Model system using coliphage phi X174 for testing virus removal by air filters

Area of Science:

• Microbiology
• Filtration Technology
• Aerosol Science

Background:

• Air sterilization is crucial in many industries to prevent microbial contamination.
• Bacteriophages are effective surrogates for evaluating the removal of airborne viruses and bacteria by filters.
• Assessing filter efficiency requires sensitive and reliable testing methodologies.

Purpose of the Study:

• To develop and validate short-term and long-term test procedures for evaluating air-sterilizing filter efficiency.
• To determine the removal efficiency of bacteriophage phi X174 by different filter types.
• To compare the performance of a standard industrial filter with novel hollow-fiber membrane prototypes.

Main Methods:

• Development of short-term (15-minute) and long-term (5-6 day) test protocols.
• Utilized bacteriophage phi X174 as a challenge organism.
• Quantified phage reduction using sensitive assays capable of detecting up to a 10(8)-fold decrease.

Main Results:

• Both short-term and long-term tests demonstrated high sensitivity, measuring a 10(8)-fold reduction in bacteriophage.
• The Domnick-Hunter Bio-X borosilicate glass filter achieved a 10(8)-fold removal of viable phage in both test durations.
• A prototype low-flux hollow-fiber membrane performed comparably to the glass filter, whereas a high-flux membrane showed a lower removal efficiency (approx. 99.999%) in short-term tests.

Conclusions:

• The developed test procedures are robust for assessing air filter efficacy against bacteriophages.
• Borosilicate glass filters offer excellent performance for air sterilization.
• Hollow-fiber membrane performance varies with flux, with low-flux prototypes showing promise for high-efficiency air filtration.