Why do we need to eradicate pathogens in respiratory tract infections?

Evidence from studies in otitis media, acute bacterial sinusitis and acute exacerbations of chronic bronchitis indicate that clinical efficacy is dependent on bacterial eradication. Failure to eradicate bacterial pathogens increases the potential for clinical failure, incurring further costs, and may also select and maintain bacteria that are resistant to a wide range of antimicrobials. Bacteriologically confirmed clinical failures have been reported in pneumococcal pneumonia with both macrolides and older fluoroquinolones (ciprofloxacin, ofloxacin, and levofloxacin). These failures were due to the involvement of resistant pathogens (macrolides) or suboptimal pharmacokinetics/pharmacodynamics (PK/PD) (quinolones). However, persistent positive blood cultures have not been reported during therapy with adequate doses of benzylpenicillins or aminopenicillins. Treatment failure, driven by the failure to eradicate pathogens, leads to both economic and environmental costs, hospitalization being the major cost driver. Failure to achieve bacterial eradication may also lead to the development and spread of resistance. Different types of antimicrobials appear to be driving resistance to different extents, and this may be due to suboptimal PK/PD. In conclusion, factors to consider when prescribing include an accurate diagnosis, knowledge of local epidemiology, the role of PK/PD principles in antimicrobial choice, clinical outcomes in relation to bacteriologic efficacy, and resistance and its bacteriologic and clinical impact. The vicious cycle of infection, inappropriate therapy, bacteriologic failure, selection/spread of resistance and further infection needs to be broken by the use of appropriate treatments to achieve bacterial eradication.