The microbes strike back

Understanding the reasons for the emergence of resistance is essential if we are to develop control strategies. The emergence of resistant bacteria requires both the evolution of resistance mechanisms and their dissemination. The evolution of resistance can occur as the result of frequent spontaneous chromosomal mutations, as occurs in the development of streptomycin resistance in tuberculosis and rifampin resistance in Staphylococcus aureus infection, or as the result of a very rarely occurring transfer of genetic material followed by clonal dissemination of the resistant bacteria, the bestrecognized examples of which are methicillin resistance in S. aureus infection (MRSA) and penicillin resistance in Streptococcus pneumoniae infection (PRSP). The former is controlled by avoiding the use of certain drugs or drug regimens for specific pathogens (such as monotherapy for tuberculosis). Controlling the latter involves detecting the introduction of a resistant clone into a susceptible population, implementing appropriate measures to limit transmission, and reducing the use of antibiotics to decrease the size of the niche available to resistant bacteria and the associated likelihood of dissemination. Finding the means to slow the rise in antimicrobial resistance is as important as appropriately managing individual patients with infections due to resistant pathogens. Fortunately, recent studies have demonstrated that safely reducing antibiotic use is not only feasible but also effective in reducing resistance. Numerous studies have found that physicians routinely prescribe antibiotics for clinical syndromes in which antimicrobials are known to have no effect.7,8 For instance, Gonzales and associates8 carried out a sample survey of practising physicians participating in the US National Ambulatory Medical Care Survey. Office visits for colds, upper respiratory tract infections and acute bronchitis, clinical conditions caused by viruses in the vast majority (more than 90%) of cases, accounted for 21% of all antibiotic prescriptions for adults. There are a number of reasons why physicians overprescribe antibiotics: patient expectations, insufficient time to discuss with patients why an antibiotic is not needed and desire to avoid misdiagnosis of bacterial infections for which an antibiotic is indicated.7 There is therefore an urgent need both to improve prescribing practices and to provide the tools for physicians to diagnose more accurately those conditions for wh