Congo red agar, a differential medium for Aeromonas salmonicida, detects the presence of the cell surface protein array involved in virulence.

AUTOR(ES)

Ishiguro, E E

RESUMO

Strains of the fish pathogen Aeromonas salmonicida which possess the cell surface protein array known as the A-layer (A+) involved in virulence formed deep red colonies on tryptic soy agar containing 30 micrograms of Congo red per ml. These were readily distinguished from colorless or light orange colonies of avirulent mutants lacking A-layer (A-). The utility of Congo red agar for quantifying A+ and A- cells in the routine assessment of culture virulence was demonstrated. Intact A+ cells adsorbed Congo red, whereas A- mutants did not bind Congo red unless first permeabilized with EDTA. The dye-binding component of A+ cells was shown to be the 50,000-Mr A-protein component of the surface array. Purified A-protein avidly bound Congo red at a dye-to-protein molar ratio of about 30 by a nonspecific hydrophobic mechanism enhanced by high salt concentrations. Neither A+ nor A- cells adsorbed to Congo red-Sepharose columns at low salt concentrations. On the other hand, A+ (but not A-) cells were avidly bound at high salt concentrations.

Documentos Relacionados

• Porphyrin binding by the surface array virulence protein of Aeromonas salmonicida.
• Chocolate agar, a differential medium for gram-positive cocci.
• Detection of Aeromonas salmonicida from fish by using polymerase chain reaction amplification of the virulence surface array protein gene.
• Congo Red-Agar Plating Medium for Detecting Pigmentation in Pasteurella pestis
• Purification and disposition of a surface protein associated with virulence of Aeromonas salmonicida.