Use of the paraffin wax baiting system for identification of Pseudomonas aeruginosa clinical isolates

Pseudomonas aeruginosa is the primary pathogen among the Pseudomonads and i s known for ifs minimal nutritional requirements, capacity to use paraffin as a sole carbon source, and biofilm formation. Because the ability of Pseu domonads to grow on paraffin is not commonly found among human pathogens an d the primary Pseudomonas human pathogen is P. aeruginosa, we studied the a daptation of the paraffin baiting system for the growth and identification of clinical isolates of P. aeruginosa. We also studied the effectiveness of combining a fluorescence assay measuring fluorescein (pyoverdin) productio n and oxidase test with the paraffin baiting assay for P. aeruginosa specia tion. Strains were tested for the capacity to use paraffin as a sole carbon source using the paraffin baiting system with Czapek's minimal salt medium . Of 111 P. aeruginosa clinical isolates tested for using paraffin as a sol e carbon source, 45% exhibited growth on paraffin at 24 h and 76.6% exhibit ed growth on paraffin at 48 h. The ability of the reference strains and cli nical isolates were then tested for their ability to associate with the par affin slide in the presence of an additional carbon source. Of 111 P. aerug inosa clinical isolates tested, 85 strains (76.6%), and 102 (93%) were asso ciated with the paraffin surface at 24 and 48 h. We successfully combined f luorescence and oxidase assays with the paraffin baiting system for identif ication of P. aeruginosa. The simple and inexpensive paraffin baiting syste m is a useful method for the identification and study of P. aeruginosa suit able for both the clinical and research laboratory. (C) 1999 Elsevier Scien ce Inc.