Evaluation of a biochemical test scheme for identifying clinical isolates of Enterococcus faecalis and Enterococcus faecium

Aims: To evaluate the full test scheme of Facklam and Sahm (1995) for the i dentification of clinical enterococcal isolates to genus and species level. Methods and Results: Fifty-nine clinical isolates, previously provisionally classed as enterococci on the basis of just four biochemical tests of Fack lam and Sahm and one other test, were subjected to genus and species identi fication using the full identification scheme of Facklam and Sahm; 98% of t hese strains were confirmed to be enterococci and of these, 69% were identi fied as Enterococcus faecalis and 31% as Enterococcus faecium. Six tests in the scheme (out of 24) gave anomalous or unreliable results for some strai ns, and two gave unexpected results for the majority of strains presumptive ly identified as Ent. faecium. Conclusions: Nine (out of 12) genus tests and nine (out of 12) species test s from the Facklam and Sahm scheme were reliable. Testing for the presence of the Lancefield antigen D was also useful. The majority of presumptive En t. faecium strains gave different results for the sorbitol and raffinose te sts from that expected. Significance and Impact of the Study: This study indicates the level of rel iability for each of the tests in a current enterococcal identification sch eme for differentiating clinical isolates, and showed that two tests gave c onsistently different test results from those expected for Ent. faecium.