A cost-effective method for the presumptive identification of Enterobacteriaceae for diagnostic microbiology...

This study evaluated the use of an abbreviated algorithm for the presumptive identification of Enterobacteriaceae isolated from clinical microbiology specimens.

Identification was based on primary isolation of bacterial pathogens on blood, lactose fermentation based on colonial morphology on MacConkey agar, oxidase and indole tests, and a limited number of conventional biochemical tests. The accuracy of the study algorithm was prospectively evaluated against commercial bacterial identification kits, using clinical isolates from blood, urine and superficial wound and tissue sites.

Of 534 isolates, 518 (97%) were accurately identified to genus level. Identification of the study isolates was achieved with a 56% reduction in technologist time and 85% reduction in reagent costs, when compared to the use of a conventional biochemical identification panel. The main limitation of the protocol in the tested bacterial population was that indole-negative Escherichia coli were likely to be misidentified as Enterobacter species.

This protocol may be suitable for the presumptive identification of commonly isolated Enterobacteriaceae from non-sterile sites by diagnostic laboratories in resource-constrained settings.