Abstract

In a seriously ill patient with suspected bacterial infection, antibiotics are often started before bacteria are isolated and the diagnosis confirmed. The aim is to prescribe an antibiotic regimen that offers a spectrum of activity against the most likely organisms. Selection depends on the prediction of the bacteria involved and on their susceptibility or resistance to specific antibiotics. A broad-spectrum regimen is used when the organisms involved are difficult to predict or where failure of a narrower spectrum regimen would have serious consequences. Many antibacterial drugs are available which alone or in combination offer differing spectra; this article discusses the choice.