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<p>Few studies have examined the antimicrobial resistance profiles and phylogenetic diversity of bacteria in Latin American beaches. The aim of this study is to provide nationwide data on <i>Escherichia coli</i> from recreational beaches along the Costa Rican coasts, contributing to the understanding of this knowledge gap. Thirty-nine strains were recovered, one per sampled site, and tested for susceptibility to eleven antibiotics using the disk diffusion method. PCR was used to detect sulfonamide resistance genes (<i>sul1</i>, <i>sul2</i>) and the class 1 integron gene (<i>intI1</i>), while phylogenetic classification was conducted following the Clermont multiplex protocol. Resistance to at least one antibiotic was observed in 84.6% of isolates, with ampicillin (58.97%) and cefazolin (51.28%) showing the highest resistance rates. Multidrug resistance was found in 20.5% of strains, and 33% had MAR indices exceeding 0.2, suggesting contamination from high-risk sources. Phylogroup B1 predominated (51.3%), indicating widespread environmental or animal-associated contamination, although human-related groups (D_E and B2) were also present. The integrase gene <i>intI1</i> was detected in 66.7% of isolates, suggesting potential for horizontal gene transfer. These results confirm the presence of resistant <i>E. coli</i> strains, including multidrug-resistant and human-associated phylogroups, in Costa Rican coastal waters. They underscore the urgency of integrating AMR surveillance into national water quality monitoring systems and improving wastewater treatment infrastructure to reduce the spread of resistant bacteria in recreational environments.</p>

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Antimicrobial resistance and phylogenetic diversity of Escherichia coli isolates from coastal recreational waters in Costa Rica

  • 期刊论文

  • 发表日期：

    2026年1月27日

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  • José R. Montiel-Mora,
  • Luis Rivera-Montero,
  • Andrei Badilla-Aguilar,
  • Kenia Barrantes,
  • Pablo Rivera-Navarro,
  • Luz Chacón

摘要

Few studies have examined the antimicrobial resistance profiles and phylogenetic diversity of bacteria in Latin American beaches. The aim of this study is to provide nationwide data on Escherichia coli from recreational beaches along the Costa Rican coasts, contributing to the understanding of this knowledge gap. Thirty-nine strains were recovered, one per sampled site, and tested for susceptibility to eleven antibiotics using the disk diffusion method. PCR was used to detect sulfonamide resistance genes (sul1, sul2) and the class 1 integron gene (intI1), while phylogenetic classification was conducted following the Clermont multiplex protocol. Resistance to at least one antibiotic was observed in 84.6% of isolates, with ampicillin (58.97%) and cefazolin (51.28%) showing the highest resistance rates. Multidrug resistance was found in 20.5% of strains, and 33% had MAR indices exceeding 0.2, suggesting contamination from high-risk sources. Phylogroup B1 predominated (51.3%), indicating widespread environmental or animal-associated contamination, although human-related groups (D_E and B2) were also present. The integrase gene intI1 was detected in 66.7% of isolates, suggesting potential for horizontal gene transfer. These results confirm the presence of resistant E. coli strains, including multidrug-resistant and human-associated phylogroups, in Costa Rican coastal waters. They underscore the urgency of integrating AMR surveillance into national water quality monitoring systems and improving wastewater treatment infrastructure to reduce the spread of resistant bacteria in recreational environments.