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University of Waterloo
BIOL 444
Christine Dupont

BIOL444 – Microorganisms & Diseases Fall 2012 Set 06 – Gastrointestinal Tract Diseases - Alimentary tract: From mouth to anus, lined with mucosal epithelium, colonized @ birth  normal microbiota, relatively constant unless disrupted by exogenous factors o Protection: Mucus, GALT (Follicles & Peyer’s patches), gut motility, bile & normal microbiota  Colonizing/symbiotic microbes are not attached to the epithelial cells lining the lumen, they form a biofilm & extend their populations into the intestine  Only pathogens attach, adherence, and invade the epithelial cells o Overcome host protection: ↕ pH, ↕ normal community & specific pathogenic agents - Periodontal diseases: Not cavities, slowly developing, chronic inflammatory process involving the gums & tissues around the root of tooth, even the jaw bones o Plaques/bstfilms are formed on pellicles (saliva proteins) of the tooth surface  1 Normal oral bacteria: Gram-positive cocci (S. sanguis, S. mutans) & Gram-negative rods  2 Filamentous & fusiform bacteria  3 More anaerobes as the plaque thickens (dominated by Gram -ve)  more tissue destruction & inflammation  Mature plaques can contain 300-400 species  Porphyromonas gingivalis can open up the gap  lots of inflammation, bone loss & damage to the roots  Periodontal disease o Brushing teeth reduces pellicles (temporarily) to maintain early colonization o Symptoms: Bleeding gums, ↑ sensitivity, bad breath, loose teeth, gum discolouration, receding gums & root exposure o Pathogenesis: Plaques at gum margins + Ca salt deposition  Dental calculus (tartar) when biofilms starts to calcify and becomes hard  Gingivitis: Extension of plaque into gingival crevice, lots of plaque  microbial enzyme (LPS, peptidoglycan) released  crevice enlarges  further colonization of Gram –ve (acid)  periodontal ligament weakens & surrounding bone softens o Treatment:  Early: Clean out inflamed crevice, remove plaque & tartar  Late: Surgery to expose & clean roots (can’t be reversed, gums can’t grow back) - Dental caries (Cavities, tooth decay) o Disease associated with dietary sucrose “artificial sweetener”  No cavities: sucrose is not a part of the diet (mostly had starch - glucose) o Streptococcus mutans (viridans strept – α-hemolysis on blood agar)  Bacteria converts sucrose into an extracellular matrix of biofilms to increase adherence to the tooth surface (sucrose is not used as an energy source)  Sucrose consumption enhances colonization of S. mutans  Glucose & other sugars are fermented  lactic acid production  pH<5 (overcomes neutralizing capacity of saliva)  tooth demineralization  cariogenic plaque formation  Low pH enhances the growth of S. mutans o Prevention: Fluoride (tooth paste, mouth wash, water) prevents tooth decay  Inhibits demineralization, enhances remineralization & inhibits bacterial enzymes - Gastritis: Inflammatory responses to bacterial products
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