Blood Inflammatory Markers and Cytokines in COVID-19 Patients With Bacterial Coinfections

Abstract

Background: Bacterial coinfection in patients with SARS-CoV-2 infection is an important risk factor for death. This study investigated whether there were differences in levels of serum inflammatory markers in COVID-19 patients with bacterial coinfections compared with those without bacterial infection.

Methods: A total of 235 inpatients with SARS-CoV-2 infection admitted to Qingdao Central Hospital from December 7, 2022, to August 7, 2024, were included. Patients were divided into a bacteria-positive group (115 cases) and a bacteria-negative group (120 cases) according to whether they had bacterial coinfections. PCT, CRP, and 12 kinds of cytokines were compared between groups, and the distribution of bacterial species in the positive group was statistically analyzed.

Results: The serum levels of CRP (Z = 8.94, p < 0.001), PCT (Z = 5.59, p < 0.001), IL-1β (t = 4.863, p < 0.001), IL-2 (t = 5.810, p < 0.001), IL-5 (t = 3.837, p < 0.001), IL-6 (t = 4.910, p < 0.001), IL-8 (t = 3.325, p < 0.001), ILIL-12p70 (t = 4.722, p < 0.001), IL-17 (t = 3.315, p = 0.001) and TNF-α (t = 4.251, p < 0.001) between the two groups were significantly different. IL-4, IL-10, IFN-α, and IFN-γ were not statistically significant (p > 0.05). Among the 115 bacteria-positive patients, 56 patients were positive for one species and 59 patients were multiple infections. Acinetobacter baumannii, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, and Haemophilus influenzae were common species.

Conclusions: Serum PCT and CRP levels in COVID-19 patients with bacterial coinfection are higher than those without bacterial infection. Cytokines such as IL-1β, IL-2, IL-5, IL-6, IL-8, IL-12p70, IL-17, and TNF-α may be involved in the progression of COVID-19 combined with bacterial infection. They can be used as potential markers to evaluate the disease condition and prognosis.

Keywords: COVID‐19; bacterial coinfection; cytokines; inflammatory markers.