Lactic Acid Bacteria – Infection, Transmission and Diseases

Lactic acid bacteria

The lactic acid bacteria , often also called lactobacillales , lactobacilli or sour milk bacteria , comprise a family of gram-positive, always anaerobic but mostly aerotolerant bacteria . These are characterized by the fact that they convert sugar into lactic acid (lactic acid fermentation): they make the milk go sour.

What are lactic acid bacteria?

Lactic acid bacteria describe a large supergroup of different types of bacteria that occur in the human body. Fundamentally, however, these different types of lactic acid bacteria hardly resemble each other.

The only similarity most of the time is that these convert sugars into lactic acid and rely on carbohydrates for energy. However, while homofermentative bacteria only produce lactic acid (lactate), heterofermentative bacteria also produce other end products such as ethanol and carbon dioxide.

Lactobacilli differ from other bacteria, which also produce lactic acid, among other things, in that they are only able to ferment in terms of metabolism. But they also do this when oxygen is added.

Meaning & Function

Lactic acid bacteria have lost the ability to synthesize many necessary substances such as amino acids , porphyrins and cytochromes due to their specialization in growth in milk and similar substances.As a result, they cannot split hydrogen peroxide. This is why lactic acid bacteria are only found in the intestines and mucous membranes of mammals, such as humans.

However, lactic acid bacteria are also found in some living or decomposing plants that come into contact with milk and milk-like substances. Nevertheless, lactic acid bacteria are among the most important representatives of the human intestinal and vaginal flora.

Various subspecies (strains) and types of lactic acid bacteria are also used to preserve food, such as yoghurt, cheese, sour milk, kefir and sauerkraut, as well as for skin care and to prevent tooth decay. Lactic acid bacteria are also used quite frequently as probiotics, which strengthen the immune system and positively stimulate, influence and thus regulate digestion.

For example, probiotics can be used to intervene in the intestinal, oral and vaginal flora. This can be intended to restore a disturbed flora, but also to improve and optimize a healthy flora.


Lactic acid bacteria have many different species and subspecies. Some of these species are less useful, but represent pathogens. Depending on the species, they can cause disturbances in the body flora.In most cases, the vaginal and intestinal flora are affected here, which are thrown off balance by harmful lactic acid bacteria. Symptoms can include vaginal dryness , inflammation, fungal infections , infertility, and digestive problems in the gut. The latter, of course, refers to the fact that the intestinal flora is affected.

Incidentally, an imbalance can also occur if the natural intestinal flora gets into the weakened vaginal flora in too large a quantity. Therefore, after going to the toilet and during the subsequent cleaning of the abdomen, you should make sure that you always “wipe” away from the vagina. However, the vaginal flora can also be thrown off balance by improper hygiene (too often, but also too rarely) or incorrect use of tampons .

However, lactic acid bacteria also come in other subspecies, which, depending on where they occur and the type, can trigger further disorders and thus pose risks. The so-called Streptococcus pneumoniae is a pathogen that belongs to the type of lactic acid bacteria that can cause pneumonia . Streptococcus mutans , on the other hand, is involved in the development of tooth decay . This often occurs when eating sugary foods in the oral flora, when lactic acid is formed directly in the mouth and after consumption.

This type of lactobacilli attacks tooth enamel and, if left unchecked, will also eat through the underlying tooth structure. Another disease that can be associated with lactic acid bacteria – but does not have to be – is lactose intolerance . Because one speaks of such when the lactose ingested through food is not properly processed. Incidentally, lactose intolerance can remain symptom-free, but it can also result in symptoms such as disorders in the gastrointestinal tract.

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Hello! I am Lisa Newlon, and I am a medical writer and researcher with over 10 years of experience in the healthcare industry. I have a Master’s degree in Medicine, and my deep understanding of medical terminology, practices, and procedures has made me a trusted source of information in the medical world.