Yersiniosis Yersinia enterocolitica. Importance.
Foodborne yersiniosis was first confirmed in the U.S.A in 1976 following an outbreak among a large number of school children from the consumption of chocolate milk contaminated with Yersinia enterocolitica. In many other countries, foodborne yersiniosis was also recorded. In Denmark, yersiniosis is one of the most common forms of gastroenteritis. Yersiniaenterocolitica was designated as an emerging foodborne pathogen.
The two most important aspects about the organism and the disease are that Yersinia enterocolitica is a psychrotrophand can grow at 0C, and its symptoms include a sharp abdominal pain with fever, mimicking an appendicitis.
Y. Enterocoliticacells are Gram-negative short rods, nonsporeforming, motile below 37C, and facultative anaerobic. The strains grow between 0 and 44C, with an optimum growth at 25-29C. Growth occurs in milk and raw meat at 1C, but at a slower rate. Cells can grow in 5% NaCl and at a pH above 4.6. cells are sensitive to pasteurization.
Y. enterocoliticais a normal inhabitant of intestines of food animals and birds, pets, wild animals, and humans. Human carriers do not show any disease symptoms. Different types of food can be contaminated from these sources.
Pathogenic strains are predominant in pigs. The organism produces a heat-stable toxin, pathogenic strains carry an invasive factor that enables the cells to colonize intestinal epithelial cells and lymph nodes. After colonization the heat-stable toxin capable of causing the disease.
Young children are more susceptible to foodborne yersiniosis. A high dose ( about 10 million cells) is required for the disease.
Symptoms are severe abdominal pain at the lower quadrant of the abdomen, diarrhea, nausea, vomiting, and fever. Symptoms generally appear 24-30 h following consumption of a contaminated food and last 2-3 days. The disease can be fatal in rare cases.
Because Y. enterocoliticastrains are found in the environment, many foods can harbor the organism. The organism has been isolated from:
Raw milk, processed dairy products, raw and improperly cooked meats, fresh vegetables, and improperly chlorinated water.
Because the cells are heat sensitive, a properly pasteurized or heated food can have this pathogen from recontamination following heat treatment. A food can be contaminated from human carrier or a pet. As the cells can grow at refrigerated temperature, even a low initial load can reach a high level during extended storage of refrigerated foods.
Because the strains are psychrotrophic, refrigeration cannot be used to control their growth.
Good sanitation at all phases of handling and processing and proper heat treatment are important to control the occurrence of yersiniosis.
Consumption of raw milk or meat cooked at low temperature should be avoided.
Human listeriosis is caused by Listeria monocytogenes.
The organism is present in many foods of animal and plant origin.
Its ability to grow in many foods at refrigerated temperature helps the organism reach from a low initial level to an infective dose level during storage of refrigerated food, which include those that originally harbored the pathogen and those that were postheat contaminated.
Any temperature abuse, even for a short time, can accelerate the growth rate.
L. Monocytogenesis a Gram-positive, psychrotrophic, facultative anaerobic, nonsporulating, motile, small rod. In fresh culture, the cells may form short chains. It is hemolytic and ferments rhamnose.
It grows between 1-44C, with optimum growth at 35-37C. It multiplies relatively rapidly at 7-10C. It ferments glucose without producing gas.
It can grow in many foods and environments.
It is resistant to freezing, drying, high salt, and pH 5.0 and above. It is killed by pasteurization, but when it is inside white blood cells, a temperature of 76.4-77.8C for 15 seconds is required to kill the cells.
L. monocytogenesis isolated from many environmental samples: soil, sewage, water, dead vegetation.
It is isolated from the intestinal contents of domesticated animals and birds.
Humans can carry the organisms in the intestine
Without any symptoms.
A large proportion of uncooked meat, milk, egg, seafoods, as well as leafy vegetables and tubers(potatoes and radishes) contain L. monocytogenes.
