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Esculin hydrolysis reaction by Escherichia coli
Journal of Clinical Microbiology
|March 1, 1978
Summary
Escherichia coli beta-glucosidase is inducible, not constitutive. Preincubation with esculin or salicin induces enzyme production, enhancing esculin hydrolysis in clinical E. coli isolates over time.
Area of Science:
- Microbiology
- Enzymology
- Clinical Diagnostics
Background:
- Escherichia coli (E. coli) exhibits variable reports regarding esculin hydrolysis.
- Esculin hydrolysis is linked to beta-glucosidase activity, crucial for bacterial identification.
Purpose of the Study:
- To investigate the inducibility of beta-glucosidase in clinical E. coli isolates.
- To determine optimal conditions for detecting esculin hydrolysis in E. coli.
Main Methods:
- Tested 113 fresh clinical E. coli isolates for esculin hydrolysis.
- Assessed hydrolysis with and without preincubation in inducible substrates (esculin, salicin) over 72 hours.
- Utilized a strip test for constitutive glucosidase detection.
Main Results:
- No E. coli strain produced constitutive beta-glucosidase.
- Preincubation with esculin or salicin induced beta-glucosidase activity.
- Esculin hydrolysis and positive strip tests were observed only after induction, increasing with time.
Conclusions:
- The beta-glucosidase in E. coli is inducible, requiring specific substrates for activation.
- Accurate detection of esculin hydrolysis necessitates employing induced cultures or rapid strip tests.
- Recommended methods include light inocula read at 18-24 hours or rapid strip/spot tests.
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