Computerized restriction endonuclease analysis compared with O‐serotype and phage type in the epidemiologic fingerprinting of Pseudomonas aeruginosa strains

Objective: To assess restriction endonuclease analysis (REA) of chromosomal DNA using Sall enzyme, low‐concentration (0.4%) agarose gels and digitalized data management of the REA patterns obtained for the typing of clinical Pseudomonas aeruginosa isolates. Method: A group of 67 clinical unrelated isolates from 10 Spanish hospitals was used to study the discriminatory power, reproducibility and typeability of REA typing. Results: A Sall REA pattern consisted of a variety (1–10) of restriction bands in the range between 12.2 and 48.5 kb and an unresolvable smear of low‐molecular‐weight bands. Forty different Sall REA patterns with an index of discrimination of 0.979 were obtained. Low tupeability (91.04%) was the major limitation of REA typing. Analysis of blinded subcultures of eight Pseudomonas aeruguinosa strains showed the reproducibility of REA typing to be 87.5%. Combined phenotypic typing (O‐serotyping and phage typing) performed on the same group of strains showed comparable discrimination but much lower reproducibility. Isolates selected from five clusters of nosocomial infections in hospitals in the UK were typed by REA typing, and the results show high agreement when compared with conventional phenotypic typing methods in distinguishing between strains. Conclusions: These data underline the usefulness of REA typing enhanced with digitalized data management for the epidemiologic subtyping of clinical Pseudomonas aeruginosa isolates.