Pathogens of Interest in the Food Industry

The Constant Challenge in the Market


Food safety is non-negotiable. The continuous urbanization and modernization of our country had brought major transformations in food manufacturing, processing, transporting, retailing, and even consumption. Consequently, a new understanding of foodborne pathogens that cause diseases have also evolved over time along with the advances in food science and economic developments. As reported by SGS News Center in 2015, the potential impact of food safety outbreaks at a single event can bring about huge economic losses. The US foodborne illness economic burden is estimated to cost US $77 billion to US $152 billion annually. As identified by the Centers for Disease Control and Prevention (CDC), four (4) known pathogens account for the majority of foodborne illnesses, hospitalization, and even death.

Salmonella spp.

Salmonella is one of the most common foodborne pathogens which comprises an approximate number of 2,500 species. Dr. Daniel E. Salmon, Doctor of Veterinary Medicine, discovered this group of bacteria that has been known to cause foodborne illness for over 125 years. The infection is called salmonellosis which commonly causes diarrhea, fever, and abdominal cramps after 12-72 hours of incubation, and can last for about 4-7 days. With its low infective dose of <101 to <109 CFU, salmonellosis is the most common cause of foodborne related hospitalizations and deaths amongst young children, elderly, pregnant women, and those with weakened immune systems. Its natural reservoirs are the intestinal tracts of domestic and wild animals, eggs, and poultry meats. However, this does not save us from being infected from other sources of contamination such as fruits, vegetables, and dry food matrices like spices and flour.

Pathogens of Interest in the Food Industry

As reported in 2015 by the CDC and the US Food and Drug Administration (US FDA), a total of 907 people from 40 different states were infected by the strain Salmonella Poona. In this incident, 204 people were hospitalized, and six deaths were reported from Arizona, California, Oklahoma, and Texas. The contamination was identified to come from a fresh produce company, and after several investigations, it was traced back to Mexico where it was imported from. Although the root cause of contamination was not identified, US FDA investigators suspected the waste water management, equipment design of pre-wash areas, and storage of packaging material as possible causes. This outbreak was included in the Six Deadliest US Foodborne Outbreaks as reported by Food Safety News.

Salmonellosis can be obtained through consuming raw and undercooked eggs, poultry, meat, contaminated raw fruits and vegetables, and unpasteurized milk or other dairy products. Moreover, possible sources include indirect transmission through contact with infected animals or contaminated hands and utensils. Even though Salmonella can be widespread, contamination or infection can be prevented by proper hygiene and thorough cooking with core temperatures of 65°C for 10 minutes or 60°C for 1 hour.

E. coli O157:H7

Escherichia coli is a large and diverse group of bacteria that was discovered by Dr. Theodor Escherich, a German-Austrian pediatrician and bacteriologist. E. coli can be found in the environment, foods, and intestines of people and animals. Most strains of E. coli are harmless and have an important role in the human intestinal tract, it is also used as a marker of fecal contamination in water. Included in the disease-causing E. coli are the ones that are capable of producing a toxin called “Shiga toxin” (STEC) which causes gastrointestinal illness and can even lead to life-threatening complications such as Hemolytic Uremic Syndrome (HUS). Sources of contamination can be raw or undercooked meat, raw sprouts, contaminated milk, contaminated water from pools, and contact with unsanitized hands. Clinical manifestation will appear after 3-4 days after exposure, the infection will last for about 4-7 days with regular intake of water.

The most common pathogenic strain of this group is the E. coli O157:H7, which was first recognized in 1982, known to have caused the outbreak of severe bloody diarrhea from contaminated hamburgers. Likewise, this strain has extremely low to statistics, about 2-7% of infections lead to HUS. This syndrome is caused by Shiga toxins that destroy the red blood cells, and which was found out to be the principal cause of renal failure among children in the US.

Amidst the E. coli outbreaks, the 1993 Jack in the Box incident was the most widespread as it had an uncommonly high incidence of HUS amongst the children in Seattle. The contamination was traced back from contaminated and undercooked burger patties that were sold from 73 different locations causing about 700 people to fall ill, wherein 171 were hospitalized and 4 deaths were reported. The following year after the outbreak, the company lost approximately US $160 million due to court trials and lost sales.

