USP 60, USP 61, and USP 62 – Testing standards comparison

Comparative analysis among the standards USP 60, USP 61 and USP 62 is indispensable, with each test targeting different microorganisms and serving different purposes in ensuring the safety of products. Understanding their differences through a testing standards comparison helps manufacturers identify which tests are best suited for their products. It also helps in meeting all regulatory requirements while giving comprehensive microbial protection to ensure no potential microbial threats go unaddressed, for safeguarding the consumer.

Overview of USP 60, USP 61, and USP 62

USP 60, titled “Microbiological Examination of Nonsterile Products: Tests for Burkholderia cepacia Complex,” describes a microbiological examination of nonsterile products for the detection of Burkholderia cepacia complex. This pathogen is of particular concern since it can survive with a bare minimum of nutritional requirements and is associated with infections among immunocompromised individuals.

USP 61, or “Microbiological Examination of Nonsterile Products: Microbial Enumeration Tests,” provides guidelines for quantitative enumeration of mesophilic bacteria and fungi that can grow under aerobic conditions. This standard is applied to determine whether a product meets the established specifications for microbial quality.

USP 62, known as “Microbiological Examination of Nonsterile Products: Tests for Specified Microorganisms,” is focused on detecting specific objectionable organisms in non-sterile products, such as Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Salmonella and Candida albicans.

Scope of products

Each of these standards applies to a wide range of non-sterile products in the pharmaceutical and cosmetic industries, emphasizing the need for a comprehensive testing standards comparison:

• USP 60 is particularly relevant for water-based products, especially those used by vulnerable populations, such as patients with cystic fibrosis or other immunocompromised conditions. Examples include nasal sprays, inhalation solutions and certain topical products.

• USP 61 covers a broad spectrum of non-sterile dosage forms of products such as tablets, capsules, ointments and creams and preparations, along with active raw materials. The standard applies to any product in need of assurance that microbial load does not exceed acceptable limits.

• USP 62 applies to products that have the probability of contamination with one or more harmful fungi, bacteria, virus, or other forms of microbial life presenting a hazard to health. This category mainly comprises oral and topical dosage forms, cosmetics and some raw materials, which might have a high risk of contamination.

Purpose and application

Each one of these standards has a certain application in the field of microbiological testing, further emphasized in testing standards comparison:

• USP 60 primarily focuses on the detection of Burkholderia cepacia complex. The test holds significant value for products that are prone to be contaminated with this microorganism. For example aqueous-based products and those used by immunocompromised individuals.

• USP 61 aims to provide a broader assessment of the microbial content in non-sterile products by enumerating the total aerobic microbial count (TAMC) and total combined yeasts and molds count (TYMC). This assessment is important in ensuring that the overall microbial load is within acceptable limits.

• USP 62 complements USP 61 by targeting specific pathogens that, although small in quantity, can put a person’s health at great risk, The test ensures that these products are well out of the reach of harmful microorganisms known to cause infections.

Similarities between USP 60, USP 61 and USP 62

Despite their differences in focus, USP 60, USP 61 and USP 62 share several commonalities that are important in testing standards comparison:

1.Objective of Ensuring Safety

All three standards are designed to ensure the consumer safety against microorganisms of non-sterile pharmaceutical and cosmetic products. In other words, the tests detect and quantify microorganisms to avoid the release of adulterated products in the market.

2.Emphasis on Sample Stability

Each standard presses the concern on the importance of maintaining the stability of the sample during microbiological testing. 

3.Reliance on selective media and techniques

USP 60, USP 61 and USP 62 all rely on the use of selective media and techniques to isolate and identify microorganisms. Detecting the test organism among the other microflora ensures the sensitivity of the test.

4.Regulatory compliance

For marketing the manufactured products in regions like the United States, the manufacturers must comply with the USP guidelines. 

5.Flexibility in methodology

Although the standards provide detailed specifications, they allow the use of other alternative methods which are validated. This flexibility is important for manufacturers who may need to tailor their testing procedures to accommodate their different product types and formulations.

Test organisms

The testing methods include certain microorganisms and understanding this difference is important when performing testing standards comparison:

Common organisms: The microorganisms Staphylococcus aureus, Pseudomonas aeruginosa and Candida albicans are addressed in both USP 61 and USP 62, in different contexts.

