To investigate the distribution characteristics and drug resistance of pathogenic bacteria in patients with chronic refractory wounds, and to guide the formulation of personalized antimicrobial treatment plans and promote rational use of antibacterial drug in clinical practice.

A retrospective study was conducted on the clinical data of 124 patients with chronic refractory wounds admitted to the Dermatology Outpatient Department, Dermatology Inpatient Unit and Vascular Surgery Inpatient Unit of the First Affiliated Hospital of Tsinghua University from January 2020 to January 2025. Wound secretions or necrotic tissues were collected by sterile swabs and sent to laboratory for bacterial culture. Species identification was performed by VITEK MS microbial identification system (bioMérieux, France) with VITEK-2 identification cards. In vitro antimicrobial susceptibility testing employed matching VITEK-2 susceptibility cards and the Kirby-Bauer disk diffusion method (Oxoid, UK). All experimental procedures and result interpretations were adhered to guidelines established by the Clinical and Laboratory Standards Institute (CLSI). The independent risk factors for positive pathogen culture in wound were analyzed by binary Logistic regression.

Total of 92 strains of pathogenic bacteria were isolated, with the isolation rate of 74.2%; Gram-positive cocci primarily included Staphylococcus aureus (27 strains, 29.3%) and coagulase-negative Staphylococci (23 strains, 25%); Gram-negative bacilli mainly comprised Pseudomonas aeruginosa (9 strains, 9.8%), Escherichia coli (4 strains, 4.3%) and Proteus mirabilis (4 strains, 4.3%). The top three etiological factors for chronic refractory wounds were lower extremity arterial vascular ulcers (43 cases, 34.7%), infectious ulcers (38 cases, 30.6%) and postoperative poor wound healing (15 cases, 12.1%). The detection rate of Staphylococcus aureus was significantly higher in patients with infectious ulcer group compared with patients of lower extremity arterial disease (χ²=6.618, P=0.014). Wound pathogen detection rates were significantly elevated in patients ≥ 60 years old compared with those < 60 years old (χ²=5.236, P=0.022). Logistic regression analysis showed that diabetes mellitus was an independent risk factor for positive wound pathogen culture (OR=2.620, 95%CI: 1.013-6.777, P=0.047). The detection rate of wound pathogen was significantly higher in patients with diabetes compared with patients without diabetes (χ²=7.079, P=0.008), the positive detection rate of other Gram-negative bacilli was also significantly higher in patients with diabetic (χ²=3.932, P=0.047). In patients with type 2 diabetes mellitus duration ≥ 15 years, detection rates of other Gram-negative bacilli were significantly higher than those with duration < 15 years (χ²=5.013, P=0.025), all with significant differences. The detection rate of Staphylococcus aureus in head and neck region was significantly higher than that in trunk (χ²=8.531, P=0.003) and limbs (χ²=11.738, P=0.001). Methicillin-resistant Staphylococcus aureus accounted for 5 strains (5.4%) and methicillin-resistant coagulase-negative Staphylococci accounted for 15 strains (16.3%), all were sensitive to vancomycin, tigecycline and linezolid. Pseudomonas aeruginosa (9 strains, 9.8%) demonstrated universal susceptibility to cefepime, meropenem, amikacin, levofloxacin, ciprofloxacin and colistin, while 1 strain (11.1%) exhibited resistance to imipenem. Among Escherichia coli isolates (4 strains, 4.3%), resistance was observed in 1 strain (25%) to amikacin, levofloxacin and sulfamethoxazole/trimethoprim, respectively. Proteus mirabilis (4 strains, 4.3%) showed resistance to tigecycline in 3 strains (75%) and 2 strains (50%) to cefuroxime and sulfamethoxazole/trimethoprim, respectively.

Infection is closely associated with the development of chronic refractory wounds, with diabetic and elderly patients being particularly high-risk populations. Wound bacteria exhibit diverse species and characteristic clinical distribution patterns. Rational individualized selection of antimicrobial agents can effectively control infection, promote wound healing, and prevent or delay the emergence and spread of antibiotic-resistant bacteria.