Assay of viable aerobic bacteria at 22°C and 36°C

The assay of viable aerobic bacteria (BAR), also known as mesophilic aerobic flora enumeration, allows for the assessment of the overall microbiological quality of a liquid or solid sample. Performed at two incubation temperatures, 22°C and 36°C, it constitutes a reference indicator of microbiological cleanliness, particularly used in the water, food processing, environmental, cosmetics, and surface testing sectors.

Why measure viable aerobic bacteria?
BAR counting doesn't target a specific pathogen, but rather measures the total bacterial load capable of growing in the presence of oxygen. It's an excellent indicator of the overall hygiene of a product, process, or water system. A high count can signal a treatment defect, contamination, a break in the cold chain, or insufficient cleaning. For manufacturers, this control is essential for several reasons: it allows them to monitor the quality of process and bottled water, verify the microbiological stability of a finished product, validate the effectiveness of cleaning and disinfection operations, and meet regulatory or normative requirements. It's an indispensable routine test in microbiological quality control.

The principle of two temperatures:
The unique aspect of this analysis lies in incubation at two complementary temperatures, which provide information on different bacterial populations. Culture at 22°C favors the growth of bacteria of environmental origin (water, soil, natural environment), while culture at 36°C targets mesophilic bacteria, whose optimal growth occurs around body temperature and which can originate from human or animal contamination. Comparing the two results provides valuable information on the probable source of contamination and on the evolution of microbiological quality over time.

How is the analysis performed?
The method involves inoculating the sample onto an agar medium, followed by incubation at a controlled temperature for 44 to 72 hours, depending on the temperature and the applicable reference standard. The colonies that develop are then counted, and the result is expressed in colony-forming units per milliliter (CFU/mL) for liquids, or per gram (CFU/g) for solids. This culture-based enumeration analysis can be supplemented, in the case of an abnormal load, by a step to identify the microorganisms (seepathogen identification by MALDI-TOF or DNA assay for microbial identification).

What matrices and associated analyses are available?
This analysis applies to numerous matrices: process water, bottled water, plant extracts, cosmetics, food products, surfaces, and industrial environments. Depending on your needs, it can be complemented by other microbiological services from our catalog: potability testing for drinking water, or challenge testing to evaluate the effectiveness of a preservative system. To learn more about the rapid identification of microorganisms, see our article on MALDI-TOF mass spectrometry. This service primarily concerns the environmental and food.

Why choose YesWeLab?
At YesWeLab, we collaborate with a rigorously selected network of laboratories, most of which are certified and/or accredited (ISO 17025, COFRAC). These laboratories are chosen based on your specific needs, the matrices to be analyzed, and the required analytical techniques or methods. If you have any particular requirements, please do not hesitate to specify them in your request: our scientific team will do everything possible to respond accurately and promptly. Since 2020, numerous manufacturers, distributors, and engineering firms have entrusted us with the management of their analyses, sending us their samples through our digital platform. To learn more or submit a specific request, contact our team today.