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

• Published in: Revista argentina de microbiología 2024-01, Vol.56 (1), p.102-111
• Main Authors: Nagel, Orlando G., Gasparotti, Maria L., Machado, Selva I., Althaus, Rafael L.
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - analysis; Anti-Bacterial Agents - pharmacology; Anti-Infective Agents; Antibiotic residues; Antimicrobial susceptibility; Análisis conglomerados; Cluster analysis; Concentraciones mínimas inhibitorias; DNA, Ribosomal - analysis; Geobacillus; Geobacillus - genetics; Milk - chemistry; Minimum inhibitory concentration; Residuos de antibióticos; RNA, Ribosomal, 16S; Susceptibilidad antimicrobiana
• ISSN: 0325-7541
• DOI: 10.1016/j.ram.2023.07.003

•Bacteria of the genus Geobacillus have different antimicrobial susceptibilities.•The bacterial susceptibilities cluster is similar to the bacterial DNA cluster.•Bioassays with different Geobacillus could be designed to improve commercial test. 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. El género Geobacillus está compuesto por bacterias termófilas que poseen diversas potencialidades biotecnológicas. Puntualmente, G. stearothermophilus se incluye como bacteria utilizadas para testeo en pruebas comerciales de inhibición microbiana para detectar residuos de antibióticos en alimentos, aunque presenta una limitada sensibilidad frente a aminoglucósidos, macrólidos y quinolonas. En este trabajo se evaluaron los perfiles de sensibilidad antibiótica de cinco bacterias utilizadas para testeo: G. stearothermophilus subsp. calidolactis C953, G. thermocatenulatus LMG 19007, G. thermoleovorans LMG 9823, G. kaustophilus DSM 7263 y G. vulcani 13174. Para ello, se determinaron las concentraciones inhibitorias mínimas (CIM) de 21 antibióticos en muestras de leche frente a las bacterias mencionadas mediante el método de inhi