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The Dangers of going Raw - Salmonella Infection

When food poisoning occurs due to the consumption of raw foods, there are only a few common suspect causative agents. One of which is Salmonella; named after the American Scientist who discovered it in 1885 Dr. Daniel E. Salmon. In the United States alone, the Center for Disease Control or CDC estimates 1.35 million cases and 26,500 hospitalizations due to Salmonella infections every year. Unfortunately, although it is rare, there are cases wherein the person afflicted would succumb to the disease and die. CDC estimates that there are 450 deaths that are caused by Salmonella infection each year.



Distinguishing properties of Salmonella

Standard Operating Procedure for microbiological identification calls for a Gram stain first and foremost. The Salmonellae bacteria are Gram-negative. They have a thin peptidoglycan cell wall and thus wouldn’t be able to hold the primary stain and take up the pink secondary stain. They do not ferment lactose so they are referred to as ‘non-lactose fermenters’ a designation which is important for bacterial identification. Furthermore, its ability to produce H2S gas is another important property for bacterial identification. They have antigens that are quite important for serological tests and for taxonomic differences. Their antigens are the cell wall ‘O’ antigen, flagellar ‘H’ antigen, and the capsular 'Vi' or virulence antigen.


Salmonella is not a single bacterium but a whole genus of bacteria. Within this genus there are various species of Salmonella. In a clinical perspective we are concerned with a few members only. These clinically important species can be divided into two categories, the typhoidal species and the non-typhoidal species. The former group can cause typhoid fever while the latter cannot. There are only two species that belong to the typhoidal group, the S. typhi and S. paratyphi. The non-typhoidal species have numerous members which include the various strains of S. enteritidis, and S. choleraesuis.


Disease Progression


How can you get Salmonella?

Salmonella is a bacteria that can inhabit the intestines of people and animals. The worst thing about this bacteria is that some people and animals are carriers or are unaffected by the bacteria but can spread the disease. When those who harbor the bacteria would defecate, their feces would carry the Salmonella bacteria with it. If for some reason these Salmonella-carrying feces would wind up in a person’s food or water, such as in the case of unhygienic food handlers, that person would get infected as well. In short, Salmonella is spread through the feco-oral route.


What is Salmonella commonly found in?

Salmonella is commonly found in the following foods:

  • Raw or undercooked eggs

  • Unpasteurized milk including dairy products made from unpasteurized milk like soft cheese, ice cream, and yogurt

  • Raw and undercooked meat of chicken, turkey, duck, beef, veal, and pork

  • Raw fruits or vegetables

  • Processed foods like chicken nuggets and nut butters

The Food and Drug administration included spices to this list because there are outbreaks that have been traced to spices.


Be warned, aside from consuming contaminated food and or water, handling animals or working with soil without proper hand washing afterwards may also introduce the bacteria to the human body.


Various Types of Salmonella infections

The causative agent is the Salmonella bacteria. The susceptible hosts are the humans. They are shed off by the infected human or animal, the reservoirs, through its feces. When these Salmonella-containing feces would contaminate a person’s food or water, that person would get infected with the Salmonella bacteria. From there the bacteria may behave differently and this difference in behavior is dependent on the Salmonella’s species. These are the different types of Salmonella infections:


Enterocolitis

Some species of Salmonella, those belonging to the Enterocolitis group, have the ability to invade the epithelial and subepithelial tissue of the large and small intestines. Once this happens the tissue becomes inflamed and excess fluid is released into the lumen, the hollow insides of the gut. This excess fluid release would lead to diarrhea and dehydration. White blood cells prevent the bacteria from spreading outwards thus bacteremia due to enterocolitis is rare. The acidity of the stomach is a defensive feature against gastrointestinal pathogens. Gastrectomy or the use of antacids lowers the stomach’s acidity which makes you more vulnerable to infection.


It takes around 12-48 hours for symptoms of enterocolitis to appear. These symptoms can include abdominal pain and diarrhea. However, in severe cases abdominal pain is intense and diarrhea is bloody. The disease usually ends after a few days and is self-limited. This means that you don’t need to do anything about it besides getting enough rest and fluids. For those who have pre-existing medical conditions that could lower their immune response, such as those who have HIV, Salmonella infections can be dangerous. These individuals must be given proper medical attention.


Typhoid fever

Salmonella species belonging to the Typhoid group can invade the mononuclear phagocytes, a type of white blood cell present in the intestine’s Peyer’s patches. The bacteria could increase in numbers here and then spread to the phagocytes of the liver, gallbladder, and spleen. Once the bacteria spreads to several phagocytes, septicemia would occur which is most likely caused by the bacteria’s endotoxin. Since the bacteria can hide within the phagocytes, it can persist within the human body and leads to cases wherein infected individuals can become carriers.


The onset of typhoid fever is slow. In most cases, fever and constipation are the first symptoms or the only symptoms to appear. Diarrhea may appear early but they often disappear once the bacteria has spread throughout the body. Bacteremia is usually established after a week. Other symptoms such as high fever, delirium, tender abdomen, and enlargement of the spleen would occur. In rare cases, Rose spots in the abdominal area would be observed. Laboratory tests would reveal a reduction in white blood cell and red blood cell count, as well as abnormal liver function tests.


Most people would recover by the third week. However, severe complications such as intestinal hemorrhage or perforation may happen. Some individuals may become chronic carriers of the Salmonella bacteria, especially those who have previous gallbladder diseases such as gallstones.


Septicemia

As mentioned previously septicemia due to Salmonella infections are rare. Only in 5% to 10% of Salmonella infections does septicemia occur. In most cases, the patients has some underlying conditions which makes them susceptible to septicemia such as sickle cell anemia, cancer, or enterocolitis.


