USP <1111> Microbial Contamination Risk Factors Re-Visited

Tony Cundell, Ph. D. Principal Consultant, Microbiological Consulting, LLC

Abstract

This review article discusses the microbial contamination risk factors presented in USP General Informational Chapter <1111> Microbiological Examination of Non-sterile Products: Acceptance Criteria for Pharmaceutical Preparations and Substances for Pharmaceutical Use and other pertinent USP chapterswhen evaluating non-sterile drug products for objectionable microorganisms. Emphasis is given to the exclusion of members of the Burkholderia cepacia complex.

Introduction

One of the challenges for microbiologists working in the pharmaceutical industry is setting up policies and procedure to meet their microbiological quality requirements and exclude objectionable microorganisms from our non-sterile drugs as required by the U.S. Federal Good Manufacturing Regulations 21 CFR 211.113 Control of Microbiological Contamination. The current FDA thinking on microbial release testing, risk associated with Burkholderia cepacia complex contamination of aqueous non-sterile drug products, exclusion of objectionable microorganisms from non-sterile drug products and devices, out-of-specification result investigations, process equipment cleaning, and product recalls may be found in the November 30, 2021 FDA Warning Letter to Dental Technologies, Inc., Lincolnwood, IL addressing their adulterated Paroex 0.12% chlorhexidine oral rinse.

It widely recognized that the risk of microbial contamination varies amongst different dosage forms. Similarly, the presence of microorganisms that are objectionable would vary by dosage form, formulation, microbial quality of the ingredients, manufacturing process, physicochemical attributes, route of administration, and the intended recipient population. USP <1111> Microbiological Examination of Non-sterile Products: Acceptance Criteria for Pharmaceutical Preparations and Substances for Pharmaceutical Use recommends microbiological quality requirements by site of administration for microbial counts and a limited range of specified microorganisms that must be absent from 1 g or mL of a product, but does not list objectionable micro-organisms as this risk-based decision is the responsibility of drug manufacturer, not the FDA as the regulator or the USP as the standard-setting organization. Industry practices may be found in the 2014 PDA Technical Report No. 67 Exclusion of Objectionable Microorganisms from Non-sterile Pharmaceutical and OTC Drug Products, Medical Devices and Cosmetics and more recent book chapters published by the author (Cundell, 2020a and b). However, in addition to the specified microorganisms listed in Table 1 (see USP <1111>), the chapter recommends that the significance of other microorganisms recovered should be evaluated in terms of the following potential risks factors:

• The use of the product: hazard varies according to the route of administration (eye, nose, respiratory tract).
• The nature of the product: Does the product support growth? Does it have adequate antimicrobial preservation? 
• The method of application.
• The intended recipient: risk may differ for neonates, infants, and the debilitated.
• Use of immunosuppressive agents, corticosteroids.
• The presence of disease, wounds, organ damage.

Analysis of the USP <1111> Risk Factors

In this section of the article, the author will discuss the implication of these risk factors as cited in <1111> and whether they should be extended. 

Hazard according to the route of administration

Drug product administered into the eye and sometimes the lower respiratory tract, but not the nose, are marketed as sterile products. For instance, USP <771> Ophthalmic Products – Quality Tests states that sterility testing is mandatory for ophthalmic products making them sterile products. The U.S. Good Manufacturing Practice Regulations 21 CFR 200.50 Ophthalmic Preparations and Dispensers require ophthalmic products be sterile. Inhalation suspension, solutions and aerosols being aqueous were in 20000 re-classifieds by the FDA as sterile products in response to serious infection outbreaks due to the bacterial contamination of some generic inhalation solutions (21 CFR 200.51 Aqueous-based drug products for oral inhalation). Otic products administered into the inner ear or when the eardrum is perforated are usually sterile (see Mucosal Drug Products—Product Quality Tests <4>).

What generalizations may be made about microbial risk by the route of administration? Do oral dosage forms have the least risk and inhalants the greatest risk of microbial infection to the recipient? What is the hierarchy of microbial contamination for non-sterile products? USP <1115> Bioburden Control of Non-sterile Drug Substances and Productslists these dosage forms in descending order based on the invasive of the route of administration only. The risk hierarchy of a partial list of dosage forms is as follows:

• Metered-dose and dry powder inhalants
• Nasal sprays
• Otics
• Vaginal suppositories
• Topicals
• Rectal suppositories
• Oral liquids (aqueous)
• Liquid-filled capsules
• Oral tablets and powder-filled capsules

This generalization may be adjusted based on a risk-based assessment of the physicochemical attributes and intended use of an individual drug product.

