PrepTest 157, Section 2, Question 11

What we’re looking for

Working the answers

• A

  This compares simple cleaning with antibiotic ointment. It might make us wonder whether the ointment has a drawback, but it says nothing about the honey. Even with this comparison, we still need to explain why adding bacteria-containing honey makes healing faster than simply cleaning the wound.

• B

  A lower concentration of bacteria isn't the same as a benefit. The bacteria in honey could be less concentrated than in an infected wound without honey actively helping a wound heal. And the fact that antibiotic ointment leaves some bacteria alive doesn't establish that honey produces better results. This makes parts of the result seem less surprising, but it doesn't give us a mechanism for honey's faster healing.

• C
  Correct

  This supplies two useful pieces. Honey inhibits bacterial growth, including growth of its own bacteria. That explains how something containing bacteria can nevertheless help control the bacterial problem in a wound. It gives honey a benefit beyond cleaning alone. Notice that this is different from our guess about helpful bacteria: the answer points to properties that restrict bacterial growth.

  Then it supplies a cost of antibiotic ointment: the ointment damages sensitive wound tissue, slowing healing. Now we have a reason an antibacterial treatment might still compare poorly with honey. C addresses both why honey can help and why the antibiotic treatment can lag behind.

  Be precise about “inhibit.” The answer says honey restricts bacterial growth. It doesn't say that honey kills every bacterium or leaves a wound completely bacteria-free. The explanation works without that stronger claim.

• D

  This is helpful, which is why it's tempting. It explains that honey's sugar inhibits bacterial growth, including growth of the bacteria in the honey. So it offers a benefit for the honey-treated wounds and addresses our initial worry about adding bacteria.

  But return to the comparison with antibiotic ointment. That treatment also acts against bacteria. Why would honey lead to faster healing than it does? D doesn't identify any disadvantage of the ointment. C gives us essentially the same benefit of honey and then adds the tissue-damage explanation. If you reach C and D, compare what each explains about the whole result. C resolves more of the puzzle.

• E

  All the wounds were cleaned, so this answer's condition does apply to the honey-treated group. E helps explain honey's advantage over ointment by identifying tissue damage from the ointment. But it doesn't explain why honey beats cleaning alone, or why the bacteria in honey don't create the infection problem we'd expect. C adds the missing positive effect of honey while also explaining a drawback of the ointment.