Hospital-Based Surveillance of Antimicrobial Resistance in Southern Brazil: Resistance Profiles and Phenotypic Carbapenemase Screening

Purpose To describe the distribution of clinically relevant bacterial pathogens and their antimicrobial resistance profiles in a tertiary university hospital in southern Brazil, with emphasis on carbapenem resistance and phenotypic carbapenemase screening. Methods This retrospective study analysed 1,513 clinical isolates recovered during 2024 after exclusion of 1,304 surveillance or colonisation records. Identification and antimicrobial susceptibility testing were performed using the BD Phoenix M50 system and interpreted according to BrCAST/EUCAST criteria. Carbapenem-resistant Gram-negative isolates were screened phenotypically for carbapenemase activity using the Blue-Carba assay. Results Among the clinical isolates, 1,397 were processed through the university hospital and 116 originated from external municipal healthcare services. Hospital-acquired, community-acquired, and non-classified infections accounted for 58.2%, 32.9%, and 8.9%, respectively. Escherichia coli , Klebsiella pneumoniae , and Pseudomonas aeruginosa were the most frequent Gram-negative pathogens. Meropenem resistance was 75.7% (28/37) among Acinetobacter baumannii and 37.8% (42/111) among P. aeruginosa . Oxacillin resistance was detected in 40.3% (27/67) of S. aureus isolates. Conclusion Carbapenem resistance was particularly concerning among non-fermenting Gram-negative bacteria, especially A. baumannii and P. aeruginosa . The findings support stronger antimicrobial stewardship, infection-prevention measures, and laboratory-based surveillance. Molecular studies are required to define the underlying resistance determinants and investigate possible clonal dissemination.