All about salmonella bacteria

• Salmonella bacteria live in the intestinal tract of humans and animals and are excreted in feces. Poultry, beef, milk, and eggs all can contain Salmonella bacteria.
• Salmonella infection is a foodborne illness that occurs from consumption of raw meats and eggs, contaminated dairy foods such as unpasteurized (raw) milk, or fruits and vegetables contaminated by food handlers.
• A Salmonella bacterial infection causes gastrointestinal symptoms, including
  • diarrhea,
  • abdominal pain,
  • nausea, and
  • vomiting.
• Symptoms develop within 12-72 hours and typically last four to seven days.
• The two most common types in the U.S. are S. typhimurium and S. enteritidis. Some types of Salmonella bacteria cause the illness known as typhoid fever.
• In most cases, no specific treatment is needed other than adequate hydration.
• Most cases of salmonellosis are not life-threatening and resolve on their own without complications.
• People at risk for complications or those with particularly severe illness or a weakened immune system may need antibiotic therapy.
• There is no vaccine to prevent Salmonella infection.
• Salmonella may infect reptiles, rodents, and birds. Contact with these animals increases the likelihood of getting the infection.
• People may prevent infection by following established food safety practices, including attention to hygiene during food preparation and handling of animals.

Many of the members of the bacterial genus Salmonella are contagious. The organisms can be transferred from person to person, by both direct (via saliva, fecal/oral spread, kissing) and indirect contact (for example, using contaminated eating utensils). In addition, a number of Salmonella species can be transmitted from animals (snakes, turtles, chickens, hamsters, cats, and dogs) to humans, usually by direct contact.

Salmonella infection, or salmonellosis, is another name for Salmonella food poisoning. Salmonella are a type of bacteria known to cause food-borne illness for over 125 years. The organism is named for a scientist named Daniel Elmer Salmon, who discovered the bacteria. Salmonellosis is a food-borne infection typically caused by consumption of contaminated foods. Salmonella causes an estimated 1 million food-borne illnesses every year in the U.S. and about 19,000 hospitalizations.

Different types (called serotypes or serovars) of the Salmonella bacteria can cause the illness. The two most common serotypes in the U.S. are S. typhimurium and S. enteritidis. Specific strains of the bacteria can be responsible for outbreaks of the disease. For example, an outbreak in 2013-2014 was linked to multidrug-resistant serotype Salmonella Heidelberg. This strain and some other strains have become resistant to many drugs traditionally used to treat the infection, posing a risk to public health.

Some types of Salmonella bacteria (S. typhi) cause typhoid fever, a serious illness that occurs most often in nonindustrialized areas of the world.

Salmonella illness causes an inflammation of the gastrointestinal tract; this is known as gastroenteritis.

• Symptoms of Salmonella poisoning usually begin 12-72 hours after infection.
• Diarrhea, abdominal cramping, and fever are common symptoms.
• The diarrhea is typically loose and not bloody.
• Nausea
• Vomiting
• Headache
• Muscle aches

The symptoms usually go away on their own after four to seven days.

Poultry, beef, milk, and eggs may contain Salmonella bacteria, since the bacteria live in the intestines of humans and animals. Thorough cooking of these foods destroys the bacteria.

Foods, including vegetables and fruits, may also be contaminated during handling or processing of the food, and this is another common source of outbreaks. For example, food may be contaminated by the feces of infected people or animals or from the unwashed hands of a person handling or preparing the food.

Small rodents such as hamsters, as well as baby chicks and ducklings, may also carry the bacteria, and contamination of food after handling these animals may also result in salmonellosis. Reptiles may also harbor Salmonella bacteria. In the 1970s, outbreaks were associated with baby turtles kept as pets. Further, the infection may be spread by contaminated surfaces (such as cutting boards) that have had contact with contaminated foods.

Contaminated foods usually look and smell normal. Over the past years, outbreaks of salmonellosis have been associated with a number of different foods, including chicken, cucumbers, alfalfa sprouts, bean sprouts, ground beef, mangoes, peanut butter, and cantaloupe. These are just a few examples. An outbreak in February 2016 caused by the strain Salmonella muenchen was linked to contaminated alfalfa sprouts. In 2017, an outbreak was linked to papayas from Mexico. A breakfast cereal known as Honey Smacks caused an outbreak in 2018.

