Study of the Adhesion of Clinical Strains of Staphylococcus aureus on an Abiotic Surface Using the Biofilm Ring Test®

Four methicillin-sensitive (MSSA) and 4 methicillin-resistant (MRSA) strains of Staphylococcus aureus were collected and isolated at the Laboratory of Bacteriology of the Provincial General Reference Hospital of Kinshasa in the Democratic Republic of Congo. The microbial adhesion to solvents (MATS) test showed that the MRSA strains had a less hydrophobic membrane than the MSSA strains. Using the Biofilm Ring Test (BFRT) to investigate on the adhesion of these bacterial strains to smooth surfaces, we observed that the MSSA strains adhered more rapidly than the MRSA strains. The biomass of the produced biofilm measured by the Crystal violet staining method (CVSM) was more important with MSSA than with MRSA strains. Ethylene glycol-bis(2-aminoethylether)-N,N,N',N'-tetraacetic acid (EGTA) inhibited the adhesion and the formation of a biofilm by MRSA strains; this inhibition was reversed by calcium, magnesium and manganese. The MRSA strains adhered less to silicon tubing and the adhesion was inhibited by EGTA in 2 of the 4 MRSA strains and none of the MSSA strains. In conclusion, the MSSA and MRSA strains adhered on an abiotic surface and formed a biofilm at distinct rates and with different sensitivities to ions. The results also confirm the utility as well as the limits of the BFRT to study the adhesion of bacteria on a surface.