- R Cantón: Rafael Cantón. Servicio de Microbiología. Hospital Universitario Ramón y Cajal e Instituto Ramón y Cajal de Investigación Sanitaria (IRYCIS). Madrid. Spain. rafael.canton@salud.madrid.org.
From a microbiological point of view, both empirical and targeted antimicrobial treatment in respiratory infection is based on the sensitivity profile of isolated microorganisms and the possible resistance mechanisms that they may present. The latter may vary in different geographic areas according to prescription profiles and vaccination programs. Beta-lactam antibiotics, fluoroquinolones, and macrolides are the most commonly used antimicrobials during the exacerbations of chronic obstructive pulmonary disease and community-acquired pneumonia. In their prescription, different aspects such as intrinsic activity, bactericidal effect or their ability to prevent the development of resistance must be taken into account. The latter is related to the PK/PD parameters, the mutant prevention concentration and the so-called selection window. More recently, the potential ecological impact has grown in importance, not only on the intestinal microbiota, but also on the respiratory one. Maintaining the state of eubiosis requires the use of antimicrobials with a low profile of action on anaerobic bacteria. With their use, the resilience of the bacterial populations belonging to the microbiota, the state of resistance of colonization and the collateral damage related to the emergence of resistance to the antimicrobials in pathogens causing the infections and in the bacterial populations integrating the microbiota.