Since foods contaminated with Salmonella are not obvious, anyone may consume contaminated foods. Owning pets such as small rodents, chicks, ducklings, small turtles and some other reptiles, and some birds may increase the risk of coming in contact with Salmonella bacteria. People who are exposed to many people, such as those living in group housing, may have an increased risk. Young children (under 5 years of age) have the highest reported incidence of infection.

People with medical conditions that lead to immune suppression are at risk for a more severe illness when they do become infected.

Around the world, Salmonella is one of the main causes of diarrhea. Other common symptoms of a Salmonella infection include abdominal cramps and vomiting.

There are many types of Salmonella bacteria, and they can cause a range of illnesses, including typhoid fever and gastroenteritis.

Most people with Salmonella infections have mild symptoms and recover without treatment. However, some require care in a hospital setting.

People often develop this type of infection after coming into contact with contaminated food or water.

In 2019, 13 people from eight states became sick after eating ground beef that contained a strain of Salmonella. The Centers for Disease Control and Prevention (CDC) issued a safety alert but declared the outbreak over by the end of the year.

Pet reptiles and amphibians can also transmit Salmonella. In 2017, an outbreak linked to pet turtles affected at least 76 people in 19 states, according to the CDC.

Share on Pinterest Washing raw fruits and vegetables before eating them may help prevent a Salmonella infection.

Salmonella is a type of bacteria that can cause diarrheal illness in humans.

There are over 2,500 subtypes, including animal and human strains. Some are present in animals but can also affect humans. Fewer than 100 strains of Salmonella bacteria are likely to infect people.

In the United States, Salmonella is a major cause of bacterial infection. According to the CDC, it causes around 1.35 million infections, leading to 26,500 hospitalizations and 420 deaths, every year.

Symptoms usually appear between 6 hours and 6 days after the initial infection and last 4–7 days, according to the CDC.

• diarrhea
• stomach cramps and abdominal pain
• a sudden fever
• nausea
• vomiting, in some cases

Some strains of Salmonella can infect the urine, blood, bones, joints, and the nervous system, including the spinal fluid and brain. Severe complications can result.

Some people with Salmonella infections experience joint pain, known as reactive arthritis. It can last for months or years, and it can become chronic arthritis.

Salmonella bacteria live in the intestines of birds, animals, and humans. Most infections in humans develop after eating food or drinking water that has been contaminated by feces.

Uncooked meat, seafood, and poultry

Contamination can occur during processing. For example, harvesting seafood in contaminated waters is a common cause of Salmonella infection.

Also, the infection can spread if a person handles contaminated raw meat, then touches other food without washing their hands.

Uncooked eggs

Eggs from a bird with a Salmonella infection can contain the bacteria.

The Food and Drug Administration (FDA) estimate that every year, 79,000 cases of foodborne illness occur in the U.S. due to eggs containing Salmonella.

Cooking the eggs can reduce the risk. However, some popular sauces, such as mayonnaise, can contain raw eggs.

Fruits and vegetables

Watering fruit or vegetable plants with contaminated water, or washing the produce in this water, can lead to Salmonella infection.

Lack of hygiene

Contamination and infection can occur if people do not keep kitchen surfaces clean and do not wash their hands during food preparation, after using the bathroom, and after changing a baby’s diapers.

When a person has the bacteria on their hands, they can spread it by touching other people or by touching frequently used objects and surfaces.

Pet reptiles or amphibians

Most reptiles and amphibians carry Salmonella in their guts without becoming ill. They shed the bacteria in their droppings.

The bacteria can then quickly spread to their skin and anything that they come into contact with, including cages, toys, clothes, furniture, and household surfaces.

People should not keep pet reptiles indoors if there are children under 5 years of age, pregnant women, older people, or people with weakened immune systems in the household.

Since 1975, the FDA have banned the sale and distribution of small turtles because of the risk of Salmonella infection.

Salmonella infections are more common in summer than in winter.

Overall, people with the highest risks of infection are:

• children
• older people
• people with weakened immune systems
• pregnant women

Because of the risk of infection, caregivers should not allow young children to handle reptiles or chicks and young birds.

If a woman develops a Salmonella infection during pregnancy, there can be additional risks. Dehydration and a lack of nutrients that result from the infection can harm the mother and baby.

In around 4% of Salmonella infections during pregnancy, the bacteria spread to the blood. This can lead to intrauterine sepsis, a potentially life threatening condition.

Salmonella: What Is It?

Salmonella is an extremely common type of bacteria. These rod-shaped organisms can be found in both cold-blooded and warm-blooded animals across the world. They are also one of the most common causes of sickness in human beings.

