Evaluation of novel chromogenic substrates for the detection of bacterial beta-glucosidase.
OBJECTIVE
To evaluate three previously unreported substrates for the detection of beta-glucosidase activity in clinically relevant bacteria and to compare their performance with a range of known substrates in an agar medium.


RESULTS
The performance of 11 chromogenic beta-glucosidase substrates was compared using 109 Enterobacteriaceae strains, 40 enterococci and 20 strains of Listeria spp. Three previously unreported beta-glucosides were tested including derivatives of alizarin, 3',4'-dihydroxyflavone and 3-hydroxyflavone. These were compared with esculin and beta-glucoside derivatives of 3,4-cyclohexenoesculetin, 8-hydroxyquinoline and five indoxylics. All substrates yielded coloured precipitates upon hydrolysis in agar. Alizarin-beta-D-glucoside was the most sensitive substrate tested and detected beta-glucosidase activity in 72% of Enterobacteriaceae strains and all enterococci and Listeria spp. The two flavone derivatives showed poor sensitivity with Gram-negative bacteria but excellent sensitivity with enterococci and Listeria spp.


CONCLUSIONS
Alizarin-beta-d-glucoside is a highly sensitive substrate for detection of bacterial beta-glucosidase and compares favourably with existing substrates. beta-glucosides of 3',4'-dihydroxyflavone and 3-hydroxyflavone are effective substrates for the detection of beta-glucosidase in enterococci and Listeria spp.


CONCLUSIONS
The data presented allow for informed decisions to be made regarding the optimal choice of beta-glucosidase substrate for detection of pathogenic and/or indicator bacteria.
Perry
J D
JD
Department of Microbiology, Freeman Hospital, Newcastle upon Tyne, UK. john.perry@nuth.northy.nhs.uk
Morris
K A
KA
James
A L
AL
Oliver
M
M
Gould
F K
FK
D000880:Anthraquinones / Q000737:chemistry; D015373:Bacterial Typing Techniques; D002863:Chromogenic Compounds / Q000737:chemistry; D003470:Culture Media; D004755:Enterobacteriaceae / Q000201:enzymology / Q000302:isolation & purification; D016983:Enterococcus / Q000201:enzymology / Q000302:isolation & purification; D005419:Flavonoids / Q000737:chemistry; D006090:Gram-Negative Bacteria / Q000201:enzymology* / Q000302:isolation & purification; D016905:Gram-Negative Bacterial Infections / Q000175:diagnosis*; D008087:Listeria / Q000201:enzymology / Q000302:isolation & purification; D001617:beta-Glucosidase / Q000032:analysis*
D000880:Anthraquinones; D002863:Chromogenic Compounds; D003470:Culture Media; D005419:Flavonoids; C010078:alizarin; D001617:beta-Glucosidase; C028288:3',4'-dihydroxyflavone; C041477:3-hydroxyflavone