CFU Count of Active Microorganisms

Colony-forming units (CFU) counting has been used for microorganism quantification, especially active bacteria, since the late 19th century approved by United States Pharmacopeia. Over the years, Creative Biolabs has accumulated further experience in providing probiotic bacteria enumeration services by CFU counting.

Active Microorganism Enumeration

The detection and enumeration of viable microorganisms are fundamental to microbiological research, food quality control, and environmental monitoring. Since the bacterial determination of patients diagnosed with urinary tract infections in 1956, active microorganism quantification plays a pivotal role in clinical diagnosis and therapeutics as well as drug discovery, especially for live biotherapeutics development.

A variety of physical and biological approaches have been developed for the enumeration of microorganisms over decades of years, of which biological methods allow us identification the number of viable growing bacterial cells in the samples. Currently, culture-based CFU, optical density measurement by a spectrophotometer, and flow cytometry (FC) are prevailing methods used for the microorganism enumeration. Other molecular methods, such as quantitative real-time PCR, fluorescent in situ hybridization, and microchip technology, are also utilized for the quantification of bacterial cells.

Probiotics Enumeration by CFU Counting

Probiotics-based live biotherapeutic is the prevention or treatment of disease by the administration of adequate viable beneficial microorganisms to the host. Accurate enumeration of viable bacteria in probiotic products is significantly critical for the therapeutic effect and biological safety evaluation. To reliably enumerate active microorganisms and assess the viability of probiotic bacteria, CFU counting, a conventional method only for the determination of living bacteria, is preferred.

CFU, also known as flat colony counting, is a method of enumerating active bacteria by counting the number of colonies formed by the diluted and cultured bacteria. The target probiotic bacteria are diluted sufficiently to form dispersed single bacterial cells. Take the single bacterial cell solution and coated on the plate. Each single-celled bacterium grows and propagates to form visible colonies after culture, and a single colony should represent a single cell in the original sample. The number of viable bacteria can be calculated according to its dilution ratio and sampling volume.

Diagram of how to prepare bacterial dilutions. Fig.1 Diagram of how to prepare bacterial dilutions. (Ayala, 2017)

Advantages of Our Services

CFU is a sensitive and reliable method for active bacteria quantification. As a professional service provider in the field of live biotherapeutics, Creative Biolabs offers standard bacteria CFU counting services for the rapid biological safety evaluation of probiotic products. For those anaerobic probiotic bacteria that are not suitable for culture, we also provide other available methods for efficient quantification.

  • Rapid counting with high reproducibility
  • Automated equipment with high accuracy
  • Professional scientists with rich experience
  • One-stop services with full customization

Please feel free to contact us and our experienced technicians will give you the most detailed solutions.


  1. Ayala, F. R., et al. Culturing Bacteria from Caenorhabditis elegans Gut to Assess Colonization Proficiency. BIO-PROTOCOL. 2017, 7(12).

For Research Use Only. Not intended for use in food manufacturing or medical procedures (diagnostics or therapeutics). Do Not Use in Humans.

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