Class Notes (835,376)
Canada (509,147)
Biology (2,253)
BIOL 444 (9)
Lecture

Set 07.docx

3 Pages
60 Views
Unlock Document

Department
Biology
Course
BIOL 444
Professor
Christine Dupont
Semester
Fall

Description
BIOL444 – Microorganisms & Diseases Fall 2012 Set 07 – Infectious Diseases of the Intestinal Tract - Developing countries: Normally viral infection (e.g. rotavirus), death due to severe diarrheal ~50% for kids - Developed countries (e.g. Canada & US): Normally due to bacterial infections - Major syndromes: o Diarrhea (e.g. cholera): Fluid-feces discharges, large amounts of fluid & electrolyte loss  Cholera: Temporary colonization, non-invasive, releases enterotoxin – cholera toxin that acts on the small intestine to induce diarrhea o Dysentery (e.g. shigellosis): Inflammation of GI tract, blood & pus are found in feces, not as much fluid loss compare to diarrhea [More serious]  Shigellosis: Invasive colonization, shiga toxin, destroys mucosal cells of the large intestine - Transmission: Fecal-oral, or via fingers, vectors, fomites etc. usually foodborne/waterborne - Control: Sanitary & hygienic measures (disinfection of drinking water) - Cholera: a disease of poor sanitation o Vibrio cholerae: Gram-negative curved rod, polar flagellum, alkali-tolerant, facultative anaerobe  Natural host are humans, but other vibrios (e.g. v. parahaemolyticus) can cause shellfish poisoning (marine organisms picked up by filter feeders such as clamps or oysters)  viable but non-culturable state, stays alive for a really long time  Serogroup “O1” is associated with epidemic cholera  The O-polysaccharide of the Lipopolysaccharide (LPS) is antigen specific  Another phage encodes particular pilli of the V. cholerae coat protein, and the PAI derived phage CTX (found in pathogenic strains) attaches to the pilli o Symptoms: Abrupt onset of massive diarrhea “rice-water” stools, can lose up to 20L of fluid/day, 50- 60% mortality if untreated, but if survived from severe dehydration, disease is often self-limiting o Pathogenesis:  Large # of V. cholerae required (thousands are needed to detect presence in intestine, V. cholerae doesn’t transit well through low pH stomach)  Adheres & multiplies on epithelium of the small intestine (non-invasive)  Cholera toxin: Heat-labile exotoxin encoded by lysogenic phage (similar to a-b toxin), binds irreversibly to GM1 on mucosal cell surface & cholera toxin acts on mucosal cells  ADP-ribosylation of G pSotein o Normal: Adenylate cyclase – G (inactive)  AC – G – GTP (active)  AC – G S S S (inactive) as G1removes GTP to form GDP & P o Cholera toxin: Ribosylation of G Srevents G fr1m acting on the activated AC – G – GTP, so GTP cannot be removed & AC – G – GTP remains activated S S  Lots of cAMP are produced o Normal: CFTR (Cystic Fibrosis Trans-membrane Conductance Regulator) controls ion flux across mucosa-lumen interface - +  Cl is pumped out via CFTR, Na & H O 2ollows via osmosis  Nearly all Na , 2 O & glucose is reabsorbed via Na /glucose sympoter o Cholera toxin: cAMP increases Cl outflow +  Na & H O2follows via electrolyte balance & osmosis  diarrhea  No time for Na & H O2to be re-absorbed o Treatment: + -  Oral rehydration solution (ORS): Containing glucose, water, electrolytes (Na & Cl)  Antibiotics may or may not be useful (bacteria died, but toxin still retained) - Dysentery: Blood and mucus in feces (serious and invasive) o Generic enteric bacterium (e.g. V. cholerae O1, E. coli O157:H7, E. coli K12)  Serotyping (OHK system): Specific antibody that are made to surface molecules  O (Somatic) antigen: Surface-associated LPS outer polysaccharides  H antigen: Flagella associated proteins BIOL444 – Microorganisms & Diseases Fall 2012  K (Vi) antigen: Capsular associated, not produced by all organisms  Type III secretion system: Gram –ves (2x bacterial membrane & 1x host plasma membrane)  E. coli injects through the transport system molecule
More Less

Related notes for BIOL 444

Log In


OR

Join OneClass

Access over 10 million pages of study
documents for 1.3 million courses.

Sign up

Join to view


OR

By registering, I agree to the Terms and Privacy Policies
Already have an account?
Just a few more details

So we can recommend you notes for your school.

Reset Password

Please enter below the email address you registered with and we will send you a link to reset your password.

Add your courses

Get notes from the top students in your class.


Submit