Similarities of Geobacillus bacteria based on their profiles of antimicrobial susceptibility in milk samples

Rev Argent Microbiol. 2024 Jan-Mar;56(1):102-111. doi: 10.1016/j.ram.2023.07.003. Epub 2023 Sep 12.

Abstract

The genus Geobacillus is composed of thermophilic bacteria that exhibit diverse biotechnological potentialities. Specifically, Geobacillus stearothermophilus is included as a test bacterium in commercial microbiological inhibition methods, although it exhibits limited sensitivity to aminoglycosides, macrolides, and quinolones. Therefore, this article evaluates the antibiotic susceptibility profiles of five test bacteria (G. stearothermophilus subsp. calidolactis C953, Geobacillus thermocatenulatus LMG 19007, Geobacillus thermoleovorans LMG 9823, Geobacillus kaustophilus DSM 7263 and Geobacillus vulcani 13174). For that purpose, the minimum inhibitory concentrations (MICs) of 21 antibiotics were determined in milk samples for five test bacteria using the radial diffusion microbiological inhibition method. Subsequently, the similarities between bacteria and antibiotics were analyzed using cluster analysis. The dendrogram of this multivariate analysis shows an association between a group formed by G. thermocatenulatus and G. stearothermophilus and another by G. thermoleovorans, G. kaustophilus and G. vulcani. Finally, future microbiological methods could be developed in microtiter plates using G. thermocatenulatus as test bacterium, as it exhibits similar sensitivities to G. stearothermophilus. Conversely, G. vulcani, G. thermoleovorans and G. kaustophilus show higher MICs than G. thermocatenulatus.

Keywords: Antibiotic residues; Antimicrobial susceptibility; Análisis conglomerados; Cluster analysis; Concentraciones mínimas inhibitorias; Geobacillus; Minimum inhibitory concentration; Residuos de antibióticos; Susceptibilidad antimicrobiana.

MeSH terms

  • Animals
  • Anti-Bacterial Agents / analysis
  • Anti-Bacterial Agents / pharmacology
  • Anti-Infective Agents*
  • DNA, Ribosomal / analysis
  • Geobacillus* / genetics
  • Milk / chemistry
  • RNA, Ribosomal, 16S

Substances

  • DNA, Ribosomal
  • RNA, Ribosomal, 16S
  • Anti-Bacterial Agents
  • Anti-Infective Agents