The N/F and Oxi/Ferm systems for identification of oxidative-fermentative Gram-negative rods: a comparative study

Two commercial systems, the Flow N/F System and the Roche Oxi/Ferm Tube for identification of oxidative-fermentative Gram-negative rods were compared. Both systems were easy to use, but several reactions in both kits were sometimes difficult to interpret. Of 53 reference strains, 70 per cent were identified correctly by the N/F System, whereas the Oxi/Ferm Tube identified 43 per cent. Incorrect identities were obtained in 9 per cent and 26 per cent of cases by the N/F and Oxi/Ferm kits respectively. The remaining isolates required additional tests for definite identification. Of 67 clinical isolates, 27 per cent were identified differently by the 2 systems and only 30 per cent were in complete agreement. The N/F System should be of considerable use to the routine clinical laboratory for the identification of this group of organisms. The Oxi/Ferm Tube requires additional tests frequently and seems to be less accurate in our hands than the N/F System.