The human gut microbiota creates a complex microbial ecosystem, characterized by its high population density, wide diversity, and complex interactions. Any imbalance of the intestinal microbiome, whether qualitative or quantitative, may have serious consequences for human health, including small intestinal bacterial overgrowth (SIBO). SIBO is defined as an increase in the number of bacteria (10³–10⁵ CFU/mL), an alteration in the bacterial composition, or both in the small intestine. The PubMed, Science Direct, Web of Science, EMBASE, and Medline databases were searched for studies on SIBO and related diseases. These diseases were divided into 12 groups: (1) gastrointestinal disorders; (2) autoimmune disease; (3) cardiovascular system disease; (4) metabolic disease; (5) endocrine disorders; (6) nephrological disorders; (7) dermatological diseases; (8) neurological diseases (9); developmental disorders; (10) mental disorders; (11) genetic diseases; and (12) gastrointestinal cancer. The purpose of this comprehensive review is to present the current state of knowledge on the relationships between SIBO and these 12 disease groups, taking into account risk factors and the causal context. This review fills the evidence gap on SIBO and presents a biological–medical approach to the problem, clearly showing the groups and diseases having a proven relationship with SIBO, as well as indicating groups within which research should continue to be expanded.

Keywords: gut microbiota; small intestinal bacteria overgrowth; SIBO; diet, dysbiosis; microbial ecology.

MicroRNAs (miRNAs, miRs) are a group of small, 17–25 nucleotide, non-coding RNA sequences that, in their mature form, regulate gene expression at the post-transcriptional level. They participate in many physiological and pathological processes in both humans and animals. One such process is viral infection, in which miR-155 participates in innate and adaptive immune responses to a broad range of inflammatory mediators. Recently, the study of microRNA has become an interesting field of research as a potential candidate for biomarkers for various processes and disease. To use miRNAs as potential biomarkers of inflammation in viral diseases of animals and humans, it is necessary to improve their detection and quantification. In a previous study, using reverse transcription real-time quantitative PCR (RT-qPCR), we showed that the expression of ocu-miR-155-5p in liver tissue was significantly higher in rabbits infected with Lagovirus europaeus/Rabbit Hemorrhagic Disease Virus (RHDV) compared to healthy rabbits. The results indicated a role for ocu-miR-155-5p in Lagovirus europaeus/RHDV infection and reflected hepatitis and the impairment/dysfunction of this organ during RHD. MiR-155-5p was, therefore, hypothesized as a potential candidate for a tissue biomarker of inflammation and examined in tissues in Lagovirus europaeus/RHDV infection by dPCR. The objective of the study is the absolute quantification of ocu-miR-155-5p in four tissues (liver, lung, kidney, and spleen) of rabbits infected with Lagovirus europaeus/RHDV by digital PCR, a robust technique for the precise and direct quantification of small amounts of nucleic acids, including miRNAs, without standard curves and external references. The average copy number/µL (copies/µL) of ocu-miRNA-155-5p in rabbits infected with Lagovirus europaeus GI.1a/Rossi in the liver tissue was 12.26 ± 0.14, that in the lung tissue was 48.90 ± 9.23, that in the kidney tissue was 16.92 ± 2.89, and that in the spleen was 25.10 ± 0.90. In contrast, in the tissues of healthy control rabbits, the average number of copies/µL of ocu-miRNA-155-5p was 5.07 ± 1.10 for the liver, 23.52 ± 2.77 for lungs, 8.10 ± 0.86 for kidneys, and 42.12 ± 3.68 for the spleen. The increased expression of ocu-miRNA-155-5p in infected rabbits was demonstrated in the liver (a fold-change of 2.4, p-value = 0.0003), lung (a fold-change of 2.1, p-value = 0.03), and kidneys (a fold-change of 2.1, p-value = 0.01), with a decrease in the spleen (a fold-change of 0.6, p-value = 0.002). In the study of Lagovirus europaeus/RHDV infection and in the context of viral infections, this is the first report that shows the potential use of dPCR for the sensitive and absolute quantification of microRNA-155-5p in tissues during viral infection. We think miR-155-5p may be a potential candidate for a tissue biomarker of inflammation with Lagovirus europaeus/RHDV infection. Our report presents a new path in discovering potential candidates for the tissue biomarkers of inflammation.

