Microbiology

Gastrointestinal diseases Salmonella

Denisa Moorehouse

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Salmonella

Salmonella (S.) is the genus name for a large number

(over 2,500) of types of bacteria.

Salmonella

Rod-shaped bacteria

Flagellated

Gram negative

Each type is distinctly identifiable by its specific protein coating (serovars)

Species Question

Various species of the genus Salmonella ??? (f.e.:S. typhi, S. typhimurium, S. enteritidis, S. cholerasuis, S. saintpaul,...)

OR

Serovars of only two species: S. enterica and S. bongori ???

History

Bacteria were first isolated:

1) In 1885

2) From pigs

3) By Theobald Smith

Named after D.E. Salmon – Smith's director

How Can We Get It?

Is a food-borne illness; can't smell or taste in the food or its presence can't be seen

Salmonellosis (infection) spreads by ingestion of Salmonella bacteria

Can contaminate almost any food type; water

Outbreaks: raw eggs, raw meat (ground beef and other poorly cooked meats), egg products, fresh vegetables, cereal, pistachio nuts, and contaminated water

Contamination can come from animal or human feces during the processing or harvesting

Potential direct sources of Salmonella are pets such as turtles, dogs, cats, most farm animals, and humans that are infected or are carriers of the organisms

Who Can Get It?

Known to cause disease in humans, animals, and birds (especially poultry)

Worldwide

Approx. 40,000 cases/year in US get reported

CDC estimate 1.4 mil/year

Approx. 400 die each year from acute salmonellosis Children <1, old people,

people that take anti-acid, people w/weakened immune system

Diseases In Humans

1) Salmonellosis

2) Bacteremia – (presence of live bacteria in the bloodstream) bacteremic illnesses:

a) Typhoid fever

b) Paratyphoid fever also called Enteric fever

Disease - Salmonellosis

Infection - 1 million–1 billion bacteria, but some can be infected with fewer vacteria

Gastroenteritis characterized by nausea, vomiting & diarrhea

Reduced or eliminated by stomach acid

Symptoms develop 8-72 hours after infection

If bacteria gets into intestine:

– attaches and penetrates the cells

– toxins produced by bacteria can damage and kill the cells that line the intestine

Disease - Bacteremia

Some Salmonella can survive in cells of the immune system

Can reach bloodstream & cause blood infection–bacteremia

Bacteria can spread from the intestine into the intestinal lymph nodes, liver, spleen and other organs via the blood where they multiply

Disease – Typhoid fever

Most commonly caused by the bacteria Salmonella typhi

Salmonella can be shed from the liver to the gallbladder, leaving the affected patient a chronic carrier of the organisms

Salmonella can then be shed with the bile from the gallbladder into the feces and then may infect other people

High fevers over 104, sweating, inflammation of the stomach & intestine, diarrhea, approx 50% develop slow heart beat & 30% slightly raised red or rose-colored spots

Common in developing countries (<400 US)

Disease-Paratyphoid fever

Also called Enteric fever

Resembles Typhoid fever

More abrupt onset, milder symptoms and a shorter course

Symptoms

I woke up in the middle of the night feeling headachy and I put it down to sinus. The next day I felt bloated all day and when I finished work I was exhausted my muscles and everything were aching and I had a bloated feeling still in my belly. For the next day I had really bad stomach cramps and felt very bloated however I just put it down to stress. The next morning I had to work at 7am and I felt very sick, but was determined to go to work, so when done with my shower I started to dry off and then I fainted. After that the diarrhea started which went on with very bad stomach pains for about 3 days with fevers and chills. I would wake up about 5 times a night with very bad stomach pans only to be relived when I went to the bathroom. I pretty much had no energy and my body was exhausted. I went to see the doctor who took a stool sample and sent it away.

Symptoms

Nausea Vomiting Chills Headache Fever Delirium Pins & needles in legs Rare cases – pains in the joints, irritation of the eyes & painful

urination – Reiter's syndrome that can cause chronic arthritis in the feet & ankles

Can cause dehydration & even a death Rash called "rose spots” only of typhoid fever (1/4 inch red spots

that appear most often on the abdomen and chest)

Diagnosis

The culture of the feces is tested for Salmonella

Occasionally, Salmonella can be cultured from blood samples (An elevated white blood cell count in blood)

An ELISA test on urine may show Vi antigen specific for the bacteria

Serovars are identified by serotyping (detecting bacterial proteins by using specific immunological tests)

Often is diagnosed because of the outbreak – it is difficult to determin the outbreak because of many possible toxins out there that cause food poisoning.

Treatment

Antibiotics such as aciprofloxacin for 10-14 days

Some doctors recommend no antibiotics because disease can self-limit itself; some investigators believe antibiotics prolong the carrier state

Cancer, AIDS and other immunosuppressed patients should receive antibiotics

Typhoid or enteric fevers needs to be treated with antibiotics, often given intravenously.

For Salmonella infections - antibiotics: fluoroquinolones and third-generation cephalosporins (children)

Carriers can infect other people and need to be cured of the carrier state. About 85% of carriers can be cured by a combination of surgery to remove their gallbladder and antibiotic treatments.

Prognosis

4-7 days symptoms usually disappear. The illness usually resolves in 2 to 4 weeks with treatment. The outcome is likely to be good with early treatment, but becomes poor if complications develop. Cases in children are milder, and are more debilitating in the elderly.

Prevention

Cleanliness

Hand washing with soap and hot water - after handling eggs, poultry, and raw meat

Antibacterial soaps

Chlorine-treated drinking water - washed produce

Not eating undercooked foods such as eggs, meat or other foods

Avoiding direct contact with animal carriers of Salmonella (turtles, snakes, pigs,...)

Vaccines are available only for typhoid fever. The CDC does not recommend that everyone get vaccinated for typhoid fever, only those who travel into developing countries

Sources

Davis, Charles. “Salmonella.” 17 Nov. 2009. <http://www.medicinenet.com/salmonella/article.htm>

CDC. “Salmonella Questions and Answers. ” 17. Nov. 2009. <http://www.fsis.usda.gov/factsheets/salmonella_questions_&_answers/index.asp>