Antimicrobial resistance occurs when a strain of a micro-organism is able to multiply in the presence of antimicrobial medicine concentrations that are higher than in the concentrations in humans receiving therapeutic doses. The development of resistance is a natural biological phenomenon and has followed the introduction into clinical practice of every antimicrobial agent. Increases in antimicrobial use have been associated with increases in rates of resistance, so much so that irrational overuse of antimicrobials is generally assumed to be a major contributing factor to the escalating global problem of antimicrobial resistance. Currently, antimicrobials are being overused in all world regions and at all levels of the health care system, in amounts that are perhaps as much as double those that are clinically indicated. Resistance rates vary locally depending upon local antimicrobial use.

The World Health Assembly has recognized antimicrobial resistance as a serious public health problem and in 1998, with resolution WHA51.17, urged Member States to develop measures to encourage appropriate and cost-effective use of antimicrobials (8). Nevertheless, the problem of antimicrobial resistance, including multidrug resistance, has since continued to grow while the rate at which new anti-microbials are introduced has decreased. WHO's Global Strategy for the containment of Antimicrobial Resistance addressed this challenge by providing a framework of interventions aimed at slowing the emergence and reducing the spread of antimicrobial resistant microorganisms (9). More than 60 interventions were identified and prioritized on the basis of invited expert opinion and peer review. An adequately funded multi-sectoral task force and reference laboratory for conducting surveillance of both antimicrobial resistance and use were, however, considered fundamental to any national containment programme.

The interventions that were deemed to be the most important are:

- patient education on preventing infection (e.g. immunization, use of bednets) and reducing transmission (e.g. hand washing, food hygiene);

- education on antimicrobial use, antimicrobial resistance containment, disease prevention and infection control;

- targeted undergraduate and postgraduate education for all health workers and veterinary practitioners on accurate diagnosis and management of common infections;

- development, updating and use of clinical guidelines and treatment algorithms;

- establishment of infection control programmes in hospitals;

- good quality diagnostic laboratories;

- limitation of availability of antimicrobials to prescription-only;

- granting marketing authorization only to antimicrobials which meet international standards of quality, safety and efficacy.

Very few countries currently have national antimicrobial resistance containment programmes in place. Furthermore, many countries do not base their choice of antimicrobials for an essential medicines list or standard treatment guidelines on epidemiologically sound antimicrobial resistance data, even though this has been shown to be crucial to ensuring best patient outcome and efficient use of antimi-crobials. Nevertheless, reductions in antimicrobial resistance have been observed in a few countries that have succeeded in significantly reducing antimicrobial consumption and improving infection control.

Containing antimicrobial resistance and ensuring that patients are treated with the most effective antimicrobial requires the linked surveillance of antimicrobial resistance and consumption. WHO is currently supporting pilot projects to develop a new model and methodology for the linked surveillance of antimicrobial resistance and consumption and the local containment of antimicrobial resistance in developing countries. However, much more political and financial commitment will be necessary in the future.