Suppose you measure the zones of inhibition between rounds 1

Suppose you measure the zones of inhibition between rounds 1 and 2 of your paired Kirby-Bauer testing and find that they get SMALLER. What does this suggest? I must have done something wrong. The bacteria has become more SENSITIVE with repeated low-dose exposure to the antimicrobial. There has been no significant change in sensitivity/resistance as a result of repeated, low-dose exposures to the antimicrobial. The bacteria has become more RESISTANT with repeated low-dose exposure to the antimicrobial.

Solution

The bacteria has become more Resistant with the repeated dose of antimicrobial

This is because, the zone of inhibition gets smaller and thebacteria is able to grow near to antimicrobial. it signifies the resistance of the bacteria.