Staphylococcus aureus bacteremia. Serological findings, phenotypic and genotypic characteristics of S. aureus strains

Abstract: The diagnosis of S. aureus infections is most often based on culture of the organism from various body sites. However, cultures could be false negative due to e.g. previous antibiotic therapy, and in some situations cultures are difficult to obtain. Antibody assays against various S. aureus antigens have been proposed as a way to diagnose S. aureus bacteremia, as well as to distinguish between uncomplicated and complicated S. aureus bacteremia, including S. aureus endocarditis. Adhesion of bacteria to host proteins is a critical first step in tissue colonization. Collagen is a major component of connective tissue and cartilage. A collagen-binding protein (CnBP) has been described and the corresponding gene, cna, has been sequenced and cloned. Most S. aureus isolates have a capsular polysaccharide (CP) and eleven different serological types have been identified. The aims of these studies was to evaluate if serological assays or combinations of assays can differentiate between uncomplicated and complicated S. aureus bacteremia, S. aureus and non-S. aureus bacteremia or S. aureus and non-S. aureus endocarditis, to examine the distribution of different CP-types and CnBP in S. aureus isolates of various origin and to determine if existence of CnBP and the corresponding cna-gene in S. aureus is a prerequisite for bone and joint infection or endocarditis in patients with S. aureus bacteremia. No serological assays or combinations of assays could differentiate between uncomplicated and complicated S. aureus bacteremia, but combinations of assays could, with high predictive values, discriminate between S. aureus and non-S. aureus endocarditis. As in previous studies, CP 8 was the most predominant CP type in clinical isolates, followed by CP 5, but there was no correlation between CP types and clinical manifestations of S. aureus infections.The cna-gene encodes the only significant collagen-binding protein in S. aureus, and was found in approximately 56% of clinical isolates, but the possession of this gene was equally distributed in clinical isolates of various origin, and is not essential in the pathogenesis of endocarditis or bone and joint infections in humans.