Water Sampling Vs. Air Sampling Methods For Environmental Monitoring
What is aseptic manufacturing?
Aseptic manufacturing is a series of aseptic processes performed in a sterile environment. An aseptic process prevents contamination by the exclusion of microorganisms. Thus, aseptic healthcare products are made and packaged in controlled environments designed to avoid microbial contamination of the product. An aseptic environment is maintained through water sampling, air sampling, and the use of specialized (often automated) equipment that prevents microbial material from technicians, raw materials, or machinery from contaminating medical devices or products. Contamination risk mitigation factors like water and air sampling can interrupt the chain of infection.
What are examples of medical products manufactured in aseptic environments?
- Pharmaceutical sterile products
- Bulk sterile drug substances
- Sterile intermediates
- Excipients
- Medical devices
- Biologics
Why is air sampling important for the environmental monitoring of aseptic manufacturing processes?
Air sampling is vital to ensure that aseptic environments maintain an exceptionally low level of microbial contamination. As a result, the air in aseptic environments is regularly sampled for any viable microbes. There are no USP standard methods for air sampling, and air sampling literature indicates that air-sampling methods are highly variable. Thus, when deciding which air sampling methodology to use, do not assume that similar air sample volumes taken by different methods will produce similar rates of microbial recovery. The top seven methods for sampling airborne microbial contaminants are described in detail below. For more information on the top sources of microbial contamination in manufacturing environments, visit our article HERE.
Why is water sampling necessary for manufactured products?
Microbes in the water can easily contaminate cosmetic or parenteral products during manufacturing. Thus, water sampling and testing are critical to the ongoing environmental monitoring and control for product manufacturing. If water samples are improperly collected, a sample could yield a false-positive or false-negative result. These results could lead to inaction (when corrective measures are needed) or to unnecessary remediation when none is necessary. Therefore, proper water sampling plan creation, water sample collection, and test result interpretation are essential to water quality control and environmental monitoring excellence.
When is air sampling performed?
Depending on cleanroom manufacturing requirements, air sampling of various locations is performed daily to weekly. Isolators are the strictest cleanroom environments.
When is water sampling performed?
Water testing data are used for process control (PC) of the water purification and distribution system or quality control (QC) of the water drawn from the purification system for manufacturing or assembly cleaning. Water testing at various system locations is performed daily, weekly, or monthly depending upon the risk assessment of the purification system and manufacturing processes undertaken.
What are the top methods for air sampling?
#1: Slit-To-Agar (STA) Air Sampler
An attached vacuum powers STA samplers. The air intake is obtained through a slit. Underneath the slit, a slowly revolving Petri dish captures any contaminants on a nutrient agar surface. Airborne Viable organisms will grow on the agar plates. Any captured organisms are later characterized and assessed for the volume and type of microorganisms present. On average, slit-to-agar devices have an 80-liters/minute sampling capacity.
#2: Sieve Impactor
Sieve impactors are a popular option for air sampling. Impactors house a container with a nutrient agar Petri dish. The cover of the container housing the petri dish is perforated with openings through which air flows. These perforations provide the “sieve” through which airborne microorganisms are captured. A vacuum pump draws a specific volume of air through the sieve cover. Airborne viable microorganisms are captured by the agar and grow. Some samplers feature nested sieves that contain perforations of decreasing size. Nested sieves sort viable microorganisms by particle size.
#3: Centrifugal Sampler
Centrifugal samplers are one of the most common sampling methods. Centrifugal samplers have a propeller or turbine that gathers a specific air volume into the unit and propels the air to impact a tangentially placed nutrient agar strip. The nutrient agar strip collects any viable microorganisms and is supported by a flexible plastic base.
#4: Sterilizable Microbiological Atrium
The sterilizable microbiological atrium is similar to the single sieve impactor. The cover of the atrium contains uniform holes of 0.25 inches in size. The bottom of the unit contains a Petri dish with nutrient agar. A vacuum pump controls the movement of air through the unit. Atrium systems offer multiple-unit control centers and remote sampling probes.
#5: Surface Air System Sampler
The entry point of the surface air system has an agar plate. Behind the agar plate, a motorized turbine pulls air through the unit’s perforated cover, over the agar contact plate, and out the back of the motor. Any viable microorganisms are captured on the agar plate. On average, surface air sampling devices have a little over 80-liters/minute sampling capacity.
#6: Gelatin Filter Sampler
The gelatin filter sampler has a vacuum pump with an extension hose that ends in a filter holder. The filter consists of gelatin fibers that retain airborne microorganisms. To assay viable microorganisms, the filter is aseptically removed and dissolved in a diluent. The resulting solution is then plated on an agar medium and assessed.
#7: Settling Plates
Settling plates are the most inexpensive way to assess airborne microbes.
Settling plates work best for determining environments over prolonged exposure times (4- to 5-hour periods). Settling plates are handy when assessing areas where sampling vacuums are intrusive or hazardous to the aseptic operation. However, settling plates are limited in the volume of air being tested. When the microbial level in the air is expected to contain low contamination levels, at least one cubic meter of air should be tested to maximize sensitivity. With settling plates, exposure to one cubic meter of air cannot be guaranteed, and exposure is based on time instead of a calculated airflow volume.
What are the top methods for water sampling?
Unlike air sampling, water sampling methods are the same for process control sampling and quality control sampling. For water sampling, the location of the water sample changes but not the aseptic methodology. Where air sampling is primarily used to control technician-driven contaminants, water sampling is primarily used to monitor and prevent bacterial biofilm formation in pipes or reservoirs. Four categories of water sources are consistently sampled to prevent or troubleshoot contamination of parenteral products. These four water sources are source water (drinking water), pretreatment and purification system water, water from the purified distribution system, and water used for water-for-injection cleaning systems. During the sampling process, valves and ports are flushed vigorously to remove any in-valve biofilms that are not representative of the entire water source.
Summary
Overall, air sampling and water sampling are essential processes for the environmental monitoring of manufactured products. Air sampling determines whether a manufacturing environment is suitable for preventing microbial contamination of medical products during manufacturing and packaging. Since microbes in the water can easily contaminate cosmetic or parenteral products during manufacturing, water sampling is critical to the ongoing environmental monitoring and control for aseptic product manufacturing. Air samples encompass multiple methods. Impaction and centrifugal samplers are the most popular forms of airborne sampling. In contrast, water sampling uses a single method for process control (PC) of the water purification and distribution system or for quality control (QC) of the water being drawn from the system for product manufacturing or assembly cleaning. All in all, ensure you choose a contract testing organization that can provide appropriate environmental monitoring and microbiology testing for your product needs.
Ethide Labs is a contract testing organization specializing in Environmental Monitoring. Ethide Labs also offers Microbiology Testing, Bacterial Endotoxin Testing, EO Residual Testing, Sterility Testing, Cytotoxicity Testing, Bioburden Testing & Package Integrity Testing services for medical device companies and allied industries. Ethide is an ISO 13485 certified facility.
References
United States Pharmacopeial Convention. <1116> Microbiological Control & Monitoring of Aseptic Processing Environments. Rockville, MD, USA. 2021. (USPC <1116>).
United States Pharmacopeial Convention. <1231> Water For Pharmaceutical Purposes. Rockville, MD, USA. 2021. (USPC <1231>).
