Colonisation at admission to an intensive care unit in an Italian University Hospital: Risk factors and clinical implications.

Background: Antibiotic resistance represents a great concern worldwide with increasing related morbidity and mortality. Multidrug resistant microorganisms are going to be detected more and more frequently even in the community setting. Therefore, patients could be colonised even at the admission to the hospital.

Objective: The aim of this study is to evaluate colonisation at admission to an intensive care unit (ICU) and the acquisition of new colonisation during the ICU stay and the related risk factors. Secondly, healthcare-associated infections and surgical prophylaxis efficacy were also evaluated.

Methods: Retrospective observational study. All the patients admitted to the post-cardiosurgical ICU from 01 January to 30 June 2021 were enrolled. Colonisation was evaluated by rectal and nasal swab at admission or at the pre-hospitalisation visit and then every 7 days during the hospital stay.

Results: 80 out of 183 patients were colonised at admission, 46 by non-susceptible microorganisms (NSM). An antibiotic treatment in the previous 3 months was identified as risk factor for NSM colonisation. According to these isolates, about one third of the surgical prophylaxis could be ineffective. During the hospital stay, 36 patients acquired new colonisations; antibiotic treatment and length of hospital stay were recognised as risk factors. At least one (≥1) healthcare-associated infection (HAI) was detected in 54 patients (68 episodes); HAIs were significantly more frequent in the colonised patients. Moreover, in 35/68 HAIs aetiology was consistent with the colonisation.

Discussion: Knowing patients' colonisations could be fundamental to tailor antibiotic treatments and prophylaxis and to avoid NSM spread.