Understanding the Threat of Listeria monocytogenes

Listeria monocytogenes, a bacterium with deadly implications, poses a significant risk to public health. This organism is not to be underestimated, as it can lead to severe conditions such as encephalitis, meningitis, blood-borne infections, and ultimately, death. Its potency is particularly alarming for vulnerable populations, including pregnant women, newborns, the elderly, and individuals with weakened immune systems. Shockingly, Listeria accounts for approximately 28% of fatalities attributed to foodborne illnesses.

What makes Listeria monocytogenes especially menacing is its remarkable resilience in adverse conditions. Unlike many bacteria, it can endure acidic environments, high levels of nitrites and salt, and even survive in refrigerated temperatures. Consequently, it proliferates in various food sources, with raw (unpasteurized) milk, soft-ripened cheeses like Brie, and ready-to-eat meats such as hot dogs and pâté being common breeding grounds. Moreover, its reach extends to raw and smoked fish, poultry, fresh produce, and even ice cream.

The insidious nature of listeriosis, the infection caused by Listeria, adds to its danger. Symptoms initially manifest as seemingly benign, including headaches, low-grade fevers, muscle aches, nausea, and vomiting. Regrettably, these signs often mimic those of viral illnesses, leading to misdiagnosis and delayed treatment. Such delays offer Listeria the opportunity to progress unchecked. Furthermore, symptoms may not surface until anywhere from 3 to 70 days after exposure, further complicating detection and intervention.

Treating Listeria infections demands a proactive approach. Injectable antibiotics such as penicillin, ampicillin, or gentamicin, as well as intravenous trimethoprim/sulfamethoxazole, are essential for combating the bacterium. However, prevention remains the most effective defense. Individuals at heightened risk should steer clear of foods prone to harboring Listeria or ensure thorough cooking until piping hot (at least 180 degrees Fahrenheit) before consumption.

In conclusion, understanding the multifaceted threat posed by Listeria monocytogenes is paramount to safeguarding public health. By recognizing its resilience, insidious onset, and the necessity for preemptive measures, we can mitigate its devastating impact and protect vulnerable populations from its pernicious effects.
Understanding the Threat of Listeria monocytogenes

Entamoeba histolytica can cause dysentery

Currently five types of protozoa are of concern: Entamoeba histolytica, Giardia lamblia, Cryptosporidium parvum, Naegleria and Acanthamoeba. Entamoeba histolytica is a microscopic endoparasitic of humans. It is chiefly found in the colon of large intestine.

Entamoeba histolytica, the cause of amoebic dysentery, is spread principally by fecal contamination of water, food, body parts and diverse objects: sexual partners make an epidemiological impact.

It can be transmitted by the poor personal hygiene of food handlers, contamination of ready-to-eat foods such as fruits or vegetables, from drinking water, and by insect vectors such as flies.

Entamoeba histolytica infection is widespread in subtopic areas. Infection begins when trophozoites of Entamoeba histolytica invade the colonic mucosa.

The majority of infected people do not display any pathology, and the parasite exists as a commensal, continuing to multiply and spread. Only a small fraction of the infected individuals show overt symptoms of amebiasis with invasion in the intestinal tissues or in some extraintestinal sites, such as liver.
Entamoeba histolytica can cause dysentery

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

Shigella infection

Shigella is a Gram-negative, non-motile bacillus belonging to the Enterobacteriaceae family. There are four species of Shigellae: S. dysenteriae, S. flexneri, S. boydii and S. sonnei.

It is an invasive disease of the colon caused mainly by Shigella sonnei and Shigella flexneri. Shigella is related to the acute inflammations. The essential steps of the colonic infections by the bacterium Shigella are including the adhesion, invasion, intracellular replication, and cell-to-cell spreading.

People who are sick with Shigella usually start experiencing symptoms 1 to 2 days after putting something in their mouth or swallowing something that has come into contact with the bacteria. Symptoms of shigellosis may include:
• Diarrhea (sometimes bloody)
• Fever
• Stomach pain
• Feeling the need to pass stool even when the bowels are empty

Yearly, about 165 million cases of Shigella diseases are recorded in the world, which lead to 1 million states of death, especially in the developing countries.

