Contribution of antibiotic pressure in the acquisition of methicillin-resistant Staphylococcus aureus (MRSA) in a university hospital.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major nosocomial pathogen, which causes severe morbidity and mortality in hospitals. Antibiotic pressure is recognised as an individual risk factor in the acquisition of MRSA, however, some authors suggest that antibiotic use must be considered as an ecological and collective problem on a unit or hospital scale. The objective of our study was to determine whether antibiotic pressure affects the acquisition of MRSA. The study was conducted during 1 year (from October 2000 to September 2001) at Besanc¸on hospital. The analysis was based on the research of a correlation between incidence of MRSA acquisition, the colonisation pressure exerted by imported MRSA and use of antimicrobials ineffective against MRSA at the unit level. Univariate analysis showed that acquired MRSA cases were significantly correlated with the use of all antimicrobials, as well as with the use of each class of antimicrobial and with colonisation pressure. In multivariate analysis, the stratification of the units into consumer classes allowed us to eliminate the scale effect of each antimicrobial class and to characterise the impact of high antimicrobial use compared to weak antimicrobial. The highest risks of MRSA acquisition were observed for β-lactams and quinolones. This study shows that “MRSA acquisition” is correlated to antibiotic use and highlights the need to improve antibiotic usage in the control of MRSA. [Copyright &y& Elsevier]