Colloidal chitin stained with Remazol Brilliant Blue R, a useful substrate to select chitinolytic microorganisms and to evaluate chitinases.

A simple and sensitive method based on the use of colloidal chitin stained with Remazol Brilliant Blue R (RBB) is proposed to evaluate chitinase activity. If this colloidal-stained substrate is included as a carbon source in a liquid medium, this technique allows the selection or the comparison of chitinolytic microorganisms. The colloidal substrate is proportionally solubilized and the dye released is spectrophotometrically quantified at 595 nm. The procedures used for the staining and fixing of RBB in the colloidal chitin, and a comparison with the commercial substrate chitin-azure, are presented. The influence of several physicochemical and enzymatic parameters on the release of dyes is also shown. Both stained substrates were used for studying the effect of pH, substrate concentration, temperature and time on the chitinase reaction of Bacillus thuringiensis Bt-107.

Biotyping of Serratia marcescens strains of clinical origin.

One hundred and ninety five Serratia marcescens strains of clinical origin isolated at the Children's Hospital of Mexico (Hospital Infantil de México) in 1978 and at the National Institute of Pediatrics (Instituto Nacional de Pediatría) in Mexico City in 1977 and from 1988 to 1989, were studied and compared. All strains were identified using the biotyping system described by Grimont and Grimont, without modification. The most numerous biogroup found was A5/8, and the frequencies of isolation of each biotype varied depending on the institution where it was isolated and the period of study.