Differentiation of Vibrio cholerae O1 isolates with biochemical fingerprinting and comparison with ribotyping

The Phene Plate (PhP) system is a commercially available typing system based on the measurements of kinetics of selected biochemical reactions of bacteria grown in liquid medium in 96-well microplates. The system uses numerical analysis to identify biochemical phenotypes among the tested strains. In the present study, a set of 16 discriminatory tests were used to differentiate 117 strains of Vibrio cholerae O1 from MExico and Bangladesh. The stability of PhP types of 16 isolates under different storage temperatures and after repeated subcultures were also evaluated. The PhP system had a reproducibility of 95%. Storage either at +4 degrees C or -70 degrees C, did not affect the reactions of the isolates, whereas 4 strains (25%) stored at room temperature and 5 strains (31%) subjected to 30 consecutive subcultures, exhibited minor changes in their biochemical reactions. Endemic isolates of V. cholerae O1 from Bangladesh were more diverse (diversity index = 0.84 to 0.93) than epidemic isolates from Mexico (diversity index = 0.73). Using a collection of 33 heterogeneous isolates of classical biotype of vibrios, PhP typing and ribotyping were compared. PhP typing discriminated more types (n = 23) than ribotyping (n = 5), whereas a combination of both yielded 27 types. The PhP system appears to be a simple, reliable and highly discriminating method for typing of V. cholerae, and may prove especially useful as a first screening method in epidemiological studies of V. cholerae.