The over-prescription of antibiotics, especially in outpatient settings in recent years, has led to increasing rates of antibiotic-resistant bacteria. Doctors today tend to be more judicious in their use of antibiotics when it comes to treating respiratory infections. Usually, an uncomplicated upper respiratory infection in an otherwise healthy adult doesn't need antibiotic treatment.
Pneumonia, however, is often treated with antibiotics. Unlike most other respiratory tract infections, which are causes by viruses, pneumonia is usually caused by bacteria. Many factors help a doctor decide which antibiotic to prescribe. Your age, your symptoms, the severity of the infection, your allergies and any underlying medical conditions all come into play. Also, doctors would consider which bacteria is the cause of your pneumonia, even though they might start you on an antibiotic that has a wide range of effectiveness, until they find out for certain. Usually, pneumonia is caused by streptococcus pneumoniae bacteria or Mycoplasma pneumoniae.
If your pneumonia can be treated at home, as an outpatient, a doctor might prescribe you one of several classes of antibiotics: macrolides (azithromycin, clarithromycin, erythromycin), tetracyclines (doxycycline), or fluoroquinolones (gemifloxacin, levofloxacin, moxifloxacin). If your pneumonia requires hospitalization, in addition to the previous antibiotics, doctors might treat you with cephalosporins (ceftriaxone, cefotaxime, cefepime), penicillin (amoxicillin, ampicillin), or vancomycin.