Molecular typing of methicillin-resistant Staphylococcus aureus by pulsed-field gel electrophoresis: Comparison of results obtained in a multilaboratory effort using identical protocols and MRSA strains

Pulsed-field gel electrophoresis (PFGE) has become the gold standard of mol ecular methods in epidemiological investigations, In spite of its high reso lving power, use of the method has been hampered by inadequate laboratory-t o-laboratory reproducibility. In the project described here we have address ed this problem by organizing a multilaboratory effort in which the same ba cterial strains (subtype variants of the Iberian and Brazilian methicillin- resistant Staphylococcus aureus-MRSA-clones) were analyzed by twenty invest igators in thirteen different laboratories according to an indentical proto col, which is reproduced here in detail. PFGE patterns obtained were analyz ed at a central laboratory in order to identify specific technical problems that produced substandard macrorestriction patterns. The results including the specific technical problems and their most likely causes are described in this communication. Also listed are seven major epidemic clones of MRSA which have been characterized by molecular fingerprinting techniques and t he prototypes of which have been deposited at the American Type Culture Col lection, from where they will be available for interested investigators for the purpose of typing MRSA isolates. It is hoped that this communication w ill contribute to the improvement of the reproducibility and technical/aest hetic quality of PFGE analysis.