OBJECTIVE To investigate the pathogens of pulmonary infection and their influencing factors in patients with initially treated pulmonary tuberculosis (PTB), and to analyze the diagnostic efficacy of systemic inflammatory response index (SIRI) for pulmonary infection.

METHODS The clinical data of 459 patients with initially treated PTB admitted to Changsha Central Hospital from Jan. to Dec. 2023 were retrospectively analyzed, and they were divided into the combined group (n=90) and the non-combined group (n=369) according to the combination of other pulmonary infections at the time of consultation. The pathogens of pulmonary infection, as well as the levels of monocytes (MN), neutrophils (NE), and lymphocytes (LYM), were analyzed, and the SIRI was calculated. The risk factors of pulmonary infection in initially treated PTB patients were explored by multivariate logistic regression analysis, and the diagnostic value of SIRI for pulmonary infection in initially treated PTB patients was evaluated by receiver operating characteristic (ROC) curve.

RESULTS The rate of pulmonary infection in 459 initially treated PTB patients was 19.61% (90/459), and a total of 103 pathogens were detected, of which 64 strains of gram-negative bacteria accounted for 62.14%, followed by 28 strains of gram-positive bacteria accounting for 27.18%, and 11 strains of fungi accounting for 10.68%, with Pseudomonas aeruginosa, Klebsiella pneumoniae and Staphylococcus aureus being predominant. Age (OR=1.908, 95%CI: 1.375-2.647), comorbid diabetes (OR=2.073, 95%CI: 1.462-2.938), pulmonary cavities (OR=2.323, 95%CI: 1.588-3.398), delayed medical treatment (OR=2.024, 95%CI: 1.467-2.791) and elevated SIRI (OR=2.855, 95%CI: 1.851-4.402) were risk factors for pulmonary infection in initially treated PTB patients (P < 0.05). ROC curve analysis showed that the area under the curve (AUC) of SIRI for diagnosing pulmonary infection in initially treated PTB cases was 0.876 (0.824 - 0.928), with a cut-off value of 4.96×10⁹/L, a specificity of 85.91%, and a sensitivity of 86.67%.

CONCLUSIONS The main pathogens in patients with initially treated PTB complicated with pulmonary infection are Pseudomonas aeruginosa and Klebsiella pneumoniae. Age, comorbid diabetes mellitus, pulmonary cavity, delayed medical treatment and elevated SIRI are all influencing factors for pulmonary infection in patients with initially treated PTB, and monitoring of SIRI can to some extent assist in diagnosis of whether patients with initial treatment PTB are complicated with other pulmonary infections.