Many heat- processed foods such as pasteurized milk and dairy products , and ready to eat meat contain the organism.
The organism is isolated in high frequency from different places of food processing and storage areas.
The virulence factor of L. monocytogenesis a hemolysin, listeriolysin O. It is produced during the exponential growth of the cells.
The pathogens invade different body tissues and multiply inside the body cells, releasing the toxin.
The toxin causes death of the cells.
Disease and Symptoms
People with normal health, following ingestion of a food contaminated with L. monocytogenes, may or may not produce symptoms which appear 1-7 days following ingestion and include mild flu-like symptoms with slight fever, abdominal cramps and diaarhea. The symptoms subside in a few days, but the individual sheds the organism in the feces for some time.
Sensitive groups(pregnant women, unborn fetuses, infants, elderly and people taking chemotherapy) show enteric symptoms(nausea, vomiting, diarrhea and fever).
The pathogen then spreads through the blood stream and invade tissues in vital organs including CNS. In pregnant women, the pathogen can invade fetal tissues through the placenta. Symptoms include bacteremia, meningitis, endocarditis. The fatality rate in fetuses, newborn infants and immunocompromised individuals is very high. The infective dose is from 100-1000 cells.
Consumption of contaminated pasteurized milk, raw milk, and dairy products, soft cheese, cold cut meats, improperly cooked chicken.
heat-treated foods were either not properly heated or were contaminated following heating.
As many raw foods of both animal and plant origin harbor L. monocytogenes, consumption of raw foods or recontaminated heat-processed foods has caused listeriosis.
Growth during long refrigerated storage and temperature abuse before eating have been implicated in many cases.
Because of ubiquitous presence of L. monocytogenes, it is impossible to have foods free of this pathogen.
In many countries, a strong listeria control program at the commercial production facilities has been imposed by regulatory agencies and industries.
Consumer education to reduce foodborne listeriosis. This includes thoroughly cooking raw foods of animal origin; thoroughly washing raw vegetables before eating; not consuming raw milk or foods made with raw milk; washing hands, knives. And cutting boards after handling uncooked foods.
gastroenteritis caused by V. parahaemolyticusis common in japan and accounts for 40-70% of the total bacterial foodborne diseases.
The high incidence is directly related to the consumption of raw seafoods.
The cells are Gram-negative, nonsporulating, motile, curved rods. Catalase and oxidase positive, they ferment glucose but not lactose or sucrose. They can grow over a temperature range of 5-42C, with the optimum 30-37C. The cells multiply rapidly in the presence of 3-5% NaCl. The cells are extremely sensitive to drying, pasteurization, refrigeration and freezing.
V. parahaemolyticusstrains are halophilic bacteria distributed in coastal waters worldwide.
They are found in estuarine environment and show a seasonal variation, being present in the highest numbers during the summer months.
During the winter months, they remain in the estuarine bottom on chitinous materials of plankton.
The foodborne pathogenic strains produce a heat-stable hemolysin and are designated as Kanagawa-positive. This hemolysin is considered to be the toxin.
The toxin production rate and its level are directly related to cell growth, cell concentration, and pH of the environment.
If the toxin forms in food, heating does not destroy it.
Disease and Symptoms
Infectious dose is around one million cells. Symptoms appear 10-24h following ingestion of live cells and last for 2-3 days. Symptoms include nausea, vomiting, abdominal cramps, diarrhea, headache, fever, and chills.
Consumption of raw, improperly cooked, or postheat-contaminated seafoods, including fish, oysters, crabs, shrimp, and lobster.
V. Parahaemolyticusgrow rapidly in unrefrigerated raw and cooked seafoodsand reach an infective dose level very rapidly.
Many outbreaks in the U.S.A. were identified to be due to inadequate cooking and cross-contamination of cooked sea foods, followed by improper holding temperature.
