Infections of the Digestive System – Flashcards

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Endogenous
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Caused by organisms that are part of the normal microbial flora of the body

(Streptococcus and Enterococcus)

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Exogenous Infections
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  • Caused by pathogens that come into the body from the outside

(C. difficile & helicobacter pylori)

  • Brought in through contaminated water and food.
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Clinical Symptoms of Gastrointestinal Symptoms
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Fever, vomiting, abdominal pain and diarrhea
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Watery Diarrhea
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  • Most common
  • Develops rapidly
  • Accompanied by vomiting, gever and abdominal pain
  • Caused by enterotoxin-secreting bacteria (Vibrio cholerae)
  • Lasts 1 to 3 days
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Dysentery
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  • Rapid onset
  • Smaller in volume
  • contain blood and pus
  • Accompanied by cramps and abdominal pain but very little vomiting
  • Center in the colon
  • Not as much fluid loss
  • Lasts longer about 3-7 days
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Enteric Fever
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  • Systemic infection
  • Prominent Feature: fever  and abdominal pain
  • Diarrhea is mild
  • Penetrations of enterocytes spread to the bile tract and liver
  • Most common: Typhoid fever (Salmonella enterica serotype typhi)
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Dental and Periodontal Infections
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  • Most common: cavities and gingivitis
  • Major source of problem: plaque
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Endemic GI Infections
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  • Occur sporadically
  • Most commonly caused by Campylobacter, Salmonella, and Shigella
  • Most commonly seen in children
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Epidemic GI Infections
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  • Involve regional, national, and international populations
  • Most common: cholera, typhoid fever and shigellosis
  • Cholera and Typhoid fever are associated with contamination of water
  • Shigellosis is associated with wars, crowding and poor sanitation
  • In U.S. most frequent are E.Coli O157:H7, Cryptosporidium, and Giardia
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Traveler's Diarrhea
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  • Caused by enterotoxigenic strains of E. coli (50%)
  • Caused by Shigella (20%)
  • Major source of transmission: improperly cooked food
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Food Poisoning
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  • Intoxication: a toxin produced by a pathogen is involved
  • Infection: pathogen is directly involved in the process
  • Incubation time is shorter in intoxication than in infection
  • Intoxication may involve organs outside the digestive tract
  • Caused by failure to cook food adequately
  • Salmonella, Clostridium perfringens and Staphylococcus aureus
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Nosocomial Gastrointestinal Infections
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  • Traced to ill employee or contaminated food
  • Caused by C. difficile and E. coli
  • Symptoms include mild diarrhea
  • C. difficile may be part of the patient's normal flora or from other patients
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Plaque
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  • Soft dental deposit that forms because of bacterial colonization of the surface of the teeth
  • Insoluble in aqeous media
  • Resists removal by brushing and flossing
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Formation of Dental Plaque
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  • Adhesion of bacteria to the pellicle is followed by growth of bacteria 
  • New layers of organisms pile on to the growing plaque
  • Biofilm because it contains channels that transport nutrients to the bacteria
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Dental Carries

 

