MULTIPOINT IDENTIFICATION OF ENTEROBACTERIACEAE - REPORT OF THE BRITISH-SOCIETY-FOR-MICROBIAL-TECHNOLOGY COLLABORATIVE STUDY

Aims-To evaluate the accuracy and reproducibility of multipoint identi fication schemes in a multicentre trial. Methods-Forty two strains of Enterobacteriaceae were distributed to 22 laboratories for identificat ion by routine multipoint methods. Analysis of results enabled inter- and intralaboratory reproducibility of a variety of tests, and the abi lity of laboratories to identify individual organisms to be determined . Results-Interlaboratory reproducibility of most of the biochemical t ests was acceptable. The least reproducible tests, both within and bet ween laboratories, were citrate utilisation, production of urease and beta galactosidase, detection of motility, and decarboxylation of lysi ne and ornithine. Inconsistent results for these tests were often asso ciated with misidentified strains. Most laboratories performed identif ications satisfactorily. Most isolates (72.1%) were identified correct ly to species level; 9.6% were incorrectly identified, and 6.4% could not be identified at all. The most difficult organisms to identify wer e Citrobacter freundii, Enterobacter cloacae, Hafnia alvei and Aeromon as hydrophila. Strains of Enterobacter, Serratia sp, and Providencia s p were difficult to speciate. Several laboratories could not identify organisms exhibiting at least one atypical biochemical reaction. Concl usion-This study emphasises the need for quality control of media and reagents for multipoint identification of Gram negative enteric bacill i.