Antimicrobial susceptibility testing: are we wasting our time?

Routine susceptibility testing of bacterial pathogens has been seen as one of the most important functions of diagnostic microbiology laboratories, but there are powerful arguments both for and against providing such a routine service. Much testing that is carried out does not contribute directly to patient management, since modern agents are usually reliably active and treatment has normally been started successfully before the result is available. Moreover, laboratory tests are so far removed from clinical reality as to be of doubtful value. On the other hand, prescribers still demand the service and there are cogent epidemiological reasons for carrying out the tests. Laboratories also have a crucial role in guiding antibiotic use and in reinforcing local prescribing policies, and routine testing helps to identify the laboratory as the source of expertise and advice. The relationship between the laboratory and its users is changing and microbiologists need to re-assess the service they provide. Many of the benefits of routine susceptibility tests would be retained if periodic surveys of the local prevalence of resistance were carried out, reserving individual testing for the seriously ill and those presenting problems of management.