Shigellosis occurs predominantly in developing countries due to overcrowding and poor sanitation. Infants, non-breast-fed children, children recovering from measles, malnourished children, and adults older than 50 years have a more severe illness and a greater risk of death. The mode of transmission occurs via the faecal-oral route, person-to-person contact, household flies, infected water, and inanimate objects.

People who have been infected with a specific type of Shigella are not likely to get infected with that specific type again for at least several years. However, they can still get infected with other types of Shigella.
Shigella infection

Cryptosporidiosis: Infection and transmission

Cryptosporidiosis is a disease caused by Cryptosporidium spp, an obligate intracellular protozoan parasite. Cryptosporidium muris was first described by Tyzzer in 1910 and Cryptosporidium parvum was described two years later. However, it was not until the 1970s that Cryptosporidium was determined to be a significant cause of gastrointestinal disease in humans.

It is a frequent cause of diarrheal disease in humans, and several groups of humans are particularly susceptible to cryptosporidiosis. In developing countries, Cryptosporidium infections occur mostly in children younger than 5 years.

In immunocompromised persons such as human immunodeficiency virus-positive (HIV) patients, the incidence and severity of cryptosporidiosis increases as the CD4 lymphocyte cell count falls.

The persistent diarrhea and malabsorption can become life-threatening, particularly in acquired immunodeficiency syndrome (AIDS) patients.

Cryptosporidium is a small protozoan parasite that infects the microvillous region of epithelial cells in the digestive and respiratory tract of vertebrates. It is an obligate intracellular parasite of man and other mammals, birds, reptiles and fish. It requires its host to multiply.

When the oocysts enter the gastrointestinal tract, the invasive Cryptosporidium causes damage to the small intestinal epithelium. It disrupts the barrier function and absorption capability that leads to mild-to-severe diarrhea and other abdominal symptoms.

Cryptosporidiosis is an opportunistic parasitosis. It is characterized by self-limiting gastroenteritis in otherwise healthy people, while it is more severe in immunocompromised subjects in HIV-infected patients and constitutes a serious threat leading to chronic or fulminant disease, wasting and death.

The infection is spread in a number of ways: from person to person, from animals, via food, and by water. Cryptosporidiosis is now the most common cause of waterborne disease in the world.

Cryptosporidium oocysts transmission can occur following direct or indirect contact with an infected host usually via the fecal–oral route. Person to-person contact, zoonosis, and the consumption of contaminated food or water are well known mechanisms for fecal–oral transmission.

The largest cryptosporidiosis outbreak reported to date in the USA occurred in Milwaukee, Wisconsin in 1993 when over 403,000 individuals were sickened out of a potentially exposed population of 1.6 million.
Cryptosporidiosis: Infection and transmission 

Salmonella Abortusovis

Salmonella Abortusovis is a bacterial pathogen that affects sheep, causing abortions and stillbirths in pregnant ewes and mortality in neonates. Abortion storms can occur when this organism is first introduced. The disease develops in the last weeks of pregnancy. Once it has become established in a flock, older ewes generally have good immunity, and abortions are typically limited to young or newly introduced animals.

Available epidemiological data indicated that Abortusovis serotype is rare in most countries and regions of the world except in Europe, where it is particularly common, with reported cases in France, Spain, Germany, Cyprus, Italy, Switzerland, Russia, and Bulgaria, southwest England and Wales and also in Western Asia.

Salmonella enterica subspecies enterica serovar (serotype) Abortusovis, which is usually shortened to S. enterica serovar Abortusovis or S. Abortusovis, is a member of the Enterobacteriaceae. It is an aerobic, Gram-negative rod.

Although Salmonella Abortusovis is the serotype most frequently associated with ovine salmonellosis, especially in Europe and Middle East, other Salmonella serovars including S. Typhimurium and S. Dublin have also been described as causative agents of abortion.

