Lactobacillus rhamnosus in clinical samples and probiotic preparations: Qualitative and quantitative culture; Molecular identification (PCR and sequencing). 

Information 2021-01-10.


According to the World Health Organization (WHO) and the Food and Agriculture Organization of the United Nations (FAO), a probiotic is a living microorganism that provides benefits to the health of its host, as long as it is administered in the adequate amounts and meet the requirements established by WHO and FAO. The term probiotic was used for the first time in 1965 by Daniel M. Lilly and Rosalie H. Stillwell, although their concept was coined by Elie Metchikof (Russia, 1908), who postulated that the longevity of Bulgarian shepherds could be due to the ingestion of fermented milk and its products, stating that they were rich in bacilli that influenced the native intestinal microbiota, balancing it in a way that diminished the harmful effect of other bacteria.

Lactobacillus rhamnosus is a gram-positive, non-sporulated, anaerobic lactic acid bacterium of the Lactobacillaceae family. It was considered a subspecies of L. casei but later studies showed that L. rhamnosus was a distinct species capable of using rhamnose as a carbon source. Other evidence shows that it is the only lactic acid bacterium with α-chymotrypsin and β-glucuronidase activity. It is considered to have beneficial effects, lacking harmful effects, even in immunosuppressed patients.

The L. rhamnosus GG strain (LGG: Lactobacillus rhamnosus Gorbach-Goldin strain) is the most studied and most widely used as a probiotic. It was isolated from the intestinal tract of a healthy individual in the early 1980s, registered and patented by the American Type Culture Collection (ATCC) as L. acidophilus GG (ATCC 53103). The LGG patent indicates that it has the ability to survive the pH of gastric acid and proliferate in the presence of bile. In addition, it has a great capacity to adhere to intestinal epithelial cells, and it is a producer of lactic acid.

There is much evidence and research that supports the use of LGG as a beneficial probiotic for human health. LGG is capable of producing a film with soluble factors that protect the intestinal mucosa, decrease cell death on the intestinal surface and protect it. In addition, LGG has an inhibitory protein for some pathogens, capable of reducing the expression of various activation and inflammation markers in monocytes, promoting the immune response, as well as increasing the production of interleukins 10 and 12 and tumor necrosis factor- α (TNF-α) in macrophages.

Its use is indicated in:

  • Acute diarrhea and gastroenteritis.
  • Diarrhea associated with antibiotics.
  • Traveler´s diarrhea.
  • Diarrhea in children who attend daycare.
  • Prevention of nosocomial diarrhea.
  • Gastrointestinal disorders that present with abdominal pain.
  • Helicobacter pylori eradication adjuvant treatment.

Its use shows the following benefits:

  • Decrease in the number of stools on the second day of treatment.
  • Shorten the duration of diarrhea.
  • Reduction in the percentage of diarrhea that lasts for more than 4 days.

There are Lactobacillus rhamnosus GG probiotic capsules for sale that contain 1010 bacteria/100 mg.

For its isolation and subsequent identification of the L. rhamnosus strain, a specific selective culture medium can be used on MRS agar (from Man, Rogosa, Shape) modified by substituting glucose for rhamnose to favor the growth of L. rhamnosus, whereas most other Lactobacillus species of the gastrointestinal tract do not. Its identification can be carried out by means of conventional or simplified metabolic tests (API). Currently, the most optimal identification is carried out by molecular methods using Lactobacillus-specific primers of the 16S rRNA ribosomal gene or the 16S-23S intergenic region, to subsequently perform its sequencing and sequence analysis.

Tests carried out at IVAMI:

  • Isolation and quantitative culture of L. rhamnosus in selective and differential modified MRS medium.
  • Qualitative molecular detection (PCR).
  • Identification of isolated colonies by molecular methods (PCR and sequencing).