Campylobacter spp.

In the article of Dr. Manny Garcia, “Spiral - Shaped Bacteria Take Center Stage in Food Safety and Gut Health,” he discussed in detail how Campylobacter has now become a highlight among microbiological concerns.

Campylobacter is comprised of twelve (12) species and six (6) subspecies, among which are two (2) of the most implicated species that cause human illness – C. jejuni and C. coli . Campylobacter is very sensitive to environmental conditions as it requires minimal concentration of oxygen. These species are widely present in most warm-blooded animals, and are similarly prevalent in food animals such as poultry, cattle, pigs, ostrich, and pets including cats and dogs. According to the World Health Organization (WHO), Campylobacter is considered to be the most common bacterial cause of human gastroenteritis in the world. In the Philippines, prevalence is yet to be further investigated as there is still the need to develop traceability and recording while increasing awareness among manufacturers and consumers.

The main route of transmission is foodborne with the consumption of undercooked meat, meat products, contaminated milk, and water. A recent research study conducted by the University of the Philippines Diliman - Institute of Biology, showed that poultry meat sold in markets in Metro Manila is contaminated with drug-resistant Campylobacter spp., wherein liver and skin samples had the greatest levels of contamination (97.4%). Also, majority of contamination was discovered in wet markets (84.65%) compared to supermarkets (70.5%). In 2017, however, as also mentioned in Dr. Garcia’s article, there was an outbreak of antibiotic resistant Campylobacter that was traced to Petland. A total of 55 people who were exposed to infected puppies sold at Petland were confirmed to have the infections. With its peculiarities, vast majority of cases occur as isolated incidences.

Listeria spp.

Listeria was first discovered in the 1920s by Dr. Everitt Murray, and was originally named as Bacterium monocytogenes. It was later on renamed to honor Dr. Joseph Lister who discovered the importance of sterilization. This genus is ubiquitous, widely distributed in nature, and considered as a prolific environmental contaminant. It can also be found in some animals, including poultry and cattle, and any food made with raw milk. Generally, low temperature is often used to control the development of certain food pathogens. Unlike other bacteria, Listeria spp. is psychrotrophic, enabling it to grow and multiply at low temperatures which increases its chance of infecting susceptible individuals especially pregnant women. In December 2017, the widest Listeria outbreak recorded occurred in South Africa, wherein around 1,000 people fell ill and 180 people died. The root cause of contamination was a ready-to-eat meat product called ‘‘polony’’.

Out of the 17 identified species, Listeria monocytogenes causes the most illness with an approximate infective dose of 10-100 CFU that varies per individual. As released by the US FDA in 2017, most recalls for frozen goods are caused by L. monocytogenes contamination, this includes ready-to-eat meals, salads, fruits, processed foods, ice cream, cheese, and other dairy products. As an environmental contaminant, Listeria is very prolific in tubes and drains forming biofilms. Nearly 30% of the food processing drains tested were positive for Listeria, according to a US FDA report.

Listeria is an intracellular parasite that attacks intestinal mucosa which leads to systemic infection affecting the whole body. Moreso, the infection caused a worldwide concern due to approximately 2,500 reported cases of listeriosis in the US each year, 20% (500 people) of which has led to death. Symptoms occur as fever, nausea, muscle aches, and headache after 31 days of exposure. In such cases, aside from its prolonged incubation period, the above-mentioned symptoms are all common flu-like symptoms, which makes it even more difficult to diagnose. Pregnant women are more susceptible which can lead to abortion and stillbirth. Furthermore, for groups of immunocompromised people, Listeria infection can lead to loss of balance, convulsions, and strokes.


In general, the four (4) major pathogens of concern have common means of transmission, infection, and symptoms, which makes detection and diagnosis even more challenging. Cases of food poisoning can never be eradicated but can be prevented through correct knowledge, and the practice of food safety - equally from both manufacturers and consumers.


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