Antimicrobial use: risk driver of multidrug resistant microorganisms in healthcare settings

Purpose of review This review explores recent evidence on the association between antibiotics usage and resistance. Recent findings A meta-analysis showed that the risk of acquiring methicillin-resistant Staphylococcus aureus was increased by 1.8-fold in patients who had taken antibiotics. Such risk was almost three-times greater after using quinolones or glycopeptides. Significant heterogeneity between studies was mainly related to study designs. A Cochrane systematic review suggested that, although the quality of the evidence was poor, interventions to improve hospital antibiotic prescribing were associated with a reduction in the incidence of antimicrobial resistant pathogens. Against this evidence, mupirocin-resistant S. aureus and linezolid-resistant vancomycin-resistant enterococci (VRE) were detected in institutions where these drugs were not widely used. Studies assessing the impact of vancomycin prescribing restriction on VRE rates were heterogeneous and the effectiveness of such interventions remains poorly defined. Important confounders of studies, other than study design, are the lack of analysis of secular trends of infections, colonization pressure in the ward and duration of follow up. Summary Available evidence, although not always of high quality, suggests that a link between antibiotics usage at individual and institutional levels and resistant bacteria does exist. Benchmark guidelines for empiric therapy in hospitalized patients, taking into consideration not only patients' needs but also ecological costs of resistance, should be rapidly developed.