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 to type reproducibly 200 strains of Pseudomonas aeruginosa, predominantly from patients with cystic fibrosis (CF). Methods included lipopolysaccharide (LPS) serotyping, phage susceptibility typing, bacteriocin production, pilin gene typing, and analysis by restriction fragment length polymorphism (RFLP) with a probe upstream from the exotoxin A gene. The methods differed substantially in their capacity to identify unique typing patterns and to type each strain reproducibly on three occasions. For strains from patients with CF, the RFLP typing method had the 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 environment and from clinical sources other than CF patients. RFLP analysis appears to be the best method for typing P. aeruginosa strains with rough LPS (such as from patients with CF). LPS serotyping appears preferable for other indications as it is simpler to perform.