These recommendations are based on those of the British Thoracic Society (BTS) [British Thoracic Society, 2004; British Thoracic Society, 2009] and the Scottish Intercollegiate Guidelines Network (SIGN) [SIGN, 2002].

• Empirical treatment is necessary, as sputum samples take too long to process to identify a causative pathogen of community-acquired pneumonia and practically influence initial management.
• CKS found no evidence from randomized controlled trials to support the use of one antibiotic over another in the treatment of pneumonia. The choice of antibiotic used is therefore dependent on the known susceptibility of the causative pathogens of bacterial pneumonia, taking into account resistance patterns.
• Amoxicillin is the preferred first-line choice in most cases [British Thoracic Society, 2009], as it has a broad spectrum of activity and most of the common pathogens involved are still susceptible to it [Bush, 2003].
• The majority of cases of community-acquired pneumonia are caused by Streptococcus pneumoniae or Haemophilus influenzae, which are still susceptible to amoxicillin if a large enough dose is given (see Dosing regimen of amoxicillin).
• Other atypical pathogens may not be sensitive to amoxicillin. However, in reality, these tend to be rare causes of community-acquired pneumonia, and will often elicit symptoms severe enough for referral or admission.
• Clarithromycin has a similar spectrum of activity to amoxicillin and is an appropriate alternative if the person has an allergy to penicillin.
• Clarithromycin is recommended as the macrolide of choice (instead of erythromycin) by the BTS guidelines, on the basis of improved gastrointestinal tolerance and an easier dosing schedule [British Thoracic Society, 2009].
• In exceptional cases where a person has severe pneumonia but is not admitted, the addition of clarithromycin to amoxicillin should be considered to maximize effectiveness and provide a broad range of cover. This recommendation is based on clinical experience rather than published studies [SIGN, 2002].
• Doxycycline is recommended as an alternative to amoxicillin and amoxicillin plus clarithromycin by the BTS guidelines because pneumococci have less resistance to it, and it has greater activity against atypical pathogens, including M. pneumoniae [British Thoracic Society, 2009]. SIGN recommend that a tetracycline should be used first-line when M. pneumoniae infection is suspected because tetracyclines have more activity against this pathogen than amoxicillin [SIGN, 2002].
• Fluoroquinolones, such as levofloxacin and, more recently, moxifloxacin, have greater activity than amoxicillin against some of the pathogens involved in pneumonia, including S. pneumoniae. They are not generally recommended for use in primary care because of rising levels of resistance to fluoroquinolones observed in countries with widespread prescribing of these antibiotics in the community. However, they may be recommended by a specialist if the person has contraindications to penicillins and macrolides.