Multilevel modelling of the prevalence of hospitalized patients infected withPseudomonas aeruginosa

Abstract

SUMMARYPseudomonas aeruginosais one of the leading nosocomial pathogens. The question of the respective contribution of endogenous and exogenous sources remains controversial. In this study, we shed new light on this issue by means of a multilevel logistic regression analysis which allowed a simultaneous investigation of factors associated with prevalence of patients infected withP. aeruginosaat two levels: patient and healthcare facility (HCF) in the eastern regions of France. A total of 25 533 in-patients from 51 HCFs were included in the analysis. The overall prevalence was 0·37% (range 0–1·65%). Multilevel modelling estimated that <14% of total variability of the outcome variable was explained by differences between HCFs and that after adjusting for patient-level variables, which explained 52% of HCF-level variance, the latter became non-significantly different from zero. A compositional effect (patient factors), rather than a contextual effect (ecological factors), explains heterogeneity of the prevalence of patients infected withP. aeruginosain the eastern HCFs of France.