COMPARISON OF BACTERIAL IDENTIFICATION SYSTEMS 257 Table III Percent agreement of APT, Flow, and Minitek With Conventional Biochemical Tests for Enteric Cultures Test APT Flow Minitek ADH 90 80 Gelatin 93 H2S 98 100 95 Tndole 98 98 95 LDC 90 95 90 Malonate 98 90 NO3-NO 2 100 100 ODC 98 93 88 ONPG 100 98 Phenylalanine • 98 100 95 Adonitol 98 98 Arabinose 98 98 95 Glucose 100 100 100 Tnositol 85 78 Lactose 85 93 Mannitol 98 Mellibiose 78 Raffinose Rhamnose 98 98 Sorbitol 95 95 Sucrose 95 Simmons Citrate 83 95 Urea 46 93 Voges-Proskauer 98 Total 92% 96% 98 98 93 95 93 49 71 90% a API and Flow use tryptophane deaminase in lieu of phenylalanine. systems had in common, with FL having the highest level of correlation with conven- tional testing for both groups of microorganisms. CAUSES OF MISIDENTIFICATIONS False positive and negative test reactions and inconsistencies in the data base interpre- tation of these reactions caused misidentifications in all systems. Tables V, VI, and VII list the causes of identification differences between conventional methods and the rapid systems for both ENTB and NFB. For API, misinterpretation of the rhamnose test by the data base resulted in the identification of two strains ofSerratia marcescens as S. liquefaciens. API listed S. marcescens as 98% rhamnose negative and S. liquefaciens as 30% rhamnose positive. Rhamnose was negative for both strains however, the identification was still directed toward S. li- quefaciens. Among NFB, Moraxella urethraIls was identified as Pasturella-Actinobacillus species due to a negative tryptophane deaminase (TDA) test. Although API listed all Moraxella species as 100% TDA negative, some species are phenylalanine positive (7) and results of these tests are usually interchangeable. API was also not able to identify any of the three strains of Pseudomonas pseudoalcaligenes evaluated. Two strains were identified as Pasturella-Actinobacillus because the data base could not separate the two

258 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS Table IV Percent Agreement of API, Flow, and Minitek With Conventional Biochemical Tests for Nonfermentative Cultures Test API Flow Minitek Acetamide 91 ADH 91 92 DNase 91 Esculin 91 Fluorescein 85 42øC 83 Gelatin 77 LDC 94 100 NO3-NO 2 94 94 NO2-N 2 87 96 94 ODC 9 ! 100 OF Glucose 74 9 ! 87 OF Lactose 85 OF Maltose 79 70 OF Mannitol 32 9 ! OF Sucrose 64 75 OF Xylose 87 89 ONPG 98 98 96 Phenylalanine a 91 89 Pyocyanin 100 Simmons Citrate 92 89 Starch 92 Urea 55 77 55 Indole 100 100 100 H2S 98 100 Voges-Proskauer 49 Total 80% 90% 88% a API and Flow use tryptophane deaminase in lieu of phenylalanine. groups of microorganisms, as most of the test reactions were negative. The third strain was placed in the other Pseudomonas spp. group, which included P. pseudoalcaligenes and six other microorganisms. As such, the identification was considered incorrect due to the apparent inability of the system to speciate this microorganism or give a smaller number of choices. A strain of ?. stutzeri was identified as Achromobacter species due to a positive urease test. This misidentification was a result of the API data base require- ment that all strains of ?. stutzeri be 100% urease negative. However, ?. stutzeri has been reported to be as much as 18% urease positive (6). With Flow, identification differences among ENTB and NFB were due primarily to false positive and negative reactions. In contrast to the API and MT systems, only one misidentification was due to an information deficiency in the data base of the system. Of the three strains of P. pseudoalcaligenes evaluated, one was identified as Achromobacter xyloseoxidans due to a positive xylose test. The FL data base required P. pseudoalcaligenes to be 100% xylose negative however, xylose could be 14% positive for this organ- ism (6). Misidentifications obtained with MT were due to a combination of false positive and negative biochemical test reactions and data base deficiencies. Among NFB, Acineto-