Susceptibility profile of <i>Aeromonas</i> spp. from clinical strains isolated in French Guiana

<i>Aeromonas</i> spp. are gram-negative bacilli of the Gammaproteobacteria class and Aeromonadaceae family. These bacteria are a public health challenge, particularly in South America. They harbor chromosomal β-lactamases belonging to classes B, C, and D, whose presence varies among species. This retrospective study aimed to evaluate the minimum inhibitory concentrations (MICs) of piperacillin-tazobactam (PTZ) and cefotaxime (CTX) for clinical strains of <i>Aeromonas</i> spp. A secondary objective was to assess the resistance profile of these strains to cefepime (FEP), aztreonam (AZT), ciprofloxacin (CIP), levofloxacin (LEV), and trimethoprim-sulfamethoxazole (SXT). The study was conducted at the Microbiology Laboratory of Cayenne Hospital (French Guiana) from January 2020 to December 2023. All isolated clinical <i>Aeromonas</i> strains, regardless of species or sample type, were included. In total, 99 strains were analyzed, comprising <i>Aeromonas hydrophila</i> (<i>n</i> = 79), <i>Aeromonas caviae</i> (<i>n</i> = 10), <i>Aeromonas veronii</i> (<i>n</i> = 6), and other <i>Aeromonas</i> spp. (<i>n</i> = 4). The median PTZ MIC was 0.5 mg/L for <i>Aeromonas</i> spp. overall, with six strains (6%) exhibiting MICs of >8 mg/L. For <i>A. hydrophila</i>, the median PTZ MIC was also 0.5 mg/L, lower than the median reported by the European Committee on Antimicrobial Susceptibility Testing (EUCAST) for strains of 4 mg/L. For CTX, the median MIC for all <i>Aeromonas</i> spp. was 0.064 mg/L, with four strains (4%) having MICs of >4 mg/L. The median ceftazidime (CAZ) MIC was 0.125 mg/L. No resistance to AZT was detected, and 3% high-dose susceptibility to FEP was found. Resistance rates to other antibiotics were low: 6% to CIP, 6% to LEV, and 6% to SXT. In conclusion, our study demonstrated low resistance rates in <i>Aeromonas</i> spp. to PTZ (6%), CTX (4%), and CAZ (4%). These findings suggest that PTZ and CTX could be effective against <i>Aeromonas</i> infections, despite the lack of established clinical breakpoints by EUCAST.IMPORTANCE<i>Aeromonas</i> spp. are clinically significant, particularly in tropical climates. This study provides essential MIC distribution data for piperacillin-tazobactam and cefotaxime, offering valuable insights for guiding empirical treatment choices. Understanding these susceptibility patterns is crucial for optimizing antimicrobial therapy, particularly in regions with limited resistance surveillance and standardized guidelines. By analyzing a large collection of clinical isolates, our findings contribute to evidence-based decision-making for <i>Aeromonas</i> infections and emphasize the importance of continued surveillance of antimicrobial susceptibility. These findings suggest that PTZ and CTX may be therapeutic options for <i>Aeromonas</i> infections, supporting their potential use in clinical practice.