Food Microbiology Glossary
Bacillus cereus bacteria are large spore forming, Gram-positive rod-shaped, facultative anaerobes. Although there are many species of Bacillus, B. cereus belongs to a group that are characterized as "large-celled, Group I" Bacillus species. In this group there are five known species of Bacillus, including B. cereus, B. thuringiensis, B. mycoides, B. anthracis, and B. megaterium.
Individuals of all ages of people are susceptible to B. cereus infection. B. cereus causes two types of food poisoning; a diarrhea type caused by a large molecular weight protein and the vomiting (emetic) type caused by a low molecular weight protein. The symptoms of B. cereus infections mimic the symptoms of Clostridium perfringens (B. cereus diarrhea type) and Staphylococcus aureus (B. cereus vomiting type) and as a result in some situations it is hard to determine the causative agent without laboratory testing.
Symptoms of B. cereus include watery diarrhea, abdominal cramps, and pain. Symptoms occur within six to fifteen hours after the consumption of the contaminated food. Nausea may also accompany the diarrhea, but vomiting is rare. The onset of a B. cereus infection is usually very rapid and symptoms may only last for twenty-four hours in most cases.
No specific complications have been associated with the diarrhea and vomiting toxins produced by B. cereus. Other clinical manifestations of B. cereus invasion or contamination have been observed; such as bovine mastitis, severe systemic and pyogenic infections, gangrene, septic meningitis, cellulitis, panophyhalmitis, lung abscesses, infant death, and endocarditis.
B. cereus are common in the environment and can be found in soil, dust, air, water, and on decaying matter such as food. Transmission and infection by B. cereus is through direct ingestion thus making contaminated food and water sources the major source of outbreaks by B. cereus.
Contaminated foods usually associated with B. cereus infections include meats, milk, vegetables, fish, rice, and other starchy foods such as potatoes, pasta, and cheese products. Food mixtures have also been to blame in items such as soups, sauces, puddings, casseroles, pastries, and salads. All of the afore mentioned sources, except for rice and starchy products, are of the large molecular weight protein type of food poisoning, whereas the rice and other starchy products are of the vomiting type of outbreaks characteristic of the low molecular weight, heat-stable protein.
B. cereus grows best at a temperature between 30° to 37°C, but may grow at temperatures as high as 55°C or as low as 5°C, and at an optimum pH of 4.3 to 9.3. The growth of B. cereus is inhibited by the presence of 0.1% acetic acid. B. cereus is able to grow in both anaerobic and aerobic conditions. It however grows best in the presence of oxygen. This ability to grow with or without oxygen and its ability to form spores allows it to survive all stages of food processing, other than retorting.
Historic outbreaks of B. cereus are suspected because of the described symptoms, but due to the similar effects of Clostrium perfringens and Staphylococcus aureus it is unknown how many were actually caused by B. cereus as the infectious organism. However since 1973 to present day it has been reported by the CDC that 2% of all food-borne illnesses in the USA were from B. cereus. Recently in 1993, Virginia had a major outbreak of B. cereus where 67 individuals (mostly children) were fed infected catered food. The results were that 14 individuals, (12 children and 2 adults) showed actual sickness from B. cereus bacteria, were treated and survived. This equated to 29% of the individuals who had consumed the infected food. The outbreak was traced to chicken fried rice from a local restaurant.
Shigella bacteria can cause an acute gastrointestinal disease in humans. Transmission of Shigella is typically through a direct or indirect fecal-oral route from person to person, with humans being the main reservoir for the organism. There are four common Shigella species; Shigella dysentariae(Group A), Shigella flexneri (Group B), Shigella boydii (Group C), and Shigella sonnei (Group D). Shigella sonnei accounts for over two-thirds of the shigellosis in the United States. Shigella flexneri is the second most common cause of shigellosis and accounts for almost all the rest of the cases in the world. In the United States these two species account for the greater majority of shigellosis reported. Other species are very rare in the United States although still are of important causes of disease in developing countries. In the developing world, Shigella dysenteriae type 1 may cause deadly epidemics.
