Rapid detection of epidemic strains of methicillin-resistant Staphylococcus aureus

Fifty methicillin-resistant Staphylococcus aureus (MRSA) initial isolates o btained from patients hospitalized in the orthopedic clinic of the Frankfur t University Hospital and 150 methicillin-sensitive Staphylococcus aureus ( MSSA) isolates were investigated in this study to determine whether the Sli de Staph-Kit is capable of differentiating between MRSA and MSSA owing to i ts unique performance characteristics. I-he Slides Staph-Kit is a combined latex hemagglutination test designed to detect clumping factor, protein A a nd a specific surface immunogen for S. aureus. Clumping factor-positive str ains cause erythrocytes sensitized with fibrinogen to hemagglutinate, there by resulting in visible red clumps. S. aureus strains deficient in clumping factor agglutinate rates particles sensitized with specific antibodies aga inst surface proteins of S. aureus, thereby resulting in visible white clum ps, Our results demonstrate that white clumping has a 99% specificity as we ll as a 98% positive predictive value for MRSA. Clumping factor-negative MR SA, which have been reported to occur in several countries, are epidemic in the Frankfurt area and account for 80% of all MRSA initial isolates in the orthopedic clinic of the Frankfurt University Hospital. Genotyping of all MRSA isolates by macrorestriction analysis of chromosomal DNA revealed that 83% of clumping factor-negative MRSA are closely related to the "southern- German" epidemic strain, This is the first study demonstrating the Slides S taph-Kit's capability for identifying epidemic clumping factor-negative S, aureus strains as methicillin resistant cl en prior to antimicrobial suscep tibility testing.