoilage: off-flavors, toxins, discoloration, rotting and formation of pathogenic or allergenic propagules.

Most moulds are known saprotrophs which reproduce by releasing spores that land on decaying organic matter. They derive nutrients through the usage of digestive enzymes to break down large molecules into smaller molecules before absorbing them.

It is estimated that approximately 1-5% of the bread production goes wrong due to fungi activity. Referring to bread, mold contamination determines not only changes in color, taste, but also loss of the food quality as a result of possible formation of mycotoxins.

The color of molds that grow on bread varies from white, golden yellow to green-gray, depending on the species and the degree of sporulation.

Molds need moisture to thrive and usually grow and reproduce spores in damp or moist places. In general, most molds prefer high water potential (aw values > 0.8) while a few xerophilic molds prefer to grow at aw values as low as 0.65.

Mouldiness is caused by external contamination of bread after baking, because the existing spores in flour during a normal technological process don’t have any multiplication conditions, and during baking they are destroyed.

Bread contamination with molds, may occur in the following steps: the transportation of bread; during cooling and storage; while cutting and packing (optional operation).

Molds, mold spores, and pieces of mold may impact a person’s health by causing minor irritations such as a runny nose or itchy, watery eyes to major health concerns such as difficulty breathing, asthma attacks, infections, fever, and major skin irritations.
Bread mouldiness

Salmonella contamination in raw foods

Sometimes Salmonella bacteria are found in raw foods. If these foods are not processed or cooked well, the bacteria stay alive in the food and can infect someone who eats it.

Factors which help an outbreak of food borne Salmonella gastro-intestinal infection are contamination of food with the Salmonella pathogen, the Salmonella pathogen should be in adequate numbers with highest viability.

Salmonellae is not known to release toxins into the contaminated food in which they are multiplying, but the ingested bacteria is responsible for the disease by multiplying in the intestine of the host and invading the gastro-intestinal tract.

Human carriers are generally less important than animals in transmission of Salmonella strains. Salmonella present on raw meat and poultry could survive if the product is not cooked to a safe minimum internal temperature, as measured with a food thermometer.

Meat, poultry, egg, dairy products, and fruits and vegetables are primary transmission vehicles; they may be undercooked, allowing the Salmonella strains to survive, or they may cross-contaminate other foods consumed without further cooking.

During the past few years, outbreaks of Salmonella illness have been linked to contaminated cucumbers, pre-cut melon, chicken, eggs, pistachios, raw tuna, sprouts, and many other foods.

The association between poultry and Salmonella genus has long since been recognized. During processing, certain stages including scalding, plucking (defeathering), evisceration, and chilling of carcasses have been recognized as likely cross-contamination pathways.

Salmonella spp. is able to survive for weeks in water and for years in soil if environmental conditions such as temperature, humidity, and pH are favorable. Low water activity (aw) represents a barrier to growth for many vegetative pathogens, including Salmonella spp. Processed foods such as powdered milk, chocolate, peanut butter, infant food, and bakery products are characteristically low-aw food products.
Salmonella contamination in raw foods

Salmonella in macadamia nuts

Nuts have been identified as a vector for salmonellosis. At least 25 recalls were issued in 2015 in the United States due to Salmonella contamination of walnuts, pecans, macadamia nuts, pine nuts, almonds, and hazelnuts.

The U.S. Food and Drug Administration (FDA) posted at least a dozen recalls in 2015 involving macadamia nuts, and another three have been announced in 2016. All of this year’s recalls to date involved nuts from Mahina Mele Farm south of Captain Cook. The farm also had a recall in August 2015 of one lot of macadamia nuts and nut butters due to potential Salmonella contamination.

In February 2015, Whole Foods Market is recalling packaged raw macadamia nuts due to possible Salmonella contamination. In August 2016, Diamond brand macadamia nuts distributed to retail stores nationwide are under recall after an FDA-contracted lab confirmed Salmonella in a package of the nuts.