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  • Saliva protects against the establishment of many bacteria
  • Caused by organisms that produce acid by-products
  • Most common: streptococcus mutans, streptococcus salivarius, Lactobacillus, Acidophils and Actinomyces species
  • Bacteria absorb and metabolize sugars producing acid by-products causing tooth decay
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Gingivitis
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  • Inflammatory condition of the gums
  • Can be corrected
  • Causes a loss of collagen
  • Continues as long as dental plaque remains on a tooth
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Periodontitis
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  • Infection of the gums that result in the loss of supportive bone and ligaments
  • Bacteria can invade the tissue
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Necrotizing Periodontal Disease
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  • Destruction of the mouth's soft tissue as well as the bone and ligaments
  • Associated with emotional stress and poor oral hygiene
  • Causes rapid ulceration of the tissues and pronounced bone loss
  • Systemic and topical administration of antibiotics relieve the symptoms
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Enterobacteriaceae
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  • Gram-negative rod shaped bacteria
  • Facultative anaerobes
  • Damage the intestines
  • Do not form spores
  • 3 serotypes (O, K and H antigens)
  • O antigen: LPS
  • K antigen: Capsule
  • H antigen: flagellum
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Escheria coli
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  • Gram-negative rods
  • Lactose fermenting
  • Have fimbraie and pili
  • Produce toxins
  • Pore-forming toxin: destroys the integrity of the cell
  • Shiga toxin: blocks protein synthesis and  causes death of the cell
  • Heat-labile toxin: accumulation of water and other lipids in the lumen of the intestine
  • Heat-stable toxin: secretion of liquids and electrolytes into the lumen of the intestine
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Enterotoxigenic E. coli
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  • Release a toxin
  • Leading cause of mental retardation and malnutrition in underdeveloped countries
  • Transmitted through consumption of food or water that is contaminated
  • Adheres to the cells of the intestines
  • Genes are found on plasmids
  • Toxin causes water and electrolytes to flow into the intestine
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Enteropathogenic E.coli
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  • Transmisison is fecal-oral
  • Infants are the reservoir
  • Use fimbriae to form colonies on intestinal cells
  • Secretes five proteins into the cell's cytoplasm
  • Proteins inhibit cell signaling
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Enterohemorrhagic E. coli
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  • Produce shiga toxin
  • Transmission: animals colonized with the pathogens
  • Mostly caused by undercooked meat
  • Attack the colon
  • Mild: no treatment required
  • Severe: liquid replacement required
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Shigella
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  • Don't ferment lactose
  • Lack flagella
  • Produce the shiga toxin
  • Causes dysentery
  • Transmission: fecal-oral route, person to person or consumption of contaminated food or water
  • Most severe: bacillary dysentery
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Pathogenesis of Shigellosis
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  • Trigger an intense acute inflammatory response of the colon
  • Kill the M cells of the colon and phagocytes
  • Use an actin tail for transport
  • Symptoms: fever, malaise and anorexia
  • Treatment: antibiotics
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Salmonella
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  • Multiple Pilli
  • Gastroenteritis: nausea and vomiting followed by cramps and diarrhea
  • Bacteremia: leads to septic shock and death
  • Enteric Fever: fever and headache followed by constipation or diarrhea
  • Chronic Infection: Bacteria enter the blood leading to myocarditis or infection of distal sites of the body
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Salmonella Gastroenteritis
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  • Results from improper food handling (Poultry)
  • Transmission from animal or human reservoirs
  • Bacteria are engulfed by Mcells and enter the lamina propria initiating a powerful inflammatory response
  • Can induce apoptosis in the cell
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Typhoid Fever
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  • Inhibit the release of the oxidative poisons used by macrophages to kill invading bacteria
  • Hemorrhaging causes perforation of the wall of the colon or at the Peyer's patches
  • Treatment: replacement of fluids and control of nausea and vomiting
  • Vaccine available
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Vibrio
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  • Gram-negative, non spore-forming rod shaped bacteria
  • Found in salt water
  • Facultative anaerobes
  • Toxin causes a intestinal infection
  • Spread by contaminated water and poor sanitation
  • Results in dehydration, hypokalemia and metabolic acidosis
  • Balancing liquid and electrolyte loss
  • Treatment: Tetracycline
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Campylobacter Enteritis
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  • Most common cause of diarrhea
  • Primary reservoir: animals
  • Transmission: ingestion of contaminated food or by direct contact with pets
  • Most common source: undercooked poultry
  • Produce a cytotoxin that arrests cell division
  • Lasts 3-5 days
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Heliobacter pylori
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  • Gram-negative rod shaped with flagella
  • Urease enzyme: allows it to survive acidic environments
  • Vacuolating cytotoxin: causes apoptosis in infected cells
  • Transmission: person to person through fecal-oral route
  • Most common cause of gastritis
  • Symptoms: nausea and upper abdominal pain
  • Treatment: antimicrobial agents
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Viral Infections of the Digestive System
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  • Rapid onset diarrhea
  • Characteristics: brief incubation periods, fecal-oral routes of transmission and vomiting
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Rotavirus
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  • non-enveloped, double-stranded RNA virus
  • Common in infants and children
  • Causes a decreased absorptive surface and decreased enzymatic function
  • Vomiting, fever and diarrhea
  • Complication: dehydration
  • Severe cases require replacement of fluid and electrolytes
  • Vaccine available
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Enterovirus
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  • Persistant to acidic environments
  • Seasonal infection patterns and predisposed to temperate climates
  • Fecal-oral transmission
  • Virus is brought into the host cell and viral RNA is released into the cytoplasm
  • No treatment
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Hepatitis A
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  • Transmission: fecal-oral route
  • Commonly caused by crowding and poor hygiene
  • Onset of fever, anorexia, nausea, upper abdominal pain and jaundice
  • Seen more in children
  • No treatment just rest and adequate nutrition
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Hepatitis B
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  • Chronic carriers are the main reservoir
  • Transmission: close contact with body liquids
  • Onset of fatigue, loss of appetitie, nausea, and upper abdominal pain
  • Can lead to cirrhosis, liver failure, or hepatocellular carcinoma
  • Vaccine available
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Hepatitis C
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  • Transmission: blood transfusions and sex
  • Most of those infected become carriers of the infection and progress to chronic hepatitis
  • Leading cause of liver transplants
  • Therapy with interferon-alpha and ribavirin
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Hepatitis D
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  • requires the presence of Heaptitis B
  • Often seen in intravenous drug abusers
  • Co-infection with Hepatitis B or superinfection of people already infected with Hepatitis B
  • Cause a relapse, reoccurence of jaundice and increased risk of cirrhosis
  • Treatment: interferon-alpha
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Hepatitis E
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  • Transmitted by the fecal-oral route
  • Resembles Hepatitis A
  • Causes disease in only pregnant women
  • Associated with contaminated drinking water
  • No treatment
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Hepatitis G
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  • Similar to Hepatitis C
  • No treatment
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Giardiasis
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  • Can survive in cold water for months and is resisitant to chlorine
  • Transmission: fecal-oral route
  • Found in fish, amphibians, reptiles, brids and mammals
  • Contaminated water or food
  • Diarrhea, abdominal cramping, nausea and fever
  • Lead to significant weight loss and malnutrition
  • 4 drugs available
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Cryptosporidiosis
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  • infects the intestinal tract of both humans and other animals
  • Domestic animals are the reservoir
  • Person-to-person transmission
  • Transmission: fecal-oral route, contamination of food and water
  • Watery diarrhea
  • No treatment needed
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Whipworm
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  • Significant mucosal damage, blood loss and anemia in children
  • Asymptomatic infections: no need for treatment
  • Severe disease: mebendazole
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