[Coagulase gene polymorphism in Staphylococcus aureus--a new epidemiologic marker].

Abstract

Nosocomial infections with Staphylococcus aureus necessitate the prompt recognition of the infectious chain as well as a rapid investigation and exclusion of infectious sources. Conventional typification procedures (e.g. phage typing) and genotyping methods with pulsed-field gel electrophoresis (PFGE) are labor-intensive and time-consuming and can be performed only in a few laboratories. A new attractive typing technique for S. aureus utilizes the polymorphism of the coagulase (coa) gene as an epidemiological marker. This typing method is performed with primers, homologous to a conserved region within the coa gene, in order to amplify the sequences encoding the C-terminal region of this molecule. Since the number of repetitive sequences varies within the coa gene, the resulting PCR products of individual strains can be of different lengths. We have assessed the coa gene length polymorphism in 150 strains of S. aureus. By the sizes of the PCR products these strains could be categorized into 10 subgroups. AluI restriction analysis of the PCR products resulted in a significantly higher degree of discrimination. Since the repeated sequences, consisting of 81 base pairs, possess a high variability of the nucleotides, a characteristic restriction fragment length polymorphism (coa-RFLP) pattern is yielded. Overall, we could distinguish 64% of the clinical isolates by RFLP analysis; in strains sharing identical antibiograms, 56% could be distinguished. 46% oxacillin-resistant strains, some of which originated from epidemic outbreaks, could be discriminated by their RFLP pattern. Comparing these results with those obtained from the PFGE method, isolates which differed by their coagulase gene RFLP also differed by their PFGE patterns.(ABSTRACT TRUNCATED AT 250 WORDS)