Browsing by Author "Vähä-Mäkilä, Helena"

The human gastrointestinal track is populated by gut microbiota that consist of viruses, bacteria, archaea, fungi and micro-eukaryotes. The gut microbiota is beneficial for the host in many ways, including synthesis of short chain fatty acids and vitamins, and supporting the maturation and normal functions of the immune system. A healthy gut microbiota provides colonization resistance by preventing the attachment and growth of pathogenic microorganisms in the intestines. The use of antibiotics is a common cause of intestinal microbiota disturbation and weakened colonization resistance, which can lead to intestinal infection after antibiotic treatment. The leading cause of antibiotic-associated diarrhea is infection caused by bacterium Clostridioides difficile. C. difficile infection is generally treated with vancomycin or metronidazole, but in approximately 20 % of the patients the infection renewed. In these cases, the infection is referred to as a recurrent C. difficile infection. A recurrent C. difficile infection is treated with a repeated course of antibiotics or a fecal microbiota transplantation (FMT). FMT is a medical procedure in which feces of a healthy pre-screened donor is infused into a patient’s intestine in order to restore a healthy gut microbiota. FMT is an effective treatment for recurrent Clostridioides difficile infections, and its efficacy to treat other diseases linked with intestinal dysbiosis is being studied. Rectal bacteriotherapy, in which a transplant consists of specific intestinal bacterial strains, is used similarly to FMT, has been studied as a substitute for FMT to further reduce possible risks of fecal transplant such as transferring yet-unknown pathogens into patients. The gut microbiota is a favorable ecosystem for enrichment of antibiotic resistant genes through horizontal gene transfer between bacteria. From individuals carrying C. difficile bacteria not everyone will develop C. difficile infection after antibiotic treatment, and not all C. difficile infections lead to recurrent C. difficile infections. The reason for this might be the colonization resistance against C. difficile provided by the antibiotic resistant microbes that weren’t affected by the antibiotic treatment. Antibiotic resistant commensal bacteria living in the intestine may have an important role in maintaining the colonization resistance during and after antibiotic treatment. Since vancomycin is used as a treatment for C. difficile infections, introduction of non-pathogenic vancomycin resistant bacteria in form of bacteriotherapy could provide a better colonization resistance during the antibiotic treatment. The aim of this study was to examine the incidence of vancomycin resistance gene vanB in the microbiota of three FMT donors and 13 recipients, and to study culturable vancomycin resistant gut bacteria isolated from FMT donors. The vanB gene carriage of FMT donors and patients before and after FMT was studied. Furthermore, a total of 68 vancomycin resistant bacterial isolates were cultivated and purified from FMT donors, and the taxonomical identification of isolates was performed based on their 16S rRNA gene. Whether the vancomycin resistance of the isolates resulted from vanB gene was assessed using a PCR method. The results showed that all the FMT donors carried a vanB gene in their microbiota. The gene was present in the patients’ intestinal microbiota one month after FMT and half of the patients carried the gene still after 8 or 12 months after FMT. The vanB gene wasn’t found in the samples collected from patients before FMT. It is likely that the vanB gene had transferred from donors to patients via FMT. However, vanB gene couldn’t be detected in any of the cultivated bacterial isolates, and thus the bacterial strains carrying the gene were left unidentified. The isolates represented 21 different bacterial species. Donors differed from each other with respect to overall species distribution, which supports the previous findings of individual specific microbiotas. All three donors carried species from the genus Bacteroides and lately reclassified genus Lactobacillus, but none of the species was found in all three donors. The isolates found in this study might be candidate strains for rectal bacteriotherapy, but further studies are required to determine the effectiveness and safety of these isolates.