[Distribution of pathogens in patients with ventilator-associated pneumonia and their association with Dectin-1/Syk signaling pathway].

Objective: To analyze the pathogens distribution in patients with ventilator-associated pneumonia (VAP), and their association with anti-β-glucan receptor-1 (Dectin-1)/spleen tyrosine kinase (Syk) signaling pathway, and to provide scientific basis for formulating more effective treatment strategies and preventive measures.

Methods: A prospective study was conducted. 160 patients with VAP admitted to the department of critical care medicine of Xingtai People's Hospital from January 2021 to March 2023 were enrolled. The respiratory secretions of patients were collected for Candida colonization analysis, and then the bacteria in the respiratory secretions were identified by automatic microbial identification instrument. The expression levels of Dectin-1 and Syk in peripheral blood mononuclear cells were detected by fluorescent immunopolymerase chain reaction. Clinical pulmonary infection score (CPIS) was performed based on imaging, clinical and microbiological criteria. The basic data, pathogen distribution, Dectin-1 and Syk expression levels and CPIS score of the two groups were compared. Spearman test was used to analyze the correlation between the expression levels of Dectin-1 and Syk and respiratory Candida colonization and CPIS score.

Results: 160 VAP patients, 97 were Candida colonized (colonized group) and 63 were not (non-colonized group). There were significantly differences in gender (males: 57.73% vs. 41.27%, P = 0.042) and age (years: 57.98±12.46 vs. 62.09±10.61, P = 0.029) between the colonized group and the non-colonized group, while there were no significantly differences in the data of duration of mechanical ventilation, underlying diseases and primary diseases. The distribution of pathogenic bacteria showed that the infection rate of Staphylococcus aureus in the colonized group was significantly higher than that in the non-colonized group (24.74% vs. 7.94%, P < 0.05), and there was no significantly difference in the infection rate of other G-positive and G-negative bacteria between the two groups. The CPIS score in the colonized group was significantly higher than that in the non-colonized group (8.73±0.43 vs. 7.31±0.39, P < 0.01), and the expression levels of Dectin-1 and Syk in peripheral blood mononuclear cells were significantly higher than those in the non-colonized group (Dectin-1/U6: 0.86±0.22 vs. 0.47±0.16, Syk/U6: 0.77±0.18 vs. 0.42±0.11, both P < 0.01). The expression levels of Dectin-1 and Syk in peripheral blood mononuclear cells of VAP patients were significantly positively correlated with the colonization of respiratory Candida (r values were 0.754 and 0.631, respectively, both P < 0.05), and were significantly positively correlated with CPIS score (r values were 0.594 and 0.618, respectively, both P < 0.05).

Conclusion: The proportion of Staphylococcus aureus in VAP patients with respiratory Candida colonization is higher, and Dectin-1/Syk signaling pathway is significantly positively correlated with respiratory Candida colonization and CPIS score.