Temporal Trends and Epidemiological Patterns of Clinically Relevant Microorganisms in a Burn Unit: An 11-Year Retrospective Study from a Tertiary Hospital in Southern Brazil

Background/Objectives: Burn patients are particularly vulnerable to microbial colonization and healthcare-associated microorganisms due to extensive skin barrier disruption, prolonged hospitalization, immune imbalance, and frequent invasive procedures. This study aimed to characterize the epidemiological profile and temporal trends of clinically relevant microorganisms isolated from patients admitted to a burn unit over an 11-year period. Methods: This retrospective observational study analyzed microbiological records from burn patients at a Brazilian tertiary hospital (2014–2024), including only the first isolate per patient, clinical episode, and specimen type. Microorganisms were categorized by taxon, group, and specimen sources. Temporal trends were evaluated using regression-based count models and nonparametric tests, while dominant taxa and distribution shifts were identified via epidemiological ranking, Pareto distribution, and heatmap analyses. Results: A total of 6769 clinically relevant microbial isolates were analyzed. Gram-negative bacteria predominated (60.6%), followed by Gram-positive bacteria (28.9%) and fungi (10.5%). The most frequently identified taxa were Acinetobacter spp. (17.3%), coagulase-negative staphylococci (13.7%), and Pseudomonas spp. (12.6%). Eight taxa accounted for 79.5% of all isolates, demonstrating a highly concentrated microbiological profile. Temporal analyses revealed a significant increase in Gram-positive bacterial isolates and a decline in fungal isolates throughout the study period. The distribution of microorganisms varied significantly according to clinical specimen type. Conclusions: The burn unit microbiological profile was dominated by Gram-negative pathogens and exhibited important temporal shifts over the 11-year period. These findings highlight the value of continuous local surveillance to inform infection prevention measures, and support institution-specific antimicrobial stewardship programs.