Shigella bacteria can infect humans in a number of ways. It may be passed from person to person by contact with stools or soiled fingers of infected individuals. This primarily occurs when basic hygiene and hand washing habits have been neglected. Shigellosis is common in toddlers.
Shigella can be transmitted to individuals through the ingestion of contaminated foods. Even though the food may look and smell normal it may be infected with Shigella. Food can become contaminated from infected food handlers that fail to wash their hands with soap after using the restroom. Vegetables may also be a source of contamination by harvesting from sewage-contaminated fields. Shigella can be transferred to food by flies. Flies may breed in infected feces and then contaminate food by alighting on the food. Another common mode of transfer to humans is by drinking or swimming in contaminated water either from water fountains, swimming pools and lakes. Shigella are not transferred through air, only by direct contact.
Over eighteen thousand cases of Shigellosis a year are reported in the United States alone. This number may be twenty times greater due to many mild cases that go unreported. Most outbreaks of Shigellosis occur in areas where hygiene and sanitation conditions are very poor. Frequently an entire community may experience an epidemic that can reoccur every few years. Shigellosis is more common in the summer since warmer conditions are favorable for the bacteria to multiply to infectious levels. The people that are most likely to be infected are infants aged 2 to 4 years old and the elderly. Common outbreaks occur in childcare settings and in families with many small children. In developing countries Shigellosis is more common. In the United States the numbers of Shigellosis cases have steadily risen in the last 30 years from 6 cases /100,000 people in 1965 to 12 cases/100,000 people in 1995.
Identification of Shigella can only be determined through laboratory testing of stools of infected individuals or testing suspected contaminated foods. Many diseases cause diarrhea and bloody diarrhea, and therefore treatment of the disease is only possible with the identification of the specific bacteria.
Shigellosis is usually treated with antibiotics. Antibiotics commonly used for treatment in serious cases are ampicillin, trimethoprim/sufamethoxazole, nalidixic acid, or ciprofloxacin. Antibiotics are only used in serious infections due to the rise in antibiotic resistance of some strains. Mildly infected usually receive no antibiotic treatment and recover quickly. Anti-diarrhea medications such as Imodium or Lomotil should be avoided and are likely to make the illness much worse. There are no vaccines to prevent Shigellosis. However the spread of Shigella from person to person can be stopped by improving hygiene conditions such as washing hands with soap, proper disposal of soiled diapers, sanitation of changing areas, and good judgment on the quality of food and water consumed.
Symptoms of Shigellosis are caused by the bacteria invading the intestinal mucosa, leading to diarrhea, fever, and stomach cramps, with the onset of systems occurring a day or two after the individual has been exposed to the bacteria. The diarrhea is often bloody and in severe cases may lead to hospitalization of an individual. Severe cases may also be associated with seizures in infants 2 years and younger. In some cases an individual may be asymptomatic. In these cases it is possible to pass the disease to other individuals. Shigellosis usually resolves in five to seven days amongst non-compromised individuals.
Individuals with Shigellosis may also experience long-term effects. Approximately three percent of individuals infected with Shigella flexneri will later develop joint pain, eye irritation, and painful urination. This is also known as Reiter's Syndrome. The length of Reiter's Syndrome may last for months or years and can lead to chronic arthritis, and mostly occurs in susceptible individuals.
If an individual becomes infected with Shigella, it may be several years before that individual is susceptible to re-infection. However the individual may become infected with a different species of Shigella.
Clostridium perfringens are anaerobic, non-motile, Gram positive, spore-forming rod-shaped bacteria.
Cooking food above 140°F will kill vegetative cells and most spores of C. perfringens, but there is the potential that a few spores may survive. Optimal growth for vegetative cells and the production of toxins is between 70° and 120°F. Spores of Clostridium perfringens are able to survive for a very long time until exposed to conditions favorable for growth.
C. perfringens is widely distributed in the environment in soil, sediments, areas subject to human and animal fecal pollution, and can even be found frequently in the intestines of humans and many domestic animals.
C. perfringens enterotoxin is produced in the small intestine after ingestion of contaminated foods and not produced in the food itself. The most common toxin produced in all strains is the Alpha Toxin that causes the majority of the illnesses. However other toxins associated with C. perfringens may also have harmful effects on the human body.
