Lactobacillus raoultii belongs to the genus Lactobacillus, a good bacteria found in the female vagina to maintain harmful bacteria balance.


Pink colored cylindrical-shaped structures1

 Illustration of pink-colored lactobacillus species

Bacterial species belonging to the Lactobacillus genre are primarily probiotic bacteria. These bacteria are found predominantly in various animals’ gastrointestinal tracts, including humans. Lactobacillus species are not only found in the gastrointestinal tract in humans but multiple parts of the body. The primary role of these bacterial species is; to maintain the microbiota, regulate immunomodulation, protect the gastrointestinal tract, and improve absorption of nutrients. Lactobacillus raoultii is a good bacteria found in the female vagina. This bacteria is involved in immunomodulation and maintain the microbiota consisting of good and bad bacteria. The imbalance in this microbiota leads to bacterial vaginosis, a vaginal infection. This infection mainly occurs in women of their reproductive age (women who haven’t reached menopause). Medications are available for bacterial vaginosis that can be administered orally or applied externally around the genital area. 

Table of Contents

Overview of Lactobacillus raoultii

Cause of Bacterial Vaginosis

Overview of Lactobacillus raoultii

Lactobacillus raoultii is a rod-shaped, non-motile, non-spore forming, gram-positive, facultatively anaerobic bacteria. They are mesophilic as they grow more effectively in the presence of less oxygen. They are catalase-negative as they do not hydrolyze hydrogen peroxide (H2O2) to form oxygen and water. This bacteria is also homofermentative as they release lactic acid as a byproduct of glucose metabolism. Lactobacillus raoultii is observed to grow at 37°C optimally. 

Orange colored long rod-shaped structures

Illustration of orange-colored Lactobacillus raoultii bacteria

Lactobacillus raoultii was first isolated from a 45-year-old woman suffering from bacterial vaginosis in France. The initial identification name provided for this bacteria was Strain Marseille P4006. This strain was isolated after preincubating for three days and then added to the vaginal sample and incubated for 48 hours at 37°C with pH 5. Strain Marseille P4006 was successfully identified by performing 16s rRNA sequencing. This bacteria was found to have 98.1% sequence similarity with Lactobacillus farraginis. For a bacterial species to be recognized as a novel species, the 16s rRNA sequence should be 98.7%. therefore, Strain Marseille P4006 was named Lactobacillus raoultii (in honor of a French scientist Didier Raoult).

Cause of Bacterial Vaginosis

The vagina contains good and bad bacteria as a part of the vaginal microbiota. When the amount of harmful bacteria increases compared to the good bacteria, infection occurs in the genital area, called bacterial vaginosis. A healthy vaginal flora consists of various lactobacillus species such as; Lactobacillus iners, Lactobacillus gasseri, Lactobacillus cripastus, Lactobacillus jensenii; and a new bacteria, Lactobacillus raoultii. Lactic acid produced by the lactobacillus bacteria and other antimicrobial components such as hydrogen peroxide and bacteriocins inhibits pathogenic growth. This vaginal ecosystem is disturbed, leading to a decrease in Lactobacillus species and an increase in anaerobic bacteria like Atopobium vaginae, which causes bacterial vaginosis. Furthermore, Gardnerella vaginalis have been observed to cause bacterial vaginosis; by forming a biofilm allowing various opportunistic microbes to grow in the vagina. 

Transparent body and pink structures surrounding a white blob

 Illustration of the human body and a cell surrounded by bacteria

Bacterial vaginosis infection is commonly observed in women of their reproductive age and usually sexually active women; although in women who have not had sex, the infection is quite rare. The most common symptom of this infection is abnormal vaginal discharge. Other symptoms include; a “fishy” odor and vaginal irritation in some women. Other women may be asymptomatic with this infection. Moreover, bacterial vaginosis is usually caused due to infection after hysterectomy and preterm delivery. The risk of bacterial vaginosis is higher in pregnant women, an intrauterine device (IUD), multiple sex partners, and using douches.

The symptoms occurring in women having bacterial vaginosis are; a “fishy” odor during discharge, menstrual cycle, and after sex; grey-greenish, off-white vaginal discharge; and seldom itchy vagina. Antibiotics such as clindamycin or metronidazole are usually prescribed. They can be administered orally as capsules or applied vaginally in the form of cream. 

Asha Rachel Thomas


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