Evaluation of the virulence profile of bacterial strains causing surgical site infections at a tertiary teaching hospital in Maranhão

Surgical site infections (SSIs) are among the most common healthcare-associated infections, posing serious challenges to patient recovery and hospital management. They are associated with increased morbidity, prolonged hospitalization, and elevated healthcare costs. This study aimed to identify the bacterial pathogens responsible for SSIs and characterize their major virulence factors, including antimicrobial resistance, hemolytic activity, and biofilm production. Conducted over a six-month period at the Hospital Universitário da Universidade Federal, the study included patients who developed SSIs following surgical procedures. Clinical samples were collected and analyzed using standard microbiological and biochemical methods. Of the 1517 surgeries performed during the study period, 45 cases (2.97%) developed SSIs. Bacterial growth was confirmed in 7 cases, yielding 8 aerobic bacterial isolates. Gram-negative bacteria predominated (87.5%), reflecting their increasing role in nosocomial infections. Among these Gram-negative isolates, 28.6% were classified as multidrug-resistant (MDR) and 14.3% as extensively drug-resistant (XDR), underscoring the growing threat of antibiotic resistance. Additionally, 25% of the isolates demonstrated biofilm-forming ability, which enhances resistance to both antibiotics and host immune responses. All isolates exhibited hemolytic activity, suggesting a capacity to damage host tissues and contribute to infection severity. In vivo infection models identified Serratia spp., Pseudomonas aeruginosa and Acinetobacter baumannii as the most virulent strains. These findings highlight the critical importance of surveillance and prompt identification of SSI pathogens, particularly in the context of rising antimicrobial resistance and virulence. Improved infection control measures and tailored antimicrobial therapies are essential to reduce the burden of SSIs.