Microsart® & Biosart® | Microbial Enumeration Solutions
Safeguarding Quality and Compliance Across Industries
Ensuring microbiological quality in pharmaceutical manufacturing, water testing, and beverage quality control is crucial to meet stringent regulatory standards. Membrane filtration, a preferred method for detecting microbial contamination, provides a fast, accurate, and reproducible solution for bioburden testing, microbial enumeration, and quality control. It is recognized by international regulatory bodies and standards, including:
- Pharmaceutical & Medical device testing: USP <61>, <62>, <1231>, Ph. Eur. 2.6.12, JP 4.05 & ISO 11737-1 – ensuring compliance with microbial limits in raw materials, in-process samples or intermediates, surfaces of the product or the packaging, and finished non-sterile pharmaceutical products.
- Water and beverage testing: ISO 7704, ISO 8199 – ensuring microbial quality in drinking water, process water, bottled water, soft drinks, beer, wine, dairy, and fruit juices to prevent spoilage.
Microbial enumeration is also essential for environmental monitoring of surface water (US EPA Method 1103.1), cooling towers, and other industrial water sources. Additionally, cosmetics and personal care products undergo microbial testing (ISO 17516) to prevent contamination risks.
By filtering liquid samples through a 0.45 µm or 0.22 µm microporous membrane, microbial contaminants are retained and cultured for enumeration, making membrane filtration a superior alternative to the Most Probable Number (MPN), pour plate, or spread plate techniques.
Membrane filtration offers high sensitivity and accuracy, enabling the detection of even low microbial loads by isolating individual colonies for precise enumeration. Capable of processing both high and low microbial load samples, it ensures comprehensive testing while also removing inhibitory substances, such as bacteriostatic or bactericidal agents that could interfere with microbial growth. Additionally, the technique minimizes contamination risks with disposable single-use systems and semi-disposable reusable workflows, reducing cross-contamination between samples.
After filtration, the captured microorganisms are transferred onto selective and non-selective culture media to promote growth and enable accurate enumeration as colony-forming units (CFUs). The choice of medium depends on the target microorganism and application. Soybean-Casein Digest Agar (SCDA), also known as Tryptic Soy Agar (TSA), supports the growth of a broad spectrum of aerobic bacteria, making it ideal for Total Aerobic Microbial Count (TAMC), while Sabouraud Dextrose Agar (SDA) is optimized for detecting Total Yeast and Mould Count (TYMC). For water testing, R2A Agar is used to recover stressed or slow-growing bacteria, ensuring a comprehensive assessment of microbial presence. Meanwhile, m-Endo Agar LES and m-FC Agar are specifically formulated for the detection of coliforms and fecal coliforms in water samples. The use of gridded membrane filters further enhances microbial enumeration by providing clear reference points for counting microbial colonies, ensuring precise and reliable results.
Choose from a comprehensive range of filtration solutions at Sartorius, including membrane filters, filtration consumables, culture media reagents, filtration manifolds, pumps, and supporting accessories, all designed to safeguard your manufacturing processes and ensure the health and safety of patients and consumers.
Resources for Microbial Enumeration
Microsart® @filter 100 | 250 — Sterile single-use filter units featuring a click-fit closure
PDF | 246.4 KB
Frequently Asked Questions
• Plate Count Method (Direct Plating): This method is commonly used for both solid and liquid samples, including raw materials and finished products. It involves spreading the sample onto an agar plate, allowing microbial growth, and then counting the resulting colonies to estimate microbial load.
• Membrane Filtration: Membrane filtration is ideal for liquid samples with low microbial concentrations, particularly in water, pharmaceuticals, and cosmetics. It allows for the analysis of larger sample volumes and is effective in detecting low levels of contamination.
• Turbidimetric Method: This method relies on the increase in turbidity (cloudiness) caused by microbial growth in a liquid medium. While it provides an estimate of microbial load, it does not offer a direct enumeration of CFUs.
• Probable Number (MPN): MPN is a statistical method that estimates the number of microorganisms in a sample based on dilution series and the presence or absence of microbial growth. It provides an estimate rather than a direct count and is generally less precise than other methods.
- Sterility testing is a qualitative assay performed to ensure that a product is free from viable microorganisms, typically using methods like direct inoculation or membrane filtration in closed filtration systems. It confirms the absence of microbial contamination in sterile products.
- Bioburden testing is a quantitative assay and measures the microbial load (quantity of microorganisms) present in raw materials, intermediate products, non-sterile products, or sterile products before sterilization. It helps assess contamination levels but doesn’t guarantee sterility.
- The USP <61> focuses on microbial limits for non-sterile products and raw materials, specifying the procedures for determining the microbial load (or bioburden).
- The USP <62> is concerned with bioburden testing for sterilized products and serves as a pre-sterilization validation step, ensuring that contamination levels are low enough to allow sterilization to be effective. Results of bioburden testing help establish the appropriateness.
Soybean-Casein Digest Agar (SCDA), also known as Tryptic Soy Agar (TSA), supports the growth of a broad spectrum of aerobic bacteria, making it ideal for Total Aerobic Microbial Count (TAMC), while Sabouraud Dextrose Agar (SDA) is optimized for detecting Total Yeast and Mold Count (TYMC). For water testing, R2A Agar is used to recover stressed or slow-growing bacteria, ensuring a comprehensive assessment of microbial presence. Meanwhile, m-Endo Agar LES and m-FC Agar are specifically formulated for the detection of coliforms and fecal coliforms in water samples.
