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Impact of Spreading Time to Recovery Rate in Suitability Test of Solid Agar Media
Hajime Teramura1, Eizo Yasuda1, Yukie Naisei2
1Integrated Diagnostic Solutions, Nippon Becton Dickinson Company, Ltd.
Abstract:
In these days, all agar media used for both pharmaceutical and industrial territories were required to meet performance criteria. There were recovery rates of assigned microorganisms as performance criteria in both pharmacopeia and ISO standards. However, in spreading plate method, there is no concrete spreading time even though it is shown only "as quickly as possible" in ISO standards. In this study, we verified the impact of spreading time in spreading plate method for the quality control of SCD (Soybean Casein Digest) agar plate. When 30s, 60s, and 120s of spreading time were compared using Bacillus subtilis ATCC 6633, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 9027, Staphylococcus aureus ATCC 6538, Candida albicans ATCC 10231, and Aspergillus brasiliensis ATCC 16404, respectively, there is no significant difference in recovery rates of all strains tested between 30s and 60s. However, recovery rates of E. coli and P. aeruginosa were decreased in 120s of spreading time. Our results demonstrated that spreading using plastic rod would be better to complete within 60s in spreading plate method since long spreading time had the impact to recovery rate of certain bacteria.
Insights
For pharmaceutical and industrial agar media quality control, spreading time impacts microbial recovery rates. Spreading Soybean Casein Digest (SCD) agar plates within 60 seconds ensures reliable results for most bacteria and fungi.
Area of Science:
- Microbiology
- Pharmaceutical Science
- Quality Control
Background:
- Agar media performance criteria are essential in pharmaceutical and industrial settings.
- Microorganism recovery rates are key performance indicators in pharmacopeia and ISO standards.
- The spreading plate method lacks standardized spreading times, often citing 'as quickly as possible'.
Purpose of the Study:
- To evaluate the impact of spreading time on the recovery rates of microorganisms using the spreading plate method.
- To determine optimal spreading times for Soybean Casein Digest (SCD) agar plates in quality control.
- To assess the influence of different spreading durations on various bacterial and fungal strains.
Main Methods:
- Comparison of microbial recovery rates using spreading plate method with spreading times of 30s, 60s, and 120s.
- Testing with a panel of microorganisms including Bacillus subtilis, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, and Aspergillus brasiliensis.
- Utilizing plastic rods for spreading the inoculum on SCD agar plates.
Main Results:
- No significant difference in recovery rates was observed between 30s and 60s spreading times for all tested strains.
- A significant decrease in recovery rates for Escherichia coli and Pseudomonas aeruginosa was noted at a 120s spreading time.
- Longer spreading times negatively impacted the recovery of specific bacterial species.
Conclusions:
- Spreading times of up to 60 seconds are acceptable for the spreading plate method when using a plastic rod.
- Spreading times exceeding 60 seconds can lead to reduced recovery rates for certain bacteria, impacting quality control accuracy.
- Standardizing spreading time within 60 seconds is recommended for reliable microbial recovery in SCD agar plate quality control.
