Not all pathogens are created equal. There are dangerous strains that cause severe illness.
Today’s news headlines often include stories of food poisoning attributed to a variety of viruses, bacteria or parasites.
Whether the outbreak takes place on a cruise ship, within a local community, a healthcare facility, or at a family reunion, there is a short list of pathogens that medical professionals consider when narrowing down the type of outbreak that may be occurring.
Knowledge is the first step to protecting both yourself and your loved ones.
Much of modern foodborne microbiology is devoted to keeping pathogenic bacteria out of food products and preventing their growth if they are present. Salmonella, E. coli O157:H7, Listeria, and Shigella are well known species of foodborne bacteria.
Viruses are thought to be the leading cause of foodborne illness in the United States based on the percentage of people ill, even though there are only a few viruses that are important foodborne pathogens.
There are about 20 different species of parasites that are known to cause illness in humans from contaminated food or water.
The most dangerous strains can damage the linings of
your intestines and kidneys.
E. coli (Escherichia coli) are a very large and varied group of bacteria found in the environment, foods, and intestines of people and animals. Most of the 700 strains of E. coli are harmless, but some strains can cause diarrhea, urinary tract infections, pneumonia, and other illnesses.
The most dangerous strains can damage the linings of your intestines and kidneys.
These dangerous types of E.coli come in contact with fruits and vegetables when fecally-contaminated water is used for irrigation, for example when a water source is polluted by cattle runoff.
E. coli infection can also be transmitted from one infected person to another as can occur in daycare centers or nursing homes. Animals can infect humans directly in settings like petting zoos.
These disease causing strains of E. coli produce powerful toxins (Shiga toxins) that can cause life threatening disease. They are called “Shiga toxin producing E.coli” (STEC), or sometimes “Vero toxigenic
E.coli” (VTEC). A common strain implicated in E. coli poisonings is O157:H7, however other STEC strains are emerging and cause even more infections than E.coli O157:H7.
Shiga toxins are among the most potent biological poisons known, categorized by the Department of Homeland Security as a possible bioterrorism agent.
There are 265,000 E.coli infections each year in the United States. This is only an estimate because many cases do not seek medical care, are never diagnosed or reported, and many labs have yet to test for STEC strains other than E.coli O157:H7.
The most vulnerable are young children, seniors, and those with weakened immune systems. However, people of all ages and health status can be severely affected.
In the United States, HUS is the principal cause of acute kidney failure in children, and most cases of HUS are caused by the strain of STEC, E. coli O157:H7. About 5-10 % of STEC infections lead to HUS.
Other foodborne pathogens such as Shigella dysenteriae and Salmonella Typhi can also cause HUS.
Many cases of HUS never have a stool culture that proves which pathogen caused illness. Often by the time a patient presents with HUS, the pathogen itself can no longer be easily isolated from a stool specimen. For any patient with HUS without a culture-confirmed STEC infection, stool can be sent to a public health laboratory or to the CDC which can use specialized techniques that can increase the sensitivity of the culture. Also, blood samples can be sent through a state public health laboratory to CDC for tests that can reveal antibodies to STEC.
Antibiotics and anti-diarrheal medicines may increase the risk of HUS. The research shows that antibiotics actually increase the production of toxins that lead to more serious disease.
One of the most common forms of food poisoning found in the United States.
According to the CDC, each year approximately 1.35 million Salmonella illnesses occur, 26,500 people are hospitalized, and 420 people die.
There are many types of Salmonella, including more than 2,500 strains. Nearly 100 of these strains cause infections in humans; and increasingly some of these types are resistant to antibiotics, an increasing public health danger which makes treatment for severe infections more difficult.
Those most vulnerable to Salmonellosis, (Salmonella infection) are children under 5 years old, adults over 65, those with a weakened immune system such as HIV and chemotherapy patients, and those on certain medications to reduce stomach acid.
Diagnosis is obtained by a stool test or blood test. Usually symptoms develop from 6 hours to one week after exposure, but some people can develop symptoms as long as several weeks after infection.
Life threatening complications can occur in those cases when disease spreads outside the intestines. If Salmonella infection enters the bloodstream (Bacteremia) it can infect other tissues throughout the body, including:
Severe Salmonella illness can lead to Reactive Arthritis, sometimes known as Reiter’s Syndrome, which is a painful inflammation in knees and joints that can last for years. Other consequences of Reactive Arthritis are eye irritation and blurred vision, as well as changes to the urogenital tract such as inflammation or pain during urination. Reactive Arthritis is difficult to treat and patients can suffer for years.
