Wisconsin State Health Authorities Alerted the CDC About an E

Multiple Choice

Wisconsin state health authorities alerted the CDC about an E. coli O157:H7 outbreak. Soon thereafter, officials from two other states reported that they also had cases of illness associated with this pathogen. Within days, the CDC determined that the E. coli strains from all three states were the same, and the likely source of the outbreak was a particular brand of pre-packaged fresh spinach. The CDC then issued a press release advising people not to eat bagged fresh spinach.
-You have identified the causative organism of the outbreak as E. coli. In an effort to characterize the strain of the organism involved, you do different tests. The results are as follows:
Gram stain-Gram-negative rods
Oxidase test-negative
Lactose fermentation-positive
Serological testing-O157:H7
Colony morphology-smooth
Creamy colonies
RFLPs-E. coli O157:H7
Antibiogram-resistant to ampicillin.
Which test(s) confirm the identity of the organism at the strain level?

A) Gram stain AND antibiogram
B) Serological testing AND colony morphology
C) RFLPs AND serological testing
D) Oxidase test AND RFLPs
E) Lactose fermentation AND oxidase test