Sheep can be infected by ingestion, or via the conjunctiva, respiratory tract or genital tract. Most infections are thought to be acquired by ingestion. Salmonella Abortusovis mainly occurs in vaginal discharges, the placenta, aborted fetuses and infected newborns, although it has been documented in milk and colostrum, and rarely in the testes or preputial fluid of rams. Respiratory secretions might be infectious in sick young lambs.
Salmonella Abortusovis

High risk group for salmonella infection

Salmonella are motile, Gram negative rods of the family Enterobacteriaceae. Humans typically acquire Salmonella, through the ingestion of contaminated food or water, although transmission by fomites or direct faecel-oral spread can occur. Children are at the highest risk for Salmonella infection.

Children under the age of 5 higher rates of Salmonella infection than any other aged group. In the United States, infants under the age of 1 year have the highest reported incidence rate of salmonellosis, with the highest rate in infants 2 months of age, and an abrupt decrease after infancy. Most cases are relatively mild.

Young children, older adults, those taking antibiotics, pregnant women, the elderly, and people with weakened immune systems are the most likely to have severe infections.
High risk group for salmonella infection

Shigellosis: characteristics and causes

Also known as bacillary dysentery, shigellosis, an invasive disease of the human colon is present worldwide. Shigellosis is a significant cause of foodborne illness in developed as well as underdeveloped countries. It is a bacterial infection cause by organsism in the Shigella genus, with four species that include S. dysenteriae, S. flexneri, S. boydii and S. sonnei.

Food microbiologists should be aware that shigella species can cause a rather severe form of foodborne illness and relatively low numbers of the organisms can cause disease.

Shigellosis is characterised by fever abdominal cramps, tenesmus, and dysenteric stools containing mucus blood and pus. These symptoms reflect invasion of the colonic mucosa by Shigella, the critical stage in the pathogenc process.

Product suspected of causing food poisoning should be analysed for shigella. Shigella sp. cause a diarrhea. The diarrhea may be bloody or nonbloody. Humans and other large primates are the only natural reservoirs of Shigella spp.

Transmission of from person to person by ingestion of fecally contaminated food or water. Disease onset typically occurs between 12 hours to 2 days after exposure. The infectious dose is quite small, as few as 10-200 organisms.
Shigellosis: characteristics and causes

Corynebacterium ulcerans

Characteristics of Corynebacterium ulcerans:
*Gram-stain-positive pleomorphic rods arranged in palisades or V-shaped forms
*May contain metachromatic granules
*Facultatively anaerobic
*Colonies (1-2 mm in diameter) on 5% sheep blood agar are gray-white, exhibit a light hemolysis, and may have a dry and waxy consistently.

Toxigenic Corynebacterium ulcerans accounts for most cases of clinical diphtheria in the United Kingdom. Sources include contact with cattle or ingestion or unpasteurized milk products.

Corynebacterium ulcerans is a commensal in animals and has been isolated from a wide host of domestic and wild animals (e.g. dogs, cats, horses, goats, cows, pigs , camels monkeys, squirrels and otters).

The animals may serve as reservoirs for human infection. Moreover, the bacterium causes mastitis in cattle and goats. In mastitis infection, the bacteria are present in milk.

Corynebacterium ulcerans usually cause skin infections but occasionally associated with diphtheria-like-lesions such pharyngitis and respiratory disease.
Corynebacterium ulcerans

Yersinia pseudotuberculosis

Yersinia pseudotuberculosis is a coccobacillary, gram negative bacteria that is motile at 25 ° C, nonmotile at 37 ° C and can live a long time in soil and water.

This oxidase-negative and urease-positive organism reduces nitrates and ferments glucose, galactose, maltose, mannose and xylose.

The Yersinia genus contains 11 identified species, 3 of which are known human pathogens: Y. pestis, Y. enterocolitica and Y. pseudotuberculosis.

Y. pseudotuberculosis belongs to the family Enterobacteriaceae. DNA hybridization studies have confirmed the close relationship between the agent of plaque and that of pseudotuberculous yersiniosis.

Both yersiniosis and pseudotuberculosis can be spread form animals to humans by contact with infected animals and their feces; human to human transmission also can occur. However, consumption of contaminated foods so the most frequent means of infection.

The distribution of the etiologic agent is probably worldwide. The greatest concentration of animal and human cases is found in Europe, the Russian Far East and Japan.

