Biofilm-forming capacity, surface hydrophobicity and aggregation characteristics of Myroides odoratus isolated from South African Oreochromis mossambicus fish

Abstract

Aims: Although Myroides spp. are primarily isolated from clinical sources, they have also been isolated from freshwater fish, stainless steel weldment and catheter biofilms. The ability of these nonmotile isolates to adhere to surfaces and the role of hydrophobicity and autoaggregation were investigated.

Methods: Adherence of Myroides odoratus isolates from tilapia was investigated using microtitre adherence assays under varying environmental conditions. Hydrophobicity, aggregation and coaggregation were measured quantitatively. Biofilm structures were investigated using flow cells and microscopy.

Results and conclusions: Myroides odoratus isolates were strongly adherent in both nutrient-poor and -rich media at room temperature and nutrient-rich medium at 37 degrees C. Isolates appeared hydrophilic, while autoaggregation indices ranged from 7% to 24.8%. Statistically significant positive correlations were observed between biofilm formation and autoaggregation. Strong coaggregation interactions were observed with several Gram-positive organisms, as well as with Listeria spp. In flow cells, M. odoratus formed an overlying carpet, with knitted chains of L. monocytogenes cells situated underneath attached to the perspex flow cell surface.

Significance and impact of study: Myroides odoratus biofilm formation was influenced by temperature variation rather than altered nutrient levels. The association of Myroides spp. with Listeria spp. isolates suggests potential association in biofilm structures when these bacteria colonize biotic and/or abiotic surfaces.