Chapter 25: Disease of the digestive system

• The digestive system consists of the mouth, salivary glands, pharynx, esophagus, stomach, small and large intestines, liver, gall bladder, and pancreas

• Part of this tract is a tube running through the body from the mouth to anus is colonized by many different normal microbiota

Disease of the digestive system

3. Diseases of digestive system are mainly of 2 types: infection an intoxicationsa. infection occurs when a pathogen enters the GI tract and multipliesb. intoxication is caused by ingestion of preformed toxins

4. Gastroenteritis = an infection of the stomach or intestinal mucosa caused by ingestion of food or water with pathogens

Bacterial Diseases of the Lower GI Tract

Staphylococcal food poisoning – 2nd most reported of foodborne disease, Salmonella related illnesses are #1

1. Staphylococcus aureus causes a food intoxication by ingesting an enterotoxin of S. aureus in contaminated fooda. enterotoxin = exotoxin that caused gastroenteritis (Staphylococcus, Vibrio, Escherichia) b. gram positive coccus

Staphylococcus food poisoning

2. Vegetative cells have a high resistance to heat – can tolerate 30 minutes at 60 C (140 F)a. the toxin is also heat stable and can tolerate 30 minutes of boiling

3. Found on hands and is easily transferred to food ( Staph aureus is a normal microbiota of nasal passages and is found in skin wounds)a. food prepared in advance and not refrigerated is a potential source of Staphylococcal food poisoning

Staphylococcus food poisoning

4. High risk foods are custards, cream pies, ham, poultry products and there is no obvious signs of spoilage – no unusual tastes, odor or appearance

5. Incubation period is 1-6 hours after ingestion, recovery in 24 hours

6. Sxs = abdominal cramps, severe nausea, vomiting, HA, fever, prostration, diarrhea (toxin causes release of water)

Salmonellosis

1. Many species of Salmonella cause foodborne infection, Gram neg rods

2. The intensity of Salmonella food poisoning depends on the number of bacteria ingested in contaminated products such as poultry

3. The bacteria replicate in the intestinal mucosa and in macrophages

4. Incubation period from the time of infection is

1-3 days before onset of sxs

Salmonellosis

5. Sxs = nausea, severe abdominal cramping, watery diarrhea, fever and possibly vomiting after 6 - 48 hours

a. sxs may last more than a week

6. Dx = isolate pathogen from px stool or leftover food

7. Tx = antibiotics are not useful, if dehydrated fluid replacement

Salmonellosis

8. Salmonella infect poultry and poultry products such as eggsa. they infect the ovary of hens and pass into the egg before the shell formsb. infect egg products – custard pies, cream cakes, egg nog, ice cream, mayonnaise

9. Not a lethal bioweapon but in 1984 in Oregon, members of a religious cult sprayed the bacteria on the salad bars of some restaurants, 750 people became ill but none died

Cholera – one of the most serious GI diseases

• Vibrio cholerae – curved, gram neg, flagellated rod – 1st isolated by Robert Koch in 1883– Grows in the small intestine where an

enterotoxin of Vibrio cholera interferes with water and electrolyte re-absorption1) the enterotoxin is an exotoxin = cholera toxin

b. Result is watery stools called “rice water stools”

Cholera

• b. 1) can lose 3 – 5 gallons of fluids/day 2) sudden loss of fluids and

electrolytes can cause shock, collapse, and death 3) blood becomes viscous and

organs can’t function 4) violent vomiting also occurs

c. dx is based on sxs and culturing the pathogen from feces

Cholera

• d. transmitted through contaminated food or watere. tx = intravenous replacement of fluids and electrolytes

1) untreated there is a 50% mortality rate

2. Non cholera vibrios a. Vibrio parahaemolyticus likes brackish water and have been associated with outbreaks of gastroenteritis associated with seafood ingestion

Cholera

2. b. Vibrio vulnificus – found in estuaries1) ingestion of raw or undercooked

seafood causes septicemia2) people with compromised immune

systems are at higher risks3) causes dangerous infections of

minor skin lesions with rapidly spreading tissue destruction that may require limb amputation

Campylobacter gastroenteritis

• Campylobacter jejuni – gram neg, spirally curved rod that is becoming a leading cause of food borne illness in the US

a. Invades and damages the mucosal surfaces of the small intestine and colon

• Sxs = bloody or watery diarrhea, abdominal pain, cramps, fever – recovery in 1 week

• Complication – 1 in 1000 cases is Guillain-Barre syndrome = a neurological disease that causes temporary paralysis

Shigellosis = Bacillary dysentery

Bacterial infections – Salmonellosis and shigellosis have loner incubation periods

(12 hrs to 2 weeks) than intoxicationsShigellosis – severe diarrhea caused by facultative

anaerobic gram neg rods• 4 species of pathogenic Shigella a. most common in US = Shigella sonnei – causes

mild diarrheab. Shigella dysenteriae – severe dysentery and prostration

1) can cause 20 bowel movements a day with abdominal cramps and fever

Diseases of the digestive tract

Shigellosis

2. Food contaminated with Shigella dysenteriae gives rise to dysentery through the production of an enterotoxin (Shiga toxin)

3. Sx = abdominal pain, fever, watery stool with mucus and blood, dehydration

4. Dx = recovery of microbe from rectal swab

5. Tx = antibiotics and oral re- hydration

Escherichia coli gastroenteritis – produce toxins

• Normally harmless but certain strains are pathogenic O157: H7

• Traveler’s diarrhea –sxs appear within 2 weeks of travel to a tropical location and last up to 10 daysa. Enterotoxigenic E. coli – not invasive, produce enterotoxin in the small intestine that causes watery diarrhea that resembles a mild case of cholera

Escherichia coli gastroenteritis

2. Traveler’s diarrheab. Enteroinvasive E. coli – invades the intestinal wall resulting in inflammation, fever, and Shigella like dysentery

3. E. coli O157:H7a. confined to the large intestine – bloody diarrhea = hemorrhagic colitisb. involves kidneys – kidney failure = hemolytic uremic syndrome (HUS)

1) seizures, coma, colon perforation, liver disorders are associated with it

Escherichia coli gastroenteritis

3. E. coli O157:H7

c. this bacteria is in the intestines of cattle and do not produce disease

1) contamination takes place during slaughter of the animal and brings E. coli to the beef product such as hamburger meat

2) excretion to the soil brings E. coli to plants such as spinach and fruits - cantaloupe

Viral Diseases of the Digestive Tract

Mumps – caused by RNA virus• Sign = swelling of salivary lands esp.

parotid glands

a. obstruction of the ducts leading from the parotid glands retards the flow of saliva and causes swelling – the skin over the glands – taut, shiny

Mumps

2. Sx/signs = painful swelling of the parotid glands, fever, chills, HA, malaise, pain when swallowing

3. In adult males may infect testicles (orchitis) and cause sterility

4. Transmitted via the saliva and respiratory secretions

a. portal of entry = respiratory tract

b. spreads to the salivary glands from the blood

5. MMR vaccine – attenuated live vaccine