β-Lactam allergy and risk of multidrug-resistant bacteria in the intensive care unit: A cohort study

Patients identified as allergic to β-lactams are frequently exposed to treatment with broad-spectrum antibiotics. However, the risk of carriage of extended-spectrum β-lactamase (ESBL)-producing isolates in this population has been poorly investigated. The aim of this study was to evaluate the characteristics and clinical outcomes of patients admitted to the intensive care unit (ICU) with and without declared β-lactam allergy at admission. A retrospective monocentric study was performed including adult patients admitted to the ICU between 2007 and 2012. The presence of multidrug-resistant bacteria was documented in rectal and nasal swabs at admission and discharge. Patients labelled allergic to β-lactams and unlabelled patients were compared. Patients labelled allergic had significantly higher rates of ESBL at admission (13.3% vs. 4.3%; P = 0.0220) and discharge (20.0% vs. 9.0%; P = 0.0460) compared with unlabelled patients, but no significant difference in rates of ESBL acquisition in the ICU was detected. No differences in mortality, duration of hospitalisation or typical risk factors for ESBL acquisition (intubation, central venous catheter and duration of hospitalisation) were reported. No differences in carriage of methicillin-resistant Staphylococcus aureus were detected. This study showed that patients with declared β-lactam allergy had a higher risk of ESBL carriage at ICU admission and discharge.