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Case Study 1: Peanut Butter is TaintedSuma and Kathryn

+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

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Affected System

Digestive system

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Parts that could be affected- Stomach

- Small intestine

- Large intestine

+Patient PB

Stomach cramping

Diarrhea

Moderately high temperature

16 hours prior to onset, peanut butter sandwich had been consumed

Escherichia coli

Pseudomonas aeuroginosa

Salmonella enetrica

Staphylococcus aureus

Streptococcus pyogenes

Haemophilus influenzae

Symptoms and History Possible Culprits

+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

Procedure

+Results (Gram stain)

Patient sample (1000x)

E. Coli (1000x)

Pink- Gram negative

Purple- Gram positive

Eliminate S. aureus and S. pyogenus

S. aureus (1000x)

Expected results What do these results mean?

+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

Incubate

Procedure

+Results (selective/differential)

Reddish pink- lac positve, gram negative

Whitish clear- lac negative, gram negative

No growth- gram positive

E. coli- pinkish red

S. aureus – no growth

Patient- whitish clear

Expected Results

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 Tetracyclin Penicillin Streptomycin Vancomycin Gentamicin Chloramphenicol

Allow bacteria to incubate

Measure zone of no growth

Compare to known values to find sensitivity/resistance

Procedure

+Results (Antimicrobial Susceptibility)

Patient sample is: Resistant to penicillin,

vancomycin Intermediate to

streptomycin, gentamicin Sensitive to tetracyclin,

chloramphenicol

Tetracyclin = 20 mm (S)

Penicillin = 16 mm (R)

Streptomycin = 14 mm (I)

Vancomycin = NA (R)

Gentamicin = 14 mm (I)

Chloramphenicol = 22 (S)

Eliminate P. aeuroginosa Resistant to chloramphenicol

Eliminate H. influenzae Different symptoms

(meningitis)

What do these results mean?

+ Salmonella enterica

A rod shaped, flagellated, Gram negative bacteria

+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

+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

Single most common cause of food poisoning in the US Salmonellosis

Salmonellosis can be prevented by Cooking food

thoroughly Washing hands and

cooking surfaces refrigeration