Changes In Lower Respiratory Tract Bacterial Isolates In ICU Patients Before and After the COVID-19 Pandemic

Mahmut Ulger; Serif Kurtulus; Remziye Can; Salim Yakut; Mehmet Celik; Hatice Kalaycioglu; Fadile Yildiz Zeyrek

doi:10.3791/70651

A subscription to JoVE is required to view this content. Sign in or start your free trial.

Research Article

Changes In Lower Respiratory Tract Bacterial Isolates In ICU Patients Before and After the COVID-19 Pandemic

127 views

⸱

DOI:

10.3791/70651

⸱

June 9th, 2026

Mahmut Ulger¹ , Serif Kurtulus² , Remziye Can³ , Salim Yakut⁴ , Mehmet Celik⁵ , Hatice Kalaycioglu¹ , Fadile Yildiz Zeyrek⁴

¹Department of Chest Diseases, University of Harran Faculty of Medicine, ²Clinic of Chest Diseases, University of Health Sciences, Mehmet Akif Inan Training and Research Hospital, ³Mustafa Kemal Atatürk vocational and Technical High School, ⁴Department of Medical Microbiology, University of Harran Faculty of Medicine, ⁵Department of İnfectious Diseases and Clinical Microbiology, University of Harran Faculty of Medicine

Summary

Here, a retrospective microbiological protocol is presented to analyze lower respiratory tract specimens in intensive care unit patients, including culture processing, MALDI-TOF MS identification, and comparison of bacterial pathogen distributions in COVID-19–negative patients before and after the COVID-19 pandemic.

Abstract

To compare the distribution of bacterial pathogens isolated from lower respiratory tract specimens in COVID-19–negative intensive care unit patients before and after the COVID-19 pandemic, culture results from patients admitted to a university hospital chest diseases intensive care unit were retrospectively analyzed. Patients without clinical or radiological suspicion of COVID-19 and with negative PCR results were included and classified as pre-COVID-19 or post-COVID-19 based on March 2020. Specimens were cultured on 5% sheep blood agar, eosin methylene blue agar, and chocolate agar, and evaluated after 24–48 h incubation at 37 °C. Only dominant microorganisms demonstrating growth in at least the second streaking sector were considered clinically significant. A total of 1,665 patients were included, with microbial growth detected in 48.9% of samples, the majority originating from the pre-COVID-19 period. Acinetobacter baumannii was the most frequently isolated organism in both periods. Logistic regression analysis showed reduced detection rates of Klebsiella pneumoniae, Pseudomonas aeruginosa, and Staphylococcus aureus (odds ratio ≈0.3), and Escherichia coli (odds ratio ≈0.4) in the post-COVID-19 period. Mortality rates were also lower in the post-COVID-19 period, although no significant difference in discharge type was observed. Overall pathogen diversity remained similar across periods; however, decreases in selected bacterial detections were observed following the onset of the pandemic. These findings may reflect changes in infection control practices during the pandemic period, although causality cannot be established due to the retrospective study design and absence of direct measurements of contributing factors.

Introduction

Lower respiratory tract infections (LRTIs) encompass inflammatory conditions of the airways, including bronchitis, bronchiectasis, bronchiolitis, pulmonary abscess, pleural effusion, and pneumonia¹. These infections represent a major cause of morbidity and mortality in hospitalized patients and pose a significant risk in high-acuity settings such as intensive care units (ICUs)². LRTIs account for approximately 10%–25% of hospital-acquired infections, with reported mortality rates ranging from 22% to 71% among ICU patients³^,⁴. They may arise from bacterial, ....