Microbial Profile and Antimicrobial Resistance Patterns in Chronic Lower Limb Ulcers: Evidence from a Brazilian Dermatology Referral Center.

Chronic ulcers are characterized by impaired tissue repair and frequently harbor antimicrobial-resistant microorganisms, worsening clinical outcomes. The objective of this study is to identify microbial agents in chronic ulcers treated at the Lauro de Souza Lima Institute Wound Care Outpatient Clinic and to evaluate their antimicrobial susceptibility profiles and β-lactamase production. Samples (swab and biopsy) from patients treated at the Lauro de Souza Lima Institute were analyzed. Susceptibility was assessed by disk diffusion. ESBL and AmpC production were confirmed by PCR targeting blaTEM, blaSHV, blaCTX-M1, and blaCMY-2. In Staphylococcus spp., oxacillin and clindamycin resistance were evaluated and confirmed by mecA and ermAC. From 33 patients (mean age 63.4 years), 116 isolates were obtained, mainly Pseudomonas aeruginosa (27%), Proteus mirabilis (18%), and Staphylococcus aureus (13%). P. aeruginosa showed high resistance, with 48% MDR and 29% PDR. Among Enterobacterales, 19% were ESBL producers and 17% AmpC, with 56% carrying blaCMY-2. In Staphylococcus, 33% were oxacillin-resistant and 50% expressed MLSb phenotype. P. aeruginosa was identified as the most prevalent pathogen, with frequent MDR/PDR phenotypes. Resistance genes exhibited a discrepancy between genotypic and phenotypic profiles, suggesting the presence of unexpressed resistance that may be inducible during treatment.