Microbiology Of Water For Parenteral Products
Why is the microbiology of water important for parenteral products?
Microbes in the water can easily contaminate parenteral products during manufacturing. Thus, knowledge of the microbiology of water is critical to monitor and control the microbial exposure of parenteral products, medical devices, and other healthcare products during manufacturing.
What types of microorganisms can contaminate water?
Numerous microorganisms thrive in water, including prokaryotes (bacteria and archaea) and eukaryotes (fungi). Viral contamination is also a concern. Most microorganisms that contaminate medical and pharmaceutical products are bacteria, yeast, and mold. These microbes may naturally exist in the water supply or can be introduced inadvertently through operational personnel. Below we cover the top microbial water contaminants.
#1: Archaea
Archaea are extremophiles, meaning that they can grow in extreme environments and at extreme temperatures. Most archaea are anaerobic, grow in environments without oxygen. Though archaea may be present in water supplies, archaea do not frequently colonize pharmaceutical water systems and are not a primary concern for microbial water contaminants.
#2: Bacteria
Bacteria are of critical concern for water and product contamination due to their exponential growth rates and ability to exist under adverse conditions. Furthermore, many bacteria are pathogenic (disease-causing) in humans. Bacterial come in two primary flavors, gram-negative and gram-positive. Gram-positive bacteria are capable of creating bacterial spores under stress. Bacterial spore forms are of most concern as spore formation is a dormant bacterial form that is extremely difficult to kill. Bacterial spores can survive high temperatures, ultraviolet irradiation, desiccation, chemical damage, and enzymatic destruction at levels much higher than traditional fully active bacteria. Gram-negative bacteria have an outer wall that houses endotoxins composed of lipopolysaccharide. These endotoxins are pyrogenic, causing fever and sometimes death in humans. Thus, gram-negative bacteria and gram-positive bacteria are problematic for medical devices, parenteral products, and other healthcare items.
Gram-positive bacteria
Gram-positive bacteria are less common in water systems as they require more nutrients than are available in chemically pure, pharmaceutical-grade water. Gram-positive bacteria include spore-forming bacteria, such as Bacillus, and non-sporulating bacteria, like Staphylococcus, Streptococcus, and Micrococcus. Traditionally, non-sporulating bacteria are the bacteria that live on human skin and mucous membranes. Gram-positive bacteria can be detected in pharmaceutical water samples. However, the most likely source of the gram-positive bacterial contamination is due to the faulty aseptic technique of an operator during sampling or testing. Indeed, gram-positive bacterial contamination of pharmaceutical-grade water would most likely be due to contamination outside of the water source itself. In rare cases, the early stages of water purification may contain gram-negative bacteria. However, as mentioned earlier, gram-positive bacteria are not known to colonize water systems. Further, any gram-positive microbes in the early stages of water purification would be removed by one or more of the purification unit operations between early water purification and the final pharmaceutical-grade water product.
Gram-negative bacteria
Gram-negative bacteria are found in soil, water, plants, and animals. As mentioned above, gram-negative bacteria are problematic to medical devices and pharmaceutical manufacturers due to their production of endotoxins. Unlike gram-positive bacteria, gram-negative bacteria prefer the water and often colonize water systems. Gram-negative bacteria are particularly tricky to irradicate from water systems when biofilms form. These biofilms are formed from extracellular matrix material and create bacterial cities that are hard to kill and remove.
Mycoplasma
Mycoplasmas are the smallest of the bacteria family. Unlike gram-negative and gram-positive bacteria, mycoplasmas do not have a cell wall. Thus, mycoplasmas are parasites that exist intracellularly within an animal or plant. Mycoplasmas cannot survive in hypotonic environments, like pure water. Thus, mycoplasmas are not of concern for pharmaceutical-grade water systems.
#3: Fungi
Fungi exist as unicellular (yeast) and multicellular filamentous (mold) organisms. Molds are found in wet and moist environments. However, molds do not colonize large bodies of water often since they require soil and decaying vegetation to grow. Yeasts exist primarily on humans and vegetation. Mold spores provide the most significant contamination risk for water supplies. Mold spores are a part of a mold’s reproductive cycle and (like bacterial spores) are resistant to adverse environmental conditions. Mold spores can spread through the air and contaminate water samples. Neither yeasts nor molds are designed to survive in pharmaceutical water systems. Thus, similar to gram-positive bacteria, the recovery of fungi in a pharmaceutical-grade water system is typically due to faulty aseptic technique during sampling or testing.
#4: Viruses
A virus is a tiny infectious agent. Viruses have no metabolic abilities of their own. Thus, viruses require a host cell to replicate. Human pathogenic viruses can be present in water sources. However, pathogenic viruses are easily destroyed using common purification methods, such as chlorination. Thus, viruses are unlikely to be present in pharmaceutical-grade waters. Additionally, due to the absence of host cells, any viruses in pharmaceutical-grade waters wouldn’t be able to replicate.
#5: Thermophiles
Both bacteria and molds can be heat-loving organisms known as thermophiles. Water-loving thermophiles need special nutrients and conditions to survive. For example, thermophiles want high concentrations of inorganic or organic nutrients and extreme pH in addition to heat. These conditions are not found in the high-purity water of pharmaceutical water systems. Indeed, bacteria that inhabit pharmaceutical water systems are found in cooler locations such as infrequently used outlets, use-point heat exchangers, sub-loop cooling heat exchangers, transfer hoses, and connecting pipes. Thus, the bacteria growing pharmaceutical-grade water systems would be gram-negative versus a thermophile. As a result, thermophilic bacteria are not a concern for hot pharmaceutical-grade water systems.
Summary
Overall, microbes in the water can easily contaminate products during manufacturing. Thus, knowledge of the microbiology of water is critical to monitor and control the microbial exposure of parenteral products, medical devices, and other healthcare products during manufacturing. Common water contaminants include archaea, bacteria, fungi, viruses, and thermophiles. Out of these contaminants, only gram-negative bacteria are of great concern for pharmaceutical-grade water systems. All in all, ensure you choose a contract testing organization that can provide appropriate environmental monitoring and microbiology testing for your product needs.
MycoScience is a contract manufacturing organization specializing in sterile syringe and vial filling. MycoScience also offers Preservative Efficacy Testing, Sterilization Validations, Bioburden Testing, Cleaning Validations, Microbial Aerosol Challenge Testing, Accelerated Aging, Microbiology Testing, Cytotoxicity Testing, Bacterial Endotoxin Testing, EO Residual Testing, Package Integrity Testing & Environmental Monitoring services medical devices and allied industries. MycoScience is an ISO 13485 certified facility.
References
United States Pharmacopeial Convention. <1231> Water For Pharmaceutical Purposes. Rockville, MD, USA. 2021. (USPC <1231>).
