In the UK, older people are particularly prone to developing community acquired pneumonia. The most common pathogen is the bacterium Streptococcus pneumoniae. In the environment, S. pnumoniae is a robust microbe that can adapt and survive in hostile conditions and in the human body. Antibiotic therapy targets the mechanisms and processes that bacteria use to metabolize, replicate and survive. However, the inappropriate use of antibiotics has allowed bacteria to become resistant to the actions of specific antibiotics, and this has led to difficulties in treating infections caused by S.pneumoniae. Although immunization is available, older people continue to die from pneumococcal pneumonia. Penicillin is still used as the main method of treatment against S. pneumoniae, but the threat of antibiotic resistance is increasing.