Because macadamia nuts are harvested from ground in orchards where organic fertilisers, eg. chicken manure may have been used, there are concerns for microbial quality of the finished product.

It may be possible for pathogens, eg. Salmonella and environmental spoilers, eg. coliforms and moulds to gain entry to macadamia kernels through occasional natural cracks in shells or by cross-contamination during factory cracking and processing.
Salmonella in macadamia nuts

Egg contamination of salmonella

It has been reported that 2.6 -7% of la fresh eggs are contaminated with Salmonella. The USDA recommends cooking all eggs until the yolks are solid to ensure destruction of all salmonella.

Egg contamination occurs whilst forming eggs are bun the productive tract, but the presence of S. enteriditis in ovaries and oviducts does not mean necessarily mean that egg contents will become Salmonella –positive.

Approximately 0.9% of eggs were eaten without cooking. Salmonella outbreaks can contribute risk factors for human infection.

These risk factors included poor refrigeration practices, improper storage of pooled eggs, use of raw eggs, substantial time and temperature abuse of eggs, and exposure of highly susceptible individuals.

The principle site of contamination in egg contents appears to be either the yolk membrane of the albumen immediately surrounding it.

Salmonella are unable to traverse the yolk membrane of fresh eggs but can do so when the membrane permeability has been altered as a consequence of storage.

According to Food Safety News (Sept 24, 2015), between 25 May and 18 June 1024, five patients died at Heartlands Hospital in the Bordesley Green area of Birmingham, England and the bacteria were traced back to eggs from the Bayern Ei (Bavarian Egg) factory in Germany.
Egg contamination of salmonella

Food irradiation reduces biological food contamination

Food irradiation reduces biological food contamination and related foodborne illness.

With the increase of some food borne infectious diseases in many countries, irradiation has been proposed as a procedure which could eliminate microbial pathogen contamination of food at the processor level and thus allow the delivery to the consumer of a safer product.

Food irradiation has been approved for use in the United States in selected foods since 1963. 

Electromagnetic radiation suitable for food irradiation may be electrons, X-rays or gamma ray. Ionizing radiation passes through the food and destroys harmful bacteria and other organisms.

Irradiation could reduce spoilage ro the need for fungicides for fruits, and increase the safety of meats.

It is also effective for seafood, eggs, precooked meats and produce. It is safe, proven process that has many useful applications.

The potential for using radiation as a way of destroying pathogens in food has been known for more than a century.
Food irradiation reduces biological food contamination

Foodborne Illness due to microbial contamination

Microbial foodborne illness also commonly called ‘food poisoning’ is illness caused by eating food contaminated with specific types of microorganisms or toxins formed by these microorganisms.

Microorganisms pose the greatest safety challenges for all food establishments. Innovations in food processing and distribution systems create new opportunities for potential microbial contamination to become manifest and there is broad national and international consideration of how best to limit these hazards.

Microorganisms that are capable of causing illness are called ‘pathogenic’ microorganisms’ or simply ‘pathogens’.

Potential microbiological contamination in food include bacteria, toxins, viruses, protozoa and parasites.

Of the microbiological contamination, the most important are bacteria and they cause a large proportion (approximately 90%) of all foodborne illnesses.

The risks associated with microbial contamination vary greatly, ranging from quite mild symptoms of short duration to very severe life threatening illnesses.

Microbial contamination derive from contamination, survival or growth of the causative agents at any stage of the supply chains, and during preparation, cooking and post cooking handling in the preparation area.

About one-third of reported food-borne illnesses are caused by the enterotoxins produced by Staphylococcus aureus. Food poisoning usually result when food is not kept hot enough or cold enough to prevent growth of this microorganism.

Microbial contaminations cause the greatest number of outbreaks of food-borne illness and are most difficult to control because they involve microorganisms.
Foodborne Illness due to microbial contamination

Current Status of Food Borne Disease

Current Status of Food Borne Disease
Food borne disease has emerged as an important and growing public health and economic problem is many countries during the last two decades.

