This question appear a little confusing because of the structure of the second sentence. However, it appears to describe how an antibiotic works. Antibiotics work against bacteria by either making the environment toxic for the bacteria (which kills it) or inhibiting the growth/reproduction of the bacteria. Both patterns will eventually lead a sharp reduction in the population of the bacteria. Even if what the antibiotic does is to inhibit the reproduction of the bacteria, this act provides the body with an opportunity to fight the "unreproductive" remnants of bacteria thereby leading to the reduction of population of the bacteria.