For some patients Irritable Bowel Syndrome and Ulcerative Colitis become long-term problems. Between 5% and 30% of salmonellosis patients develop chronic gastrointestinal symptoms after acute infection with Salmonella.
Most Salmonella infections (Salmonellosis) resolve on their own within 4-7 days with home care, but up to 20% of cases require hospitalization.
You may be prescribed anti-diarrheal medication for gastroenteritis, an inflammation of the gastrointestinal tract. These medications can help relieve abdominal cramping, but they may also prolong the diarrhea associated with Salmonella infection.
Because the vomiting and diarrhea of Salmonella infection cause dehydration, it’s very important that you replace fluids and electrolytes. Pedialyte, Gatorade, and other oral rehydration solutions can be helpful for children.
If dehydration is not able to managed through home care, hospitalization may be needed so that you can receive intravenous fluids. Signs of severe dehydration are urinating only in small amounts, dry mouth, and sunken eyes.
Severe dehydration, bloody diarrhea, and ongoing fever are symptoms which need immediate medical evaluation and care.
Antibiotics are usually not prescribed for uncomplicated cases (those cases with gastroenteritis only) in patients 12 months to 50 years old because they may lengthen the time period you carry the bacteria and can infect others. Also, antibiotics can increase your risk of relapsing if your infection is uncomplicated.
However, if you are at risk for severe infection, the potential for antibiotics to improve disease or prevent complications seems to outweigh the risks of antibiotic use. Antibiotics are prescribed for the following patients with Salmonella infection:
If your doctor suspects your infection may have spread to your bloodstream or if you are at risk for developing invasive infection, blood tests will be ordered and you will be treated with antibiotics.
In rare cases, infection may spread from the intestines to the bloodstream and then to other parts of the body like tissues around your brain and spinal cord, the lining of your heart or heart valves, bones or bone marrow, the lining of your blood vessels. In these cases, salmonellosis can cause death unless treated on time with antibiotics.
Campylobacter is globally the most common cause of human gastroenteritis. In developing countries children under 2 are frequently infected, sometimes resulting in death. In the United States, Campylobacter is the primary bacterial cause of diarrheal illness, affecting 1.5 million Americans each year. Many infections are never diagnosed, much less reported to public health departments.
Typical symptoms are diarrhea (sometimes bloody), stomach cramps, nausea, headache, vomiting and fever. Symptoms can begin 2-5 days after infection and continue for a week to 10 days. Most cases resolve on their own with adequate fluids and do not require antibiotics. Some people continue to shed campylobacter for weeks in their stool after they recover.
Some people who have severe illness or who are in a more vulnerable category may need antibiotics.
Very young children, pregnant women, adults 65 and over, and people with weakened immune systems such as HIV, those undergoing chemotherapy, and patients with blood disorders are all more susceptible to developing severe disease.
Complications can include:
Most people with Campylobacter infection (Campylobacteriosis) usually fully recover within one week.
If you have Campylobacter infection you should be especially careful to replace fluids and electrolytes lost to vomiting and diarrhea. Ice chips, water, and fluids like Gatorade and Pedialyte can be helpful to restore electrolytes and avoid dehydration. Severe dehydration may require hospitalization so that you can be given intravenous fluids.
If you feel very sick or have any of the following symptoms, you should seek medical care:
Antibiotics are appropriate in less than half of patients seen for medical care.
Patients with a high fever, bloody diarrhea, or stools more frequent than eight times per day are considered good candidates for antibiotic-treatment.
People with, or at risk for severe illness may need antibiotic treatment. This more vulnerable group includes adults over 65, pregnant women, and anyone with a compromised immune system such as a blood disorder, with HIV, or undergoing chemotherapy.
Shigella causes disease only in humans and primates and is one of the leading causes of diarrhea worldwide.
The various strains of Shigella are genetically closely related to the pathogen, E.coli. Shigella causes dysentery in an estimated 165 million infections across the globe, killing 600,000 each year. In the United States, about 500,000 people report having Shigella infection each year.
Infection with Shigella is diagnosed by culturing a stool sample.
