A rapid method for determining decarboxylase and dihydrolase activity

Area of Science:

• Clinical microbiology
• Bacterial enzyme activity testing

Background:

• Accurate identification of bacterial enzyme activity is crucial for clinical diagnostics.
• Conventional methods for determining decarboxylase activity often require extended incubation periods.

Purpose of the Study:

• To evaluate a rapid method for detecting lysine, arginine, and ornithine decarboxylase activity and arginine dihydrolase activity.
• To compare the performance of the rapid method against conventional Møller decarboxylase broth and an agar-based method.

Main Methods:

• A rapid method was tested on 764 clinical isolates, including Enterobacteriaceae and non-fermentative Gram-negative rods.
• Parallel testing was performed using Møller decarboxylase broth and a 0.3% agar method.
• Incubation intervals were hourly for up to eight hours, with final readings after 24 hours at 37°C.

Main Results:

• The rapid method identified more positive decarboxylase/dihydrolase reactions than both conventional methods in Enterobacteriaceae and non-fermentative Gram-negative rods.
• Lysine and ornithine decarboxylase detection occurred within 2–4 hours, while arginine decarboxylase and dihydrolase required 6–8 hours.
• The rapid method demonstrated comparable accuracy to conventional techniques but with significantly reduced incubation times.

Conclusions:

• The rapid method offers comparable accuracy to conventional techniques for determining decarboxylase activity.
• Shorter incubation times make this rapid procedure highly suitable for routine clinical laboratory use.
• This method enhances efficiency in bacterial identification and characterization.