MULTICENTER EVALUATION OF ARBITRARILY PRIMED PCR FOR TYPING OF STAPHYLOCOCCUS-AUREUS STRAINS

Fifty-nine isolates of Staphylococcus aureus and a single strain of St aphylococcus intermedius were typed by arbitrarily primed PCR (AP-PCR) . To study reproducibility and discriminatory abilities, AP-PCR was ca rried out in seven laboratories with a standardized amplification prot ocol, template DNA isolated Tn a single institution, and a common set of three primers with different resolving powers. The 60 strains could be divided into 16 to 30 different genetic types, depending on the la boratory. This difference in resolution was due to differences in tech nical procedures (as shown by the deliberate introduction of experimen tal variables) and/or the interpretation of the DNA fingerprints. Howe ver, this did not hamper the epidemiologically correct clustering of r elated strains. The average number of different genotypes identified e xceeded those of the more traditional typing strategies (F. C. Tenover , R. Arbeit, G. Archer, J. Biddle, S. Byrne, R. Goering, G. Hancock, G . A. Hebert, B. Hill, R. Hollis, W. R. Jarvis, B. Kreiswirth, W. Eisne r, J. Maslow, L. K. McDougal, J. M; Miller, M. Mulligan, and M. A. Pfa ller, J. Clin. Microbiol. 32:407-415, 1994). Comparison of AP-PCR with pulsed-field gel electrophoresis (PFGE) indicated the existence of st rains with constant PFGE types but variable AP-PCR types. The reverse (constant AP-PCR and variable PFGE patterns) was also observed. This i ndicates additional resolution for combined analyses. It is concluded that AP-PCR is well suited for genetic analysis and monitoring of noso comial spreading of staphylococci. The interlaboratory reproducibility of DNA-banding patterns and the intralaboratory standardization need improvement.