Lactobacillus spp.

Lactic acid bacteria that are also contained in many probiotics – they produce lactic acid, lower the pH, inhibit pathogens and produce lactase. In the vagina they shape the acidic environment; in the gut they live mainly in the small intestine and make up only a small part of the flora in the large intestine.

What lactobacilli do in the gut

Lactobacilli ferment sugars into lactic acid, partly also into acetate and ethanol, and thereby lower the pH of their surroundings. In the gut they live mainly in the small intestine and in smaller numbers in the large intestine. They occupy attachment sites on the mucosa, produce bacteriocins – proteins that inhibit other bacteria – and split milk sugar with the enzyme beta-galactosidase. In the vagina, some species shape the acidic environment that keeps unwanted microbes in check. Since 2020, the former umbrella genus Lactobacillus has been divided into several genera, such as Lactiplantibacillus and Limosilactobacillus; in the report they are often still grouped under the old name.

Low lactobacilli – what happens in the gut?

With few lactobacilli, less lactic acid is formed in the small intestine, attachment sites remain free and other microbes can settle more easily. In the large intestine, lactate also serves certain bacteria as raw material for butyrate, so this supply is lower. The amount often falls after antibiotics. In the vagina, a decline in lactobacilli causes the pH to rise, allowing other bacteria such as Gardnerella to multiply.

High lactobacilli – what happens in the gut?

High amounts in stool show vigorous lactic acid production; the gut contents become more acidic. Studies have observed raised levels with acid blockers (proton pump inhibitors), because more bacteria from the mouth and stomach then reach the gut alive, and also with regular consumption of fermented foods. Very rarely, for example after extensive bowel surgery, the D-lactate form can accumulate in the body.

The interpretation is given in your report.