C. perfringens is transmitted from contaminated foods, mainly meat, meat products, and gravies where spores have survived during the cooking process, and during the cooling process, or afterwards in storage, germinate and reproduce to high levels. It usually takes many organisms, approximately or greater than, one hundred million vegetative cells to produce illness. As a general rule any raw food may contain the C perfringens spores.
Children and the elderly are at most risk for C. perfringens infection. There are very few complications with individuals under the age of 30 years old. Elderly persons are more likely to experience more severe symptoms and take longer to recover.
Common symptoms of food poisoning from C. perfringens are diarrhea, abdominal pains, and in certain instances gas gangrene. Symptoms occur from 8 to 22 hours after consumption of contaminated foods containing large numbers of C. perfringens. The duration of this illness lasts on average of twenty four hours, but has been reported to last as long as one to two weeks in the elderly but with less severe symptoms. A few deaths have been reported due to severe dehydration and other complications.
One strain of serious interest is C. perfringens Type C. This strain is often fatal and a serious concern in developing countries, but in the USA it is very rare. This strain causes necrotic enteritis (also known as pig-bel syndrome). Pig-bel syndrome victims have necrosis of the intestines and a resulting septicemia.
Diagnosis and identification of C. perfringens as the causative agent can be aided by the individuals symptoms, the delayed onset of the illness, and by detecting large numbers of the bacteria in either the individuals fecal matter or by lab analysis of suspected contaminated foods.
C. perfringens is one of the most commonly reported food-borne illnesses in the US. In 1981, there were 1,162 cases in 28 separate outbreaks. In the last 2 decades, there have been at least 10 to 20 outbreaks each year infecting dozens to hundreds of people at a time. The CDC estimates that about ten thousand people a year in the USA infected by C. perfringens but many go unreported due to the rapid recovery of infected individuals. Most outbreaks of C. perfringens occur in the feeding facilities of institutions such as schools, hospitals, prisons, nursing homes, etc. where large quantities of food are prepared hours before serving and allowed to sit prior to consumption. C. perfringens has been labeled the Food Service Germ.
Clostridium botulinum are anaerobic, Gram positive, rod shaped, spore forming bacteria. The spores are oval, sub-terminal and swell the cell. The spores are able to survive in a dormant stage for a very long time until exposed to favorable growth conditions.
There are three types of botulism produced by Clostridium botulinum. The first and most important is food-borne botulism, caused by eating foods that are infected with the botulism toxin. The second is wound botulism that occurs when C. botulinum enters the wound of an injured individual and produces a toxin. The third is infant botulism where the infant consumes the spores of C. botulinum that then grow in the intestines and release the toxin. All 3 of these types of botulism have the potential to be fatal and are considered a medical emergency. However the food-borne botulism is of most concern and the most dangerous since it has the potential of infecting many people at one time.
Clostridium botulinum are very common in the environment and are most common in soil.
Botulism is fairly common in the United States. Each year about 110 cases are reported. Approximately 25% are food-borne, 72% are infant, and about 3% are wound botulism. Food-borne outbreaks occur mostly in outbreaks of 2 or more people after eating contaminated home-canned foods. The number of cases of botulism from the food-borne and infant types has changed very little in recent years, but wound botulism is on the rise due to the increase in black-tar heroin users. California has exceptionally high numbers of wound botulism compared to the rest of the United States.
Classic symptoms associated with this disease are double vision or blurred vision, drooping eyelids, slurred speech, dry mouth, difficulty swallowing, and muscle weakness. Infants with botulism may show signs of lethargy, lack of appetite, constipation, a weak cry, and poor muscle tone. All of these symptoms are the result of the bacterial toxin causing muscle paralysis. If symptoms are left untreated, the disease may cause paralysis of the arms, legs, trunk, and respiratory muscles.
When one is infected with the food-borne botulism, symptoms may begin as early as 6 to 36 hours after eating contaminated food with C. botulinum, or as late as 10 days after consumption.
