A MULTICENTER COMPARISON OF METHODS FOR TYPING STRAINS OF PSEUDOMONAS-AERUGINOSA PREDOMINANTLY FROM PATIENTS WITH CYSTIC-FIBROSIS

Typing methods in seven laboratories were compared for their ability t o type reproducibly 200 strains of Pseudomonas aeruginosa, predominant ly from patients with cystic fibrosis (CF). Methods included lipopolys accharide (LPS) serotyping, phage susceptibility typing, bacteriocin p roduction, pilin gene typing, and analysis by restriction fragment len gth polymorphism (RFLP) with a probe upstream from the exotoxin A gene . The methods differed substantially in their capacity to identify uni que typing patterns and to type each strain reproducibly on three occa sions. For strains from patients with CF, the RFLP typing method had t he greatest discriminatory power (30 unique patterns, 105 [70%] of 150 typed reproducibly). LPS serotyping appeared to be equivalent to RFLP typing for discriminating among P. aeruginosa strains from the enviro nment and from clinical sources other than CF patients. RFLP analysis appears to be the best method for typing P. aeruginosa strains with ro ugh LPS (such as from patients with CF). LPS serotyping appears prefer able for other indications as it is simpler to perform.