Colony counting on hydrophobic grid-membrane filters

Area of Science:

• Microbiology
• Analytical Chemistry
• Filtration Technology

Background:

• Manual scoring of hydrophobic grid-membrane filters (HGMF) can be subjective.
• Variability in scoring can impact microbiological analysis accuracy.
• Standardized methods are needed for reliable HGMF assessment.

Purpose of the Study:

• To introduce a novel device for manual HGMF scoring.
• To evaluate the inter-analyst and inter-laboratory variability of the device.
• To propose a standardized scoring procedure for routine microbiological analysis.

Main Methods:

• Development of a device to aid manual scoring of HGMF.
• A study involving 41 analysts from six laboratories scoring specimen HGMF.
• Comparison of scores from positive and negative grid-cell counts.

Main Results:

• Score variations were consistently below 2.5% between analysts.
• Good agreement was observed between positive and negative grid-cell counts.
• The device facilitated consistent scoring across different laboratories.

Conclusions:

• The developed device significantly reduces variability in HGMF manual scoring.
• A recommended scoring procedure is suitable for routine microbiological applications.
• The method is effective for HGMF at various saturation levels.