OBJECTIVE  To investigate the adjuvant therapeutic effect of thymosin α1 combined with ulinastatin in patients with severe pneumonia caused by multidrug-resistant bacteria.

METHODS  A retrospective collection of clinical data was conducted on patients with severe pneumonia caused by multidrug-resistant bacteria, who were treated at Honghui Hospital Affiliated to Xi'an Jiaotong University from Jan. 2022 to Jan. 2024. After 1∶1 propensity score matching, the patients were assigned as the control group and the study group with is cases in each group. The control group received conventional treatment based on drug susceptibility results, while the study group received thymosin α1 combined with ulinastatin in addition to the treatment given to the control group. Clinical efficacy, time of clinical symptom improvement, relevant indicators （time required for body temperature normalization, disappearance time of pulmonary rales, length of stay in the intensive care unit, hospital stay and ventilator weaning time）, disease severity, pathogen clearance, 28-day mortality rate and the rate of adverse drug reactions were compared between the two groups. T lymphocyte subsets （CD₈⁺, CD₄⁺, CD₃⁺ and CD₄⁺/CD₈⁺） and levels of inflammatory factors C-reactive protein （CRP）, procalcitonin （PCT）, tumor necrosis factor-α （TNF-α） and interleukin-10 （IL-10） were measured and compared between the two groups before and after treatment.

RESULTS  The therapeutic efficacy in the study group was superior to that in the control group （P=0.020）. The time required for body temperature normalization, disappearance time of pulmonary rales, length of stay in the intensive care unit and ventilator weaning time in the study group were （3.52±0.78） days, （13.62±2.40） days, （7.22±1.05） days and （3.54±1.22） days, respectively, all shorter than those in the control group （P＜0.05）. The clearance rate of pathogens in the study group was 90.67%, higher than that in the control group （P＜0.001）. On day 14 of treatment, the levels of CD₄⁺, CD₃⁺, CD₄⁺/CD₈⁺ and IL-10 in the study group were （47.55±2.11）, （49.55±2.17）, （1.73±0.28） and （133.51±14.71） pg/L, respectively, higher than those in the control group, while the levels of CD₈⁺, CRP, PCT and TNF-α were （27.44±1.85）, （19.05±3.51） mg/L, （0.61±0.24） μg/L and （55.02±7.51） ng/L, respectively, lower than those in the control group （P＜0.05）. There was no statistically significant difference in the 28-day mortality rate or adverse drug reactions between the two groups.

CONCLUSIONS  Thymosin α1 combined with ulinastatin demonstrates favorable effects in patients with severe pneumonia caused by multidrug-resistant bacteria, which contributes to improving pathogen clearance rates and immune function status, reducing levels of inflammatory factors, and alleviating disease progression.