Pneumococcal pneumonia was the most prevalent form of bacterial pneumonia in the community at over 70% of cases but that number has drastically fallen presumably due to the use of pneumococcal vaccines.
Antibiotics are the mainstay of treatment in S pneumoniae infections. Until the 1970s, essentially all pneumococcal isolates were sensitive to easily achievable levels of most commonly used antibiotics, including penicillins, macrolides, clindamycin, cephalosporins, rifampin, vancomycin, and trimethoprim-sulfamethoxazole. Beginning in the 1990s, many pneumococcal isolates in the United States showed decreased susceptibility to penicillin and other commonly used antibiotics. Continued increases in these isolates have led to the need for re-establishment of susceptibility standards.
As of 2007, isolates of drug-resistant S pneumoniae have become increasingly common worldwide. The CDC, as well as many state health departments, maintain a population-based surveillance system (the ABC system) that investigates the epidemiology and susceptibility patterns of invasive pneumococcal infections in the United States. In 2010, only 10.6% of all isolates obtained showed intermediate or resistant susceptibility patterns to penicillin (down from 24.8% in 2008; 25.6% in 2007).  The prevalence of resistance varies greatly among countries, states, counties, and within populations in particular cities and may be as high as 30%-40% in some locations. [85, 86] Resistance rates are generally higher in most European countries, as well as in Hong Kong and Thailand. [87, 88]
With such high resistance rates, Penicillin is not recommended as drug of first choice to treat pneumonia.