OBJECTIVE  To measure the levels of monocyte chemoattractant protein-1 （MCP-1） and interleukin-17 （IL-17） in bronchoalveolar lavage fluid （BALF） of patients diagnosed with lower respiratory tract Acinetobacter baumannii infection after endotracheal intubation, and to evaluate their diagnostic value for the infection.

METHODS  A total of 60 patients diagnosed with lower respiratory tract A. baumannii infection after endotracheal intubation at Cangzhou Hospital of Integrated TCM-WM from Jan. 2023 to Apr. 2024 were selected as the infection group and further divided into mild （n=32） and severe （n=28） subgroups based on clinical pulmonary infection score （CPIS）. Another 60 patients without lower respiratory tract infection under endotracheal intubation during the same period were selected as the control group. Clinical data and MCP-1/IL-17 levels were collected and compared between the infection and control groups. Logistic regression analysis was carried out to analyze influencing factors of the infection, while receiver operating characteristic （ROC） curve analysis was employed to assess the auxiliary diagnostic value of MCP-1 and IL-17 for the infection.

RESULTS  In the infection group, the duration of oxygen therapy, the proportion of oropharyngeal airway opening, duration of endotracheal intubation, the proportion of endotracheal suctioning, as well as the levels of C-reactive protein （CRP） and procalcitonin （PCT）, were significantly higher/longer than those in the control group （P＜0.05）. In the infection group, BALF levels of MCP-1 and IL-17 were （18.75±4.29） pg/ml and （35.97±5.46） pg/ml, respectively, both higher than their serum levels （14.56±3.68） pg/ml and （28.58±5.27） pg/ml. In the control group, BALF levels of MCP-1 and IL-17 were （12.84±3.41） pg/ml and （27.33±5.08） pg/ml, respectively, also higher than their serum levels （10.92±3.07） pg/ml and （24.16±4.52） pg/ml （P＜0.05）. Endotracheal intubation duration （OR=2.173）, CRP （OR=2.548） and PCT （OR=3.071） were identified as risk factors for post-intubation lower respiratory tract A. baumannii infection （P＜0.05）. The area under the curve （AUC） of the joint detection of MCP-1 and IL-17 was 0.903, significantly high than that of the single detection （P＜0.05）. The severe subgroup showed high sequential organ failure assessment （SOFA） scores （2.04±0.45）, MCP-1 （22.03±4.46） pg/ml and IL-17 （39.78±5.72） pg/ml compared to the mild subgroup （P＜0.05）.

CONCLUSIONS  Patients with post-intubation lower respiratory tract A. baumannii infection demonstrate significantly elevated levels of MCP-1 and IL-17 in BALF, both exceeding serum levels. These two factors may serve as auxiliary diagnostic markers for post-intubation A. baumannii infection, with their levels closely correlated to infection severity and clinical condition.