Genotype-phenotype characteristics of biofilm formation in clinical isolates of Staphylococcus aureus in acute tonsillitis

N. Kravets; M. Shevchenko; T. Tsarenko; S. Klymnyuk

doi:10.15421/0226075

N. Kravets I. Horbachevsky Ternopil National Medical University
M. Shevchenko Bila Tserkva National Agrarian University
T. Tsarenko Bila Tserkva National Agrarian University
S. Klymnyuk I. Horbachevsky Ternopil National Medical University

Keywords: biofilm formation, adhesion genes, ica operon, clfA, clfB, tonsillitis, phenotypic methods, PCR, Congo red agar.

Abstract

Staphylococcus aureus is not a primary etiological agent of acute tonsillitis but may contribute to disease progression and persistence, particularly in polymicrobial infections. Its ability to form biofilms can complicate treatment and contribute to persistent infection. However, the relationship between the presence of adhesion genes and their phenotypic expression r e mains unclear. The objective of the study was to comprehensively evaluate biofilm formation in clinical S. aureus isolated from patients with acute tonsillitis using combined genotypic and phenotypic approaches. A total of 14 S. aureus isolates were analysed. Biofilm formation was assessed using phenotypic methods: microtiter plate assay, tube method , and microscopy. Exopolysaccharide production was evaluated using Congo red agar and a modified liquid medium. PCR was performed to detect the icaABCD operon, clfA , clfB genes as well as the species-specific markers (nuc, au-nuc). All isolates carried the full set of adhesion-related genes. However, phenotypic analysis revealed a variability in the biofilm formation: A ccording to the microtiter plate assay , 7.1% of the isolates were non-producers, 42.8% weak, 21.4% moderate , and 28.6% strong biofilm producers. Using three phenotypic methods, 71.4% of the isolates showed complete agreement in their scores, and a strong correlation between the methods within the study sample. All isolates tested positive on Congo red agar and broth. The pre s ence of adhesion genes alongside variable phenotypic expression may indicate the probable involvement of regulatory mec h anisms in biofilm formation. Combining genotypic and phenotypic methods provides a comprehensive assessment of the biofilm-forming potential of clinical isolates of S. aureus .

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