Your otherwise healthy adolescent patient is diagnosed with bronchitis. There is no wheezing present on the physical exam. His mother is insisting on treatment with an antibiotic. What would be an appropriate response to her request?

a. Antibiotics are not indicated, but he can take dextromethorphan and guaifenesin for symptom relief
b. Antibiotics are not indicated, but he should start a beta-2 agonist immediately
c. Bronchitis is caused by bacterial organisms, and antibiotics are always indicated
d. Bronchitis is caused by viruses, and antibiotic therapy is never indicated