Characteristics of Immunocytes and Cytokines in Patients with Bloodstream Infections Caused by Carbapenem-Resistant Klebsiella pneumoniae in China

Objective: To evaluate the characteristics of immunocytes and cytokines associated with bloodstream infections (BSIs) caused by Klebsiella pneumoniae (CRKP). Methods: Patients with BSIs K. pneumoniae (BSIs-Kpn) were enrolled in our hospital between 2015 and 2022. Whole blood and serum samples were collected on the first day after diagnosis. Immunocytes and cytokines profiles were assessed using multicolor flow cytometry and multiplex immunoassays, respectively. The test cytokines included interferon-gamma (IFN-gamma), tumor necrosis factoralpha (TNF-alpha), interleukin (IL)-2, IL-4, IL-6, IL-10, and IL-17A. Results: A total of 313 patients had BSIs-Kpn, including 145 with CRKP, 43 with extended-spectrum beta-lactamases (ESBL) producing Kpn (ESBL-Kpn) and 125 with non-CRKP or non-ESBL-Kpn (susceptible Kpn, S-Kpn). Absolute number of leukomonocyte (CD45 +) in CRKP, ESBL-Kpn and S-Kpn were 280.0 (138.0-523.0) cells/mu L, 354.5 (150.3-737.3) cells/mu L, and 637.0 (245.0-996.5) cells/ mu L, respectively. Compared with S-Kpn group, the absolute numbers of leukomonocyte (including T lymphocytes, B lymphocytes and natural killer cells) in patients with CRKP were significantly lower than that in patients with S-Kpn (P < 0.01). The levels of cytokines IL-2 and IL-17A were significantly higher in patients with S-Kpn than in those patients with CRKP (P<0.05). The area under receiver operating curve (AUC) of IL-2, IL-4, and IL-17A for S-Kpn was 0.576, 0.513, and 0.561, respectively, whereas that for the combination of these three cytokines with immunocytes was 0.804. Conclusion: Patients with BSIs-CRKP had lower leukomonocyte counts. High levels of IL-2 and IL-17A combined with immunocyte subpopulations showed relatively high diagnostic value for BSIs-S-Kpn from BSIs-CRKP.