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Case Study 1: Peanut Butter is Tainted
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Case Study 1: Peanut Butter is Tainted



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  • 1. Case Study 1: Peanut Butter is Tainted
    Suma and Kathryn
  • 2. Background Information
    425 people from 44 states were ill
    Diarrhea, fever, abdominal cramps
    Illness usually lasted 4-7 days, some cases of diarrhea were so severe patient needed to be hospitalized
    Out of 351, 71 (20%) were hospitalized
    No deaths
    Onset dates ranged from August 1st to February 16th, and 67% of cases occurred after December 1st
  • 3. Affected System
    Digestive system
  • 4. Parts that could be affected
    • Stomach
    • 5. Small intestine
    • 6. Large intestine
  • Patient PB
    Stomach cramping
    Moderately high temperature
    16 hours prior to onset, peanut butter sandwich had been consumed
    Escherichia coli
    Pseudomonas aeuroginosa
    Salmonella enetrica
    Staphylococcus aureus
    Streptococcus pyogenes
    Symptoms and History
    Possible Culprits
  • 7. Gram stain
    Add bacteria sample, E.coli(negative control), and S. aureus (positive control)to individual drops of water
    Let dry
    Heat fix slide
    Cover smears with crystal violet dye for one minute, then rinse with DI water
    Repeat with Gram’s iodine, but rinse with decolorizer acetone alcohol
    Repeat with safranin, rinse with DI water
    Blot dry, view using oil immersion
  • 8. Results (Gram stain)
    Expected results
    What do these results mean?
    Pink- Gram negative
    Purple- Gram positive
    Eliminate S. aureus and S. pyogenus
    Patient sample (1000x)
    E. Coli (1000x)
    S. aureus(1000x)
  • 9. Selective/differential plate
    Use MacConkey Agar because patient sample is gram negative
    Spread E. coli (positive control), S. aureus (negative control), and patient sample in a V-formation on the plate
  • 10. Results (selective/differential)
    Expected Results
    Reddish pink- lacpositve, gram negative
    Whitish clear- lac negative, gram negative
    No growth- gram positive
    E. coli- pinkish red
    S. aureus – no growth
    Patient- whitish clear
    What do these results mean?
    • eliminate E. coli
  • Antimicrobial Susceptibility Test
    Coat a plate with a thin film of bacteria, making sure not to miss any spots
    Place six antibiotic discs around the edges of the plate, evenly spaced apart
    Allow bacteria to incubate
    Measure zone of no growth
    Compare to known values to find sensitivity/resistance
  • 11. Results (Antimicrobial Susceptibility)
    Tetracyclin = 20 mm (S)
    Penicillin = 16 mm (R)
    Streptomycin = 14 mm (I)
    Vancomycin = NA (R)
    Gentamicin = 14 mm (I)
    Chloramphenicol= 22 (S)
    What do these results mean?
    Patient sample is:
    Resistant to penicillin, vancomycin
    Intermediate to streptomycin, gentamicin
    Sensitive to tetracyclin, chloramphenicol
    Eliminate P. aeuroginosa
    Resistant to chloramphenicol
    Eliminate H. influenzae
    Different symptoms (meningitis)
  • 12. Salmonella enterica
    A rod shaped, flagellated, Gram negative bacteria
  • 13. Salmonella enterica
    Arranged in a cluster- tetrad form
    Anaerobic- can live with low oxygen conditions
    Affects gastrointestinal region, through the fecal oral route
    Injects a protein called SipA to enter cell
    Disturbs the membrane, causes levels of free calcium to rise and disorganizes cytoplasm
  • 14. Epidemiology
    Causes diarrhea, fever, vomiting, abdominal cramps
    Can spread from intestine to blood stream, cause bacteremia
    raw meat, eggs (can be found on any food surface)
    Normal bacterial flora in reptiles and amphibians
    contaminated water or soil
    Salmonellosis can be prevented by
    Cooking food thoroughly
    Washing hands and cooking surfaces
    Single most common cause of food poisoning in the US