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Microbiology

Microbiology Testing

Microbial assays involve a variety of tests, from the determination of the numbers and types of organisms naturally present on a product to the assessment of controlled environments. With our comprehensive menu of microbiology services, the Medical Device Testing division provides services across the product development lifecycle and beyond, from R&D and screening to in-process release, validation, and finished product delivery.

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Bacterial Endotoxin (LAL)

Pyrogens are fever-producing materials that most often originate from Gram-negative bacterial cell walls but can also originate as leachates from some chemicals and materials. Pyrogens from bacterial cell walls (the most commonly encountered type of pyrogen) are referred to as bacterial endotoxins and are readily detected by Limulus Amebocyte Lysate (LAL) testing system.

Kinetic Chromogenic
Quantitative assay for the detection of Gram-negative bacterial endotoxin. The presence of the endotoxin causes a color change, and the solution becomes yellow.

Kinetic Turbidimetric
Quantitative assay for the detection of Gram-negative bacterial endotoxin. The presence of the endotoxin causes the lysate to gel and the solution to become cloudy or opaque.

Limulus Amebocyte Lysate (LAL) Test Validation (Inhibition/Enhancement)
Validation of the inhibition or enhancement properties of materials on the test system.

LAL Limit Test – Finished Product Testing
Quantitative determination of endotoxin level for finished devices or other materials.

LAL Liquid Test
Endotoxin testing of water system samples or other non-biological liquids.

Sterility Method Suitability (B/F)

The Sterility Method Suitability Test (B/F) is necessary to demonstrate that there are no substances produced by the test materials (in the specified volume of test medium) that would cause inhibition of bacterial or fungal growth in a sterility test (i.e., a false negative interpretation).

Sterility Method Suitability (Bacteriostatis/Fungistasis)
Sample device or material in the sterility test medium is tested for growth inhibition using the current USP organisms for Soybean-Casein Digest Medium (SCDM) and Fluid Thioglycollate Medium (FTM). (Additional organisms available upon request.)

Sterility Method Suitability Test (B/F) – AAMI
The medical device in the sterility test medium is tested for growth inhibition via AAMI standards using Soybean-Casein Digest Medium (SCDM).

Product Sterility

Product sterility testing is typically performed in the validation of sterilization processes and, in some cases, for monitoring sterilization cycles. Sterility tests involve total immersion, membrane filtration, or a rinse method. The number of samples tested, the growth medium used, and the incubation conditions are based on the particular standard involved – USP, AAMI/ISO or FDA/CFR.

Sterility Immersion
This test is used in sterilization validations (e.g., radiation, EO) and to monitor sterilization loads. This test follows USP, AAMI, ANSI and ISO standards.

Sterility Membrane Filtration
This test is used in sterilization validations (e.g., radiation, EO) and to monitor sterilization loads. This test follows USP, AAMI, ANSI, and ISO standards.

Pyronema Screening
This test is used to determine the presence of Pyronema in sterilized products.

Bioburden

Bioburden testing is an assessment of the numbers and types of microorganisms present on a product and is used for assessment of incoming materials, indication of manufacturing conditions, and support of sterilization validations.

Aerobic Bioburden
Aerobic count

Fungal Bioburden
Mold and yeast counts

Spore Bioburden
Aerobic spore count

Anaerobic Bioburden
Anaerobic count

Total Bioburden Panel Aerobe / Anaerobe / Spore / Fungi
Intended for items for which a full characterization of the bioburden is needed. Additional combined bioburden testing is available.

Bioburden Recovery Efficiency – Repetitive Recovery Method
Devices with a high naturally occurring bioburden are extracted multiple times to determine overall efficiency of the first extraction.

Bioburden Recovery Efficiency – Spore Inoculation Method
Devices with a low naturally occurring bioburden are inoculated with a known quantity of bacterial spores to determine overall efficiency of the extraction process.

Biological Indicators

Biological indicators (BIs) are carriers, such as a paper strip, that are inoculated with a specified level of a particular organism (typically a Bacillus species). BIs are used to validate and/or monitor certain sterilization.

Biological Indicator
Spore strips are transferred from their primary package to Soybean Casein Digest Medium (SCDM) and incubated for the recovery of the indicated organism. BI occurs through three different methods: direct transfer, within product, or self-contained in the product or packaging.

 

Inoculated Product

Inoculated products consist of actual devices or materials that have been inoculated with a specified level of a liquid biological indicator (BI) suspension or a BI carrier strategically placed within the device. Inoculated products are used to validate and / or monitor certain sterilization processes.

USP Biological Indicator: Total Viable Spore Count
Before a new lot of BIs for sterilization load monitoring, the average population per unit should be independently confirmed per USP regulations. This may be conducted with suspension, composition of four BI carriers, or a composite per the manufacturer’s instructions.

 

Microbial Identification

Microbial identification is important for determining sources of contamination as well as the best sterilization techniques.

Microbial Identification
Microbes are identified based on their Gram stain and colony morphology.

Gram Stain
Differential staining technique used to categorize microorganisms based on their cell wall structure. Also shows cellular morphology.

Colony Morphology
Description of an organism’s macroscopic (colony) appearance, including shape, color, and texture.

Gram Stain and Colony Morphology
Description of an organism’s macroscopic (colony) appearance, including shape, color and texture, plus differential staining to determine organism category based on cell wall structure.

Bacterial / Microbial Identification
Identification of a microbial isolate to at least the genus level.

Fungal / Microbial Identification
Identification of a microbial isolate to at least the genus level.

 

 

 

Microbiological Examination

Microbiological Examination Tests, as outlined in USP <61> and <62>, are designed to provide an estimate of the number of viable aerobic microorganisms, both bacteria and fungi, and / or to screen for specific target microbial species.

Microbial Enumeration Tests – Suitability (USP <61>)
This test is designed to demonstrate that the USP <61> procedure used to test the product is suitable for the enumeration of bacteria.

Microbial Enumeration Tests – Testing of Products (USP <61>)
The USP <61> procedure provides a quantitative count of the microbes present on the device or packaging and demonstrates the number of aerobic mesophilic microbes – the total aerobic microbial count and total yeast and mold counts that can be recovered from the test material under the conditions and by the methods outlined in USP <61>.

Tests for Specified Microorganisms – Suitability (USP <62>)
This is designed to demonstrate the USP <62> procedure used to test the product is suitable.

Tests for Specified Microorganisms – Testing of Products (USP <62>)
The USP <62> procedure is designed to demonstrate freedom of the test material from Bile-tolerant Gram-Negative Bacteria, Escherichia coli, Salmonella, Pseudomonas aeruginosa, Staphylococcus aureus, Clostridia spp., and Candida albicans.

Growth Promotion

Prepared media must be tested prior to use to ensure it will support the growth of low levels of microorganisms. We offer this testing per USP requirements as well as customized per client request.

Growth Promotion for Liquid Media (3 or 6 organisms per media per USP <71>)
Sterility Test Medium is tested for growth promotion using the current USP <71> organisms for each media type SCD and/or FTM.

Growth Promotion for Solid / Liquid Media (5 organisms per USP <61>)
Growth Medium is tested for growth promotion using the identified USP <61> organisms.

Growth Promotion per Organism
Growth Medium is tested for growth promotion using selected organisms in specified media.