← Diseases of Gastrointestinal System Export Options Alphabetize Word-Def Delimiter Tab Comma Custom Def-Word Delimiter New Line Semicolon Custom Data Copy and paste the text below. It is read-only. Select All Structure of the digestive system • Divided into two parts • Gastrointestinal tract (GI tract) The pathway from the mouth to the anus • Accessory digestive organs Organs involved in grinding food or providing digestive secretions (a) Salivary gland (b) Liver (c) Gallbladder (d) Pancreas Function of GI tract • Digest food • Absorbs nutrients and water into the blood • And eliminate waste Components of GI tract • Mouth site where food is moistened and chewed • Esophagus tube leading to the stomach • Stomach secretes HCI, enzyme: pepsin • Small intestine- digestion and absorption of nutrients • Large intestine (colon) - completes absorption of nutrients: water, steroids, and minerals • Rectum and anus eliminates waste Normal microbiota of the digestive system • Tongue, teeth, small intestine, colon, rectum • Heavily colonized with various bacteria • Oral cavity contains up to 700 bacterial species • Esophagus, stomach, duodenum • Almost sterile- how can that be? • HCI in stomach; peristalsis and the rapid transport of food help prevent colonization by microbes Dental Caries(Tooth Decay) • Accumulation of microbe on the surface of the teeth is called dental plaque-biofilm • The plaque is made up of streptococci(Streptococcus mutans) and filamentous bacteria Actinomyces • Bacteria hydrolyze the sucrose into glucose and then use glucose to synthesize dextran(gummy polysaccharide) • Inside the plaque, bacteria ferment the fructose into lactic acid. Lactic acid damages the enamel of the tooth. • Bacteria invade the dentin (calcified tissue of the tooth) • Bacterial population inside the dentin is composed of Gr+ bacilli and filamentous bacteria( about 300 bacterial species are identified) • If not treated, the tooth decay advances to pulp and roots( contain blood vessels and nerves) • Infection can spread to the neighboring soft tissue • Prevention of dental caries- reducing the amount of sucrose in the diet and, proper brushing and flossing • Periodontal Disease Peri=around, odont= tooth • Initial stage- gingivitis Symptoms: swelling, bleeding of gingival, formation of pockets • Advanced stage- periodontitis Symptoms: tissue destruction, formation of deep pockets, build up of calculus(deposits of CaCO3), loosing of teeth, bone loss • Causative agent: polymicrobial biofilm Mumps • Mumps virus- paramyxovirus • Disease of parotid(salivary) gland(located bellow the ears) • The virus is acquired by respiratory rout • Symptoms: swelling of parotid gland, fever, pains during swallowing • Complications: inflammation of testis (possible sterility), meningitis, inflammation of ovaries • Available vaccine (MMR) Virulence factor of mumps virus • The virus induces the infected cell to fuse with the adjacent cell- a large multinucleate cell is formed (syncytia) • The virus particles freely pass from cell to another- evading the antibodies Gastric user • Lesions in the mucus membrane of the stomach caused by Helicobacter pylori • The bacterium can survive in the acidic environment in the stomach by producing urease that neutralizes the acid • H. pylori causes destruction of the protective mucus layer that leads to erosion of the wall • Symptoms: abdominal burning pain Diagnosing Helicobacter • Visually by endoscopy • A flexible tube is inserted through the mouth into the stomach • Elisa test- blood tested for the presence of antibodies against Helicobacter Acute Diarrhea • A frequent loose or liquid bowel movement • An average person experiences 1.2 to 1.9 cases of diarrhea per year • More frequent in children • In tropical countries experience more than 10 episodes of diarrhea per year • Cause: food contaminated with bacteria and/or their toxins Salmonellosis • Caused by Salmonella- Gr- facultative anaerobic rods, there are about 2000 serotyps • Bacteria invade the intestinal mucus membrane. From there they can enter the lymphatic system • Incubation time is 12-36 h but it depends on the number of cells ingested • Recovery- after few days typically self- limited infection • Antibiotics not effective • Source of infection: poultry, eggs, egg products Typhoid Fever • Caused by Salmonella typhi • Bacteria multiply in phagocytic cells; can be found in blood, urine, feces • Incubation period is up to 3 weeks • Symptoms: headache, high fever and diarrhea (after 2nd week) • Susceptibility: travel in areas with poor sanitation • Patients can become chronic carriers of the disease. They shed bacteria from their gall bladder • Treatment: Antimicrobial drugs Shigellosis (Bacilary Dysentery) • Caused by shingella- facultative anaerobic Gr- rods • Bacteria multiply in the small intestine in the cells of mucous membrane produce the shiga toxin • Symptoms: sever diarrhea with blood in stool, abdominal cramps, and fever • Treatment: Fluid and electrolyte replacement and antimicrobial treatment E.coli O157:H7 • Considered as an emerging pathogen • First recognized in 1980 • Symptoms: gastroenteritis, bloody diarrhea, anemia, kidney damage, blindness, seizure, and stroke • Virulence factors • Shiga toxin- gene introduced through phage- mediated transfer • Type 3 secretion system (set of proteins) Intimin enables E.coli to attach to the host cell Insert bacterial products into the host cell • Transmission: ingestion of contaminated and undercooked beef, lettuce, and vegetables • Treatment: supportive therapy, antibiotics of no use Cholera • Causitve agent: Vibrio cholerae, slightly curved rod with a single polar flagellum • The bacterium grows on the epithelial cells in the small intestine(does not enter the host cell) • Produces enterotoxin- causes excessive secretion of water and electrolytes • Symptoms: sever diarrhea with sudden loss of fluids, shock, collapse, and even death • The blood becomes very viscous • Treatment: replacing lost fluids and electrolytes, tetracycline • Mortality rate • Untreated - 50 % • Treated- 1 % Cryptosporidiosis • Cryptoporidium hominis ( infects humans) • Contracted by ingestion of the oocysts; drinking or recreational water • Water contamination- animal waste • Oocytes develop into sporozoits- embedded in the epithelial cells of the intestine • Symptoms: diarrhea • Treatment: usually not requited in the case of healthy individuals; antidiarrheal agent Acute Diarrhea with vomiting- Food poisoning • The symptoms are violent and incubation period is very short 1-6 h • Disease caused by ingestion of preformed toxin ( bacterial or some other) Staphylococcal food poisoning • Caused by staphylococcus aureus- lives in nasal cavity • Food provides favorable environment for multiplication of bacteria( if left at room temperature) • S. aureus can outgrow other competing bacteria (tolerates higher osmotic pressure higher temperature, low moisture level) • Foods such as custards, sauces, processed meats • Contaminated and left unrefrigerated • Toxins are released. Taste and smell of the food is not altered • Further coking can eliminated bacteria but not the toxin • The toxin damages the tissues • Symptoms of intoxication: abdominal cramps, vomiting, and diarrhea • The disease is self limiting, recovery within 24 hours Chronic diarrhea (diarrhea lasting longer than 14 days) • Giardiasis • Causative agent Giardia lamblia • A flagellated protozoan • Infection via contaminated water • Attaches to intestinal wall, interferes with food absorption • Symptoms: nausea, intestinal gas, weakness, abdominal cramps, and diarrhea • Healthy carriers shed cysts in their feces • Prevention: avoid consuming untreated water (backpackers in wilderness) • Treatment: Metronidazole Hepatitis • Hepatitis is an inflammation of the liver caused by an infection with viruses • There are five known viruses that can cause hepatitis: (Hepatitis A,B,C,D,E) • Symptoms include jaundice, abdominal pain, fatigue, nausea, vomiting, appetite loss Hepatitis A • Causative agent: single stranded RNA virus, no envelope • Infection is acquired via oral rout (fecal contamination of food, water, and oysters) • In 50% of cases symptoms are subclinical • Symptoms: anorexia, nausea, fever, abdominal discomfort, fever, and chills, and jaundice • Vaccine is available Hepatitis B • Causative agent: hepatitis B virus (BV), double stranded DNA virus with the envelope • Transmission: break in skin- body fluids(blood, saliva, breast milk, and semen) • Multiplies exclusively in the liver • Symptoms: loss of appetite, fever, joint pains and jaundice • 10% of patients become carries(reservoirs of the disease). They can more likely to get liver cancer. • Vaccination recommended for health care professionals and other high risk groups • Vaccine is obtained by genetic engineering.