Identifying biofilm-forming strains of Staphylococcus epidermidis isolated from intravascular-catheterized patients by icaA and icaD genes

Abstract Staphylococcus epidermidis has gained a substantial importance in recent years because it is one of the main causative agents of nosocomial infections. It requires a predisposed host in order to switch from a normal inhabitant of the human skin to a pathogenic flora. This study aimed to use icaA/icaD genes as biomarkers in differentiating biofilm-forming S. epidermidis, obtained from patients with intravascular catheter (IVC) infections, from other saprophytic strains. Twenty isolates of S. epidermidis obtained from 100 cases of intravascular catheter infections were investigated for the presence of the intracellular adhesion icaA and icaD genes by polymerase chain reaction (PCR) and for phenotypic biofilm production by qualitative Congo red agar assay (CRA). Results: Nine (~45%) S. epidermidis isolates out of 20 isolates collected from IVC infections were positive for both CRA (produce black colonies) and icaA/icaD genes; while 11 (~55%) S. epidermidis isolates were negative for CRA and icaA/icaD genes. Detection of icaA/icaD gene is a reliable, efficient, and more rapid tool for characterizing biofilm-forming strains of S. epidermidis. Keywords: Staphylococcus epidermidis; icaA; icaD; biofilm