# Antibiotic Resistance Patterns of Bacteria Involved in Colonization and/or Infection of Patients in Intensive Care Units in Northeastern Romania

## TL;DR

This study examines antibiotic resistance patterns in ICU patients in Romania, showing how colonization by drug-resistant bacteria can lead to infection.

## Contribution

The study identifies specific bacteria and antibiotic resistance patterns in ICU patients, highlighting the link between colonization and infection.

## Key findings

- Gram-negative bacilli, especially Acinetobacter baumannii and Klebsiella pneumoniae, were most commonly involved in colonization and infection.
- K. pneumoniae, E. coli, and P. aeruginosa showed high diversity in antibiotic resistance patterns, while A. baumannii had a dominant antibiotype.
- Infections often involved the same antibiotic resistance patterns as colonization for K. pneumoniae and E. coli, but not always for P. aeruginosa.

## Abstract

Background/Objectives: Healthcare-associated infections caused by multidrug-resistant (MDR) bacteria pose a significant and growing public health challenge, particularly in high-risk settings such as Intensive Care Units (ICUs). Colonization is often asymptomatic but can precede infection and contribute to hospital outbreaks, making early detection critical for infection control and containment. The aim of the study is to evaluate the antibiotic susceptibility patterns of MDR bacteria involved in colonization and/or infection among patients admitted to the ICU at a tertiary care hospital in Northeastern Romania and to investigate the relationship between MDR bacterial colonization and subsequent infection. Methods: A total of 118 patients from ICU were included in this study and a total of 609 bacterial strains were isolated, involved in both colonization and infection, with multiple isolates per patient included if obtained from different sites or time points. Results: A predominance of Gram-negative bacilli was found to be involved in both colonization and infection in the ICU, with Acinetobacter baumannii (n = 146; 26.64%), Klebsiella pneumoniae (n = 146; 26.64%), Escherichia coli (n = 60; 10.95%), and Pseudomonas aeruginosa (n = 56; 10.22%) as the main bacteria involved in colonization, and A. baumannii (n = 23; 37.7%), K. pneumoniae (n = 19; 31.1%), and P. aeruginosa (n = 15; 24.6%) as the main bacteria involved in infections. The study revealed a high diversity of antibiotypes among K. pneumoniae (43 distinct antibiotypes), E. coli (35 distinct antibiotypes) and P. aeruginosa (27 distinct antibiotypes). In contrast, only 6 antibiotypes were identified for A. baumannii, with most strains belonging to a single dominant antibiotype. For K. pneumoniae, E. coli and A. baumannii, infections mainly involved the same antibiotype as that found in colonization, while infections with P. aeruginosa were often linked to different antibiotypes than those involved in colonization. Conclusions: This study demonstrates a high colonization-to-infection link among ICU patients in a Northeastern Romanian tertiary care hospital, and these findings underscore the importance of systematic colonization screening to identify patients at high risk in ICU settings.