Bacillus cereus Detection via PC-PLC Hydrolysis
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Solution Overview
Problem
Current microbiological testing methods for detecting Bacillus cereus group bacteria are hindered by false positives and negatives, long detection times, and the need for complex inhibitor systems, which complicates rapid and accurate identification in food and clinical diagnostics.
Innovation Solution
A method using a reaction medium with a fluorescent PC-PLC substrate and an inhibitor for Gram-negative bacteria, optimized for pH 6.8-8.0 and a detection time of 6-30 hours, allowing for rapid and specific detection of Bacillus cereus group bacteria by adapting the pH and time for substrate hydrolysis, thereby reducing false positives and negatives and simplifying the detection process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional selective plating culture media (PEMBA or MYP) are used for detection, then the detection process is simplified, but false positives and false negatives occur due to ineffective inhibitor systems and absence of key characteristics in certain strains
Solution Approach 1:
The patent changes the pH parameter of the reaction medium to a range of 6.8-8.0, which optimizes the activity of PC-PLC enzyme from Bacillus cereus group bacteria while minimizing background hydrolysis from other Gram-positive bacteria. This parameter adjustment improves detection reliability without adding complex inhibitor systems.
Solution Approach 2:
The patent extracts and utilizes the specific enzymatic activity of PC-PLC (phosphatidylcholine phospholipase C) from Bacillus cereus group bacteria as the basis for detection. By focusing on this specific enzyme activity rather than relying on multiple morphological and metabolic characteristics, the method achieves high reliability while simplifying the detection approach.
2Reliability
If inhibitor cocktails are added to improve specificity, then false positives are reduced, but the growth of target microorganisms is delayed
Solution Approach 1:
The patent adjusts the pH parameter to 6.8-8.0 and optimizes the incubation temperature to 37°C, creating conditions that favor the growth and enzymatic activity of Bacillus cereus group bacteria while suppressing background activity from other Gram-positive bacteria. This eliminates the need for inhibitor cocktails that would delay detection.
Solution Approach 2:
The patent uses a fluorescent substrate (4-methylumbelliferyl choline phosphate) as an intermediary that amplifies the detection signal. The substrate hydrolysis produces a fluorescent product that can be detected at very low concentrations, allowing specific detection without requiring strong inhibitors that would slow bacterial growth.
3Reliability
If complex inhibitor systems are used to limit growth of other microorganisms, then selectivity is improved, but the detection process becomes more complex and time-consuming
Solution Approach 1:
The patent employs parameter changes (pH 6.8-8.0, temperature 37°C) to create a selective environment that naturally favors Bacillus cereus group bacteria. This physiological parameter optimization provides selectivity without requiring complex chemical inhibitor systems, thereby maintaining simplicity in the detection system.
Solution Approach 2:
The patent replaces the mechanical/chemical approach of using inhibitor cocktails with a biochemical approach based on enzyme-specific substrate hydrolysis. The PC-PLC enzyme from Bacillus cereus group bacteria specifically hydrolyzes the fluorescent substrate, providing a simple yet selective detection mechanism that does not require complex inhibitor systems.
4Productivity
If rapid detection is achieved by reducing incubation time, then productivity is improved, but detection sensitivity may be compromised
Solution Approach 1:
The patent uses a fluorescent substrate (4-methylumbelliferyl choline phosphate) as a highly sensitive intermediary that amplifies the detection signal. The fluorescent product generated by PC-PLC hydrolysis can be detected at very low concentrations and short time periods, enabling rapid detection (6-30 hours) without compromising sensitivity.
Solution Approach 2:
The patent optimizes the pH parameter to 6.8-8.0, which maximizes the catalytic efficiency of PC-PLC enzyme. This parameter optimization accelerates the hydrolysis reaction rate, allowing sensitive detection to be achieved within 6-30 hours rather than requiring longer incubation periods that would reduce productivity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method enables rapid, sensitive, and specific detection of Bacillus cereus group bacteria, reducing false positives and negatives, and allowing for automated reading, improving the speed and accuracy of microbiological testing in both clinical and industrial settings.
Implementation Method 1
by hydrolysis of a fluorescent substrate for lecithinase or phosphatidylcholine phospholipase C, hereinafter referred to as PC-PLC
Implementation Method 2
detecting the hydrolysis of the PC-PLC substrate by means of the appearance of fluorescence
Data Source
AI summary
The present invention relates to a method for identifying bacteria of the Bacillus cereus group, comprising the following steps: (a) providing a sample that may contain bacteria of the Bacillus cereus group, a reaction medium comprising at least one fluorescent phosphatidylcholine phospholipase C (PC-PLC) substrate and an inhibitor of Gram-negative bacteria; (b) inoculating the reaction medium with the sample; (c) incubating the inoculated reaction medium; and (d) identifying the bacteria of the Bacillus cereus group by detecting the PC-PLC substrate hydrolysis reaction, in which the pH of the reaction medium and the time necessary for detecting the PC-PLC substrate hydrolysis reaction are adapted such that said hydrolysis reaction by bacteria of the Bacillus cereus group is detected before hydrolysis of the PC-PLC substrate by any Gram-positive bacteria other than those belonging to the Bacillus cereus group, that may be present in the sample.