The nature of the product 

Questions asked in USP <1111> are does the product support growth and does it have adequate antimicrobial preservation?  Product attributes like water activity, pH, osmolality, salt content, redox potential, presence of chelating agents, single-use or multiple-use packaging, storage temperature, and antimicrobial preservative effectiveness will mitigate the microbial contamination risk. The measurement of the effectiveness of antimicrobial preservative system is described in USP <51>. Some pharmaceutical microbiologists have noted the absence of Burkholderia cepacia from the list of challenge organisms. However, the chapter does recommend adding additional challenge organisms, stating “The standard battery of challenge organisms described in this test need not prevent the inclusion of other species of microorganisms if deemed useful to measure the biological activity of the preservative system for a specific product”.

Aqueous, multiple-use non-sterile drugs must be either inherently antimicrobial or contain a preservative system that meets the product category requirements of USP <51> Antimicrobial Preservative Effectiveness. 

The USP has official test chapters for measurement of water activity <922>, pH < 791> and osmolality <785 > but not redox potential. As a non-sterile product never has a single physico-chemical attribute, what is the relative effectiveness of each of these attributes versus a combination of two or more attributes? Adding the concept of hurdle technology derived from the food industry in Bioburden Control of Non-sterile Drug Substances and Product <1115> would be worthwhile (Leistner, 2000).

The method of application

The role of the method of application is largely unexplored. For example, do leave-on versus wash-off non-sterile products have different risk levels for specific routes of administration? One would expect so. Is there a different microbial risk associated with a topical ointment, cream, gel, lotion, wipe, or spray? Would the difference be related to drug penetration, skin barrier disruption, or retention on the surface? The answers to these questions are largely unknown.

The intended recipient: risk may differ for neonates, infants, and the debilitated.

Immunological efficacy and bio-genomic development varies with age, disease, and medical intervention. It is well known that newborns have an undeveloped microbiome making them more susceptible to invasive pathogens. For example, the strict anaerobe Clostridium botulinum can colonize the intestinal tract of infants between 3 and 6 months old that have poorly developed intestinal microbiome, producing the neurotoxin that results in infant botulism (Brook, 2007). The progress of the colonization of the intestine of a newborn differs as to whether the infant was delivered vaginally or by Caesarean section as lactobacilli derived from the birth canal colonizes the infant intestine (Houghteling and Walker, 2015). Currently, Purified Honey, NF is the only pharmaceutical ingredient with an absence of Clostridium spp. requirement when the ingredient is used products administered to infant less than I year of age. Also, patient treated aggressively with broad-spectrum antibiotics are highly susceptible to invading pathogens such as Clostridium difficile, the cause of chronic diarrhea (Mullish and Williams, 2018). 

What are the relative risk associated with neonates, infants, children, young adults and the elderly? Can chronological age be cited as a risk factor in terms of immunological function? In general, infants less than 1 year old and the elderly greater than 75 years old are included in high-risk groups.

Old age is not solely the consequences of wear and tear, as once believed, but both our genes and the environment in fact regulate aging.  It is characterized by deregulated nutrient-sensing, genomic instability, telomere attrition, loss of protein homeostasis, epigenetic alterations, mitochondrial dysfunction, cellular senescence, stem cell exhaustion, and intracellular communication. Most pertinent to microbial infection in humans are cellular senescence, stem cell exhaustion, immune-senescence, and inflammation (Singh et al, 2019). Table 1 describes the different elements contributing to the immunological response to microbial infection. Newborns have innate immunology and develop adaptive immunology as they are vaccinated or exposed to community infections (Simon et al, 2015).

Should non-sterile products used during invasive medical interventions, e.g., central line catherization, surgery, mechanical ventilation, wound dressing, etc. contain a warning of potential infection or be marketed as single-use sterile products? The recent infection outbreak associated with ultrasound transmission gel is instructive (FDA recall notification). The Canadian manufacturer Eco-Med recalled multiple batches of widely-distributed non-sterile gel that was contaminated with a member of the Burkholderia cepacia complex that caused blood stream infection when used in conjugation with an invasive surgical procedure (FDA Letter to Health Care Providers 2021). According to the CDC, the recalled ultrasound gel was most likely used to guide ultrasonography using the placement of central and peripheral intravenous catheters or transcutaneous procedures like paracentesis. At the time of writing, the cause of the contamination has not been established, but based on the experience of the author, the lack of microbial control of the purified water system, poor equipment cleaning practices, and an inadequate antimicrobial preservative system would be prime candidates.

