[Evaluation of a rapid method for the identification of the Enterococcus genus]

The evaluation of the reliability of a group of three tests: pyrrolidonil-arilamidase, rapid test in NaCl esculin broth and group D antistreptococci agglutination for the rapid identification of the Enterococcus genus were performed.

One hundred fifty-eight strains of streptococci: 110 strains of Enterococcus faecalis, 8 E. faecium, 3 E. avium, 16 Streptococcus intermedius, 7 S. salivarius, 4 S. bovis, 4 S. constellatus, 2 S. sanguis and 1 strain of S. equinus, S. mitis, S. uberis and S. mutans were studied. The tests used were: rapid test in NaCl- esculin broth, pyrrolidonyl-arilamidase and antigroup D streptococcus agglutination (Patho Dx Strep D/PYR; Diagnostic Product Corporation). All catalase-negative gram-positive cocci or coccibacilli which were positive in the three tests were considered to belong to the Enterococcus genus. The usefulness of Gram staining in culture in thioglycolate broth was also studied comparing it with the results obtained with solid medium.

The results of the proposed identification scheme were evaluated calculating different parameters: sensitivity 98%, specificity 100%, positive predictive value, 100%, and negative predictive value 94%. No significant differences were observed between the results obtained with Gram staining with thioglycolate broth and those obtained with solid medium except in the case of the Streptococcus mutans strain.

The application of a combination of tests: pyrroidonyl-arilamidase, antistreptococci group D agglutination and rapid test in NaCl-esculin broth to catalase-negative gram-positive cocci and coccobacilli allows reliable identification in a maximum of three hours of strains belonging to the Enterococcus genus.