Many tests may be considered to differentiate other diseases from botulism. They may include a brain scan, spinal fluid examinations, nerve conduction test (EMG), and a tensilon test for myasthenia gravis. However the most direct confirmation method for the diagnosis of this disease is to demonstrate the presence of the botulinum toxin is in the patient's serum or stool by injecting the patient's serum or stool directly into mice and observing the mice for symptoms of botulism.
The effects of botulism on the body can be severe and may require a patient to be on a breathing machine if respiratory failure and paralysis have occurred. This may also lead to many weeks of intensive medical and nursing care. In time paralysis should slowly improve. In food-borne and wound botulism, if diagnosed early, the patient may be treated with an antitoxin that will block the action of the toxins circulating in the blood stream. This may not cure the individual initially, but will at least prevent the victim from worsening. At the present time, the antitoxin is not given routinely for infant botulism, only in specific, rare cases.
Individuals with the food-borne botulism may be treated by inducing vomiting or by using enemas to remove as much of the toxin from the body as possible.
Wounds with botulism should be treated surgically by removing the source of the toxin-producing bacteria.
Overall, good supportive care in a hospital is key to treating all forms of botulism. Most deaths from botulism are from respiratory failure. However in the last 50 years the deaths from respiratory failure has reduced from 50% down to 8% due to early detection and better hospital equipment available. Those that are on intensive care for respiratory failure may require a breathing machine for several months. These individuals may have long-term effects for years including shortness of breath and long-term therapy to aid in the recovery.
Food-borne botulism can be prevented by properly canning foods in a sterile environment. Wound botulism can be prevented by cleaning all dirt and debris, and by applying an antiseptic, such as hydrogen peroxide.
Serratia are facultative anaerobic, motile, Gram-negative rod-shaped bacteria. Serratia grow well at a pH of 9 and at a temperature between 20° and 37°C. Growth in all strains of Serratia is inhibited when the pH is less than 4.5 or when the temperature exceeds 45°C.
The genus Serratia is in the family of Enterobacteriaceae. There are seven common species of Serratia: S. odorifera, S. liquifaciens, S. rubidaea, S. ficaria, S. pymuthica, S. fonticola, and S. marcescens. S. marcescens is the species of most interest since it causes the most number of infections each year and is steadily rising due to increasing antibiotic resistance and increasing virulence. S. marcescens is responsible for a large percentage of nosocomical urinary and respiratory tract infections, amongst cystic fibrosis and burn victims. S. liquifaciens, S. rubidaea, and S. odorifera have only rarely been implicated as the infectious agents in these infections.
Serratia bacteria naturally occur in soil, water, plant leaves, shrubs, fruits, vegetables, herbs, mushrooms, mosses, insects, and in the intestines of animals and humans. Most species of Serratia are commonly found in human fecal matter.
Individuals can become infected by direct contact of water droplets containing Serratia organism. Also direct hand-to-hand contact by hospital personnel and medical equipment has been associated with the spread of Serratia in hospitals. Sources documented to contain Serratia include catheters, saline irrigation solutions, and other supposedly sterile solutions.
Serratia has only been recognized as a human pathogen only since the 1960's. Before that time, the red pigment found in some strains of Serratia made them attractive as a marker organism to study bacterial transmission. In 1951 and 1952 the U.S. Army conducted a study called Operation Sea-Spray over San Francisco with S. marcescens. The study involved studying wind currents that may carry biological weapons. The government filled balloons with S. marcescens and then burst them over San Francisco releasing the bacteria over the city. Shortly after doctors noticed a drastic increase in the population having pneumonia and urinary tract infections directly associated with S. marcescens. From there on, Serratia has been an important organism of study due to its proven pathogenicity.
Rope spores are from the bacteria Bacillus subtilis and Bacillus mesentericus (also known as Bacillus pumilus). The organisms infect bread products and bread ingredients. Contamination breaks down the components of the bread and leaves behind a sticky, pasty, stringy mass. The ropey-ness is referred to when the bread is pressed together and then pulled apart. If it is ropey then it will stretch into long, sticky, web-like strands. The bread product will also have a strong odor similar to an overripe cantaloupe.
Sources of Rope Spore organisms in bread products are mostly present in the ingredients, especially flour and yeast. Unlike molds that are killed when exposed to baking temperatures, Rope Spore organisms are able to form spores and survive the baking process, germinate, and continue to grow.
