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