TYPING OF METHICILLIN-RESISTANT STAPHYLOCOCCUS-AUREUS ISOLATES FROM DUSSELDORF BY 6 GENOTYPIC METHODS

Nosocomial infections caused by methicillin-resistant Staphylococcus a ureus (MRSA) represent an increasing problem in hospitals. Quick and r eliable typing methods are required to obtain information about the re latedness of MRSA isolates and to allow faster implementation of appro priate infection control measures. This investigation describes the di stribution of MRSA isolates from 11 hospitals in the Dusseldorf region of Germany, and the ability of six different genotypic typing techniq ues - pulsed-field gel electrophoresis (PFGE), random amplification of polymorphic DNA (RAPD), 16S-23S rDNA spacer amplification, protein A- gene PCR, PCR characterisation of the hypervariable region (HVR) adjac ent to mecA, and coagulase gene-PCR - to detect different unrelated ty pes. Of 7814 S. aureus isolates tested, 489 (6.3%) were MRSA, of which 183 were selected for subsequent molecular analyses on the basis of b eing the first MRSA isolated from colonised or infected patients. Larg er hospitals had a higher incidence of MRSA and a greater variability in genotypes than smaller hospitals. All methods confirmed the presenc e of two main clonal types. The ability of techniques to detect differ ent unrelated types was found to be as follows: PFGE, 28 types; 16S-23 S rDNA spacer-amplification, 10 types; RAPD, nine types; protein A-gen e PCR, five types; HVR-PCR, five types; and coa gene-PCR, two types. C ombination of PFGE and one other PCR-based method (spacer-amplificatio n, RAPD or protein-A gene PCR) provided the best resolution of types a nd allowed the identification of subtypes. Similar molecular types wer e identified with international MRSA isolates. Although PCR-based tech niques have the advantage of rapid performance and easy handling, thei r discriminatory capacity is inferior compared to the more labour inte nsive PFGE.