The reader would be most familiar, due to parenting, with use of the binding gels for pre-natal sonograms, which with non-invasive procedures such as transthoracic echocardiograms, bladder and vascular scans are low risk procedures. Higher risk procedures include those with mucous membrane contact such as trans-esophageal echocardiograms, and trans-vaginal ultra-sonograms to the highest risk with invasive procedures such as trans-rectal prostate biopsy, thyroid biopsy, epi-aortic ultra-sonograms, and stereotactic breast biopsy (Olezkowicz et al, 2012; Rutala and Weber, 2019)

In terms of risk mitigation, invasive procedures should employ single-use sterile ultrasound gel. Other risks include failure to sanitize ultrasound probes between use, replenishing non-sterile ultrasound bottles from a bulk gel container, and using readily contaminated water baths to warm the gel to body temperature.

Use of immunosuppressive agents, corticosteroids

More emphasis should be given to the specific drug, dosage level and duration of treatment in terms of possible promotion of microbial infection. This is well described for corticosteroid usage (Fardet et al, 2016). A recent publication highlighted that low-dose glucocorticoid treatment in patients with rheumatoid arthritis increased infection rates (George et al, 2020). In addition, drugs that repress gastric acid secretion, i.e., e., proton pump antagonists, are an additional risk for oral dosage forms taken with these products because microorganisms are not destroyed by the low pH in the stomach (FDA Drug Safety Communication 2017) and immunosuppression drug use to prevent organ transplant rejection reduce the immunological response to infection (Fishman, 2017). Does the use of the newer monoclonal antibodies, gene and cell therapies, and inflammation-suppressing drugs change the risk of infection? Probably this is so.

The presence of disease, wounds, organ damage.

What are the diseases with increased rate of infection? Are common diseases like cancer, heart disease, diabetes, rheumatoid arthritis, asthma, and chronic obstructive pulmonary diseaseassociated with increased risk? Are they all associated with immunosuppression or are there other risk factors? When is a non-sterile drug product targeted for a specific patient population in contrast to the general population is the risk increased? Can this be identified? Is the effect of organ damage on infection rates well established? 

Additional Questions

The author believes that setting microbial limits, screening for specified microorganisms, and excluding objectionable microorganisms by route of administration does mitigate risk by rejecting non-sterile drugs contaminated with objectionable microorganisms. 

Unfortunately, many drug manufacturers release non-sterile drugs continuant on meeting the narrow compendial requirement overlooking there are not different microbial requirements based on the medical status of the recipient of the non-sterile drug. Should there be so?

Should the risk assessment go beyond genus and species to strain, antibiotic resistance, and other genotypic and phenotypic features? This approach is being taken by the USP <64> Probiotics Tests with the identification of lactobacilli and bifidobacterium strains in probiotics and could be taken to good advantage with microbial contamination of non-sterile drugs. For example, although Escherichia coli is used as a pathogen indicator organism not every member of the genus Escherichia and species E. coli are pathogenic and they are part of the normal human intestinal microbiotia (Yu et al, 2021). With Gram-negative bacterium associated with opportunistic bacterial infections those species and strains with resistance broad-acting antibiotics are a more serious public health threat.

Should additional risk factors be added to the list? For example, risk associated with invasive surgical procedures, the immaturity and/or malfunctioning of the micro-biome, emerging medical treatments, and organ and medical device transplant.

Other Pertinent USP Chapters

Other than the general microbiological requirements recommended in USP <1111>, where does the USP address specific non-sterile dosage forms? The pertinent sections of following chapters are quoted and the content analyzed. 

USP <2> Oral Drug Products – Product Quality Tests

Microbial Content

The chapter states: “The presence of certain microorganisms in non-sterile preparations may have the potential to reduce or even inactivate the therapeutic activity of the product and has a potential to adversely affect the health of the patient. Some liquid oral products can be subject to extreme microbiological control, and others require none. The needed microbial specification for a given liquid oral product depends on its formulation and use and is indicated in the monograph”.

This position is consistent with ICH Q 6a Specifications: Test procedures and acceptance criteria for new drug substances and new drug products Decision Trees #6 and 8 and USP <1112> Application of Water Activity Determination to Non-sterile Pharmaceutical Products.

