Role Of icaA and icaD Genes in Determining the Pathogenicity of Bacteremic Isolates of Coagulase -Negative Staphylococci

Abstract

The genus of Staphylococcus consists of at least 40 different species. The ability to produce biofilm is essential in pathogenesis of CoNS. Biofilms seem to protect bacteria from unfavorable external conditions. The biofilm is primarily composed of polysaccharide intracellular adhesion (PIA), usually encoded by intracellular adhesion gene (ica). Coagulase-Negative Staphylococcus is the third most common cause of bloodstream infection and the most common cause of nosocomial BSI .In addition, the incidence and detection of serious nosocomial bacteremia due to CoNS is increasing, due to more frequent use of vascular access devices and more sensitive blood culture systems. Coagulase-negative staphylococci are the most commonly isolated contaminants from blood cultures, yet they are the most frequent cause of true bloodstream infections. This distinction has practical importance because of its therapeutic-effects in terms of unnecessary use of antibiotics and emergence of resistance. Furthermore, failure to recognize and treat true bacteremia can lead to higher rates of morbidity and mortality, especially in the critically ill or immunocompromised patients. The aim of the current study was to evaluate the hypothesis that isolates of pathogenic CoNS associated with bacteremia are more likely to be positive for icaA and icaD genes as compared to non-pathogenic (commensal) CoNS. Also, to determine the relationship between the presence of the icaA and icaD genes, in bacteremic isolates of CoNS, and the ability of these isolates to produce slime when subcultured on Congo red agar. This study was carried out at the Central Microbiology Laboratory of the Clinical Pathology Department in Faculty of Medicine, Ain Shams University over the period between May 2014 and November 2014.