If bakery products are contaminated with Rope Spore organisms, then it may be necessary to treat the bakery with special chemicals and a thorough steam cleaning to rid the bakery of the organisms.
Bacillus subtilis are Gram positive, rod shaped bacteria. Bacillus mesntericus are Gram positive, rod shaped bacteria. Baciillus mesentericus grows best between 10° and 40°C.
Two species of Bacillus comprise the flat sour spore group. These are Bacillus coagulans (Bacillus thermoacidurans) and Bacillus stearothermophilus. These bacteria are thermophilic aerobic spore formers and are found in acidic food products such as canned tomato and dairy products. If the conditions are favorable these organisms may germinate and lead to food spoilage. Flat sour organisms are a big concern for individuals involved in processing canned foods. Growth of flat sour organism may cause the pH to drop to between 0.3 and 0.5. The organisms may grow in cans, yet the ends of the cans will remain flat, compared to other organisms such as Clostridum thermosaccharolyticum that will swell the ends of the cans when spoiled. The spoilage of the food is due to a drop in pH from the growth of the organisms.
There are 3 categories of thermophilic sporeformers that cause food spoilage:
Bacillus stearothermophilus is relatively common in the environment and can be found in soil, hot springs, desert sand, arctic waters, ocean sediments, food, and compost. It grows very well at 65°C and has a limited tolerance to acid. It is a Gram-positive rod shaped bacteria.
Bacillus coagulans is found rarely in soil but may be found in many food products. They have been found to multiply very rapidly in acidic foods such as canned tomato juice, silage, medicated creams, and antacids. B. coagulans is also a Gram positive rod.
The history of controlling flat sour spores goes as far back as the 1930's when the National Canners Association developed a standard media to isolate flat spores from spoiled canned foods. Being able to isolate and identify the organisms changed the industry and increased the understanding of flat sour spores.
Flat sour spores are not directly pathogenic to people. These organisms only cause spoilage in canned foods if the product is not cooled properly. If not cooled properly, the organism has the potential to grow and decrease the shelf life of the canned foods. A food spoiled by flat sour organisms will produce a sour smell and taste. Flat sour spore testing is of most interest for food processors that want to ensure a long shelf life of a product and to prevent early spoilage in sensitive tomatoes and dairy food products.
Vibrios are Gram negative, facultative anerobic, rod or curved shaped bacteria that are usually motile, and measure 0.5 to 0.8 micrometers in width by 1.4 to 2.6 micrometers in length. These bacteria do not form endospores or microcysts. In the genus of Vibrio there are more than 30 known species. Of these 30 species there are about 13 that are known human pathogens. These 13 species are V. cholerae, V. parahaemolyticus, V. vulnificus, V. mimicus, V. fluvialis, V. furnissii, V. alginolyticus, V. carchariae, V. damsela, V. cicinnatiensis, V. hollisae, and V. metschnikovii. In particular the Vibrio species of most concern and the result of most outbreaks is Vibrio cholerae.
Individuals of all ages are known to be susceptible to Vibrio infection. Children and adults have both become severely sick from consumption of contaminated seafood and from wounds infected with contaminated seawater.
Many Vibrio species produce the same common symptoms. Usually an infection manifests as acute gastroenteritis with severe diarrhea and dehydration. Symptoms vary from individual to individual, and from species to species of Vibrio. Infections may be asymptomatic, to mild, to severe and possibly lead to death. Death is usually the result of severe dehydration. In many cases of involving V. cholerae, an individual may become infected and die within 5 hours if untreated. Other species of Vibrio such as V. damsela have caused a rapidly progressive necrotizing infection. Currently there are no known long-term health affects due to Vibrio infection and most patients usually recover very quickly if treated promptly.
Vibrio may be found in contaminated seafood and shellfish, mostly in developing countries. It has been linked to people eating foods such as raw oysters, raw seafood, half-dried sardines, coconut milk, crabs, and seafood cocktails. It may also be found in contaminated seawaters worldwide. The most common outbreaks of V. cholerae are from the gulf coast waters and annually affect many gulf coast states in the United States and in Latin America, although it may also be found worldwide in Africa, Asia, and South America. Most Vibrio outbreaks in the United States outside the gulf-states are from consumption of imported contaminated seafood or shellfish from developing countries with poor sanitary conditions. These are usually travelers visiting developing countries and bringing home exotic foods.
