Microbiology
Our experienced microbiology team can offer expertise and solutions to your problems
Expert Microbiology Testing
Our microbiology laboratory is equipped to support anti-microbial products from a range of sectors including medical devices, wound care, disinfectants and textiles. A selection of commonly requested standards are summarised below and we are always happy to create customised methods according to our customers needs.
Some of the commonly used bacteria and fungi from our collection are listed below, please enquire if you are interested in a species you don’t see here.
Commonly Used Methods
AATCC Test Method 100 (modified)
Test method for antibacterial finishes on textile materials
The modified AATCC Test Method 100 is requested by the FDA for wound dressings with an antimicrobial claim. A preconditioning step is included to simulate a worst-case scenario and the test dressing is compared to a non-active control after 24 hours incubation with the challenge inoculum. For a full antimicrobial claim 3 Gram-positive, 3 Gram-negative, one yeast and one mould should be tested, with a 4 Log reduction demonstrated for each. Adaptations may be needed to allow for high or low absorption products. Contact us to discuss how we can support with a flexible work package during your screening phase or with generation of robust data for submission.
Required organisms: for an antibacterial claim, 3 Gram-positive and 3 Gram-negative bacterial species should be tested. For an antifungal claim, one fungal species should be tested in addition. For the full antimicrobial claim, all of the above plus one mould.
Sample requirements: a non-active control is required alongside the antimicrobial dressing (sterile)
Contact time: Dependent on recommended wear time of dressing. This may include a preconditioning step
End point: Colony counts
Efficacy: ≥ 4 Log reduction for FDA submission
ISO 22196
Measurement of antibacterial activity on plastics and other non-porous surfaces
ISO 22196 is used to determine the antibacterial activity of plastics and other non-porous surfaces. If efficacy is demonstrated, these products can be used to suppress the growth of bacteria, which can help to keep surfaces clean. This method is suitable for a wide range of materials, providing the inoculum is not absorbed by the material. Staphylococcus aureus and Escherichia coli are referenced in the standard but the method can be adapted for other organisms. Contact us to discuss how we can adapt this method for products with non-standard shapes and sizes.
Required bacteria: Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative), can be adapted for other species on request.
Sample requirements: 5 x 5 cm control and antibacterial specimens (sterile or can be sterilised)
Contact time: 24 hours, other contact times can be added
End point: Colony counts
Efficacy: Not set by standard, to be agreed on by all interested parties
MIC (ISO 20776)
Susceptibility testing of infectious agents and evaluation of performance of antimicrobial susceptibility test devices
The minimum inhibitory concentration (MIC) of an active is the lowest concentration that can prevent bacterial growth under the conditions tested. Assays such as ISO 20776, utilise a dilution series to compare the activity of a large range of concentrations under identical conditions. This method is very adaptable and is useful for the screening stage of a project. For products with two or more actives, a chequerboard assay can be used to calculate the fractional inhibitory concentration (FIC), which determines whether actives are synergistic, antagonistic or indifferent.
Required bacteria: Not specified
Contact time: 18 hours, or as required for bacterial growth
End point: growth/no growth, optical density, colony counts.
ASTM D7907
Determination of bactericidal efficacy on the surface of medical examination gloves
ASTM D7907 determines the bactericidal activity of medical gloves. The gloves of healthcare providers frequently come into contact with contamination from patients or bacteria which can survive for long periods of time on surfaces.
The presence of an organic load can also be included to represent the challenge likely to be present in a healthcare environment. Virologica added the ASTM D7907 method to the scope of their ISO 17025:2017 accreditation in March 2025.
Required bacteria: Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa and Klebsiella pneumoniae
Required contact times: 0, 5, 10 20 and 30 minutes. Other times may be added.
End point: Colony counts and Log reductions and percentage reductions compared to the control glove and challenge inoculum.
Acceptance criteria: Not set by standard, to be set by appropriate agency for regulatory submissions or manufacturer for screening.
ASTM E3383
Standard test method for determining the microbial barrier properties of wound dressings
While absorbing exudate from the wound and (in some cases) reducing the microbial load, many wound dressings also protect the wound from microbial penetration through the dressing. ASTM 3383 is a qualitative test that can determine the microbial barrier properties of a dressing. A dressing is placed onto an agar plate and the non-wound facing surface is inoculated with the challenge organism. If there is no growth underneath the dressing after the chosen incubation time then the dressing is considered to have barrier properties.
Required: Three gram-positive, three gram-negative, one yeast and one mold (examples supplied)
Contact time: 72 hours or as appropriate according to the label claim
End point: Visual assessment of growth underneath the dressing.
Efficacy: Absence of growth indicates barrier properties
All of our microorganisms are sourced from a certified culture collection, propagated in-house and stored cryogenically.
We regularly add to our collection, is there a virus not listed here you would like work with? Contact us.
| Name | Classification | Comments |
|---|---|---|
| Bacillus spizizenii | Gram-positive bacteria | Spore forming bacteria |
| Bordetella bronchiseptica | Gram-negative bacteria | Bacterial causative agent for kennel cough |
| Escherichia coli | Gram-negative bacteria | |
| Enterococcus faecalis | Gram-positive bacteria | |
| Enterococcus faecium | Gram-positive bacteria | |
| Enterococcus hirae | Gram-positive bacteria | |
| Klebsiella pneumoniae | Gram-negative bacteria | |
| Pseudomonas aeruginosa | Gram-negative bacteria | |
| Staphylococcus aureus | Gram-positive bacteria | |
| Streptococcus agalactiae | Gram-positive bacteria | |
| Streptococcus pyogenes | Gram-positive bacteria | |
| Aspergillus brasiliensis | Filamentous fungi | |
| Candida albicans | Yeast |
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