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Digestive System Infections Chapter 23 – Gastrointestinal tract (GI tract) • Digests food, absorbs nutrients and water into blood, and eliminates waste • Mouth, esophagus, stomach, small intestine, large intestine (colon), rectum and anus – Accessory digestive organs • Organs involved in grinding food or providing digestive secretions • Tongue, teeth, salivary glands, liver, gallbladder, pancreas •Most organs of GI tract protected by peritoneum Normal Flora • Tongue and teeth – Viridans streptococci most prevalent – Form biofilms • Esophagus, Stomach, Duodenum – almost free of microbes – Peristalsis, rapid transport of food and acids • Lower small intestine and colon – Enterobacteria (enterics) dominant – Anaerobic Bacteriodes and Lactobacillus – Mutualism • Defenses – Normal flora • Microbial antagonism – Saliva – Acid and digestive enzymes – Continuously shed cells of mucus membrane Dental Caries • Most common bacterial disease of humans – Main reason for tooth loss • Causative agent – Streptococcus mutans – Dextran and pili allow biofilm formation – Lactic acid fermenter • Signs and symptoms – Usually advanced before symptoms arise • • • • Throbbing pain Discoloration, roughness or holes in tooth (caries) Tooth can break while chewing Gingivitis – inflammation of gums – May lead to periodontal disease • Inflammation and infection of surrounding tissues • Epidemiology – Worldwide distribution • Incidence varies – Mainly on availability of dietary sucrose and dental care • In US, 78% of children have at least one cavity by 17 – 99.5% by age 65 • Prevention – Restriction of dietary sucrose – Mechanical removal of plaque • brushing and flossing – Application of sealant – Fluoride treatment • Treatment – Drilling out cavity and filling with amalgam – Crown or root canal – Antibacterial rinses and scaling for gingivitis Peptic Ulcers • Erosions of stomach or duodenum lining • Causative agent – Helicobacter pylori • Gram-negative; vibrio • Multiple polar knobbed flagella • Signs & Symptoms – Abdominal pain – Nausea, vomiting (with or without blood), weight loss and bloody stools – May lead to internal bleeding and shock • Due to perforations of stomach or intestine • Virulence factors • • • • Adhesions Urease Protein to inhibit acid production Enzyme to inhibit digestion by WBCs – Inflammatory response and bacterial toxins causes decrease in mucus production – Stomach lining not protected from acidic environment – Chronic infection • Epidemiology – Transmission most likely fecal-oral route • Flies also capable of transmission – 20% of US population infected • Many asymptomatic carriers • Diagnosed by assessing damage to stomach lining and isolation of urease+, Gram- vibrios • Prevention – Change lifestyle to eliminate risk factors – Good hygiene to avoid fecal-oral transmission • Treatment – Combined antibiotic treatment – Medication to inhibit production of stomach acid – Surgery may be required if ulceration is extensive or perforation occurs Mumps • Acute viral illness – Attacks large parotid salivary glands • Causative agent – Mumps virus • Enveloped, -ssRNA Rubulavirus • Signs & Symptoms – Long incubation period – Fever, loss of appetite, headache, parotitis and sore throat – Symptoms disappear in about a week – Symptoms much more severe past puberty • May cause orchitis or meningitis • Pregnant women often miscarry – Virus reproduces in the upper respiratory tract • Spreads to salivary glands – In salivary glands • Destroys epithelium and releases virus into saliva causing inflammation • Epidemiology – Humans only natural host – Contact transmission • Droplets or fomites • Peak infection time from 1-2 days before swelling until swelling subsides • Prevention – Prevention directed at immunization • MMR • Lifelong immunity • Treatment – Treatment directed at alleviating symptoms – No effective antiviral treatment