Colonization with multiresistant bacteria in acute hospital care: the association of prior antibiotic consumption as a risk factor

Background Antibiotic resistance poses a worldwide threat and knowledge concerning risk factors for colonization with multiresistant bacteria (MRB) is limited. Objectives To examine the impact of prior antibiotic consumption on MRB colonization, with focus on type of antibiotic and timeline between antibiotic prescription and MRB colonization. Methods A nationwide case–control study was conducted and adults visiting emergency departments were invited to participate. All patients were swabbed in the throat, nose and rectum, and analysed for colonization with ESBL-producing Enterobacteriaceae (ESBL-E), MRSA, carbapenemase-producing enterobacteria and VRE. Antibiotic history 2 years prior to enrolment was collected at an individual level through a national register. Multivariate analyses were performed to examine the association between antibiotic consumption and MRB status. A subgroup analysis of ESBL-E-colonized cases was made. Results We included 256 patients colonized with MRB and 4763 controls. In the 2 years prior to study inclusion, 77% of cases and 68% of controls had at least one antibiotic prescription (P = 0.002). We found a significant increase in risk of colonization with ESBL-E if penicillins (OR = 1.58–1.65) or fluoroquinolones (OR = 2.25–6.15) were prescribed. The analysis of all MRB-colonized patients showed similar results. An assessment of the timeline showed a significant increase in risk of colonization up to 2 years after exposure to penicillins, fluoroquinolones and macrolides. Conclusions The prevalence of ESBL-E colonization was related to fluoroquinolone, macrolide and penicillin consumption for at least 2 years after antibiotic treatment.