As aqueous, multiple-use, oral drug products may contain Burkholderia cepacia that may overcome the antimicrobial preservative system, the newer chapter Test for Burkholderia cepacia complex <60> should be cited in <2>.

USP <3> Topical and Transdermal Drug Products—Product Quality Tests

Microbial Limits

The chapter states: “Microbial examination of non-sterile drug products is performed according to the methods given in Microbial Enumeration Tests <61> and Tests for Specified Microorganisms <62>, unless the formulation itself is demonstrated to have antimicrobial properties. Acceptance criteria for non-sterile pharmaceutical products based on total aerobic microbial count and total combined yeasts and molds count are given in Microbiological Examination of Non-sterile Products: Acceptance Criteria for Pharmaceutical Preparations and Substances for Pharmaceutical Use <1111>. “ 

As aqueous topical drug products may contain Burkholderia cepacia that may overcome the antimicrobial preservative system, the newer chapter Test for Burkholderia cepacia complex <60> that became official in December 2019 should be cited in <3>. 

Sterility

The chapter states: “Depending on the use of the dosage form (e.g., products that will be applied to open wounds or burned areas), sterility of the product should be demonstrated as appropriate (see Sterility Tests <71>).”

USP <4> Mucosal Drug Products—Product Quality Tests

Otic Route

The chapter states: “The otic route is characterized by administration of a preparation into, or by way of, the ear. Demonstration of sterility (see Sterility Tests <71>) is not always required for products delivered to the ear. Typically, sterility is required where the product is administered to the inner ear or where the eardrum is damaged. Where sterility is not required, the quantitative enumeration of mesophilic bacteria and fungi that grow under anaerobic (sic) conditions, Microbial Enumeration Tests <61>, or the determination of the absence or limited occurrence of specified organisms, Tests for Specified Microorganisms <62>, may be required.”

This section mistakenly describes the enumeration is conducted under anaerobic not aerobic conditions.

Ophthalmic Route

The chapter states: “The ophthalmic route is to the eye. In addition to the generally necessary tests, the following specific tests for ophthalmic drug products should be considered (see Table 1), for products that are injected or implanted into the eye (see ICH Q3B (R2) Impurities in New Drug Products, 2006). Some of the important product quality tests for products administered by the ophthalmic route are listed below. See Ophthalmic Products – Quality Tests <771> for details and other product quality information. “

• Particulate and Foreign Matter
• Sterility
• Particle Size and Particle Size Distribution
• Antimicrobial Preservative

USP <5> Inhalation and Nasal Drug Products—General Information and Product Quality Tests

Microbial Limits

The chapter states: The microbial quality of dosage forms where indicated in <2> General Quality Tests for Inhalation Drug Products and <3> General Quality Tests for Nasal Drug Products normally is controlled by appropriate validated test(s) and acceptance criteria for total aerobic count, total yeasts and molds count, and freedom from designated indicator pathogens. Acceptance criteria can be expressed on a per-container basis. Refer to Microbial Enumeration Tests <61> Alternative Microbiological Sampling Methods for Non-sterile Inhaled and Nasal Products <610>, and Microbiological Examination of Non-sterile Products: Acceptance Criteria for Pharmaceutical Preparations and Substances for Pharmaceutical Use <1111> for additional information.

The chapter should be revised to use the terminology as found in <62> referencing specified microorganisms not designated indicator pathogens. As aqueous nasal drug products may contain Burkholderia cepacia that may overcome the antimicrobial preservative system, the newer chapter Test for Burkholderia cepacia complex <60> should be cited in <5>. 

Sterility

The chapter states: “All aqueous-based inhalation dosage forms are sterile preparations and should meet the requirements of Sterility Tests <71>. “ 

Recommendations

The author believes that the risk factors emphasized in <1111> should be extended to include the following:

• Non-sterile topical drugs used during invasive medical interventions, e.g., central line catherization, surgery, mechanical ventilation, wound dressing, etc. should contain a warning on the labeling of the potential for microbial infection or be re-classified as sterile products.
• Immunological efficacy and biogenomic development that varies with age and medical intervention.
• Emerging medical treatments, and organ and medical device transplants.
• Microbial risk assessment going beyond genus and species to strain, antibiotic resistance, and other genotypic and phenotypic features

To <1111> Table 1 should be added the absence of B. cepacia complex in 1 g or mL as a specified microorganism for aqueous preparations for oral use, oromucosal use, cutaneous use, auricular use, and nasal use.

