Salmonella Detection Culture Medium Using Para-Aminobenzoic Acid
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Solution Overview
Problem
Existing methods for detecting Salmonella bacteria in complex samples face challenges in achieving both sensitivity and selectivity, particularly due to the competition of costly substrates like alafosfalin, which are expensive and not conducive to the growth of Salmonella genus bacteria, leading to false-negative results and high costs.
Innovation Solution
A culture medium containing para-aminobenzoic acid as a selective agent, which inhibits the growth of gram-negative bacteria, thereby promoting the detection of Salmonella genus bacteria, combined with chromogenic or fluorogenic substrates and bile salts to enhance selectivity and sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If alafosfalin is used as a selective agent, then selectivity against gram-negative bacteria is improved, but cost increases and Salmonella growth is inhibited leading to false-negative results
Solution Approach 1:
The patent replaces the expensive alafosfalin substrate with a much cheaper selective agent system. The new medium uses affordable components while maintaining selective inhibition of gram-negative bacteria, eliminating the need for costly suicide substrates that compromise Salmonella growth.
Solution Approach 2:
The patent changes the chemical parameters of the selective agent from alafosfalin (a phosphonic acid derivative) to a different chemical system that achieves selective inhibition without the harmful side effects. This parameter change allows Gram-negative bacteria to be inhibited while Salmonella can still grow and be detected.
2Reliability
If alafosfalin is used as a selective agent, then selectivity against gram-negative bacteria is improved, but Salmonella detection sensitivity deteriorates due to growth inhibition
Solution Approach 1:
By replacing alafosfalin with a cheaper alternative selective agent, the patent eliminates the growth inhibition problem that caused false-negative results. The new selective system allows Salmonella to grow normally while still preventing gram-negative bacteria growth, thereby restoring sensitivity.
Solution Approach 2:
The patent converts the harmful effect of alafosfalin (inhibiting Salmonella growth) into a beneficial outcome by using a different selective mechanism that specifically targets gram-negative bacteria without affecting Salmonella. This allows the medium to be both selective and sensitive.
3Difficulty of detecting and measuring
If chromogenic substrates are used to differentiate Salmonella, then detection capability is improved, but false-negative results increase due to masking by non-target microorganisms
Solution Approach 1:
The patent applies preliminary selective inhibition of gram-negative bacteria before the chromogenic differentiation step. By pre-inhibiting non-target microorganisms using the new selective agent, the medium prevents them from growing and masking Salmonella colonies, ensuring that chromogenic signals are not obscured.
Solution Approach 2:
The patent segments the detection process into two distinct functions: (1) selective inhibition of gram-negative bacteria using the new selective agent, and (2) chromogenic differentiation of Salmonella. This segmentation ensures that the two functions do not interfere with each other, maintaining both detection capability and reliability.
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
The use of para-aminobenzoic acid in the culture medium effectively inhibits non-target gram-negative bacteria, allowing for the specific detection of Salmonella bacteria with improved sensitivity and selectivity, reducing false-negative results and costs compared to previous methods.
Implementation Method 1
para-aminobenzoic acid as a selective agent, which inhibits the growth of gram-negative bacteria, thereby promoting the detection of Salmonella genus bacteria
Implementation Method 2
they contain enzyme substrates specifically cleaved or digested by the target bacteria, such that a coloured reaction product is generated
Implementation Method 3
enzyme substrates specifically cleaved or digested by the target bacteria
Implementation Method 4
bile salts are present in the medium to selectively inhibit the gram-positive species
Data Source
AI summary
The field of the invention is the analysis of target microorganisms in a complex sample. The present invention more particularly relates to a culture medium for the detection of at least one target microorganism including: at least one natural or synthetic fermentation or enzymatic activity substrate, and at least one selective agent, which inhibits non-target microorganisms, constituted by para-amino benzoic acid, one of its derivatives or one of their salts, at a concentration of between 0.05 and 1 g/L.