Evaluation of novel beta-ribosidase substrates for the differentiation of Gram-negative bacteria.
OBJECTIVE
To synthesize novel substrates for the detection of beta-ribosidase and assess their potential for the differentiation of Gram-negative bacteria.


RESULTS
Two novel chromogenic substrates, 3',4'-dihydroxyflavone-4'-beta-D-ribofuranoside (DHF-riboside) and 5-bromo-4-chloro-3-indolyl-beta-D-ribofuranoside (X-riboside) were evaluated along with a known fluorogenic substrate, 4-methylumbelliferyl-beta-D-ribofuranoside (4MU-riboside). A total of 543 Gram-negative bacilli were cultured on media containing either DHF-riboside or X-riboside. Hydrolysis of DHF-riboside or X-riboside resulted in the formation of clearly distinguishable black or blue-green colonies, respectively. Hydrolysis of 4MU-riboside was evaluated in a liquid medium in microtiter trays and yielded blue fluorescence on hydrolysis which was measured using fluorimetry. beta-Ribosidase activity was widespread with 75% of strains, including 85.6% of Enterobacteriaceae, showing activity with at least one substrate. Genera that demonstrated beta-ribosidase activity included Aeromonas, Citrobacter, Enterobacter, Escherichia, Hafnia, Klebsiella, Morganella, Providencia, Pseudomonas, Salmonella and Shigella. In contrast, strains of Proteus spp., Acinetobacter spp., Yersinia enterocolitica, Vibrio cholerae and Vibrio parahaemolyticus generally failed to demonstrate beta-ribosidase activity.


CONCLUSIONS
The novel substrates DHF-riboside and X-riboside are effective for the detection of beta-ribosidase in agar-based media and may be useful for the differentiation and identification of Gram-negative bacteria.


CONCLUSIONS
This is the first report describing the application and utility of chromogenic substrates for beta-ribosidase. These substrates could be applied in chromogenic media for differentiation of Gram-negative bacteria.
Butterworth
L A
LA
Department of Microbiology, Freeman Hospital, Newcastle upon Tyne, UK.
Perry
J D
JD
Davies
G
G
Burton
M
M
Reed
R H
RH
Gould
F K
FK
D015373:Bacterial Typing Techniques / Q000379:methods*; D002863:Chromogenic Compounds; D003470:Culture Media; D004926:Escherichia coli / Q000145:classification / Q000254:growth & development; D006090:Gram-Negative Bacteria / Q000145:classification* / Q000201:enzymology / Q000254:growth & development; D006868:Hydrolysis; D009699:N-Glycosyl Hydrolases / Q000378:metabolism
D002863:Chromogenic Compounds; D003470:Culture Media; D009699:N-Glycosyl Hydrolases