INTERNATIONAL QUALITY-CONTROL OF PHAGE TYPING OF STAPHYLOCOCCUS-AUREUS

A questionnaire was sent to the 48 national typing centres for Staphyl ococcus aureus and 31 replies were received. Methods of phage typing v aried and molecular methods were not universally available, although p ulsed-field gel electrophoresis was offered by 13 centres. Results for a quality control phage typing exercise were received from 25 centres . Increased standardisation of methods and definitions are indicated. Differences from the consensus patterns were mainly due to typing at a n inappropriate dilution of phage, but five strains caused difficultie s in many centres, Overall reproducibility was good. Phage typing rema ins a cost-effective method for epidemiological studies, particularly on a large scale. The strains selected for the quality control exercis e included many strains suitable for controlling molecular methods as well as testing phage typing. Molecular methods help in the validation of the conclusions which may be drawn from phage typing.