Antibiotic improve treatment outcome as the combined effect of both antibiotics is better than their individual effect. Methicillin-resistant Staphylococcus aureus infections may be treated with a combination therapy of fusidic acid and rifampicin. Antibiotics used in combination may also be antagonistic and the combined effects of the two antibiotics may be less than if the individual antibiotic was given as part of a monotherapy. For example, chloramphenicol and tetracyclines are antagonists to penicillins and aminoglycosides. However, this can vary depending on the species of bacteria. In general, combinations of a bacteriostatic antibiotic and bactericidal antibiotic are antagonistic. Antibiotics are commonly classified
Quinolone antibiotic not be used as a first-line agent for community-acquired pneumonia, instead recommending macrolide or doxycycline as first-line agents. The Drug-Resistant "Streptococcus pneumoniae" Working Group recommends fluoroquinolones be used for the ambulatory treatment of community-acquired pneumonia only after other antibiotic classes have been tried and failed, or in cases with demonstrated drug-resistant "Streptococcus pneumoniae". Resistance to quinolones can evolve rapidly, even during a course of treatment. Numerous pathogens, including "Escherichia coli", commonly exhibit resistance. Widespread veterinary usage of quinolones, in particular in Europe, has been implicated. Fluoroquinolones had become the class of antibiotics most commonly prescribed to adults in 2002. Nearly