TABLE 1.

CHROMagar orientation organism identification by Biomic V3 compared to experienced technologists using visual and conventional methods

Organism(s)a	No. of isolates from:		Agreement between methods (%)	Color likeness (%)b
	Pure cultures	Mixed cultures		Avg	Range
Escherichia coli	44	8	98	71	24-100
Enterococcus species	37	23	88	87	35-100
Klebsiella, Enterobacter, and Serratia group	45	13	95	87	34-100
Proteus, Morganella, and Providencia group	23	3	100	95	67-100
Staphylococcus saprophyticusc	6	1	86	97	80-100
Group B streptococci	4	4	100	86	42-100
Other (staphylococci, yeast, Pseudomonas aeruginosa, others)d	23	12	83d	NA	NA
Total isolates	182	64	94

^aA positive result from a pyrrolidonyl aminopeptidase test (performed with blood agar) is required to distinguish Enterococcus spp. from group B streptococci. Some color overlap is common between these two species, so laboratory protocols should include the performance of PYR when such morphologies are seen. Very young (small) colonies of the Enterobacter group could also be mistaken for Enterococcus due to similar color ranges, although additional incubation results in increased colony size for Enterobacter group strains but not for enterococci, which can be distinguished by a microbiologist.

^bColor likeness is the percentage of color that matches the established color profile for each species. A higher percentage indicates a more typical color on CHROMagar orientation plates. A lower percent color likeness indicates greater heterogeneity in color reactions of a genus or species (e.g., E. coli). NA, not applicable.

^cColony morphology, Gram staining, specimen source, and novobiocin 5-μg disk diffusion (resistance) are required to identify S. saprophyticus. Biomic misidentified one isolate as S. saprophyticus.

^dFour of thirty-five organisms had an incorrect color reading by the instrument, which led to incorrect (i.e., false-positive) identifications.