Reliable Antibiotic Potency Testing for Pharmaceutical Development and Quality Control

Antibiotic potency determination is a cornerstone of pharmaceutical research and development, manufacturing and quality control, serving as the critical link in assessing the activity and efficacy of antibiotic drugs.

Why antibiotic potency testing is necessary

Antibiotic potency testing quantitatively analyzes an antibiotic’s ability to inhibit specific microorganisms, ensuring it meets clinical treatment needs and quality standards.

Because antibiotics vary widely in type, mechanism of action and sensitivity to external factors such as strain sensitivity, culture conditions and experimental methods, standardized potency tests are required to verify biological activity. Pharmacopoeias – including the Chinese Pharmacopoeia (ChP), the United States Pharmacopeia (USP) and the European Pharmacopoeia (EP) – along with regulatory authorities worldwide, explicitly mandate antibiotic potency testing to ensure drug safety and efficacy.

Key challenges

• High requirements for strain standardization: internationally recognized reference strains must be used, with strict controls on storage, subculture and activity verification
• Complex experimental operations: multi-step processes – including microbial culture, standard dilution, sample preparation and inhibition zone measurement – demand high technical proficiency of personnel, operational consistency and precision
• Difficulty in exploring suitable test conditions: variables such as bacterial suspension concentration, dispersion and medium coagulation must be finely tuned for each antibiotic to ensure compliance with the requirements for inhibition zone diameter and/or recovery rate in different pharmacopoeias. Even minor deviations can alter inhibition zone results, making optimization time-consuming and complex
• Poor reproducibility of results: operator technique and strain growth conditions often cause fluctuations, complicating the stable reproduction of results

Why reference strains are required

Reference strains are critical for ensuring comparability and reproducibility of potency testing. With stable genetic characteristics and predictable sensitivity, they provide a reliable benchmark for evaluating antibiotic activity.

In line with USP-NF 81 and the ChP, reference strains must be regularly traced to their source and verified for activity to ensure accuracy and reliability of results.

Controlling experimental errors

To overcome variability and ensure reproducibility, laboratories adopt strict error-control measures:

1. Adherence to validated testing procedures
2. Standardization of incubation temperature, humidity and time
3. Use of automated inhibition zone measuring instruments to eliminate subjective bias and enhance data accuracy

SGS solutions

With comprehensive capabilities and extensive project experience, our experts can rapidly design scientific, compliant testing protocols tailored to different antibiotic types. We have developed a comprehensive suite of development and validation protocols and standardized operating procedures (SOPs), enabling efficient, precise testing services for global clients. To ensure accuracy and reliability, all SGS laboratories use authenticated reference strains as the foundation of antibiotic potency testing.

Operating under cGMP-qualified laboratory requirements, our antibiotic potency testing teams provide customized protocol design, data verification and global regulatory compliance support. Through these capabilities, we help enterprises achieve efficient product release while maintaining the highest standards of safety, efficacy and regulatory alignment.