OE:
Situation Antibiotic-resistant salmonella caused an outbreak of
illness in a European country where patients need prescriptions to
obtain antibiotics and where doctors dispense such prescriptions less
readily than in other European countries.
Reasoning What evidence would most strongly suggest that
overuse of antibiotics was likely responsible for the outbreak, despite
the cited facts? The microbiologist reasons that because patients
need prescriptions to obtain antibiotics in the country where the
outbreak occurred, and the country’s doctors dispense such
prescriptions less readily than doctors in other European countries
do, antibiotics are probably not being overused in the country—so
antibiotic overuse was probably not responsible for the outbreak.
Implicit in the microbiologist’s reasoning is the assumption that
overuse of antibiotics, if it had occurred, could probably have resulted
only from overprescribing of antibiotics by physicians to treat illness
in people in the country in question. Any evidence casting doubt on
this complex assumption would suggest a weakness in the
microbiologist’s reasoning.
A. This strengthens the argument by providing additional evidence that
antibiotics are not being overprescribed in the country.
B.
Correct. This weakens the microbiologist’s argument by indicating
that an assumption implicit in the argument may be false: the
salmonella outbreak could easily by explained by overuse of
antibiotics in livestock feed (perhaps imported from other
countries).
C. Even if antibiotic use has risen in the two neighboring countries,
antibiotics still might be underused in both countries.
D. This suggests that antibiotic-resistant salmonella arises only in
countries where antibiotics are used; even if this were true it would
be quite compatible with the microbiologist’s argument and does
not weaken that argument.
E. This describes one mechanism by which salmonella can spread in a
population; it says nothing about whether an outbreak of antibioticresistant
strains of salmonella might have been caused by antibiotic
overuse.
The correct answer is B.