An investigation of three commercial methods for rapid identification of non-enteric gram-negative rods. Application on Pseudomonas paucimobilis and some other Pseudomonas species.

Abstract

Three commercial systems for the identification of non-enteric gram-negative rods were compared with conventional bacteriological methods as reference. The three systems were the API 20 NE, BIO-TEST ID-Trident, and ROSCO Diagnostic Tablets. The systems were tested on a set of 47 strains from the genus Pseudomonas, with the emphasis upon the yellow-pigmented species. The overall identification accuracy was 97% with the API, 19% with the BIOTEST and 68% with the ROSCO system. The API system was thus reliable, and it presented no major practical problems. The BIOTEST system was very handy. The main reason for the low accuracy was an error in the code book. The ONPG reaction was depicted as negative in the species P. paucimobilis. A positive ONPG test is a keymark in this species and 76% of the 20 strains of P. paucimobilis included in this investigation were also found positive with the BIOTEST system. The ROSCO tablets are convenient if the result of single reactions is desired. The time consumption per strain was 5.4, 4.4, and 6.2 min for the API, BIOTEST, and ROSCO systems respectively.