You have just finished your swabbing, and now you wait with anticipation for the results to come back from the lab. You receive the results, and you’ve gotten mostly negative or acceptable counts, which is excellent. However, you also received an out of spec (OOS) count for an indicator organism and/or a presumptive positive notification for a pathogen. Now what do you do?
The answer: Best practices suggests vector swabbing. Vector swabbing is an additional investigative process in your Environmental Monitoring Program (EMP). You can begin this type of swabbing once the presumptive positive notification is received, or after a confirmed positive result is received. It is best to immediately quarantine the area where the indicator organism was found to prevent any spread of the contamination.
Think of it like this: you are a detective trying to solve the mystery as to why you got a presumptive positive or OOS result and if the contamination has spread. With each new swab, it brings you another clue closer to your answer or root cause. Discovering the root cause empowers you to conduct aggressive corrective actions such as reenforcing GMPs, changing traffic patterns, repairing and modifying equipment, all of which could help prevent contamination and delays in the future.
The key to vector swabbing is to take additional swabs around the initial positive site to see if the contamination has spread. Best practices suggest using at least five swabs in varying directions away from the initial positive site for 3 consecutive days. Not sure how to take a swab? Check out this video.
When swabbing, select a representative area and sites around the initial positive site, see figure 1. Next, we take swabs of the initial positive site and around the positive site in a circular pattern.
Once the initial positive site and surroundings have been sampled, the area should be appropriately cleaned and sanitized. After sanitizing is completed, additional swabs are then used to sample the initial positive site and surrounding areas again. The reasoning behind this follow-up step is to show that the contamination, if spread, has been eliminated. This process is repeated, without cleaning and sanitizing for an additional 2 days. When 3 consecutive negative results are received, you are free to release the area. The idea behind the 3 consecutive day swabbing and only sanitizing one day instead of all three is to allow the source of contamination to potentially grow again, or to confirm contamination elimination.
When conducting your swabbing, consider the probability of spread, for example, was the positive found in an area that is isolated? Or could the pathogen make its way to the floor and then be spread to your entire facility because of foot traffic? If you would like help developing your program or training on vector swabbing, we would be happy to help.
Keys to Vector Swabbing
- Quarantining the area to prevent further contamination
- Specific written procedures with a minimum number of swabs for your vector swabbing procedure
- Good record keeping
- Sound and effective swabbing sampling technique
You should base your corrective actions on the zone where you found the positive result and performed your investigation. For more zoning information, check out our article “The Benefits of Environmental Monitoring.”
When taking swabs, create an internal sample log such as a physical logbook or an Excel spreadsheet. Trending your EMP data will help you understand and monitor what is happening in your facility’s environment and enable you to make data-driven and risk-based decisions.
Try to record:
- The date and time the samples were taken
- The specific location where the initial sample was taken
- The name of the person who took the samples
- The date you submitted samples to the lab and the results you received
- Any corrective actions that need to be taken
Establishing a Baseline
The first step in making data-driven decisions is to collect your data. If you ask your current lab, they may be able to send you a template. Recording the data you’ve collected can help establish a baseline. Having a baseline for your program allows you to set a population level for each indicator to serve as a target level. This information also helps you establish unacceptable levels, develop key performance indicators (KPIs), and allows you to conduct corrective actions more efficiently. In the table below, we show an example of how you could set up your EMP baseline. Remember that you will need to track indicators and create a unique baseline based on the type of product being handled.
The below chart is from the Pathogen Environmental Monitoring Program (PEM) resource by the Almond Board of California and provides an example for a low moisture tree nut environment.
Although vector swabbing can take additional time, it is a time well spent as it is a powerful tool to determine the spread and elimination of a contaminated site. Vector swabbing enables us to have the power to find, remediate, and control microbes that can harm consumers.
If you need help developing your Environmental Monitoring Program or would like to learn more about vector swabbing give us a call at 916-206-7445.