Frequent outbreaks caused by new pathogens, the use of antibiotics in animal husbandry and the transfer of antibiotic resistance to human, as well as the ongoing concerns about bovine spongiform encephalitis (BSE) are just a few examples.

Countries with reporting systems have documented significant increases in the incidence (number of cases) of food borne disease during the two decades.

It is estimated that, each year, food borne disease causes approximately 76 million illnesses, 325000 hospitalizations, 5000 deaths in the US and 2366000 cases, 21138 hospitalizations, 718 deaths in England and Wales.

Contamination of food may occur through environmental pollution of the air, water and soil, such as the case with toxic metal, polychlorinated biphenyls and dioxins.

Other chemicals hazards, such as naturally occurring toxicants, may arise at various points during food production, harvest, processing and preparations.

The contamination of food by chemical hazards is generally well controlled in certain countries although such hazards remain a public health concern to many consumers.

The safe use of various chemicals such as food additives, pesticides, veterinary drugs and other agro-chemicals is also largely assured by proper regulation, enforcement and monitoring.

However, sporadic problem with chemical hazards continue to occur pointing to the need for constant vigilance with regards to both the levels of chemicals in the diets as well as their potential to cause health effects in the population.
Current Status of Food Borne Disease

Control measures of Salmonella

Control measures of Salmonella
In spite of efforts to improve the general standards of food hygiene, surveillance from many countries indicate an increase in salmonellosis.

Epidemiologic data clearly indicate that on a worldwide basis, the major sources of the Salmonella problem are contamination of raw animal products and mishandling of these products during preparations.

Reduction of the incidence of Salmonella contamination of foods requires number of approaches to the problem, beginning at the farm and going right through to the kitchen.

Foodborne salmonellosis problem can be solved by one of three undertakings:

• Eradicate salmonellae from feed, farm environments and animals

• Eliminate salmonellae from the raw foods of animal origin by pasteurization, through cooking or by radicidation (pasteurization by irradiation)

• Educate people to the dangers of salmonellosis, the sources of salmonellae and the ways to prevent transmission of disease-producing quantities of salmonellae in foods that are prepared in food processing plants, food service establishments, and in home kitchens.

Control measures of Salmonella

Shigella association with Foods

Shigella association with Foods
The principal foods involved in Shigella outbreaks were a variety of salads and seafood which became contaminated during handling by infected workers.

This was frequently coupled with improper refrigeration. After the initial infection from contaminated food, the disease readily spreads from person to person by the fecal-oral route of transmission.

Shigellas usually are considered to be relatively fragile; i.e., they do not survive well outside the host. Like most other members of the family Enterobacteriaceae, they are readily killed by most heat treatments employed in the processing and preparation of foods, and do not survive well at pH below 4.5.

However, studies on the survival of Shigella suggest that under certain selected conditions, they can survive for extended periods in foods.

For example, Shigella sonnei and Shigella flexneri have been reported to survive at 25 degree C (77 degree F) in flour and in pasteurized whole milk for more than 170 days; in eggs, clams, and shrimp for more than 50 days; and in eggs whites for more than 20 days.

At lower temperatures such as -20 degree and 0.5 degree C survival for longer periods has been reported.

Laboratory data suggest that Shigella may survive for extended periods on foods and may grow under selected conditions. However, in practice, shigellae are rarely isolated from processed products.

Manufacturers do not routinely test their products, raw materials or processing environment for Shigella, and there is no evidence to suggest that routine testing is warranted.

Most outbreaks result from contamination of raw or previously cooked foods during preparations in the homes or in foodservice establishments. Generally, the source of contamination can be traced to a carrier whose personal hygiene is poor.
Shigella association with Foods

Salmonella Association with Foods

Salmonella Association with Foods
The bulk of human salmonellosis is clearly related directly to man’s association with animals, both wild and domestics. Salmonella are host adapted; however most Salmonella are not host adapted. Although any Salmonella is a potential pathogen for humans, most food borne salmonellosis is caused by non-host adapted serotypes.

