Fast phage detection and quantification: An optical density-based approach.

Area of Science:

• Microbiology
• Virology
• Biotechnology

Background:

• The Double Agar Layer (DAL) method, established in 1959, remains a standard for bacteriophage detection and quantification.
• Existing sophisticated methods are often too complex or costly for routine use in clinical, environmental, and industrial settings.
• There is a need for rapid, simple, and inexpensive bacteriophage detection methods.

Purpose of the Study:

• To develop and validate a novel method for bacteriophage detection and quantification based on optical density kinetics.
• To assess the method's sensitivity, speed, and applicability across various phage and host concentrations.
• To establish optical density kinetics as a viable tool for quantifying phage abundance.

Main Methods:

• The study analyzed optical density changes in bacterial cultures upon exposure to phage-containing samples.
• Experiments involved 90 different combinations of bacteria and phage concentrations.
• Kinetics were monitored to determine sensitivity ranges, assay duration, inhibition percentages, and lysis patterns.

Main Results:

• The developed method can detect as few as 10 phage particles per assay volume within 3.5 hours.
• Assay duration can be reduced to 45 minutes, with a limit of detection of 10^8 plaque-forming units (pfu)/ml.
• The method demonstrates sensitivity and response times comparable to high-end techniques despite its simplicity.

Conclusions:

• Optical density kinetics provide a sensitive, rapid, and cost-effective approach for bacteriophage detection and quantification.
• The method's simplicity allows for potential miniaturization and automation for high-throughput applications.
• This technique is suitable for routine analysis in diverse environments, offering a practical alternative to traditional methods.