Environmental Monitoring-Viable Particles: A Primer

by Fran McAteer and Jim Barbato
February 2005

Environmental Monitoring (E/M) is a program designed to demonstrate the control of viable and non-viable particles in sensitive areas. These areas include clean-rooms, filling lines, tank rooms, laminar flow hoods, isolators and laboratories. This article will discuss viable monitoring. Viable testing is for bacteria, yeast and molds. It includes surface monitoring, personnel monitoring and air monitoring. Companies will check their clean room environments to make sure they meet the desired/ required standards. This is called environmental monitoring.

The areas that are sampled in a clean room include:
1. Air - the air in a clean room is checked on a regular basis (e.g., daily, weekly) for particle counts and viable counts (the number of living microorganisms in the air).
2. Surfaces (including floors, walls, tables, etc.) - are checked on a regular basis for viable counts.
3. Personnel - are monitored on a regular basis for viable counts. Personnel monitoring utilizes contact plates to assess microbial contamination of clean room personnel.

How the Air is Sampled in a Clean Room:
1. Settling (Gravity Plates) - Petri dishes containing sterile growth media are exposed (opened) to the
environment. Viable microorganisms which settle onto the media surface will grow after the plates
are incubated. Plates are generally exposed for 30- 60 minutes. Settling plates offer ease of use and
are very cost effective. However, they do not correlate microbial contamination with measured air volume.
2. Air Samplers - There are several types of air samplers. Most draw an exact amount of air into the device whereby the company can determine the number of viable microorganism per cubic foot or liter of air. Air samples are active monitoring devices that do correlate microbial contamination with air flow.

How Surfaces are sampled in a Clean Room:
1. Contact (Rodac) Plates - are special petri dishes which contain sterile growth medium (agar), prepared in a manner that results in the surface of the media protruding above the sides of the plate. The contact plate is pressed against any flat regular surface that needs to be sampled. Any viable microorganisms on the surface will stick to the agar surface and will grow upon proper incubation. This technique estimates the number of viable microorganisms on a surface. Contact plates are easy to use and widely available. Contact plates are not appropriate for irregular surfaces.
2. Swabs - are sterile “Q-tips” which are immersed (dipped) in a suitable sterile liquid. The swabs are then rubbed over the test surface. The microbiologist can determine the number of microorganism on the swab by subculturing to media. Swabs are used for surfaces that are not flat, like certain pieces of equipment. Swabbing is more qualitative than quantitative and is technique-dependent.

How Personnel Are Monitored in a Clean Room:
1. Contact Plates - Personnel in the clean room are monitored for microbial contamination utilizing contact plates. The contact plates monitor areas of the body that may interact with the sterile field or
product exposure areas. These include gloved hands, forearms, shoulders, chest, seat and feet. Personnel monitoring is a good indication of how well personnel are gowning when they enter the clean room. Many companies utilize this testing for proficiency-based training programs for clean room personnel.

Sampling locations are selected based on many factors including potential product exposure areas, processing parameters, equipment design and validation data. Frequency of monitoring depends on product and quality requirements. Sampling frequency changes should be based upon trending analysis and changes in equipment, processing or personnel. A sampling plan describing procedures and identifying sample sites, sampling numbers and sample frequency should be developed. Testing should be performed during static and dynamic situations.

Alert and action levels should be implemented based on your products. An alert is the level of microbial growth that provides an early warning of possible potential problem from normal operating conditions. Exceeding the alert level usually causes the company to increase sampling intensity or frequency. Alert levels are lower than action levels. Companies also establish action levels. An action level is the level of microbial contamination that triggers a planned sequence of corrective actions. The purpose of these corrective actions is to return the facility to acceptable limits of viable microorganisms. The corrective actions will include a determination of what caused the viable counts to be above the acceptable limits and how it will be rectified in the future. Alert and action levels can be adjusted depending on data from the trend analysis. Environmental isolates should be identified to demonstrate what organisms are potential contaminants. These “house organisms” will provide the company with important information in monitoring and preventing potential contamination pitfalls. A disinfectant study should be implemented to demonstrate the effectiveness of the sanitizers used against “houseorganisms.” This effectiveness study exhibits to regulatory agencies that the company is using the correct sanitizer at appropriate dilutions and contact times to combat potential contamination.

Overall the Environmental Monitoring Program provides proactive feedback regarding the cleanliness of the manufacturing operation. It is a proven effective measurement of quality levels for organizations.