Salmonella poisoning can infect people in one of two ways. It is most often spread from animals to people through the food supply. This is how the bacteria can cause the nauseating disease gastroenteritis. Typhoid-causing Salmonella, however, is usually spread from person to person.

In this article, you will learn all about Salmonella. You'll find out how it can make you sick, how the bacteria are fighting back against antibiotic medicine and what we can do about it, how to keep your grub safe from these illness-causing organisms, and even what happens when Salmonella grows in space.

Symptoms of Salmonella poisoning

Salmonella symptoms vary depending on the type of Salmonella that has caused the infection. Most Salmonella infections lead to problems with digestion known as gastroenteritis, though some strains of the bacteria can cause typhoid fever.

For most infected people, symptoms develop from 12 hours to three days after eating food containing the bacteria. Symptoms often include abdominal cramps, diarrhea, and fever. These symptoms usually disappear after two to seven days, though returning to normal bathroom habits can take several months. However, in a few rare cases, Salmonella infections can lead to long-term joint pain known as reactive arthritis, which can over time develop into chronic arthritis.

Salmonella Outbreaks and Serotypes

Not all Salmonella bacteria are the same. In fact there are more than 2,500 types of Salmonella. Each type is identified and labeled as a different serotype. Some of these serotypes will only infect one particular animal, or only exist in one specific place. Of these, less than 100 are responsible for the majority of human infections.

Knowing the serotype of a given organism is important for scientists who want to observe and control the spread of outbreaks. Since the 1960s, the US government has paid researchers to discover outbreaks of Salmonella with the hope of tracking the source of the infection. Depending on the serotype, a Salmonella outbreak could be mild or extremely severe.

Important Salmonella Serotypes

The scientists who watch for Salmonella outbreaks are concerned about three specific groups of serotypes. These three groups are responsible for sickening millions of people across the world each year, and some of those illnesses result in death.

Non-typhoidal Salmonella are the serotypes that sicken the most people. As the name suggests, these bacteria do not cause typhoid fever. Instead, they lead to diarrhea and related symptoms. Of all the varieties of non-typhoidal Salmonella, there are two that are responsible for half of all human infections in the United States: S. typhimurium and S. enteritidis. S. typhimurium is usually caused by food from animals. S. enteritidis is usually caused by infected eggs and poultry.

Every year in the United States, non-typhoidal Salmonella sickens an estimated 1.2 million people. Of these, 23,000 are admitted to the hospital and 450 die.

Typhoidal Salmonella typhi infections cause typhoid fever. Someone with typhoid fever will need to take antibiotics. It is important to take the full round of antibiotics and not stop just because you begin to feel better—this disease is notorious for being passed to others after a person's symptoms decline. We will describe the symptoms and treatment for typhoid more completely later in this article.

How Many People Does Salmonella Sicken?

Foodborne diseases as a whole infect 550 million people each year. According to the German government, Salmonella infections account for about 90 percent of foodborne infections in recent years. The CDC estimates that approximately 1.2 million illnesses occur due to non—typhoidal Salmonella per year in the US.

Who Is Most at Risk of Salmonella Poisoning?

According to the World Health Organization, most cases of Salmonella infection are mild. However there are three groups of people who need to be particularly careful. These are the elderly, young children, and anyone whose immune system is weakened, either due to HIV/AIDS, cancer treatment, or some other cause.

Salmonella Treatment

Salmonellosis symptoms range from mild to severe, and treatments should be dictated accordingly. For those with mild symptoms, the WHO recommends no antibiotic treatment, as these bacteria are becoming increasingly resistant to these drugs, and administering them for every patient is likely to lead to further resistance. However, anyone in a particularly vulnerable group, including infants and those older than 65 years old, should receive antibacterial medications. That's also true for anyone whose infection has spread beyond the digestive system.

Can Salmonella Resist Antibiotics?

Antibacterial resistance is a real and growing problem when it comes to this infectious bacterium. For non-typhoidal serotypes, about 5% are resistant to five or more drugs as of 2011. About two out of every three typhoidal serotypes show some level of resistance to ciprofloxacin in the United States. Typhoidal serotypes show resistance to other common antimicrobial drugs in other parts of the world, according to the CDC.

You may reach for antibacterial soap to keep your family safe from harm. Killing more bacteria has got to keep them safer, right? Not necessarily, according to the Food and Drug Administration. The FDA says there is no evidence washing up with plain soap and water is any less effective at preventing illness.

