USP Antibiotic Testing

Microtest is a highly experienced provider of USP antibiotic testing services to evaluate the potency of an antibiotic against USP standards in whether a pharmaceutical substance or medical device exhibits antibacterial activity. An antiobiotic present in a sample that is not neutralized can render later testing less useful by making it unlikely a low level of inoculant will be detected. If inhibition is found the test method must be modified to neutralize any antibiotic present.

The zone of inhibition is a qualitative test. Samples — usually 100 g or 100 mL each — are submitted in sterile containers. Our microbiologists cultivate these samples in a nutrient (agar) medium. Any zones wherein bacterial growth is inhibited are measured, and compared to controls.

Microtest also conducts quantitative testing to measure microgram quantities of antibiotics in biological products, drug products, or animal tissue.

Using the cylinder plate method, our specialists determine if the stated potency meets USP standards. Test sensitivity depends upon the assayed antibiotic. Antibiotics adhering to United States Pharmacopeia (USP) reference standards are used to generate a standard curve.

Turbidimetric tests also help quantify the amount of antibiotic in the sample.

The agar growth medium Microtest uses in the relevant tests above consists of ATCC strains, all quality-controlled under our rigorous GMP program to ensure optimal recovery of specific organisms. And as usual with Microtest (though not with many other laboratories in the field), highly experienced, certified regulatory microbiologists perform all antibiotic testing procedures.