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 find 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). Begin this type of swabbing as soon as you receive the presumptive positive notification or a confirmed positive result. Immediately quarantine the area where you found the indicator organism to prevent the spread of 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 re-enforcing GMPs, changing traffic patterns, repairing and modifying equipment, all of which could help prevent contamination and delays in the future.
Vector Swabbing
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 you sample the initial positive site and its surroundings, clean and sanitize the area appropriately. After completing the sanitizing, use additional swabs to sample the initial positive site and surrounding areas again. This follow-up step demonstrates that you have eliminated the contamination if it spread. Repeat this process for two more days without cleaning and sanitizing. After receiving three consecutive negative results, you can 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, did you find the positive in an isolated area, or could the pathogen reach the floor and then spread throughout your entire facility due to 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.”
Record Keeping
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:
- Sample date and time
- Sample location
- The name of the person who took the samples
- The date you submitted samples to the lab and the results you received
- Corrective actions 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.
Indicator | Levels | Before Sanitation | After Sanitation |
---|---|---|---|
Enterobacteriaceae | Objective Reasonable Unacceptable | <10 <100 >125 | <10 <50 >50 |
APC | Objective Reasonable Unacceptable | <100 <500 >500 | <10 <100 >100 |
Salmonella | Objective Reasonable Unacceptable | Negative Negative Positive | Negative Negative Positive |
Take additional time for vector swabbing; it is time well spent, as it powerfully helps 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.