Abstract:

Objective: To evaluate an antimicrobial stewardship model guided by microbial culture and dynamic procalcitonin (PCT) monitoring in older patients with pulmonary infection. Methods: This retrospective study included 96 patients aged 60 years or older who were hospitalized with pulmonary infection between June 2025 and June 2026. According to the antimicrobial management strategy documented in the medical records, the patients were assigned to a control group or an intervention group, with 48 patients in each group. The control group received routine empirical antimicrobial therapy, whereas the intervention group was managed using standardized respiratory specimen collection, microbial identification and susceptibility testing, serial PCT monitoring, and multidisciplinary reassessment of antimicrobial therapy. Process indicators, pathogen distribution, antimicrobial use, inflammatory markers, and 28-day outcomes were compared. Results: The qualified rate of observation-combination specimens, evidence-based adjustment rate within 72 h, de-escalation therapy rate, and rational application rate of antimicrobial agents in the observation group were 89.58% (43/48), 83.33% (40/48), 43.75% (21/48), and 91.67% (44/48), respectively, which were higher than those in the control group (68.75% (33/48), 56.25% (27/48), 20.83% (10/48), and 70.83% (34/48)), with statistically significant differences (χ²=6.341, P=0.012; χ²=8.382, P=0.004; χ²=5.761, P=0.016; χ²=6.838, P=0.009). The duration of antimicrobial agent use ((6.37±1.72) d) and the mean antimicrobial therapy days per case ((9.86±2.75) d) in the observation group were shorter than those in the control group ((8.64±2.13) d and (13.52±3.84) d), with statistically significant differences (t=5.748, P<0.001; t=5.359, P<0.001). At 3 days of treatment, procalcitonin (PCT)((0.71±0.33) ng/ml), C-reactive protein (CRP)((34.28±11.67) mg/L), and neutrophil-to-lymphocyte ratio (NLR)(4.85±1.39) in the observation group were lower than those in the control group ((1.04±0.45) ng/ml, (45.76±13.85) mg/L, 6.34±1.76), showing statistically significant differences (t=4.094, 4.392, 4.607; all P<0.001); at 7 days of treatment, these indicators ((0.22±0.11) ng/ml, (12.36±5.41) mg/L, 2.81±0.86) were also lower than those in the control group ((0.39±0.18) ng/ml, (19.84±7.62) mg/L, 3.68±1.04), with statistically significant differences (t=5.584, 5.542, 4.459; all P<0.001). There were no statistically significant differences between the observation group and the control group in clinical effective rate (93.75% (45/48) vs. 81.25% (39/48)), antimicrobial-related adverse reaction rate (4.17% (2/48) vs. 16.67% (8/48)), and 28-day recurrence/readmission rate (4.17% (2/48) vs. 14.58% (7/48))(Fisher’s exact test, P=0.120, 0.091, and 0.159, respectively). Conclusion: The structured antimicrobial stewardship model was associated with more frequent evidence-supported adjustment and de-escalation, more appropriate antimicrobial use, and shorter antimicrobial exposure. Its effect on short-term clinical outcomes requires confirmation in larger prospective studies.

Key words: Aged, Pulmonary, Infection, Patient care management, Physician’s practice patterns