The pathophysiological of Y. pseudotuberculosis infections involves colonization of the digestive tract translocation through the gut epithelium, establishment within Peyer’s patches, and transport to other organs.

Infection with Y. pseudotuberculosis is associated with wide variety of clinical symptoms including fever rash, abdominal pain, vomiting, diarrhea and arthritis.
Yersinia pseudotuberculosis

Anisakiasis

Anisakiasis is an infection by the larval stages of ascaridoid roundworm Anisakis simplex from the family Anisakidae of the order Ascaridida.

Epidemiological studies conducted in Japan, have shown that cases of anisakiasis were likely to be encountered in coastal areas where individuals were involved in the fish industry.

Cases in Europe, the United States and elsewhere also appear to be on the rise, but are more likely the result of culinary habits associated with ethic groups or restaurants.

The adult Anisakis spp, inhabits the stomachs of sea mammals, such as small whales, dolphins, and seals, and passes eggs with feces into the oceans. Larvae hatch and are ingested by tiny crustaceans, which become infected and are in turn eaten by fish and squid.

The larval stage is found in a wide variety of fish, of which herring cod and the Alaskans Pollack are the most significant for human infection because they are most frequently eaten raw.

Humans are accidentally hosts in the life cycle of anisakid nematodes and although the parasites almost never develop further within human alimentary tract they may penetrate the tract and associated organs, with severe pathological consequences.

Ingestion of Anisakis larvae with seafood is often responsible for acute allergic manifestations such as urticaria and anaphylaxis, with or without accompanying gastrointestinal symtomatology.
Anisakiasis

Definition of cost of illness

The cost of illness approach is based on the premise that reduction in national output, which arises as a consequence of an incidence of a foodborne-disease measures the reduction in welfare that it causes.

An accounting approach is adopted which sums up medical expenses, foregone earnings of affected individuals and associated productivity losses to employers.

Once the cost to the individual of varying degrees of severity of infection have been estimated they are combined with epidemiological information on cases an outbreaks of disease to estimate the aggregate costs.

One problem with this approach is that the epidemiological information is notoriously under-reported, for example.

There was a report that only 1-5% of cases are reported in US and there were suggestions a range of 1- 10% in the UK.

For the United States there have been estimated the actual number of acute food-borne illnesses, hospitalization and deaths and these numbers can be used in economic analysis.

Missing from the report numbers are the chronic complications that occur in a small percentage of cases but are associated with most pathogens.

These are important since the economics costs of possibly lifelong complications, such as kidney failure, mental retardation, and paralysis, have a high economics cost to society.
Definition of cost of illness

Streptococcus in food poisoning

Streptococcus can cause a wide variety of disease including pharyngitis, meningitis, pneumonia, endocarditis, erysipelas and necrotising fascilitis.

Streptococcus may be found in the nose and throat and can cause a wide range of infections in humans.

While no longer a major cause of foodborne illness, streptococcus was among the first to be recognized as pathogens transmitted by milk and prepared food stuffs. These bacteria are found sometimes in poultry too.

B-haemolytic streptococci, St. pyogenes and Ent, faecalis have been implicated in food poisoning to a significant degree, causing classical symptoms such as diarrhea, as well as being responsible for other food-borne infections such as epidemic tonsillitis.  However, foodborne infection is infrequent.

In addition, no enterotoxin or other mechanisms of enteropathogenicity have been found in streptococcal strains associated with food poisoning. Heat treatment to at least 165 °F is an adequate measure to destroy any viable Streptococci that might be present in the uncooked food.

Streptococcus received their descriptive name from the Greek words streptos, meaning twisted chain and kokkos, meaning grain or seed.
Streptococcus in food poisoning

Roundworm

Roundworms are elongated, cylindrical individuals that may have evolved from flatworms. Roundworms or nematodes infect either the intestines or subcutaneous tissues.

Roundworms have a completed digestive tract.

The three most important roundworms that parasitize human beings are the Ascaris, the pinworm and the Trichinella worm.

The Ascaris lumbricoides is the most commonly encountered parasitic worm, infecting around 1.4 billion people worldwide.  It is a large roundworm, about the size of a large earthworm that lives in the intestinal tract.