No consumption of raw seafoods, proper heat treatment of seafoods, proper sanitation to avoid cross-contamination of heated foods,
Proper refrigeration of raw and heated products.
Consumption of food within a reasonable period of time.
Temperature abuse, even for a short duration, of a seafood should be avoided.
Unlike bacteria, human enteric viruses do not multiply in food, some may die off rapidly under various conditions of food storage and preservation.
Foodborne viral infections can occur only from enteric pathogenic human viruses.
Hepatitis A, Norwalk-like viruses, Rota viruses have been associated with foodborne infections.
They are excreted in very high numbers in human feces. They do not multiply outside human body.
Pasteurization can effectively kill the enteric viruses.
Enteric viruses can cause infection at a considerably low dose level.
Following ingestion of hepatitis A viruses through contaminated food, an individual may or may not develop symptoms.
In affected individuals, symptoms occur from 2-7 weeks. The general symptoms are fever, nausea, vomiting, abdominal discomfort, and inflammation of liver which may follow with jaundice. Symptoms may last for 1-2 weeks, the viruses are shed in feces.
NLVs cause gastroenteritis characterized by vomiting and diarrhea. Symptoms appear 12-24h after ingestion and last for 1-2 days. The viruses are excreted in feces of infected persons.
Food contaminated with fecal matter of infected people directly(from food handlers) or indirectly (via sewage and polluted water) is the main source of both hepatitis A and NLV outbreaks.
Infected food handlers, even without symptoms, can contaminate ready-to-eat food with fecal matter.
Vegetables(salads) can be contaminated with polluted water.
Shellfish harvested from water polluted with sewage and eaten raw or improperly heated before eating have been implicated in many outbreaks of both types of viruses. The virus can survive in shellfish for a long time.
The two major preventative methods of foodborne virus infections are to kill the viruses in contaminated foods and adopt good sanitation and personal hygiene habits to control contamination.
Proper heat treatment, such as pasteurization, is enough to kill the viruses.
Sanitation using oxidative agents such as hypochlorite, can kill viruses in contaminated equipment and in water used for processing.
Vaccination against hepatitis A is available and is used to control the disease.
Human brucellosis is caused by :
They are Gram-negative, nonmotile, nonsporeforming, aerobic small rods pathogenic to animals and human.
In infected animals, the organisms are located in the uterus of pregnant animals and in the mammary glands of lactating females. Thus, the pathogens can be excreted in milk.
People working with animals can become infected with Brucella spp.
People working with meat can be infected.
Consumption of raw milk and products made from raw milk(e.g cheeses) have been implicated in foodborne brucellosis.
The cells survive for a long time in milk and milk products.
Pasteurization kills Brucella cells.
Symptoms of brucellosis in humans include undulant fever with irregular rise and fall of temperature, profuse sweats, body aches, aching joints, chills, and weakness.
Symptoms appear in 3-21 days following consumption of a contaminated food.
Control measures include pasteurization of milk, manufacturing of dairy products from pasteurized milk, and proper sanitation to prevent recontamination of pasteurized products.
This organism has been isolated from animals with mastitis.
Foodborne infections have been recorded from the consumption of contaminated raw milk and milk products made with raw milk and different types of salads(contaminated by infected food handlers).
Control measures include pasteurization of dairy products and avoiding the consumption of raw milk and products made with raw milk.
People who are suffering from streptococcal infections or the carriers should not handle ready-to-eat foods such as salads.
Proper sanitation in all phases of processing and proper refrigeration will help reduce the incidence.
Q fever in humans is caused by a rickettsia,
Animal carry this organism without symptoms.
People handling animals, raw milk, and meat can be infected by the rickettsia and develop symptoms of Q fever.
Symptoms include fever, malaise, anorexia, muscular pain, and headache. Symptoms appear 2-4weeks after infection and last for 2 weeks.
Coxiellaburnetiiis more resistant to heat than many pathogenic bacteria. Proper pasteurization kills the bacteria.