A 45-year-old male with community-acquired pneumonia caused by *Streptococcus pneumoniae* is started on intravenous penicillin G. The clinician notes that the patient's clinical response is suboptimal despite appropriate dosing and susceptibility. The physician then adds tetracycline to the regimen, hoping to enhance bacterial killing. However, the patient's condition worsens. The bacteria at the time of treatment initiation are in the phase marked **B** in the bacterial growth curve diagram. Which of the following best explains the clinical deterioration after adding tetracycline to penicillin?