Following making an accurate diagnosis of a community acquired pneumonia, which of the following antibiotics would you start as first-line treatment, bearing in mind that the patient has normal renal function and no known drug allergies?

c. Antibiotic use in community-acquired pneumonia varies with GP preference. The recommended antibiotic for a simple case is amoxicillin (provided that the patient is not allergic to penicillins). Amoxicillin is derived from ampicillin which is better absorbed, producing higher plasma and tissue concentrations, and whose absorption is not affected by the presence of food in the gut. Augmentin is a compound preparation of amoxicillin and the beta-lactamase inhibitor clavulanic acid. The clavulanic acid protects the amoxicillin from the penicillinases produced by virtually all staphylococci and therefore this should not be given as first-line therapy since Staphylococcus is not one of the most common infective organisms. Metronidazole provides cover for anaerobes and works by breaking DNA strands. Erythromycin may be used in patients with allergies to penicillins.