Chapter 20: Infectious Diseases Affecting the Gastrointestinal Tract Flashcards
GI Tract Defenses
- intestinal surfaces coated with layer of mucus
- IgA found on most surfaces
- peristalsis
- saliva
- lysozyme and lactoferrin
- stomach acid
- bile
- appendix
- GALT
GALT
- tonsils and adenoids in the oral cavity and pharynx
- small areas of lymphoid tissue in the esophagus
How does E. coli assist with digestion?
Synthesizes vitamin K
Which of the following types of organisms are not considered normal biota of the gastrointestinal system?
A.bacteria
B.archaea
C.fungi
D.protozoa
E.None of the choices is correct.
B. archaea
Causative agents of chronic diarrhea
- E. coli
- Cyclospora
- Giardia
- Entamoeba
Causative agents of food poisoning
- Staphylococcus aureus
- Bacillus cereus
- Clostridium perfringens
Causative agents of dental carries and periodontitis
- Streptococcus mutans
- Scardovia wiggsiae
Causative agent of mumps
Paramyxovirus
Causative agent of Salmonella
- S. enteritica
- other bacteria may cause also
Properties of Salmonella
- ferment glucose; Motile
- can survive outside the host in hospitable environments, fresh water and freezing temperatures
- resistant to chemicals
- Most strains come from animals
- Salmonella are normal intestinal biota in cattle, poultry, rodents, and reptiles
Signs and Symptoms of Salmonella
- Severe forms of salmonellosis can include
- elevated body temperatures
- septicemia
- Milder forms of salmonellosis
- Vomiting
- diarrhea
- mucosal irritation
- blood can appear in the stool
- death is infrequent except in debilitated
Illnesses caused by salmonella
- Typhoid fever
- caused by the typhi variant. Salmonella typhi infects humans exclusively
- Gastroenteritis
- caused by paratyphi, hirschfeldii,
and typhimurium
Salmonella’s virulence factors
- its ability to adhere effectively to gut mucosa
- endotoxin
Prevention and Treatment of Salmonella
- Avoid contact with bacteria
- trimethoprim-sulfamethoxazole (TS)
- when disease is severe
Salmonella has a high ID50, meaning…
A lot of organisms must be ingested for disease to result
Salmonella commonly found in
milk and eggs
Shigella bacteria characteristics
- gram-negative rods
- non motile
- non-spore-forming
- primarily human parasites, but can infect Apes
Signs and symptoms of Shigella
- Frequent, watery stools
- Fever
- Intense abdominal pain
- Nausea and vomiting are common
Dysentery
- diarrhea containing blood
- Mucus from the GI tract is also present in the stools
Virulence Factors of Shigella
- Shigella invades the villus cells of the large intestine rather than the small intestine
- Causes inflammatory response
- Enterotoxin
Shiga Toxin
- Produced by Shigella dysenteriae
- may be responsible for more serious
damage to the intestine
- also causes systemic effects, including injury to nerve cells
Transmission of Shigella
- Oral route
- direct person-to-person
- sanitation, malnutrition, and crowding
True or False: Shigella can establish a chronic carrier condition in some people that can last several months
True
Prevention and Treatment of Shigella
- Good hygeine
- trimethoprim-sulfamethoxazole (TS)
most virulent enterohemorrhagic E. coli or
EHEC
E. coli O157:H7
Signs and Symptoms of E. coli O157:H7
- Mild gastroenteritis, Fever, Bloody diarrhea
- 10% of patients develop severe hemolytic anemia in kidney and can cause kidney damage and failure
- Neurological symptoms such as blindness, seizure, and stroke
Virulence factors of E. coli O157:H7
- Shiga toxin
- interrupts protein synthesis on target cells
lesions in large intestines & produce bloody diarrhea
- interrupts protein synthesis on target cells
Transmission of E. coli O157:H7
- Most common mode of transmission for EHEC is ingestion of contaminated or undercooked beef
- other foods and beverages can be contaminated
- any farm product can become contaminated with cattle feces
- Products eaten raw such as lettuce, vegetable, and apples used in unpasteurized cider are particularly problematic
Culture and Diagnosis of E. coli O157:H7
stool culture or with ELISA or PCR
Prevention and Treatment of E. coli O157:H7
- never to eat raw or rare hamburger and to wash raw vegetables
- supportive therapy, including plasma
transfusions to dilute the toxin in the blood is the only option
* antibiotics may increase pathology
Campylobacter
Considered to be the most common bacterial
cause of diarrhea in the U.S
Signs and symptoms of Campylobacter
- Frequent, watery stools
- Fever
- Vomiting
- Headaches
- Severe abdominal pain
- Symptoms may last longer than 2 weeks
Causative agents of Campylobacter
Campylobacter jejuni
Transmission of Campylobacter
- ingestion of contaminated beverages and food
- water, milk, meat, and chicken
Yersinia
- Gram-negative bacteria
- includes the species Yersinia pestis,
- cause of the plague
Species of Yersinia that cause GI tract diseases
- Y. enterocolitica
- Y. pseudotuberculosis
GI Yersinia is often mistaken for what?
appendicitis
Clostridium difficile
Gram-positive endospore forming rod as normal flora
Signs and Symptoms of Clostridium difficile
- Diarrhea
- severe cases exhibit
- abdominal cramps
- Fever
- colon is inflammed and gradually sloughs off loose, membranelike patches called pseudomembranes
- if the condition is not stopped, perforation of the cecum and death can result
Virulence factors of Clostridium difficile
- Superinfection
- opportunistic
- Enterotoxin
- necrosis
Treatment of Clostridium difficile
- Replacement of lost fluids and electrolytes
- antibiotics in severe cases
Causative agent of Cholera
Vibrio cholerae
Signs and symptoms of cholera
- Abrupt symptoms of vomiting followed by copious, watery feces called secretory diarrhea
- contains flecks of mucus and is described as “rice water stool”
- Oodles of fluid loss
- sometimes up to 50% of body weight
- Potassium depletion
- If cholera is left untreated, death can occur in less than 48 hours & mortality rate approaches 55%
Virulence factors of cholera
- Cholera toxin
- fluid loss
Transmission of cholera
- Seasonal
- Water and food
Prevention and Treatment of Cholera
- Proper sewage treatment
- Vaccines available to travelers
- Prompt replacement of fluids and electrolytes
- Oral antibiotics: trimethoprim-sulfamethoxazole (TS)
GI Viruses
- Rota virus
- Adenoviruses
- noroviruses (Norwalk viruses)
- astroviruses
Transmission of GI viruses
- fecal-oral
- food contamination
Food poisoning should be suspected when…
- severe nausea and frequent vomiting accompanied by diarrhea
- patient reports that companion also has similar symptoms after eating the same thing
- onset within last 1-6 hours
Bacteria that produce the food poisoning toxin
- Staphylococcus aureus
- Bacillus cereus
- Clostridium perfringens
