Typing of Staphylococcus aureus from surgical site infections: comparison of pulsed-field gel electrophoresis (PFGE) and PCR technique using repetitive extragenic palindromic (rep) and Tn916-Shine-Dalgarno (TnSD) target sequences

Staphylococcus aureus continues to be the main cause of surgical site infec tions. DNA typing is useful for studying this type of infection and establi shing control programs within hospitals. In this study 19 S. aureus strains were isolated from surgical site infections of 19 patients, between August and December 1994 at the Rio de Janeiro University Hospital. The strains w ere typed by pulsed-field gel electrophoresis (PFGE) and by two polymerase chain reaction techniques targeting the repetitive extragenic palindromic a nd Tn916-Shine Dalgarno sequences. Analysis of the PFGE patterns divided th e collection into 15 types, while PCR techniques identified 11 distinct str ain patterns. There were two clusters, 1 of four strains and 1 of two strai ns with related PFGE and PCR patterns. Of the remaining strains, 10 were cl ustered in 5 PCR patterns but their PFGE patterns showed 4 to 6 different b ands, and they were considered to be possibly related. The comparison of th e S. aureus typing systems in the present study indicated that the PCR meth ods are useful for initial screening of genetically related isolates, but s trains with identical PCR fingerprint need to be typed with PFGE for detail ed strain differentiation.