Septicemia usually begins with a fever with mild enterocolitis, in some cases fever is the only symptom. Other symptoms may appear depending on which organ is affected. Most of the time the following organs are affected, bone, lung, or mininges.


In general, salmonella infections would present with diarrhea, fever, and stomach cramps. Symptoms may appear six hours after exposure. However, in some cases it may take up to six days. The infection usually lasts for four to seven days but in some cases would last weeks. In some cases, especially for the typhoid group the infection may reach the urinary tract, blood, bones, joints, and the nervous system. In this case, the infection becomes more severe.


Symptoms that require immediate medical attention

Since this illness usually lasts for a week, experiencing symptoms for more than one week necessitates a visit to your doctor.


Children, older adults, and individuals with weakened immune systems must see a doctor if they exhibit the following symptoms:

  • Bloody poop

  • Ongoing high fever

  • Dehydration



Salmonella complications

Since diarrhea is a symptom of Salmonella, dehydration is a dangerous complication. It is imperative that the person affected must be given enough fluids even if they are not showing signs of dehydration.


Those who had previous salmonella infections may experience joint pains even after the infection has resolved. Doctors refer to this condition as reactive arthritis or Reiter’s syndrome. Aside from joint pains, this condition may also cause pain during urination, and sore eyes. Symptoms of this condition may last for months or longer.


If Salmonella infection leads to bacteremia or the presence of bacteria in the blood, other parts of the body may become the target for the bacteria. Usually, this includes the following parts:2

  • Tissues surrounding the brain and spinal cord

  • The heart valves and the lining that surrounds the heart

  • The bones and the bone marrow

  • The lining of the blood vessels.


Risk Factors

Be extra careful during the warmer months like in summer. The Salmonella bacteria favors higher temperatures. When food is contaminated with Salmonella and is not refrigerated, the bacteria may increase in number quickly.


Other risk factors include:

  • Age - children, especially under the age of 5, and older adults

  • Being immunocompromised, AIDS, Sickle cell disease, and Malaria.

  • Taking anti-organ rejection immunosuppressant drugs and corticosteroids

  • Travel to places with poor sanitation

  • Taking antacids

  • Taking broad spectrum antibiotics that may kill ‘good’ bacteria

  • Having inflammatory bowel disease

  • Owning pet birds and or reptiles

Laboratory Diagnosis

Depending on the specific illness, Salmonella infections are diagnosed through a variety of laboratory methods. Enterocolitis is almost never recovered from a person’s blood. Stool samples can be used when it comes to enterocolitis. Enteric fevers can be quite complicated because the organism may transfer from one organ system to the next. During the first 2 weeks it is recovered in the blood. However, after that they are present in the bone marrow.


When Salmonella is grown on a MacCongkey culture media, colorless bacterial colonies would be observed. This is due to the fact that this bacteria is non-lactose-fermenting. When they are grown on a Triple Sugar Iron agar, the slant would be red and the butt would be black with yellow sometimes. This TSI reaction means that the bacteria fermented glucose but did not ferment lactose, and sucrose. Aside from that, this also means that the bacteria produced H2S gas.

Salmonella infection is a disease that is easily detected. When numerous cases would appear suddenly, authorities should be notified immediately so that an investigation could be conducted promptly.


Treatment

Similar to Salmonella’s laboratory diagnosis, treatment also varies depending on the specific Salmonella-caused illness.


Enterocolitis is generally self-limiting, supportive treatment such as fluid and electrolyte replacement are enough. Antibiotic treatment of enterocolitis is not recommended as it does nothing against the organism. It may even worsen the condition. So basically, you just need to drink a lot of water to combat diarrhea.


Typhoid fever and septicemia, on the other hand, requires aggressive treatment using antibiotics such as Ceftriaxone or Ciprofloxacin. For individuals who are known carriers of Salmonella, they are given Ampicillin or Ciprofloxacin. In some cases, the gallbladder needs to be removed to end their carrier state.


How long does it take to recover from Salmonella?

In general, most people would recover from enterocolitis within a few days but may reach up to three weeks for severe cases. For typhoid fever, it may take seven to ten days with proper antibiotic treatment.

Antibiotic treatment may be mandatory for:

  • People with the severe form of the illness

  • Those who are immunocompromised like those who have HIV infection

  • Those who are 50 years old or older

  • Infants or those who are younger than 12 months


Prevention

There are a lot of ways to lessen your exposure to Salmonella which are outlined below:

  • Don’t eat raw eggs, and meat especially poultry

  • Don’t drink unpasteurized milk or juice

  • Wash your hands properly before and after handling food

  • Clean your kitchen surfaces regularly and before preparing food on them

  • Use a separate knife and chopping board for meats

  • Don’t wash raw poultry, meat, or eggs before cooking.

  • Wash raw fruits and vegetables thoroughly and peel them if possible

  • Do not wash the fruits and vegetables in the same container as you would with meat products

  • Do not prepare food if you have diarrhea or have been vomiting

  • Refrigerate food properly

  • Don’t mix raw food and cooked food

  • Meat must be cooked to its correct minimum temperature

  • Always wash your hands properly after touching animals, their toys, or their bedding.


Sources:

  1. https://www.cdc.gov/salmonella/general/index.html

  2. https://www.webmd.com/food-recipes/food-poisoning/what-is-salmonella#1

  3. https://www.mayoclinic.org/diseases-conditions/salmonella/symptoms-causes/syc-20355329

  4. Review of Medical Microbiology & Immunology, Tenth Edition, Warren Levinson, MD, PhD

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