Improper cooling, inadequate cooking of thermal processing, ingestion of contaminated raw products and cross contamination were frequently identified as contributing factors in the implicated foods. Raw foods of animal origin are the major sources of salmonellae in kitchens of restaurants, institutions and homes. Salmonella may survive in these foods as a result of improper cooking, more commonly, cross contamination of foods after cooking is the source of Salmonella. Foodservice workers or in home preparers may transfer salmonellae from raw products to cooked or other uncontaminated foods as a result of not washing between handling of these foods. Salmonella can also be transferred from contaminated raw foods to equipment surfaces e.g., knives cutting boards, counter tops, etc, and then from equipment to previous uncontaminated foods. Once contamination occurs, the situation may further complicated by insufficient storage of the product before serving. Contaminated foods are sometimes kept at room temperature, improperly refrigerated, or held in warmers within the growth range for salmonellae.

Although responsible for fewer outbreaks, contamination of foods by infected workers cannot be ignored as a cause of foodborne salmonellosis. Improper hygiene practices by these individuals may lead to either contamination of foods or direct person-to-person contamination. Historically egg-products were a significant source of human salmonellosis in the United States but mandatory pasteurization of egg products has been responsible for greatly reducing eggs as an important cause of salmonellosis.
Salmonella Association with Foods

Ignorance of food handling procedures contribute to foodborne diseases

Ignorance of food handling procedures contribute to foodborne diseases
Almost all the factors that contribute to food disease result from ignorance of proper food-handling procedures or from the unwillingness of some individuals in food industries (including food processor) to comply with the basic guidelines for proper food handling. Thus foodborne diseases will continue to occur at unnecessarily high rates as long as:

• Food handlers do not employ strict sanitation in both their personal habits and in the maintenance of their work area and equipment
• Foods are not properly refrigerated
• Foods are not adequately processed
• Cross contamination situations are not avoided
• Management does not realize the importance of preventing foodborne disease

Proper food handling procedures include rather simple techniques, such as holding at specified temperatures, but they also include complex procedures, such as those for calculating processing times and predicting certain biochemical reactions that might result from processing modifications.

Ordinarily, therefore, at some level in the food processing stage, the services of a professional food technologist are required. Once a food has been properly processed, the remaining handling it undergoes does not require a professional food technologist, but it does require periodic quality control checks by personnel qualified in microbiology and sanitation.
Ignorance of food handling procedures contribute to foodborne diseases

Foodborne illness bacteria: Clostridium perfringes

Foodborne illness bacteria: Clostridium perfringens Clostridium perfringens contamination Clostridium perfringens (both vegetative cells and spores) is found in soil, sewage, manure, water, and dust. It has been found in the intestinal tract of healthy humans and animals. 

Many raw foods, particularly meats and vegetables, are likely to be contaminated with Clostridium perfringens when they reach food preparation areas. Outbreaks of illness usually involve foods high in protein. Clostridium has a requirement for 12 to 13 amino acids.) The foods include: meats, poultry, soups, gravies, sauces, stews, and casseroles. 

When food is cooked, the vegetative cells are destroyed. However, spores survive if protein-rich foods, such as roast beef, turkey, gravies,, and sauces are allowed to cool slowly and remain at temperatures that allow outgrowth of the surviving spores, vegetative cells will multiply rapidly to large numbers in the food and create a significant hazard. 

Foodborne illness 

Foodborne illness due to Clostridium perfringens usually occurs to 24 hours after ingestion. The illness is caused by ingestion of a large number of vegetative cells. When the vegetative cells reach the intestine, they form spores and release an enterotoxin that causes diarrhea and severe abdominal pain. Nausea is uncommon; fever and vomiting are unusual. 

Fatalities can occur in the very young and elderly. The infective dose is a cell population of 500,000 cells or more per gram of food. This number of cells can form rapidly in foods because Clostridium perfringens has a very rapid generation time and can double ion number every 7 minutes at 42 C. Clostridium perfringes grows at temperatures between 15 C and 53 C. 

Foodborne illness bacteria: Clostridium perfringens