Eggs lived in the soil and get into the body by human host swallowing infected food. They reenter the intestine, where they attach to the mucosa and suck blood for nourishment. Severe infections may cause intestinal bleeding, anemia or intestinal obstruction.

The small roundworm Enterobius vermicularis is usually called simply the pinworm because of its, small size which generally measures less than 1 cm in length.

Transmitted by the oral-fecal route, pinworms live in the intestine and usually cause no symptoms; however, in some patients the worm crawls onto perianal skin and causes intense itching.

Another small roundworm, Trichinella spiralis, causes a severe parasitic infection called trichinosis. The organism parasitizes not only humans but also a wide variety of animals.

Clinical appearance of these infections often lacks specific symptom and is rarely recognized by the infected person, even when causing significant health damage.

Intensity of infection, and thus morbidity is directly related to the number of worms harbored.
Roundworm

Food Infection

Food Infection
The cause of food borne diseases is mainly the ingestion of infected food. Apart from gastrointestinal problems and related illness due to improper diet, nutritional deficiencies and over heating, the causes of food borne illness may be due to either

1. Food Infection
   
2. Food Intoxication

The entry of pathogenic organisms and parasites into the body and the reaction of the body to the presence of organisms or their metabolites cause of the body to the presence of organisms or their metabolites cause food infection.

Pathogenic organisms make their entry through the food chain i.e. by consuming foods contaminated with such organisms. Bacterial food infection refers to food borne illness cause by the entry of bacteria into the body.

Food intoxication or poisoning is cause by consuming food contaminated with toxic substances.

Food infections may be broadly sub classified into two types.

1. Those in which the contaminated food does not ordinarily support the growth of the pathogenic organisms but merely carries them. Such food infections include diseases such as diphtheria, dysentery, typhoid, cholera, tuberculosis, infectious hepatitis, etc.
   
2. Food infections in which the food serves as a culture medium for the growth of pathogens to increase in number and cause infection when such food is consumed leading to diseases such as salmonellosis, shigellosis, gastroenteritis, etc.

Food infections can lead to outbreak of diseases in epidemic propositions.
Food Infection

Food Borne illnesses

Food Borne illnesses
Since food is biological in nature and is capable of supplying consumers with nutrition, it is equally capable of supporting the growth of contaminating microorganisms. Two types of bacterial food borne disease are recognized: intoxications and infections.

Food borne bacterial intoxication is caused by the ingestion of food containing preformed bacterial toxin resulting from bacterial growth in food.

Food borne infection, on the other hand, is caused by the ingestion of food containing viable bacteria which then grow and establish themselves in host, resulting in illness. Some pathogens occur in normal, healthy animals and in some instances man. Certain microorganisms are thus ubiquitous in nature, occurring on soil and vegetation, in animal wastes, and on animal carcasses. Human skin surfaces and nasal passages harbor staphylococci. Water supply may contain pathogens when contaminated with fecal mater.

Coastal waters in particularly may also naturally harbor recognized as pathogen Vibrio vulnificus. It is thus obvious how difficult to prevent one or more pathogens from entering raw foods.

The most common symptoms associated with food borne illness is diarrhea. Depending on the pathogenicity of the organisms and the susceptibility or health status of the host, the illness may be acute and self-limiting, or it may lead to other serious chronic and life threatening sequellae. Food borne illnesses are more likely to be life-threatening for the immune compromised, the aged , and those individuals debilitated by underlying health problems such as cirrhosis, hepatitis, hemachromatosis. The increase number of sporadic outbreaks of hemorrhagic colitis and the sequella hemolytic uremic syndrome has caused health officials to speculate that Escherichia coli serotypes may be the source of many diarrheal disease of unknown etiology. Food borne disease however, may not necessarily manifest itself in diarrheal illness but may illicit other symptoms such as abdominal cramps or pseudo appendicitis. Although a number of unusual outbreaks related to processed foods have occurred on the past few years , the majority of food borne illnesses are attributable to improper handling , cooking , and syirage practices on food service operations pr in the home.
Food Borne illnesses