MCB Exam 3-E

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MCB Exam 3-E
2011-03-29 20:03:33
Microbial Diseases Digestive System

Microbial Diseases of Digestive System
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  1. Dental Caries

    What org & what it does
    • Streptococcus mutans
    • Anaerobic env allows bacteria to thrive, releasing acid & forming plaque
    • VF: dextran (sticky material) and pili allow biofilm formation on tooth
  2. Gingivitis & Periodontal Disease

    How happens
    • Tarter trapped at base of teeth triggers, causing receding gums
    • VF: proteases brk down gum tissue
  3. Peptic Ulcers
    Helicobacter pylori

    How get it
    • Fecal-oral transmission
    • VF: flagella, adhesions, urease & other enzymes
    • Acid from stress or eating acidic or spicy food causes small holes in stomach lining where org can get in
  4. Urease
    Enzyme brks down urea & produces ammonia, producing ammonium hydroxide which raises pH = less acid, causing ulcers
  5. Bacterial Gastroenteritis

    What it is
    • General term for inflammation of stomach or instestines by drinking or eating bacterial contaminated water, or poor living conditions
    • Symptoms: vomiting, diarrhea, abdominal pain
    • Dysentery: severe form; loose frequent stool w/mucus & blood
  6. 3 ways gastroentero bacteria enter
    • Attaches to cell surface--> water loss--> watery diarrhea
    • Enters cell---> bloody diarrhea & tissue loss
    • Passes thru intestinal wall "sub-mucousal" & into blood stream, entering rest of body (passes right thru intestine to go to blood & body)
  7. Cholera
    Vibrio cholerae

    Where get it
    How it works in body
    • Water or raw seafood
    • Cells can't absorb water- ions become highly concentrated in intestine, causing water flow in, but water cannot be reabsorbed by intestines
    • Most die from dehydration so trmt is fluid replacement
  8. Traveler's Diarrhea
    E. coli

    How get it
    What it does in body
    • Fecal-oral
    • Goes into cell, stopping protein synthesis, causing tissue loss (shiga-like toxin)
  9. Shigellosis
    Same as Traveler's Diarrhea
  10. Campylobacter Diarrhea
    Campylobacter jejuni

    Abt it:
    How get it:
    • Leading cause of diarrheal disease in US in summer
    • Fecal-oral
    • VF: adhesions, cytotoxins, endotoxin
    • Diagnosis: not tested for b/c difficult to grow in lab, just give Rx
  11. Salmonellosis
    Salmonella enterica

    How get it:
    • Chicken, poultry, eggs
    • S&S: typical symptoms w/fever, headache, muscle pain, malaise
  12. Typhoid Fever
    Salmonella typhi

    Abt it
    • More serious infection by salmonella (one of most serious microbial infection)
    • S&S: complications such as intestinal hemorrhage, perforation; Can become systemic, kidney failure; can travel thru intestines & into gallbladder where it can live, becoming a chronic carrier
    • If antibiotic isn't finished, can become carrier
  13. Bacterial Food Poisoning (Intoxication)

    Org causes:
    How it affects body:
    Time for S&S
    • Staphylococcus aureus
    • Toxins cross mucous membranes of intestinal tract (doesn't have to be live bacteria)
    • Symptoms w/in 4-6 hrs
  14. Clostridium Difficile-Associated Diarrhea (CDAD)

    How & who gets it
    • Can get from hospital or normal flora; antibiotics allow it to take over
    • Susceptibility: mostly children, newborns
    • Makes Toxin A&B
    • S&S: can cause loss of tight junctions (of where 2 cells meet); usually asymptomatic colonization; mild to severe diarrhea
    • Can lead to colitis & toxic megacolon
  15. Toxic megacolon
    Excessive tissue growth from loss of tight junctions, and colon becomes enlarged
  16. Viral Hepatitis diagnosis by:
    • Excess liver enzymes in blood
    • Presence of antibody in blood (ELISA test)
  17. Immunopathology vs Cytopathology
    Effect of body trying to protect itself & remove infecton, causing inflammation which damages cells

    Effect of virus itself, which damages cells
  18. Hepatitis A
    Hepatitis B & C
    Fecal-oral, food-borne; sometimes takes several wks to show up so immunization can be effective (not chronic)

    Percutaneous, permucosal; blood
  19. Hepatitis B aka serum hepatitis

    Abt it:
    Modes of transmission
    • Associated w/liver cancer
    • Modes of transmission:
    • Sexual
    • Parenteral- pierce skin
    • Prenatal- mom to child
  20. Hepatitis B top 3 risk factors
    • 41% heterosexual
    • 31% unknown
    • 15% injecting drugs
  21. Hepatitis C

    Abt it:
    Transmitted routes:
    • Chronic, low fatality
    • Transmission:
    • Percutaneous- drug use; transfusion
    • Permucosal- perinatal, sexual
  22. Hepatitis C top 3 risk factors
    • 44% other high risk/low socioeconomic status
    • 38% injecting drugs
    • 10% sexual/household
  23. 3 Protozoan Diseases of Intestinal Tract (few cause GI infections)
    • Giardiasis
    • Cryptosporidiosis
    • Amebiasis
  24. Giardiasis
    Giardia intestinalis

    How & who gets it:
    • Enter via ingestion of infectious cyst
    • Esp in hikers
    • Incubation: 1-2 wks
    • S&S: greasy, frothy, fatty diarrhea w/bad odor, abdominal distention, cramps
    • Trmt: Metonidazole (adults), Furazolidone (children)
  25. Cryptosporidiosis
    Cryptosporidium parvum

    How & who gets it
    • Enters via water contamined w/oocysts, also fecal-oral
    • Immunocomp ppl at risk for severe disease
    • S&S: acute, short-term; severe watery diarrhea w/headache, muscular pain, cramping, nausea, fatigue, life-threatening complications
    • Diagnosis: oocysts in stool
    • Trmt: supportive
  26. Amebiasis
    Entamoeba histolytica
    • Enter via ingestion in regions of poor sanitary conditions
    • Incubation: 6-20 dys
    • S&S:
    • Luminal amebiasis- asymptomatic
    • Invasive amebic dysentary- severe diarrhea, colitis, appendicitis
    • Invasive extraintestinal amebiasis- necrotic lesions on organs
    • Trmt: oral rehydration & antiamebic drugs