ID- GI tract Flashcards
Defenses of GI tract
Mucus (main defense), secretory IgA, peristalsis, fluids with antimicrobial properties (saliva, stomach fluid, bile), GALT tissues (tonsils, adenoids, lymphoid tissue in the esophagus, peyer’s patches, appendix), and microbial antagonism.
Normal biota of GI tract
Large variety, especially in the oral cavity alone (more than 550 known species). Esophagus and stomach much more sparsely populated. Large intestine contains billions of microorganisms.
Acute diarrhea
1.2-1.9 cases per person per year for adults in US-children are twice the amount. Tropical countries have 10 cases per person per year and 3 milllion children per year die in developing countries from this. 2/3 cases are transmitted by contaminated food in US. Most cases get better without treatment. Some cases can be devestating (E coli)
Acute diarrhea caused by E coli
3 children died from eating undercooked hamburger from jack in the box in washington state in 1993. Caused by the most virulent strain of e coli (o157:h7). Symptoms range from mild gastroenteritis with fever to bloody diarrhea. About 10% of pts develope hemolytic uremic syndrom (little blood flow to kidneys leading to damage and failure). Can also cause neurological symptoms such as blindness, seizure, and stoke. Most likely to occur to children under 5 and the elderly.
Virulence factors of acute diarrhea caused by ecoli
Bacterium produces shiga toxins (extremely virulent). This toxin interrupts protein synthesis in target cells. Effact gut epithelial cells cause lesions in the gut (effacement)- usually large intestine which produces bloody diarrhea.
Transmission and epidemiology of acute diarrhea caused by ecoli
Most common source of transmission is contaminated and undercooked beef. Other food and beverages such as raspberries, lettuce, unpasteurized apple juice or cider can also be a source of transmission. Contamination occurs when intestinal contents of animal comes in contact with meat. Infection can occur with ingestion of as few as 10 organisms (small ID) and is spread through fecal-oral route (especially in young children).
Diagnosis of acute diarrhea caused by ecoli
Confirmed with stool culture, PCR, or ELISA
Prevention and treatment of acute diarrhea caused by ecoli
Best prevention is not eating raw or rare hamburger. Shiga toxin is inactivated by heat. No vaccines are available and antibiotics are contraindicated as they may increase pathogenicity. Supportive care is the only option or treatment.
Acute diarrhea caused by four other categories of e coli
Enterotoxigenic, enteroinvasive, enteropathogenic, tneroaggregative
Enterotoxigenic e coli (ETEC)
Presentation varies depending on which type of e coli is causing the disease. Traveler’s diarrhea- eat or drink something not used to- watery diarrhea, low-grade fever, nausea, and vomiting.
Enteroinvasive E coli (EIEC)
Cause a disease similar to shigella dysentary, invade gut mucosa and cause widespread destruction, blood and pus found in stool, significant fever.
Enteropathogenic E coli (EPEC)
Profuse, watery diarrhea (rice water stool), fever and vomiting, produce effacement of gut surfaces. Closest to 0157.
Enteroaggregative E coli (EAEC)
Can cause chronic diarrhea in young children and in AIDS pts. Commonly spread in daycares and preschools.
GI tract
Composed of eight main sections (mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, anus) and four accessory organs (salivary glands, liver, gallbladder, pancreas). GI tract is an internal tube that passes through the body and the only chemicals absorbed gain entrance to the internal portions of the body.
