The objective of our study was to determine whether antibiotic pressure in the units of a teaching hospital affects the acquisition of methicillin-resistant Staphylococcus aureus (MRSA), independently of the other collective risk factors previously shown to be involved (MRSA colonization pressure, type of hospitalization unit, and care workload). The average incidence of acquisition of MRSA during the 1-year study period was 0.31 cases per 1000 days of hospitalization, and the use of ineffective antimicrobials reached 504.54 daily defined doses (DDDs) per 1000 days of hospitalization. Univariate analysis showed that acquisition of MRSA was significantly correlated with the use of all antimicrobials, as well as correlated with the use of each class of antimicrobial and with colonization pressure. Multivariate analysis with a Poisson regression model showed that the use of antimicrobials was associated with the incidence of acquisition of MRSA, independently of the other variables studied, but it did not allow us to determine the hierarchy of the different antimicrobial classes with respect to the effect.

No abstract

To investigate the relationship between glycopeptide use and decreased susceptibility to teicoplanin in coagulase-negative staphylococci (CNS) isolates, data on teicoplanin susceptibility and glycopeptide use from existing microbiology laboratory and pharmacy databases were collected for the period between July 2000 and March 2001. Pooled data for the entire study period were first used to analyse associations. Univariate analysis showed that the incidence of CNS with decreased susceptibility to teicoplanin was significantly correlated with the use of glycopetides, particularly with vancomycin use. This association was confirmed by multivariate analysis. This study suggests that variations in antimicrobial resistance are related to variations in antimicrobial use in the model of CNS with decreased susceptibility to teicoplanin, thus confirming the usefulness of restricting antimicrobial prescribing as a means of controlling resistance.