Background and Objective:
Infections with extended-spectrum beta-lactamase-producing Enterobacteriaceae (ESBL-E) are frequent in nursing home for dependent elderly people and several risk factors for ESBL-E infection are described in the literature. In patients hospitalized in nursing homes or healthcare facilities, malnutrition reaches 70%. The objective of this study was to analyse the relationship between malnutrition and ESBL-E infection.

Methods:
A retrospective matched case-control study was carried out on adult patients hospitalized at Grenoble Alpes University Hospital between January 2010 and December 2015. Cases presented ESBL-E infection and controls had Enterobacteriaceae infection without ESBL resistance. The exposure factor, malnutrition, was based on national High Authority of Health (HAS) 2019 criteria adapted to French population. Patients without any measurement attesting the malnutrition were considered as not malnourished. The following ESBL-E infection risk factors were included: history of antibiotic prescription, history of hospitalization, risky procedures, history of ESBL-E colonization. The crude and adjusted odds ratio (OR) and its 95% confidence interval (95% CI) were evaluated by conditional logistic regression.

Results:
A total of 16,143 patients had at least one positive clinical sample for Enterobacteriaceae (1,364 ESBL and 14,779 no-ESBL). After matching, 1359 cases and 2663 controls were included in the analysis. Malnutrition was a significant risk factor for ESBL-E infection in bivariate analysis (OR 1.24; 95% CI 1.08-1.43). By adjusting for risk factors, undernutrition was no longer a significant risk factor (adjusted OR 1.24; 95% CI 1.08-1.43). The usual risk factors: history of antibiotic prescription, history of hospitalization and history of ESBL-E colonization were significant in both analyses.

Conclusion:
A significant relationship between undernutrition and the occurrence of ESBL-E infection was observed in bivariate analysis, but this factor is no longer significant when adjusting for other known risk factors. Further investigations, as subgroup analyses, could assess the importance of malnutrition as a risk factor.