Staphylococcus pseudintermedius is a major opportunistic pathogen in dogs, responsible for a wide range of infections including pyoderma, wound infections, otitis externa, and urinary tract infections. Its increasing prevalence has raised concerns due to its association with antibiotic resistance, particularly methicillin-resistant strains (MRSP). One critical factor contributing to the persistence and recurrence of these infections is biofilm formation, a complex process that enables bacteria to evade host immune responses and resist antimicrobial treatments. This study aimed to comprehensively evaluate the biofilm-forming ability of 60 canine-derived S. pseudintermedius isolates using three phenotypic methods—microtiter plate test (MtP), Congo red agar (CRA) method, and tube adherence test—and to correlate these results with the presence of key biofilm-associated genes, icaA and icaD.
Phenotypic testing revealed that 93.3% of isolates were positive for biofilm formation across all three assays, indicating a high capacity for biofilm development. The microtiter plate test classified 41.6% as weakly adherent, 35% as moderately adherent, and 16.6% as strongly adherent, while the tube adherence test identified 75% as weak producers, 18.3% as moderate, and only 6.6% as non-producers. The CRA method detected black or almost black colonies—indicative of slime production—in 86.6% of isolates, suggesting strong biofilm potential. Notably, all four negative results from the CRA test were confirmed by PCR analysis as lacking both icaA and icaD genes.
Genotypic analysis showed that icaA and icaD genes were present together in 55 out of 60 isolates (91.7%), confirming their co-localization within the ica operon. No isolate exhibited only one gene, supporting the hypothesis that the entire operon functions as a unit. The absence of both genes in five isolates correlated with negative biofilm phenotypes. Statistical analysis demonstrated strong agreement between PCR results and CRA outcomes (kappa = 0.7), and near-perfect concordance between MtP and tube adherence tests (100% match).Atrasentan Endothelin Receptor However, some discrepancies were observed: three isolates positive for icaA/icaD failed to form biofilms in phenotypic assays, suggesting the existence of ica-independent mechanisms.PADI3 Proteinweb Additionally, four isolates tested negative by PCR but positive by both phenotypic methods, raising questions about false positives or alternative biofilm pathways.PMID:35202797
These findings highlight the high prevalence of functional ica operons in canine S. pseudintermedius isolates and confirm their role in in vitro biofilm formation. Nevertheless, the presence of biofilm-producing strains without detectable ica genes indicates that other virulence factors—such as accumulation-associated protein (Aap) or Bap—may contribute significantly to biofilm development. Given the variability among phenotypic methods and the limitations of single-assay approaches, this study recommends combining genotypic and phenotypic evaluations for accurate assessment of biofilm potential. Such integrated strategies are essential for understanding pathogenicity, guiding treatment decisions, and improving control measures against persistent S. pseudintermedius infections in veterinary medicine.MedChemExpress (MCE) offers a wide range of high-quality research chemicals and biochemicals (novel life-science reagents, reference compounds and natural compounds) for scientific use. We have professionally experienced and friendly staff to meet your needs. We are a competent and trustworthy partner for your research and scientific projects.Related websites: https://www.medchemexpress.com