Individuals may become infected when an open wound comes in contact with contaminated seawater. In one case a child contacted Vibrio carchariae after a shark attack in contaminated seawater. The seawater entered the wound and produced an infection. Vibrio is never transferred from human to human, or in the air.
The known history of Vibrio goes back as far as the 1800's when 7 pandemic outbreaks of V. cholerae occurred raising concern of the spread of this disease. Over the past 200 years outbreaks have occurred annually around the world due to the many species of Vibrio and are still a major health concern.
Vibrio is very common worldwide but less frequent in the USA. In 1990 the World Health Organization confirmed just less than 100,000 cases of V. cholerae worldwide. In 1991 and 1992 Latin America had 745,309 cases of Vibrio related infections and 6,403 confirmed deaths from V. cholerae. In the USA however, V. cholerae is very rare and only a few individuals are affected annually from foreign foods.
Treatment of Vibrio victims may require immediate medical care since this disease has a rapid onset of sickness. Since the disease causes severe diarrhea and dehydration, proper treatment involves drinking lots of water and replenishing salts. In many instances a prepackaged mixture of salts and sugars diluted in large amounts of water do well in re-hydrating an infected person. In severe cases intravenous fluid replacements may be necessary. To date there are no vaccines for Vibrio. Besides re-hydrating the body, no other pharmaceuticals are necessary to bring an individual back to health.
How can a person prevent being infected with Vibrio? Since the risk for Vibrio exposure is very low in the US, it is of most concern to travelers visiting other countries. A person can avoid being contaminated in a foreign country by following a few simple rules. For water consumption make sure water is boiled or treated with chlorine or iodine. Also buying beverages that are bottled and made with purified water will lower your chances of exposure. When eating foods it is best to eat foods that are thoroughly cooked and are hot when consuming. Foods such as raw fish, shellfish, and vegetables should be avoided unless you can peel the vegetables. Street vendors should be avoided to reduce exposure to Vibrio in foreign countries.
Yersinia bacteria are facultative anaerobic, Gram negative, bacteria. They measure 0.5 to 0.8 micrometers in diameter by 1.0 to 3.0 micrometers in length. Endospores are not formed. There are 11 known species of Yersinia with 3 of these species being known human pathogens. The 3 human pathogenic species are Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica. Of the three, Y. pseudotuberculosis and Y. enterocolitica are food borne pathogens whereas Y. pestis is transmitted by other methods. Y. enterocolitica is of most concern to public health.
Individuals of all ages are susceptible to infection from all 3 of the pathogenic species listed above but symptoms may be different in children than in adults. Y. enterocolitica however is more prevalent in children than adults.
The symptoms of Yersinia vary depending on the age of the individual infected. Generally children under 15 years old are at most risk for infections. With Y. enterocolitica, children may have a fever, abdominal pains, and possible bloody diarrhea. Symptoms will start developing about 4 to 7 days after exposure to and may last as long as 1 to 3 weeks after the onset of symptoms. For older children and adults the symptoms may be much different and may be confused with appendicitis since the symptoms are abdominal pains in the right side and fever but no diarrhea. This may lead to unnecessary appendix operations and misdiagnosis by doctors. In a few cases, adults may have other symptoms such as joint pains, skin rashes, vomiting, and the spread of bacteria into the bloodstream. In Y. pestis, individuals can contract sylvatic plague and show signs of pneumonia. There are no known long-term affects associated with Yersinia infection except for joint pains that may persist for 1 to 6 months.
Yersinia can be found in a wide range of hosts and foods. It has been found in pigs, birds, beavers, rabbits, squirrels, sheep, rodents, fleas, cattle, dogs, horses, and cats. The main host for food consumption with Yersinia is in pigs with the flea being the vector. In pigs, the bacteria may actually be found directly on the tonsils. Yersinia has also been found in lakes, ponds, milk, ice cream, and various meats, particularly pork. In some instances Yersinia has been isolated from the environment in the soil.
