How do you perform a sterility test?

Sterility testing: An Overview

An environment is said to be sterile when it is free of any microorganisms that can contaminate it. However, the conditions that can model perfect sterility for an environment are considered very harsh for many active ingredients.

When people think of sterility testing of pharmaceutical products, a container that holds a particular product is sterile when there is no presence of replicating or duplicating microorganisms present. The chances of it being present are about one in a million.

Practically, it is not possible to test every container to rate its sterility for safety and utility. However, a specific set of samples are taken at different times during the various filling processes, the samples representing the lot that is being tested.

These particular sets of samples can model the rest’s conditions to a high degree of accuracy and are used to monitor sterility. Any discrepancies in the sterility rates of the few samples tested can indicate a flaw in the rest of the samples.

In other words, the existence of only a few containers that can have their sterility compromised can suggest that the probability of detecting such contaminated containers among a large number of such samples is very low.

Equipment or sensors having a comprehensive sensitivity are usually used in sterility testing. The standard test is where samples are incubated in a growth medium that allows the growth of many microorganisms, and the rate of replication is detected through visual means.

The sterility testing of pharmaceutical products can also refer to different procedures and measures to prevent the spread of biological contaminants.

The most standard guidelines for sterility testing that many companies usually follow is that of WHO, where the guidelines can be applied across a vast range of products such as blood, cell, tissues, products of biotechnology, and vaccines.

Advanced methods such as the NAT are used to detect specific viruses, although many organizations stick to broader testing procedures. Many tests are also done in combination with cell culture after an authorized validation from the respective authorities.

Sterility tests are essential in the field of microbiology and medicine. The global market for sterility testing is expected to reach 1.18 billion dollars by 2026, showing the significance and importance of this field in modern medicine.

Performing A Sterility Test:

Sterility tests are always essential to ensure that the drugs reaching the clients or customers and patients are always clean and safe. These tests are aimed to detect any microbial growth or contamination in a container or medicinal sample. Listed below are the different reasons why sterility tests must be performed:

  • When the medicinal and pharmaceutical products are stored beyond their expected shelf life or period.
  • When samples are considered high-risk and produced together in large numbers.
  • When multiple doses are prepared for different patients.
  • When medicinal preparations are exposed beyond a certain period between the temperatures of 2°C and 8°C.

Different Methods Of Sterility Testing:

There are two general methods for performing a sterility test: the membrane filtration method and the direct inoculation method.

  • Membrane Filtration Method: Membrane filtration is done for pharmaceutical products that are filterable and is usually the preferred method of testing for many pharmaceutical companies.

The specific sample of the product is allowed to pass through two separate canisters with different filters designed to retain microorganisms. The canisters are then rinsed to ensure that no drug products are left in the filters as it affects the growth of the microorganisms.

The canisters are then filled with sterility growth media that can provide an environment for the development of yeast, bacteria, and mold. The different organisms can grow depending upon the type of growth media used and the temperature at the time of growth.

  • Direct Inoculation Method: As the name suggests, the drug or sample is directly introduced into the growth media. Only a predefined quantity of the sample is used, followed by a dilution process that is strong enough to overcome any antimicrobial properties in the sample product.

Method Suitability:

Method suitability is a set of standards of testing that validates a test process. It ensures that the method chosen works effectively for a particular pharmaceutical product or medicinal sample.

After the containers are allowed to go through an incubation period within a specific temperature range, the samples are tested. Signs of growth or contamination of microbes, turbidity of the container, or cloudiness of the medium are tested either electronically or visually.

If there is no growth, then the drug complies with sterility standards and is safe to use or distribute. Sterility is achieved when the drug has no indications of growth or contamination of any bacterial or microbial nature.

When the sample product fails the sterility tests, the product is not considered sterile and is marked for further investigations. Such drugs are barred from use or distribution until their sterility is proved or achieved through additional testing procedures.