Selecting a Rapid Microbiological Test

Placing a sample into an automated rapid microbiological tester.

Food producers want to employ rapid methods in order to improve decision making. This implies the rapid method will provide superior information in addition to providing it faster. However, there are a number of indirect issues to consider when deciding to commit to a rapid test method that ultimately influence the method’s overall effectiveness.

The Laboratory Environment

Among the elements to be considered are energy, space, and waste. Many of the existing approaches are culture methods that rely on the incubation of samples in a selective or nutrient medium in order to grow, count, and identify the relevant organism.

Routed in 19th century microbiology, classic culture methods come from an era when almost all processes were manual. For example, due to readability limitations of plate counting methods, multiple replicate plates are necessary. Successive dilutions of the original sample are needed to be able to identify target colonies.

These processes take up significant space in large incubators. Most culture methods are conducted for a fixed time. Therefore, the laboratory incubator ends up being large and energy inefficient. In places were energy costs are still relatively low, this might not appear to be a problem. However, in most of the world, energy cost reduction is a central driver to operating a successful business. When the rapid method is considered, the cost of the energy to produce a result is rarely taken into account.

Similarly, space is at a premium in the food QC laboratory because most of the space is naturally allocated for preparation, processing, production, and packing. As noted, the large incubators needed to operate internal microbiology QC have an impact on the space as well as energy cost.

Bench-top space is a major issue because most labs try to use flexible spaces for multiple tasks. Yet, introducing a piece of analytical equipment usually needs a dedicated space, so it makes sense that “footprint size” is considered for test equipment.

The use of consumables and labware has evolved considerably since the mid-20th century. While there is still a need for reusable glass dishes and containers, much of the developed world has moved to disposable labware. The amount of waste from the average lab operation has increased markedly. Once again, in the case of plating methods, the basic concept of serial dilution and pipetting of samples creates a lot of waste. Any rapid method should hope to mitigate waste generation.

It is interesting to consider alternate testing spaces. Some QC operations would like to test food samples as close to critical control point as possible. However, the constraints of the traditional methods force manufacturers to consider either a microbiology lab or a dedicated space within another functional lab, such as a chemistry or materials lab. QC professionals should seek out rapid methods that can be used outside the traditional lab environment.

A good example of placing a rapid method in a more productive location can be found in meat carcass cleaning and preparation operations. The traditional method is to swab the meat carcass at various stages of processing. This is done in order to ensure no contaminants have infiltrated the cleaning process.

Transporting swabs to the microbiology lab requires the use of transport media and coolers with ice packs to stifle microbial growth. Yet the use of a rapid method that can test on site affords the production and QC staff a number of advantages. One is the very short path to the analytical equipment. Another is the reduction in sampling and transfer steps. With good aseptic technique and adequate training, the measurement goal is achieved without the need for a traditional microbiology lab.

Human Resource Factors

Absolute automation of microbial sampling and analysis is still a theory, at least for the average food producer. People have to conduct sampling, testing, analysis, and recording with the goal of generating consistent, correct, and useful information to maintain quality. Adoption of a rapid method should seek also to reduce manual steps, thereby reducing variability. The technique may be fast, but it cannot be complete unless it removes as many potential error sources as possible.