Gram Typing Bacteria Panels in Whole Blood Using a Biphasic Duplex-Loop-Mediated Isothermal Amplification Assay

Area of Science:

• Microbiology
• Molecular Diagnostics
• Clinical Chemistry

Background:

• Bloodstream infections require timely bacterial identification for effective antibiotic treatment.
• Current diagnostic methods (blood culture, Gram staining, PCR) are time-consuming, delaying treatment and contributing to antimicrobial resistance.
• Rapid differentiation of Gram-positive and Gram-negative bacteria can guide initial antibiotic selection.

Purpose of the Study:

• To develop a rapid, culture-free assay for identifying bacterial Gram type directly from whole blood.
• To enable faster clinical decisions in suspected bacteremia cases.
• To provide a sensitive and specific method for detecting common bloodstream pathogens.

Main Methods:

• Development of a duplex probe-based detection of amplification by release of quenching (DARQ) loop-mediated isothermal amplification (LAMP) system.
• Targeting six common bloodstream pathogens, differentiating Gram-negative from Gram-positive bacteria.
• Utilizing a biphasic sample preparation technique for small sample volumes (4 μL).

Main Results:

• The assay identifies bacterial Gram type from a panel of six bacteria with a sensitivity of 1-5 CFU/μL within 1.5 hours.
• Successfully distinguishes between four Gram-negative and two Gram-positive bacterial species.
• Demonstrates potential to replace traditional blood culture methods for initial Gram typing.

Conclusions:

• The developed DARQ-LAMP assay offers a rapid, culture-free method for Gram typing of bacteria in whole blood.
• This technology can significantly reduce diagnostic time, enabling quicker, more targeted antibiotic therapy.
• The assay holds promise for improving patient outcomes and mitigating antimicrobial resistance by guiding early treatment decisions.