Gut Mycobiota Could Contribute to the Long-term Consequences of Antibiotic Treatments - Folkhälsan

29 March 2022

Gut Mycobiota Could Contribute to the Long-term Consequences of Antibiotic Treatments

The results of our newly published study show that the use of antibiotics affects the gut fungal microbiota of infants causing an imbalance in the microbiota composition. This was seen as a larger proportion of the fungi Candida, as well as a greater variety of fungi in the newborns who had been treated with antibiotics. It seems that antibiotics facilitate fungal growth in the intestine by killing intestinal bacteria, which gives the fungi less competition. This can be a partial cause of the long-term side effects that antibiotics have, such as various chronic inflammatory diseases.

The intestinal flora contains various bacteria, fungi, archaea, viruses and occasionally protozoa. The composition of this microbiota is quite significant for human health, and there are studies showing that the intestinal microbiota is connected to both mental health factors and several aspects of physical health. Most microbiota-related studies have focused on the bacteria, even though the fungal microbiota, or mycobiota, may have a significant role as well. In previous studies, imbalance in the composition of the mycobiota has been shown to be associated with various diseases, such as inflammatory bowel disease, celiac disease and colorectal cancer.

Antibiotics, which categorically only affect prokaryotes, can cause increased fungal growth, especially in the genus Candida, and thus cause major changes in the composition of the intestinal flora. In addition, antibiotics have been shown to increase the risk of yeast infections as well as circulatory infections.

The bacteria and fungi coexist in the intestine. Here they compete for food sources and fight microscopical wars against each other by producing antibacterial or fungicidal chemical compounds respectively. The candida fungus is part of the healthy and natural intestinal mycobiota. At the same time, it seems to be a driving force that causes imbalance in the composition of the intestinal flora and is associated with several intestinal diseases.

When the bacteria are killed by antibiotics, the fungi have a chance to grow. This changes the balance of the gut microbiota composition.

Antibiotics may have some harmful side effects, frequently long-term and especially observed among children, and often associated with abnormal intestinal microbiotic composition. The effect that antibiotics have on the intestinal bacteria is well studied, but there are not that many studies that have examined the effect that antibiotics have on the fungal flora specifically.

A recent study at the Folkhälsan Research Center examined the effect of antibiotics on infant intestinal mycobiota by examining differences in its composition among antibiotic-treated infants compared to infants who have never received antibiotics.

– The gut mycobiota of these infants were significantly affected by the antibiotics, although these affect the growth of bacteria. This highlights the importance to study other parts of the gut microbiota, in addition to bacteria, says Rebecka Ventin-Holmberg. Doctoral student at Folkhälsan Research Center and first author of the study article.

The study included 37 participants with respiratory syncytial virus, and whom had never received antibiotics. Of these, 21 patients received one to four antibiotic treatments due to disease complications, and 16 went without antibiotics during the course of the study. Fecal samples were taken before, during and after the antibiotic treatments, with a follow-up period of up to 9 and a half months. The intestinal mycobiota was studied by Illumina MiSeq sequencing of the ITS1 conserved region, a common method for studying the fungal composition of the intestine. The results of the sequencing showed that the use of antibiotics clearly affected the fungal flora in the intestine, in the form of a higher relative abundance of the genus Candida and a higher fungal diversity and richness in the antibiotic-treated infants compared to those who never received antibiotics.

Graphical abstract of the study.

– When the bacteria are killed by antibiotics, the fungi have a chance to grow. This changes the balance of the gut microbiota composition, says Rebecka Ventin-Holmberg.

The use of antibiotics affects newborns' intestinal mycobiota and causes imbalances in the natural microbiotia composition - as the antibiotic kills bacteria in the gut, the fungi have a chance to multiply in a less contested habitat. This imbalance may be a possible explanatory factor for why antibiotic treatments can sometimes have far-reaching adverse side effects.

– Our results hint that the fungi also seem to play a role in the long-term effects caused by disturbing the gut microbiota, for example with antibiotics, during the most important developmental phase of the gut microbiota in infancy, Rebecka Ventin-Holmberg summarizes.

Original article:

Ventin-Holmberg R, Saqib S, Korpela K, Nikkonen A, Peltola V, Salonen A, de Vos WM, Kolho K-L. The Effect of Antibiotics on the Infant Gut Fungal Microbiota. Journal of Fungi. 2022; 8(4):328. https://doi.org/10.3390/jof8040328

Simon Granroth, Science Communicator