Genomic and Phenotypic Insight into Antimicrobial Resistance of Pseudomonas fluorescens from King George Island, Antarctica

Myllena Silverio ¹ Junia Schultz ² Mariana Teixeira Dornelles Parise ³ Doglas Parise ³ Marcus Vinicius Canário Viana ³ Wylerson Nogueira ^2,3,4 Rommel Thiago Juca Ramos ⁴ Aristóteles Góes-Neto ³ Vasco Ariston De Carvalho Azevedo ³ Bertram Brenig ⁵ Raquel Regina Bonelli ¹ Alexandre Soares Rosado ^2*

• ¹ Federal University of Rio de Janeiro, Rio de Janeiro, Rio de Janeiro, Brazil
• ² King Abdullah University of Science and Technology, Thuwal, Saudi Arabia
• ³ Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
• ⁴ Federal University of Pará, Belém, Pará, Brazil
• ⁵ Department of Molecular Biology of Livestock, Institute of Veterinary Medicine, Georg August University,, Göttingen, Lower Saxony, Germany

Antimicrobial resistance has been detected in even isolated environments. The genus Pseudomonas includes metabolically versatile microorganisms occupying diverse niches from environmental habitats to plant pathogens and has clinically significant strains. This study characterizes 25 strains of Pseudomonas fluorescens with unusual antimicrobial resistance profiles isolated from ornithogenic soil, native plant rhizospheres, and mosscovered soil on King George Island in the Antarctic Peninsula. Antimicrobial susceptibility testing revealed that all strains were susceptible to neomycin and exhibited varying degrees of intermediate or full resistance to aztreonam and colistin. Additionally, 11 strains demonstrated intermediate resistance to ceftazidime, and six were resistant to cefepime. The clonal relationships were examined using repetitive extragenic palindromic polymerase chain reaction (BOX-PCR), from which 14 strains were selected for whole-genome sequencing. The genomic analysis identified various efflux pumps, predominantly from the ABC transporter and resistance-nodulation-division families.Resistance genes were detected against eight classes of antimicrobials, listed by prevalence: beta-lactams, tetracyclines, polymyxins, aminoglycosides, fosmidomycin, fosfomycin, quinolones, and chloramphenicol. Genes associated with heavy-metal resistance, prophages, and adaptations to extreme environments were investigated. The genotypic and phenotypic findings are consistent, suggesting that efflux pumps and betalactamases play a critical role in antimicrobial extrusion. One notable isolate exhibited the highest number of pathogenicity and resistance islands, including the carbapenemase gene blaPFM-2. Only one plasmid was identified, which did not exhibit antimicrobial resistance determinants. This study offers valuable insight into the evolution of antimicrobial resistance in P. fluorescens, particularly in extreme environments, such as Antarctica. By exploring the antimicrobial resistance mechanisms in P. fluorescens, the study sheds light on how isolated ecosystems drive the natural evolution of resistance genes.