Those most vulnerable are young children, the immunocompromised such as HIV and cancer patients, adults over 65, and men who have sex with men.
Common symptoms of Shigella infection vary in intensity. They include watery, sometimes bloody diarrhea, vomiting, fever, nausea, and abdominal cramps. It takes between 2 days and a week before symptoms appear. Symptoms can last for several days but can continue for weeks. Most cases resolve on their own with adequate hydration and electrolyte solutions. Medicines to relieve diarrhea are not indicated as they can worsen infection.
You should seek care if diarrhea becomes bloody, you have a fever, are dehydrated, or suffer severe abdominal pain.
Complications may include:
Those with mild symptoms of Shigellosis usually recover with home care in 5 to 7 days.
Home treatment for mild Shigella infection is similar to that for any foodborne illness:
People who have fever, bloody diarrhea, severe stomach cramping or tenderness, dehydration, weakened immune systems (such as from HIV/AIDS or chemotherapy) are more likely to develop severe disease that requires hospitalization. Children under 5 years, malnourished patients, children after measles, adults over 50 are all more likely to have bad outcomes.
For symptomatic adult patients with documented Shigella infection, many doctors suggest antibiotic therapy. Antibiotics are effective in shortening both the duration of fever and diarrhea and the duration of pathogen shedding in stool which can the risk of person-to-person spread.
Antibiotics are recommended for:
Antibiotic sensitivity tests will be run to make sure that the appropriate antibiotic is used to treat the specific strain of Shigella causing illness. Increasingly, antibiotic resistance is complicating treatment for this infection.
Complications of Shigellosis can include:
Regarded as one of the most virulent pathogens, Listeria ranks third
in the number of deaths it causes, with a higher fatality
rate than Salmonella, and botulism.
Listeria monocytogenes causes 1,600 illnesses and 260 deaths each year in the United States.
Among severe cases of invasive infections, 20% will be fatal.
High risk individuals include newborns, pregnant women, people with a weakened immune system, adults 65 and over, diabetics.
The time to develop symptoms after infection ranges from a few days to 3 weeks.
The symptoms are different depending on which part of the body is affected.
People with Listeria infection in the brain and spinal cord can have:
People with Listeria infection in the bloodstream can have:
People with Listeria infection in the digestive system can have:
You should seek medical care if you have any of the symptoms listed above and you are pregnant, older, have a serious medical condition, or take medicines that weaken the immune system.
Call a doctor or nurse if your newborn baby:
Tests used to diagnose Listeria infection will depend on your symptoms, whether you are pregnant, and if you have other medical conditions.
They may include:
Pregnant women usually only develop only mild flu like symptoms, but their infection can lead to spontaneous abortion, still birth, or life threatening infections for the newborn. Because of these dangers, pregnant mothers are advised not to eat soft cheeses, raw sprouts, unpasteurized dairy, or luncheon meats.
Listeria infections for people other than pregnant women can involve flu-like symptoms, persistent fever, muscle aches. Symptoms such as stiff neck, headache, confusion, loss of balance, and convulsions require urgent medical care.
Treatment for Listeriosis depends on how serious symptoms are and how healthy the infected person is.
If symptoms are mild (fever, aches and pains, chills, vomiting or diarrhea) and the person is otherwise in good health, treatment may not be necessary. Instead, the doctor may instruct home care with close follow-up. Home treatment for mild Listeria infection is similar to that for any foodborne illness.
Pregnant women, anyone with a medical condition that weakens the immune system (diabetes, cancer, HIV), children and older adults are more likely to have invasive illness.
This means that the bacteria will have spread to the blood (bacteremia). These patients will be hospitalized and treated with IV antibiotics, and the patient will be closely monitored for any complications that might develop.
Invasive cases of Listeriosis have a high mortality rate of between 16-20%.
Any pregnant woman with a fever higher than 100.6°F and signs and symptoms that are consistent with Listeriosis for whom no other cause of illness is known should be tested and treated for presumptive Listeriosis.
Newborn babies with the infection will receive antibiotics as soon as they are born to treat sepsis, a life-threatening illness caused by an immune response to infection, and meningitis.
An infant born with Listeriosis may remain on antibiotics for several weeks while their body fights the infection.
Severe complications of Listeria infection can include:
The largest group of problematic
Thought to be the leading cause of
foodborne illness in the United States.
Several have emerged as significant causes of foodborne and waterborne illness.