Unique organisms: Burkholderia cepacia complex is unique to USP 60, while Escherichia coli and Salmonella spp. are uniquely targeted by USP 62.

USP 60, USP 61, and USP 62 – Testing standards comparison

Differences in sample preparation and testing

Sample preparation under USP 60, USP 61 and USP 62 varies depending on the requirement of the specific test. This is a key point in testing standards comparison.

• USP 60 : Product samples contaminated with Burkholderia cepacia shall be prepared in such a way that conditions will be optimal for the recovery of the organism. Generally, the use of diluents and pre-enrichment steps specifically designed to neutralize inhibitory substances in the product may be required.

• USP 61 places great importance on the need to neutralize any antimicrobial activity that may be present in the sample to prevent false-negative results. This may be through neutralizing agents or dilution to decrease the level of the antimicrobial agent.

• USP 62 also requires neutralization, but it is more concerned with the preparation of the sample in a manner so as not to introduce contaminants or interfere with the detection of the particular organisms being tested .

Key test methods

Standard test methods vary with the nature of the microorganism targeted and the type of product tested. Understanding these variations is crucial in testing standards comparison.

USP 60 – The method of culturing Burkholderia cepacia complex from samples in USP 60 relies on the technique of selective enrichment. The procedure consists of incubation of the sample with a selective medium that encourages the growth of Burkholderia cepacia while suppressing the growth of other bacteria. The sample is plated out onto a differential medium to confirm the presence of the pathogen.

USP 61 – USP 61 describes three main methods for microbial enumeration, namely the membrane filtration technique, plate count technique and most probable number technique. Each of these methods differs in its application based on the product type and microbial detection needs. Making them essential considerations in testing standards comparison:

• Membrane filtration: The sample is filtered through a membrane, which retains the microorganisms and is then cultured on an agar medium. It is especially useful for products that contain low numbers of microorganisms.

• Plate-Count method: The plate count method is generally applied to products with higher microbial loads. By preparing a particular dilution, the sample is then subjected to agar plating. The grown colonies on the agar plate are counted to arrive at an estimate of the number of microorganisms in the original sample.

• MPN method: This method applies when the sample under analysis has a very low microbial load. It thus involves serial dilution of the sample in a series of tubes containing the growth medium. Presence or absence of growth in these tubes is used statistically to estimate the microbial count.

USP 62 relies on specific enrichment, isolation and identification techniques for each microorganism in question. For example, the absence or presence of Staphylococcus aureus is detected by incubation in a selective medium followed by subculturing on a differential medium to confirm its presence. 

Interpretation of results

The interpretation of results differs across the three standards, reflecting the distinct objectives of each test, making it a crucial aspect of testing standards comparison.

• USP 60 results are generally reported as either presence or absence of Burkholderia cepacia complex. A positive result indicates the product is unsafe for use, particularly in vulnerable populations.

• USP 61 provides quantitative results in regard to acceptable limits of microbial load in the product. The results are often expressed as colony-forming units, CFU, per gram or milliliter of the product.

• USP 62 test is also reported as positive or negative, but the result in this case refers to the presence of the respective target pathogens. Any product which turns out to be positive for one or more target microorganisms is, therefore, declared non-compliant on the grounds of safety.

Passing criteria

• USP 60: Passes if no Burkholderia cepacia complex is detected in 10 g or 10 mL of the sample.

• USP 61: Passes if TAMC and TYMC are within specified limits (e.g., ≤1000 CFU/g for TAMC in oral products).

• USP 62: Passes if specified pathogens like S. aureus and E. coli are absent in the required sample size.

The USP 60, USP 61 and USP 62 are three important testing standards for assessing microbial safety of non-sterile products in the pharmaceutical and cosmetic industries. Each of the standards addresses a different aspect of microbial quality, whether regarding the detection of specific pathogens or the enumeration of total microbial load. Adherence to these standards gives the ability to manufacturers to protect public health, ensure compliance with the regulations and maintain consumer trust. Testing standards comparison can assist the manufacturers to choose the test best suited for them.

At Microbe Investigations Switzerland (MIS) , we understand the complexities and challenges of microbiological testing. Contact us today to learn how we can support your testing and validation needs, ensuring the safety and efficacy of your products.