These types of tests are done as specified by the client and in compliance with various guidances, e.g., USP <51> Antimicrobial Effectiveness, USP<61>Microbial Enumeration Tests and USP<62> Tests for Specified Organisms for Microbiological Examination of Nonsterile Products.
Zone of inhibition (ZOI) tests of area in a bacterial lawn may also be done to determine relative growth inhibition by antimicrobial or antibiotic products. The various assays are done to quantify activity, potency, and potential effectiveness of finished or intermediate products and raw materials, pharmaceuticals, topical compounds, antimicrobials, antibiotics, preservatives, and various combination products and devices. Tests are done to assess the presence, numbers and types of microorganisms in association with the tested materials alone or when “spiked” with known quantities of test organisms followed by growth assays. Neutralization validation studies are done to determine test effectiveness and viable microbe recovery which may be quantified as Colony-Forming Units (CFUs).
Test panels are done in liquid and/or agar cultures that are pre-assayed for suitability in supporting growth of selected, known numbers of test organisms. Common test organisms are: Pseudomonas aeruginosa, Staphylococcus aureus, Methicillin resistant S. aureus (MRSA; multiple strains), Bacillus subtilis, Clostridium species, Klebsiella pneumoniae, Streptococcus species, Candida albicans, Escherichia coli, Acinetobacter, or other selected species or clinical isolates requested or provided by clients. Culture plates (liquid and agar; including multi-wells), biofilm assays, serial dilutions of materials and other methods are routinely applied, as appropriate for the material being tested. Types of testing are: aerobic, anaerobic, bacteria, fungi, and sporulating organisms and turnaround times of 5-14 days plus reporting. Numbers of samples, controls and replicates depend on the test design and quantitative and statistical analyses to be done.