Multidrug-Resistant Bacterial Colonization and Infections in Large Retrospective Cohort of Mechanically Ventilated COVID-19 Patients1

Abstract

Few data are available on incidence of multidrug-resistant organism (MDRO) colonization and infections in mechanically ventilated patients, particularly during the COVID-19 pandemic. We retrospectively evaluated all patients admitted to the COVID-19 intensive care unit (ICU) of Hub Hospital in Milan, Italy, during October 2020‒May 2021. Microbiologic surveillance was standardized with active screening at admission and weekly during ICU stay. Of 435 patients, 88 (20.2%) had MDROs isolated ≤48 h after admission. Of the remaining patients, MDRO colonization was diagnosed in 173 (51.2%), MDRO infections in 95 (28.1%), and non-MDRO infections in 212 (62.7%). Non-MDRO infections occurred earlier than MDRO infections (6 days vs. 10 days; p<0.001). Previous exposure to antimicrobial drugs within the ICU was higher in MDRO patients than in non-MDRO patients (116/197 [58.9%] vs. 18/140 [12.9%]; p<0.001). Our findings might serve as warnings for future respiratory viral pandemics and call for increased measures of antimicrobial stewardship and infection control.

Keywords: COVID-19; MDR; MDRO; SARS-CoV-2; antimicrobial resistance; antimicrobial stewardship; bacteria; colonization; incidence rate; infections; intensive care unit; large retrospective cohort; mechanically ventilated patients; multidrug resistant; multidrug-resistant bacteria; multidrug-resistant organism; respiratory infections; zoonoses.

Figure 1

Study flowchart showing patient selection process for multidrug-resistant bacterial colonization and infections in large retrospective cohort of COVID-19 mechanically ventilated patients admitted to ICU in Milan, Italy, October 2020–May 2021. ICU, intensive care unit; MDR, multidrug resistant. Asterisks indicate subgroups. *Patients are grouped on the basis of the worst MDR event diagnosed in MDR colonization or MDR infection, irrespective of the presence of previous or later MDR colonization. †At ICU admission, there were 78 colonizations and 10 infections. During ICU stay, 35/78 (44.9%) colonized patients had MDR infections develop.

Figure 2

Study flowchart showing microbial isolates selection process for multidrug-resistant bacterial colonization and infections in large retrospective cohort of COVID-19 mechanically ventilated patients admitted to ICU in Milan, Italy, October 2020–May 2021. ETA, emergency treatment area; ICU, intensive care unit; MDR, multidrug resistant; MDRO, multidrug-resistant organism. *Of 338 patients, 159 (47.0%) had either MDRO or non-MDRO infections; 74/338 (21.9%) had both MDRO and non-MDRO infections.

Figure 3

Multidrug-resistant bacterial colonization and infections in large retrospective cohort of COVID-19 mechanically ventilated patients admitted to ICU in Milan, Italy, October 2020–May 2021. Kernel density plot (violin plot) shows healthcare-associated infections by onset time comparing MDRO with non-MDRO. Red lines indicate mean and green lines median onset times; medium blue shading indicates interquartile ranges, and the light blue shading indicates 95% CIs of the mean (p<0.001 by Wilcoxon rank-sum test). ICU, intensive care unit; MDRO, multidrug-resistant organism.