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-

COMPARISON OF BACTERIAL IDENTIFICATION SYSTEMS 259 Table V Causes of Identification Differences Between Conventional Methods and API a Cause of Conventional Identification Identification API Identification Differences Enterobacteriaceae E. gergoviae (4) b E. aerogenes URE(- ), CIT(- ), SORB(-) E. gergoviae (1) S. liquefaciens LDC ( - ), SORB( + ), GEL( + ) K. pneumoniae (1) Klebsiella species CIT(- ), URE(-) S. marcescens (2) S. liquefaciens Data base interpretation of neg. rhamnose c Nonj•rmentative Bacilli A. anitratus (1) P. paucimobilis N2( + ), GLU(- ), MEL(-) A. haemolyticus (1) A. anitratus Omission of A. haemolyticus from data base M. urethralis (1) Pasturella- Omission of TDA ( + ) Actinobacillus Moraxella from data base c P. maltophilia (1) P. cepacia ODC ( + ) P. pseudoalcaligenes (2) Pasturella- All test reactions A ct inobaci llus negative P. pseudoalcaligenes (1) Pseudomonas species Data base could not identify organism to species level P. putrefaciens (1) Pseudomonas species H2S (-) P. stutzeri (2) P. aeruginosa ADH ( + ) P. stutzeri (1) Achromobacter species Data base required P. stutzeri to be 100% URE ( - )c a First choice of the systems' spectrum of identifications. b Number in parenthesis indicates the number of strains misidentified. c Information deficiencies in the data base interpretation of biochemical test results contributed to or caused misidentification. bacter anitratus was identified as Cardiobacterium hominis, which illustrated an information deficiency in the system's data base. C. hominis was listed as 100% indole positive and A. anitratus as 100% indole negative. Although the microorganism was indole negative, it was still identified as C. hominis. Two strains of P. aeruginosa were misidentified because of positive urea tests. The MT data base did not allow for any urea positive strains of P. aeruginosa, even though positive urease production as high as 74% has been reported (6). One strain of P. maltophilia was not in the MT data base as a result of false positive anaerobic dextrose reactions and positive sucrose and xylose reactions. MT required P. maltophilia to be 100% sucrose negative and 91% xylose negative. However, reports of studies with conventional methods have found sucrose and xylose to be 92% and 56% positive (6) respectively. DISCUSSION Each of the methods utilized in this study had unique characteristics therefore, one would not expect identifications obtained with one system to correlate 100% with those