An individual can become infected with Y. enterocolitica by eating contaminated food such as undercooked meat products or drinking contaminated un-pasteurized milk or untreated water. Yersinia is prevalent in these products since the organism has the ability to grow at refrigerator temperatures. In other cases children can be infected by caretakers who handle raw pork intestines and do not wash their hands thoroughly enough before changing diapers. Infections of Yersinia enterocolitica have also been through direct contact with infected animals and in rare cases past from person to person after coming into contact with the stools of an infected person and entering the mouth of another person. This only happens in situations where hygiene is lacking or inadequate. Yersinia is rarely transferred during medical operations requiring a blood transfusion.
Known Yersinia outbreaks go back very far in human history, especially with the species pestis. It has been traced back as far as 1320 BC with large epidemics of the Plague in Europe and Asia. Throughout history the plague has taken many lives and continues to still be a problem today. Three of the most notable plagues in history are Justinian's Constantinople pandemic from 540 to 590, the Black Death pandemic from 1346 to 1361, and the Great Plague of London pandemic in 1665. In the United States many epidemics have also occurred in modern times especially in the southwestern United States, Arizona and New Mexico in particular, where every few years a couple cases are reported. Outbreaks in Arizona have been estimated to reoccur every 10 years and in periods of high rainfall. In the world today there is about 10,000 cases reported annually.
The CDC estimates that about 17,000 cases of Yersinia occur each year in the United States. This disease however seems to be more prevalent and more of a problem in Northern Europe, Scandinavia, and Japan, but is still a concern in the USA.
In most cases of Yersinia infections, the victims tend to recover on their own without medical treatment. In more severe cases, the use of antibiotics such as doxycycline, trimethoprim-sulfamethoxazole, aminoglycosides, or fluoroquinolones may help in the recovery of an infected individual with Yersinia.
To prevent infection avoid the consumption of uncooked or undercooked pork, and other meat products, and un-pasteurized milk. The washing of hands with soap after the contact with animals will also decrease the chances of being infected. Proper cleanup of animal feces and providing a clean environment for animals will reduce the spread of the organism. In the kitchen, sanitary conditions should be practiced and by thoroughly cleaning cutting boards, utensils, and kitchen surfaces before and after the preparation of meat.
Escherichia coli (E. coli) are gram negative, facultative anaerobic, rod-shaped bacteria. E. coli 0157:h7 differs from other E. coli strains in the fact that it exhibits slow or no fermentation of sorbitol and has no glucoronidase activity.
Many strains of E. coli can cause stomach pains and diarrhea, but 0157:h7 causes the most severe infection. The disease is referred to as hemorrhagic colitis. A patient with a persistent condition can also become afflicted with hemolytic uremic syndrome, which can be a fatal kidney disease.
Non-pathogenic E. coli are found in the intestinal tract of warm blooded animals, including humans, and are integral microbes in the digestion of foods.
E. coli infections are fairly common in the United States. According to the Centers for Disease Control there are about 73,000 cases of infection per year and 61 deaths from these bacteria. The most common way of contracting E. coli is via contaminated foods, such as raw or undercooked beef, raw milk, alfalfa sprouts, or drinking water contaminated with sewage. Beef becomes contaminated with the bacteria when the slaughter is performed improperly and becomes widespread when that beef is ground together with other beef.
The symptoms of hemorrhagic colitis are severe abdominal cramps, bloody diarrhea, occasional vomiting, and a low grade or absent fever. Symptoms appear about 72 hours after exposure and the disease usually lasts for an average of 8 days.
The disease is diagnosed from the isolation of the bacteria or their toxins from stool samples. The toxins produced by the bacteria are verotoxin or shiga toxin. Shiga toxin is very similar to the toxin associated with Shigella dysenteriae.
Most patients recover without any special treatment in about a week. In fact antibiotics should not be used. Studies have shown that increased complications have been associated with the use of antibiotics.
E. coli outbreaks can easily be prevented by cooking all beef thoroughly, until there is no pink and the juices run clear.
