A new bacterial infection is spreading through a city. Doctors start prescribing penicillin, but they soon find that the bacteria is resistant to the antibiotic.
Testing reveals that a penicillin resistance gene is located on a plasmid that is increasing in the bacteria population through conjugation and selection due to the use of penicillin. Doctors start using rifampicin, another antibiotic that works through a different mechanism than penicillin.
Which of the following is MOST likely to occur in the bacteria population?