The COVID-19 pandemic has led to an increased incidence of ventilator-associated pneumonia (VAP) among critically ill patients. However, in a context of high prevalence of multidrug-resistant organisms (MDROs) there is a lack of direct comparison between the incidence of VAP in COVID-19 and non-COVID-19 cohorts.

The investigators conducted a prospective, single-center cohort study comparing COVID-19 patients admitted to the intensive care unit (ICU) of the Città della Salute e della Scienza University Hospital in Turin, Italy, between March 2020 and December 2021 (COVID-19 group), with a historical cohort of ICU-mixed patients admitted between June 2016 and March 2018 (NON-COVID-19 group).

The study aims to explore the occurrence and characteristics of ventilator-associated pneumonia (VAP) in critically ill patients during two distinct periods: the pre-pandemic era and the COVID-19 pandemic. VAP, a serious complication arising from invasive mechanical ventilation (IMV) lasting at least 48 hours, had a crude incidence of 5% to 40% before the COVID-19 pandemic, whereas COVID-19 patients experienced even higher rates, reaching 48-64%.

The COVID-19 pandemic triggered an unprecedented rise in ICU admissions due to severe acute respiratory syndrome caused by the SARS-CoV-2 virus, leading to a considerable number of patients requiring IMV. Mechanical ventilation is a known risk factor for VAP, and COVID-19 exacerbates this risk due to factors like disease-induced immunoparalysis, prolonged mechanical ventilation and sedation, and more frequent application of prone positioning.

Despite the widespread need for prolonged mechanical ventilation in COVID-19 patients, few studies have compared the impact of VAP between pre-pandemic and COVID-19 populations. Additionally, limited research exists on the risk factors for VAP development in COVID-19 patients and the use of scoring systems like SAPS and SOFA as prognostic factors in this specific context. Although the coVAPid study offered insights into VAP risk factors in COVID-19 patients compared to those with influenza, it inadequately addressed the prevalence of multidrug-resistant organisms (MDROs) in this population, particularly carbapenem-resistant Acinetobacter baumannii (CR-Ab). Hence, this study aims to bridge this knowledge gap by investigating VAP's impact in a setting characterized by a high incidence of multidrug resistance.

To achieve this, the study will take place at the Molinette Hospital of the "Città della Salute e della Scienza" University Hospital in Turin, Italy, over a six-year period, spanning from January 2016 to December 2022. This retrospective, observational, and monocentric study will focus on two distinct cohorts: the pre-pandemic cohort (NON-COVID-19) and the COVID-19 cohort.

Researchers will identify ventilator-associated pneumonia (VAP) episodes based on the current definitions provided by the European Center for Disease Prevention and Control (ECDC). Patients will be monitored until hospital discharge to assess outcomes, including ICU mortality, overall mortality, duration of ICU stay, and duration of hospitalization.

Inclusion Criteria:

• All adult patients diagnosed with ventilator-associated pneumonia
• Patients admitted to the intensive care units
• Patients who underwent mechanical ventilation for a duration longer than 48 hours

Exclusion Criteria:

• Patients in extreme end-of-life conditions
• Pregnant individuals
• Patients under 18 years of age
• Patients who did not meet the diagnosis criteria for ventilator-associated pneumonia
• Patients who underwent mechanical ventilation for a duration equal to or shorter than 48 hours
• Ventilator-associated tracheobronchitis

The study population consists of patients diagnosed with ventilator-acquired pneumonia admitted to the intensive care unit of the primary hospital "Molinette," Città della Salute e della Scienza, Turin, Italy.