A famous outbreak of E. coli occurred at the Jack in the Box fast food chain in 1993 when many people became ill from eating contaminated beef.
Listeria monocytogenes are Gram-positive bacteria, motile via flagella. L. monocytogenes is unique because it can grow at temperatures as low as 3º C, which means that it can multiply in refrigerated foods. It also resists freezing, desiccation, and heat, which is astonishing since the bacterium does not form spores.
The disorders caused by L. monocytogenes are commonly called listeriosis. Listeriosis usually targets pregnant women and their fetus, immunocompromised individuals and the elderly.
Studies suggest that 1-10% of humans may be intestinal carriers of L. monocytogenes, and it has been found in at least 37 mammalian species, 17 avian species, and possibly some species of fish and shellfish. In the environment it is mostly isolated form soil and silage. Foods most commonly associated with L. monocytogenes are raw or improperly pasteurized milk or other dairy products, raw vegetables, raw meats and fish, and some ready to eat foods.
L. monocytogenes can be attributed to about 1600 illnesses and 400 deaths each year in the United States. The majority of these cases are sporadic, making epidemiological links to food very difficult.
The symptoms of listeriosis start off as flu-like symptoms including a persistent fever. Listeriosis manifests in a few different ways including septicemia, meningitis and cervical infections in pregnant women. Mortality rates can be very high for these forms. Septicemia can have mortality rates up to 50%, meningitis can have rates up to 70%, and cervical infection can have rates greater than 80% for the fetus. The cervical infections usually result in spontaneous abortion or stillbirth. The onset of symptoms from these serious forms of listeriosis is unknown, but may range from a few days to three weeks. Fewer than 1,000 total organisms may cause disease in susceptible persons.
Listeriosis is diagnosed by culturing the organism from blood, cerebrospinal fluid, or stool.
Treatment of listeriosis is by giving patients doses of antibiotics. Ampicillin alone, or a combination of Ampicillin with Gentamicin, is most commonly used to treat patients.
A notable outbreak of occurred in 1985 when many pregnant women contracted cervical listeriosis from contaminated un-pasteurized Mexican style cheese. As a result of the listeriosis many of the women had stillbirths
Salmonella are gram negative, facultative anaerobic, rod shaped bacteria. Many Salmonella species are motile via flagella.
Salmonella can cause two types of disease in humans, salmonellosis and a typhoid-like fever. Salmonellosis is caused by various strains of Salmonella and the typhoid-like fever is caused by S. typhi.
Salmonella can be found in many animals, but is especially prominent in poultry and swine. Environmental sources include water, soil, insects, animal feces, and kitchen or factory surfaces. Foods usually associated with disease are raw poultry, raw pork, eggs, un-pasteurized milk or other dairy products, fish, shrimp, frog legs, yeast, and many others.
Salmonellosis is one of the most common food borne diseases in the United States, with an estimated 2 to 4 million cases reported each year. According to research the incidences of salmonellosis seem to be rising in the United States and other industrialized nations.
Acute symptoms of salmonellosis include nausea, vomiting, abdominal cramps, diarrhea, fever and headache. Chronic arthritic symptoms may also persist for up to a month after the onset of acute symptoms. Acute symptoms usually last only for 1 to 2 days. The onset of symptoms after contact with the organism can take anywhere from 6 to 48 hours, depending on the amount of organisms ingested and the health of the infected person. It takes as little as 15-20 Salmonella cells to cause disease in some individuals. Symptoms for the typhoid-like fever are high fever, body aches and weight loss.
Salmonella is diagnosed in patients by serological identification of a culture from a stool sample. The serological identification consists of a latex agglutination test.
Treatment for a patient with salmonellosis is basic. Most people recover on their own in a few days, but they may require fluids to prevent dehydration from the diarrhea and vomiting.
Prevention of disease is pretty simple. First is to cook poultry or any meat thoroughly and insure that no pink remains in the center. Secondly is to completely wash all cooking utensils that come in contact with raw meat. Thirdly is to practice good hygiene and wash your hands thoroughly anytime you come in contact with any raw foods.
The largest outbreak of salmonellosis in the United States occurred when 16,000 people in 6 states became ill from contaminated milk.