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Blog: A 3-Minute Introduction To Rapid Sterility Testing

Rapid sterility is an alternative test method to the US Pharmacopeia (USP) General Chapter <71>, Ph.Eur. 2.6.1, and JP 4.06 sterility tests that allows for shorter incubation periods and faster results. A typical sterility test has 14 full days of incubation and uses analyst observations to generate results, whereas a rapid sterility test is reduced to just five days of incubation – a 64% reduction in processing time. Rapid sterility also incorporates more sophisticated, computer-generated results, which eliminate observation bias. Alcami utilizes the Milliflex® Rapid System for the rapid sterility test, which uses adenosine triphosphate (ATP) bioluminescence for detection of microorganisms after five days.

USP / Ph. Eur. / JP METHOD
With the traditional harmonized compendial method, the analyst employs a specialized peristaltic pump to pass liquid drug product through dual canisters containing a filter membrane. The analyst rinses the canisters with rinsing fluid, fills the canisters with broth media, and the incubated canisters are manually observed for growth with an incubation period of not less than 14 days. Written observations are used to generate results, along with USP <71> requirements of multiple manual reads. These studies entail the analyst swirling broth media, observing for turbidity, and documenting the visual observations.


  • Lengthy incubation time results in increased holding/inventory costs
  • Requires multiple manual reads based on analyst observation
  • Not ideal for products with short shelf lives and beyond use dates (BUDs)
  • Limits facility throughput

In comparison to the traditional method, the rapid sterility test utilizes similar initial sample preparation. First, the analyst passes the liquid drug product through funnel units using vacuum filtration. The analyst then rinses the funnels with rinsing fluid, applies the membrane to agarose media, and incubates for no less than five days. The incubated membranes are separated from the agar, and the Milliflex® Rapid AutoSpray Station automatically applies two reagents across the membrane surface in order to reveal ATP, if present. When ATP produced by microorganisms is present, the bioluminescent indicator applied during the AutoSpray procedure binds to ATP. Next, the treated membranes are photographed using a specialized camera that detects bioluminescent signal due to presence of ATP. Advanced software generates the final result, determining growth or no growth of microorganisms, based on whether or not ATP from microorganisms was detected. The Milliflex® Rapid System software is 21CFR Part 11-compliant and uses independent analyst log-in credentials that are time and date stamped and captured by an audit trail. With a highly specialized piece of equipment like the Milliflex® Rapid System, colonies will be detected before they are visible to the naked eye.

At Alcami, comparability studies were performed side-by-side between the harmonized USP <71> sterility test and rapid sterility test, meeting the requirements of USP <1223> and Ph. Eur. 5.1.6. The comparability studies included a variety of microorganisms specifically relevant to the sterility test, including the 6-microorganism panel listed by USP <71>/Ph. Eur. 2.6.1, as well as environmental isolates from Alcami’s laboratory environments. Each was stress-treated in alignment with USP <1223>, and recoverability and identification studies were performed post incubation. The results demonstrate statistically equivalent recoverability of microorganism between the rapid and referee methods, generating confidence in the new test methodology.


  • Faster release of drug product, especially valuable in the case of market shortage products
  • Corrective action can be implemented sooner if the product does not meet specification
  • Scientifically demonstrated to have comparable recovery to the harmonized USP <71> reference method
  • Like the reference method, microorganisms detected using the Milliflex® Rapid System can later be identified to the species level
  • Reduced observation bias

The USP test methodology for sterility has been used for many years, serving as a quality verification of drug product sterility. Modern microbiology improves upon the original design by reducing incubation time and utilizing objective computer-based systems for generating results. The Milliflex® Rapid Sterility System is an ideal rapid method that has proven comparability to USP <71>. The use of ATP bioluminescence as an early detection mechanism for microorganisms modernizes the sterility test while leaving microorganisms intact for microbial identification, if detected. For clients looking for alternate ways to obtain fast results, the Milliflex® Rapid Sterility System is a great benefit for sterile drug product testing.


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