[Surveillance of multiresistant bacteria: justification, role of the laboratory, indicators, and recent French data].

In France, several organizations have given priority status to programs aimed at controlling outbreaks of nosocomial infections due to multiresistant bacteria (MRB), most notably methicillin-resistant Staphylococcus aureus (MRSA) and extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBLE), thus recognizing the widespread distribution and marked pathogenic potential of MRB. To evaluate the impact of preventive measures, surveillance systems have been set up by bacteriology laboratories. These systems rest on a number of indicators: (1) the percentage of strains of a given bacterial species recovered from diagnostic specimens that were multiresistant; (2) the number of new patients (cases) with recovery of a MRB strain from at least one diagnostic specimen (or at least one screening specimen); (3) the incidence, or incidence density, of cases per 1000 hospital days or 100 admissions; (4) the distinction between cases acquired in and transported to the hospital or department. Studies conducted in France between 1990 and 1995 found that the percentage of Klebsiella pneumoniae that were multiresistant was around 20% overall and 25 to 35% among nosocomial strains, and that the prevalence and incidence of cases were about 0.1 to 0.3 per 100 admissions. The proportion of S. aureus strains exhibiting resistance to methicillin was 35 to 40% overall and 50% among nosocomial strains, and the prevalence and incidence of cases ranged from 0.5 to 1 per 100 admissions.