A 6-year-old girl presents with a 2-day history of cough and fever. At your office, she has a temperature of 39.4degC (103degF), a respiratory rate of 45 breaths per minute, and decreased breath sounds on the left side. Her chest x-ray is shown below. Which of the following is the most appropriate initial treatment?

(b) Source: (Hay et al, pp 1171, 1173-1174. Kliegman et al, pp 905-906, 1474-1479. McMillan et al, pp 1407-1411. Rudolph et al, pp 997, 1092.) The x-ray reveals a lung empyema on the left side, characterized by nearly complete white out of that side by the pleural or extrapleural fluid collection. Lung abscesses are usually caused by S aureus, S pneumoniae, or S pyogenes. These organisms, previously sensitive to penicillin, now have a variety of resistance patterns requiring extended spectrum antibiotics or vancomycin. Patients who do not improve quickly with antibiotic therapy alone are also surgical candidates.