Bacterial Disease

Bacterial Diseases of the Lower Digestive System

A gastrointestinal infection is caused by the growth of a pathogen in the intestines.

Incubation times, the times required for bacterial cells to grow and their products to produce symptoms, range 12 hours to 2 weeks. Symptoms of infection generally include a fever.

A bacterial intoxication results from the ingestion of preformed bacterial toxins.

Symptoms appear 1-48 hours after ingestion of the toxin. Fever is not usually a symptom of intoxication.

Infections and intoxications cause diarrhea, dysentery (severe diarrhea accompanied by blood or mucus), or gastroenteritis (inflammation of both the stomach and intestinal mucosa).

These conditions are usually treated with fluid and electrolyte replacement.

Staphylococcal Food Poisoning (Staphylococcal Enterotoxicosis)

Staphylococcal food poisoning is caused by the ingestion of an enterotoxin produced in improperly stored food.

S. aureus is inoculated into foods during preparation. The bacteria grow and produce enterotoxins in food stored at room temperature.

The exotoxin is not denatured by boiling for 30 minutes.

Foods with high osomotic pressure and those not cooked immediately before consumption are most often the source of staphylococcal enterotoxicosis.

Diagnosis is based on symptoms. Nausea, vomiting, and diarrhea begin 1-6 hours after eating and last about 24 hours.

Laboratory identification of S. aureus isolated from foods is used to trace the source of contamination.

Serological tests are available to detect toxins in foods.

Shigellosis (Bacillary Dysentery)

Shigellosis is caused by four species of Shigella.

Symptoms include blood and mucus in stools, abdominal cramps, and fever. Infections by S. dysenteriae result on ulceration of the intestinal mucosa.

Isolation and identification of the bacteria from rectal swabs are used for diagnosis.

Salmonellosis (Salmonella Gastroentritis)

Salmonellosis, or Salmonella gastroenteritis, is caused by many Salmonella species.

Symptoms include nausea, abdominal pain, and diarrhea and begin 12-36 hours after eating large numbers of Salmonella. Septicemia can occur in infants and the elderly.

Fever might be caused by endotoxin.

Mortality is lower than 1%, and recovery can result in a carrier state.

Heating food to 68 degrees C will usually kill Salmonella.

Laboratory diagnosis is based on isolation and identification of Salmonella from feces and foods.

Typhoid Fever

Salmonella typhi caused typhoid fever; the bacteria are transmitted by contact with human feces.

Fever and malaise occur after a 2-week incubation period. Symptoms last 2-3 weeks.

S. typhi is harbored in the gallbladder of carriers.

Vaccines are available for high-risk people.

Cholera

Vibrio cholerae O:1 and O:139 produce an exotoxin that alters the membrane permeability of the intestinal mucosa; the resulting vomiting and diarrhea cause a loss of body fluid.

The incubation period is approximately 3 days. The symptoms last a few days. Untreated cholera has a 50% mortality rate.

Diagnosis is based on the isolation of Vibrio from feces.

Fluid and electrolyte replacement provide effective treatment.

Noncholera Vibrios

Ingestion of other V. cholerae serotypes can result in mild diarrhea.

Vibrio gastroenteritis can be caused by V. parahamolticus and V. vulnificus.

The onset of symptoms begin within 24 hours after eating contaminated foods. Recovery occurs within a few days.

The disease is contracted by eating contaminated crustaceans or contaminated mollusks.

Escherichia coli Gastroenteritis

E. coli gastroenteritis can be caused by enterotoxigenic, enteroinvasive, or enterohemorrhagic strains of E. coli.

The disease occurs as epidemic diarrhea in nurseries, as traveler's diarrhea, as endemic diarrhea is less developed countries, and as hemorrhagic colitis.

In adults the disease is usually self-limiting and does not require chemotherapy.

Enterohemorrhagic E.coli, such as E.coli O157:H7, produces Shiga toxins that cause inflammation and bleeding of the colon, including hemorrhagic colitis. Shiga toxins can also affect the kidneys to cause hemolytic uremic syndrome.

Campylobacter Gastroenteritis

Campylobacter is the second most common cause of diarrhea in the U.S.

Campylobacter is transmitted in cow's milk.

Helicobacter Peptic Ulcer Disease

Helicobacter pylori produces ammonia, which neutralizes stomach acid; the bacteria colonize the stomach mucosa and cause peptic ulcer diseases.

Bismuth and several antibiotics may be useful in treating peptic ulcer diseases.

Yersinia Gastroenteritis

Y. enterocolotica and Y. pseudotuberculosis are transmitted in meat and milk.

Yersinia can grow at refrigerator temperature.

Clostridium perfringens Gastroenteritis

A self-limiting gastroenteritis is caused by C.perfringens.

Endospores survive heating and germinate when foods (usually meats) are stored at room temperature.

Exotoxin produced when the bacteria grow in the intestines is responsible for the symptom.

Diagnosis is based on isolation and identification of bacteria is stool samples.

Bacillus cereus Gastroenteritis

Ingesting food contaminated with the soil saprophyte Bacillus cerus can result in diarrhea, nausea, and vomiting.