Blood inflammatory markers and cytokines in patients with COVID-19 and bacterial coinfections

Abstract Background Bacterial coinfection in patients with SARS-CoV-2 infection is an important risk factor for death. This study investigated and analyzed whether there were differences in the levels of serum PCT and CRP and the expression of 12 cytokines, including IL-6, IL-10, IL-2, TNF, and other markers, in patients with SARS-CoV-2 infection combined with bacterial infection compared with those without bacterial infection, aiming to provide references for early clinical diagnosis and empirical treatment. Methods A total of 121 inpatients with SARS-CoV-2 infection admitted to Qingdao Central Hospital from December 7, 2022, to February 7, 2023, were included. Patients were divided into a bacteria-positive group (61 cases) and a bacteria-negative group (60 cases) according to whether they had bacterial infections. PCT, CRP, and 12 cytokines were compared between groups, and the composition of bacterial species in the positive group was statistically analyzed. Results There was no significant difference in the sex ratio or age between the two groups (P > 0.05). The serum levels of CRP (Z = 3.95, P < 0.001), PCT (Z = 3.20, P = 0.001), IL-1β (t = 2.90, P = 0.008), IL-2 (t = 3.83, P = 0.001), IL-12p70 (t = 3.28, P = 0.004), IL-17 (t = 2.22, P = 0.039) and TNF-α (t = 3.02, P = 0.007) between the two groups were significantly different. IL-17 increased more significantly than other markers, while IL-6, IL-8, IL-10, interferon-α, interferon-γ, IL-4 and IL-5 were not statistically significant (P > 0.05). Among the 61 bacteria-positive patients, 27 patients were positive for one species, mainly Staphylococcus aureus, Haemophilus influenzae , and Acinetobacter baumannii. Eleven patients were two species positive, and Acinetobacter baumannii combined with Pseudomonas aeruginosa was common. Fourteen patients were three species positive, and 6 patients were four species positive. Conclusions Serum PCT and CRP levels in SARS-CoV-2-infected patients with bacterial coinfection are higher than those in patients without bacterial infection. Cytokines such as IL-1β, IL-2, IL-12 p70, 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.