What's more, studies have shown that using these antiseptic soaps can kill off certain bacteria, but they leave other bacteria alone. By doing so, they may be contributing to the rise of so-called “super bugs,” which are more resistant to antibiotics and more potentially damaging to human health. So while our first instinct may be to use antimicrobial soaps for better health, in the long run these soaps may be causing more harm than good.

Typhoid Fever

Compared to gastroenteritis from salmonella poisoning, typhoid fever is very rare. About 5,700 cases occur in the United States every year, and about 75% of those are contracted overseas. Compare that with more than 1 million sickened in the U.S. by nontyphoidal salmonella bacteria.

In developing regions, typhoid fever remains a serious and relatively common disease. Worldwide about 21.5 million people are afflicted with it each year, resulting in 200,000 deaths. Each year another 2 million people worldwide are estimated to contract the related disease paratyphoid fever.

Typhoid comes on gradually. Symptoms don't develop for about a week after infection. Then it takes about three to four days for a low-grade fever to rise, sometimes as high as 104 degrees. These fevers tend to be worse in the afternoon and evening.

Along with fever, almost all people with typhoid experience headaches, loss of appetite, and the soreness and uneasiness associated with an approaching sickness known as malaise. Many people experience diarrhea, constipation, and pain in their abdomens, and their spleen and liver may swell. Sometimes people with this condition develop rosy spots that move from place to place along their trunk.

Treatment for typhoid is crucial. Without treatment, the fever lasts for about a month and as many as 30% of those infected will die from the disease. Antibiotics are used to eradicate the disease, though this takes about three to five days, during which time a patient's symptoms may actually get worse. This effort is hampered by the increasing resistance Salmonella bacteria have shown to antimicrobial medicine.

There are two vaccines that help lower your chances of contracting typhoid fever. One is a shot of the inactivated (killed) bacteria, while the other is an oral medicine of a weakened form of the microbe. The shot can be administered to people older than 2, but needs a booster after two years. The oral medicine is for ages 6 and up, and needs a booster every five years.

The vaccines are not 100% effective, though. If you are traveling to an area where typhoid is a known problem, you will want to take additional precautions. Be careful about where you find your food and water—these are common sources of infection. Also, do your best to avoid anyone sickened by the disease. This isn't perfectly effective either, though, because someone who is contagious may not have symptoms.

Salmonella Food Poisoning

Salmonella infections are usually caused by food poisoning. In fact, about 95% of infections come from the foods we eat. Animal products such as beef, pork, chicken, milk, and eggs are particularly susceptible, but vegetables can also harbor the disease.

To preventing food poisoning, every point in the food chain needs to be carefully controlled. Harvesting, butchering, processing, and preparation should all involve proper hygiene to ensure safety. The WHO provides the following five points for food handlers both at home and in restaurants to prevent infection:

• Keep food clean
• Cook meats and vegetables completely and thoroughly
• Maintain ingredients at safe temperatures
• Keep raw and cooked items separate in the refrigerator and elsewhere
• Make sure your water and materials are clean and safe

Salmonella in Eggs: How Common Is It?

Salmonella infections from raw eggs is a major cause of salmonellosis food poisoning. These infections are usually caused by Salmonella enteritidis (SE). SE accounts for as much as 80% of egg contamination. This is because SE can infect the ovaries of an egg-laying hen without the hen showing any outward signs of infection.

In a major assessment of US egg production and SE, the USDA concluded in 2005 that 1 in every 3,600 shelled eggs has some amount of the bacteria. Of these contaminated eggs, 85% pose no risk to humans if they are properly stored and cooked. That frequency of infection is probably lower today. In 2010 the Food and Drug Administration set higher standards for egg producers. These standards are expected to reduce SE food poisoning from eggs by 60%.

As of 2005, the USDA estimated that less than one half of 1% of all eggs produced in America are pasteurized. In order to be pasteurized, an egg must be covered in hot water long enough to destroy SE bacteria, but not long enough to cook the liquid inside the egg.

If US egg producers began pasteurizing their eggs, illnesses would drop from about 130,000 per year down to between 41,000 and 19,000, depending on the method of pasteurization, according to USDA estimates.

Proper storage makes a big difference in protecting consumers from food poisoning as well. If every US egg were stored below 45 degrees Fahrenheit within 12 hours of being laid, yearly illnesses would drop from 130,000 to an estimated 28,000.

