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Antimicrobial Preservative Efficacy

Antimicrobial Preservative Efficacy

The Antimicrobial Preservative Efficacy test measures the effectiveness of antimicrobial preservatives added to non-sterile dosage forms or multi-dose containers in order to inhibit the growth of microorganisms that may be introduced inadvertently, either during the manufacturing process or product use.

Antimicrobial effectiveness must be demonstrated on all injections packaged in multiple-dose containers, multiple-dose topical and oral forms, and for other dosage forms which contain antimicrobial preservatives. This test should be performed on all aqueous-based products that include ophthalmic, otic, nasal, oral, irrigation and dialysis fluids.

Testing performed by Nelson Laboratories meets the criteria set forth by the USP General Chapter 51 on Antimicrobial Effectiveness Testing. This test can also be performed to comply with requirements detailed in the European Pharmacopoeia or other international standards. We have extensive experience working with the USP organisms, as well as an excellent understanding of preservative systems and effective neutralization techniques. We provide scientifically sound data by plating in triplicate and offering multiple replicate testing. We also have the resources to test samples with minimal wait time.

Applicable Standards

  • USP 51
  • USP-EP

Test Options

Standard turn around times (TAT) are listed below. Ask an expert for a specific consultation on your product.

Code Test TAT (days) Request Quote
APE105 APE, USP 51: Qualification of neutralization Add
APE110 APE, USP 51: Five organisms (one replicate, in triplicate) 0 Add
APE115 APE, USP 51: 5 orgs. (2 reps, ea. triplicate) 0 Add
APE120 APE, USP 51: Additional organism fee Add
APE205 APE, USP-EP protocol: Qualification of neutralization Add
APE210 APE, USP-EP: 5 orgs. (1 rep., tripl.) 0 Add
APE215 APE, USP-EP protocol: Five organisms (2 replicates, triplicate) 0 Add
APE220 APE, USP-EP protocol: Additional organism fee Add
APE105 - APE, USP 51: Qualification of neutralization
Standard TAT not available for this product
APE110 - APE, USP 51: Five organisms (one replicate, in triplicate)
0 days
APE115 - APE, USP 51: 5 orgs. (2 reps, ea. triplicate)
0 days
APE120 - APE, USP 51: Additional organism fee
Standard TAT not available for this product
APE205 - APE, USP-EP protocol: Qualification of neutralization
Standard TAT not available for this product
APE210 - APE, USP-EP: 5 orgs. (1 rep., tripl.)
0 days
APE215 - APE, USP-EP protocol: Five organisms (2 replicates, triplicate)
0 days
APE220 - APE, USP-EP protocol: Additional organism fee
Standard TAT not available for this product

Sample Specifications

APE110: Minimum 100-120 mL or grams
APE115: Minimum 100-120 mL or grams
APE210: Minimum 100-120 mL or grams
APE215: Minimum 100-120 mL or grams

Study Outline

The Antimicrobial Preservative Efficacy study tests antimicrobial preservatives against the following organisms: Candida albicans (ATCC 10231), Aspergillus niger (ATCC 16404), Escherichia coli (ATCC 8739), Pseudomonas aeruginosa (ATCC 9027) and Staphylococcus aureus (ATCC 6538).

The bacteria are grown on soy casein digest agar plates (SCDA) and harvested on the day of testing. The yeast is grown on sabouraud dextrose agar (SDEX) and harvested on the day of testing. The mold is grown on SDEX and harvested within a week before testing. All organisms are adjusted to approximately 1.0 x 108 colony-forming units (CFU)/mL by diluting in sterile saline.

Individual test samples and a positive control are prepared for each organism. At the 0-hour, the test samples and positive controls are individually inoculated with eachorganism to reach a concentration of 1.0 x 105 – 1.0 x 106 CFU/mL. The volume of the inoculum used is between 0.5% and 1.0% of the volume of the product. The positive controls and samples are assayed immediately after inoculation to determine the challenge level and to provide confirmation that the samples were inoculated.

After the samples have been inoculated and the 0-hour assay has been performed, the samples are stored in a 20 – 25°C incubator for the remainder of the test. At 7 days, 14 days and 28 days after inoculation, the samples are removed from the incubator and assayed for surviving organisms. At each of these time points, an aliquot is removed from the samples, diluted in an appropriate neutralizer and plated according to the standard plate count procedure to determine the remaining concentration of organisms.  The organisms recovered from each time point are compared to those seen in the 0-hour positive control. Changes in the concentrations of organisms are converted to Log reduction values for assessing the antimicrobial effectiveness of the samples, according to the ISO14730, EP or USP 51 criteria.