As USP chapter <1111> is a harmonized chapter, any changes would need to be approved by the European and Japanese Pharmacopeias. In the interim period, the revisions may be added to the chapter as local requirements and brought up for review at future Pharmacopeial Discussion Group meetings. Another strategy would be to add an expanded discussion of microbial contamination risk and exclusion of objectionable microorganisms to the USP general informational chapter <1115> Bioburden Control of Non-sterile Drug Substances and Products that is not harmonized.

REFERENCES

1. Brook, I 2007 Infant botulism J. Perinatology (2007) 27, 175–180

2. Cundell, T.  2020a Chapter 2 - Microbial Contamination Risk Assessment in Non-sterile Drug Product Manufacturing and Risk Mitigation in Pharmaceutical Microbiological Quality Assurance and Control – A Practical Guide for Non-Sterile Manufacturing. D. Roesti and M. Goverde (editors) J. Wiley & Sons 

3. Cundell, T. 2020b Chapter 11 - Exclusion of Objectionable Microorganisms from Non-sterile Pharmaceutical Drug Products in Pharmaceutical Microbiological Quality Assurance and Control – A Practical Guide for Non-Sterile Manufacturing. D. Roesti and M. Goverde (editors) J. Wiley & Sons 

4. Fardet, L. I. Petersen and I. Nazareth 2016 Common Infections in Patients Prescribed Systemic Glucocorticoids in Primary Care: A Population-based Cohort Study Plos Medicine 13(5): e1002024

5. Fishman, J.A. 2017 Infection in Organ Transplantation. Amer. J. Transplant. 17: 856–879 

6. FDA Drug Safety Communication (2017): Clostridium difficile associated diarrhea can be associated with stomach acid drugs known as proton pump inhibitors https://www.fda.gov/drugs/drug-safety-and-availability/fda-drug-safety-communication-clostridium-difficile-associated-diarrhea-can-be-associated-stomach

7. FDA Letter to Health Care Providers - Stop Using All Eco-Med Ultrasound Gels and Lotions Due to Risk of Bacterial Contamination Sept. 2021https://www.fda.gov/medical-devices/letters-health-care-providers/stop-using-all-eco-med-ultrasound-gels-and-lotions-due-risk-bacterial-contamination-letter-health

8. George M.D., J. F. Baker et al 2020 Risk for Serious Infection With Low-Dose Glucocorticoids in Patients With Rheumatoid Arthritis A Cohort Study. Ann Intern Med. 173(11): 870–878 

9. Houghteling, P.D. and A. W. Walker 2015 Why is initial bacterial colonization of the intestine important to the infant’s and child’s health?  J Pediatr Gastroenterol Nutr. 60(3): 294–307

10. Leistner L. 2000 Basic aspects of food preservation by hurdle technology. Int J Food Microbiol. 55(1-3):181-186

11. Mullish, B.H., and H.R.T. Williams 2018 Clostridium difficile infection and antibiotic-associated diarrhea. Clin. Med. 18 (3): 2370241

12. Murphy, K. and C. Weaver (editors) 2017 Janeway’s Immunobiology Figure 1.5 Garland Science 9th edition

13. Olezkowicz, S. C., P. Chittick et al, 2012 Infections associated with Use of Ultrasound Transmission Gel: Proposed Guidelines to Minimize Risk. Infect. Cont. & Hosp. Epidem. 33(12): 1235-1237

14. Rutala, W.A. and D.J. Weber, 2019 Guidelines for Disinfection and Sterilization in Healthcare Facilities www.cdc.gov/infectioncontrol/guidelines/disinfection/

15. Simon, A.K., G.A. Hollander et al 2015 Evolution of the Immune System in Humans from Infancy to Old Age. Proc. R. Soc. B. 282: 20143085 

16. Singh, P. P., B. A. Demmitt, et al 2019 The Genetics of Aging: A Vertebrate Perspective. Cell 177(1): 200–220. 

17. Yu, D, G. Banting and  N.F. Neumann 2021 A review of the taxonomy, genetics, and biology of the genus Escherichia and the type species Escherichia coli. Can. J. Microbiol. • 31 March 2021 • https://doi.org/10.1139/cjm-2020-0508

Subscribe to our e-Newsletters
Stay up to date with the latest news, articles, and events. Plus, get special offers
from American Pharmaceutical Review – all delivered right to your inbox! Sign up now!