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Digestive System Infections
Chapter 23
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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
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Accessory digestive organs
Organs involved in grinding food or providing digestive secretions Tongue, teeth, salivary glands, liver, gallbladder, pancreas
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Most organs of GI tract protected by peritoneum
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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
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Lower small intestine and colon
Enterobacteria (enterics) dominant Anaerobic Bacteriodes and Lactobacillus Mutualism
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Defenses Normal flora Saliva Acid and digestive enzymes
Microbial antagonism Saliva Acid and digestive enzymes Continuously shed cells of mucus membrane
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Dental Caries Causative agent Most common bacterial disease of humans
Main reason for tooth loss Causative agent Streptococcus mutans Dextran and pili allow biofilm formation Lactic acid fermenter
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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
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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
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Prevention Treatment 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
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Peptic Ulcers Erosions of stomach or duodenum lining Causative agent
Helicobacter pylori Gram-negative; vibrio Multiple polar knobbed flagella
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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
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Virulence factors Adhesions Urease Protein to inhibit acid production
Enzyme to inhibit digestion by WBCs
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Inflammatory response and bacterial toxins causes decrease in mucus production
Stomach lining not protected from acidic environment Chronic infection
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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
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Prevention Treatment 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
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Mumps Acute viral illness Causative agent
Attacks large parotid salivary glands Causative agent Mumps virus Enveloped, -ssRNA Rubulavirus
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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
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Virus reproduces in the upper respiratory tract In salivary glands
Spreads to salivary glands In salivary glands Destroys epithelium and releases virus into saliva causing inflammation
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Humans only natural host Contact transmission
Epidemiology Humans only natural host Contact transmission Droplets or fomites Peak infection time from 1-2 days before swelling until swelling subsides
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Prevention Treatment Prevention directed at immunization MMR
Lifelong immunity Treatment Treatment directed at alleviating symptoms No effective antiviral treatment
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