Proper Cooking Temperatures for Salmonella

If you're cooking meat, how can you be reliably safe from food poisoning? One of the most important steps is to bring your food to the proper temperature. A good internal thermometer is crucial to get this right. The proper temperature depends on what you're cooking:

• For lamb, veal, pork, and beef, bring the internal temp to at least 145 degrees Fahrenheit.
• Ground meats, including beef and pork, should be heated to 160 F.
• Poultry (including chicken and turkey) should be heated to 165 F.
• Fish should be heated to 145 F.
• Any sauces, gravies, or soups should be brought to a boil.
• Leftovers should be heated to at least 165 F.

Salmonella Food Safety Without Cooking

Even when you aren't eating eggs or animal products, you may still be at risk of Salmonella food poisoning. This bacteria can be found in fruits, vegetables, peanut butter, and some processed foods as well.

Be especially careful during the summer. As temperatures rise, they create ideal circumstances for the bacteria to thrive. Picnics and backyard barbecues are especially at risk of an unwanted visit from this sneaky pathogen. Make sure you keep your hot foods hot and your cold foods cold. Refrigerate all leftovers right away. Never let your food sit for more than two hours—or more than one hour if it's hotter than 90 degrees Fahrenheit outside.

You should also follow basic safety precautions year round. That means keeping your hands, cutting boards, counters and utensils clean, keeping animal products separate from other foods both inside the fridge and out, and never preparing food if you have diarrhea or if you have been vomiting.

Does Your Pet Have Salmonella?

Just about any animal can be a carrier for these bacteria. That includes cats and dogs. However some are at a higher risk of carrying this disease than others. Some of these are water frogs, turtles, and baby chickens and ducks (chicks and ducklings).

Reptiles and amphibians have been singled out by the CDC for the Salmonella they carry, which poses a particular risk to children under 5. Small turtles were responsible for a 2015 outbreak that sickened more than 200 people. Some of the sick people hadn't even touched the turtles.

Because pets can become carriers, it is crucial that you wash your hands carefully and completely with soap and water after petting or feeding an animal. Animal areas should be cleaned and disinfected regularly by adults or children ages 6 and over. Avoid eating or drinking around animals that are at a high risk of carrying the disease.

Salmonella in Space

When researchers studied the impact of space on microorganisms by growing Salmonella on a space shuttle, they discovered something startling. Compared to samples of the bacterium grown on Earth, the space Salmonella was deadlier.

This was proven when some of the space sample was injected into hundreds of lab mice. The mice died two days earlier and with lower doses than others who received terrestrially grown bacteria.

Discovering this strange fact has changed the way scientists think about long-term space travel, such as a manned trip to Mars. It's impossible to completely disinfect a spacecraft because so many bacteria are found on humans already. That means we will need to come up with a way to fight off these especially dangerous organisms if we want to travel beyond Earth's orbit.

Salmonella: Cancer Fighter?

For all the terrible, harmful things this bacteria causes, it's worth considering one way they may actually be used for our benefit. A scientist in California is studying whether he can turn these nasty bugs into cancer fighters. Professor Jeff Hasty of UC San Diego has engineered the bacteria to remove their disease-causing tendencies and replace them with the power to attack cancer tumors.

If they are as successful in humans as they have been in mice, these engineered cells could have further medical uses beyond cancer treatment. They could be programmed to release drugs at predictable times, which could help people with common ailments like diabetes and high blood pressure.

IMAGES PROVIDED BY:

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3. Science Source / Photo Researchers, Inc
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5. MedicineNet
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• The Atlantic: "How Salmonella could be used to kill cancer."
• Bundesinstitut für Risikobewertung: "Salmonella and their importance as pathogens."
• CDC: "Infectious Diseases Related to Travel," "NARMS 2012 Human Isolates Final Report—Tables," "Salmonella Atlas," "Salmonella Infection," "Salmonella is a Sneaky Germ: Seven Tips for Safer Eating," "Salmonella Questions and Answers," "Take Care with Pet Reptiles and Amphibians," "Typhoid Fever," "Typhoid Fever Vaccine."
• FDA: "Antibacterial Soap? You Can Skip It—Use Plain Soap and Water."
• MIT Technology Review: "Deadly Bacteria from Outer Space."
• Nature: "Synchronized cycles of bacterial lysis for in vivo delivery."
• USDA: "Risk Assessment of Salmonella Enteritidis in Shell Eggs and Salmonella spp. In Egg Products."
• WHO: “Salmonella (non-typhoidal).”