The diverse clinical picture and the non-specificity of symptoms in Lyme disease (LD) require the implementation of effective diagnostics, which should take into account the heterogeneity of Borrelia antigens. According to available guidelines, laboratories should use a two-tier serological diagnosis based on the enzyme-linked immunosorbent (ELISA) screening test and confirmation of the immunoblot (IB). The aim of the study was to investigate the immunoreactivity of LD patient sera to Borrelia antigens and to attempt to identify the genospecies responsible for LD using an ELISA–IB assay combination. Eighty patients with suspected LD and 22 healthy people participated in the study. All samples were tested with ELISA and IB assays in both IgM and IgG antibodies. In the case of the ELISA assay, more positive results were obtained in the IgM class than in the IgG class. In the case of the IB assay, positive results dominated in the IgG class. Positive results obtained in the IB assay most often showed IgM antibodies against the OspC and flagellin antigens, whereas the IgG antibodies were against VlsE, BmpA, OspC, p41, and p83 antigens. The IB assay is an important part of LD serodiagnosis and should be mandatory in diagnostic laboratories.

A wide range of options for studying Candida species are available through genetic methods. Twins, particularly monozygotic ones and their families may be fitting subjects for studying those microorganisms. The question is: How specific can yeast flora be in an individual? The study aimed to analyze the strain relatedness among commensal yeasts isolated from various parts of the bodies of healthy people and to compare correlations between the genotypes of the isolates. Yeasts were isolated from 63 twins and their family members (n = 25) from the oral cavity, anus, interdigital space and navel. After species identification, Candida albicans (n = 139), C. parapsilosis (n = 39), C. guilliermondii (n = 25), C. dubliniensis (n = 11) and C. krusei (n = 9) isolates were analyzed using the random amplified polymorphic DNA polymerase chain reaction (RAPD-PCR) optimization method. The similarities between the strains were calculated based on the Dice (Sab) coefficient and are displayed graphically as dendrograms. Using cluster analysis, the following relatedness was distinguished: 13 genotypes and three unique (Un) patterns among C. albicans; 10 genotypes and four Un patterns among C. parapsilosis; three genotypes and one Un pattern among C. guilliermondii and C. dubliniensis; and three genotypes among C. krusei isolates. The presence of identical, similar or both genotypes among the strains isolated from family members shows the transmission of yeasts between ontocenoses in the same person and between individuals. The similarity between the genotypes of C. albicans, C. guilliermondii, C. dubliniensis and C. krusei was more remarkable than between the genotypes of C. parapsilosis in the strains isolated from ontocenoses of the same individual and their family members. The degrees of genetic similarity between Candida spp. strains isolated from monozygotic twins and those obtained from their relatives did not differ.

Intestinal trefoil factor 3 (TFF3) is a protein secreted by many cell types, and its serum and urine levels vary in patients with kidney disease. Therefore, the present study aimed to determine the diagnostic value of TFF3 in allogeneic kidney transplant patients included in the one-year follow-up. To analyze the influence of the diagnostic method used, we studied the type of biological material and the time elapsed since renal transplantation on the parameter’s value. The study also aimed to investigate the relationship between TFF3 levels and creatinine and estimated glomerular filtration rate (eGFR) values in the serum and urine of the patients studied. The study used blood and urine samples from adult patients (n = 19) 24–48 h, 6 months, and 12 months after kidney transplantation. We collected one-time blood and urine from healthy subjects (n = 5) without renal disease. We applied immunoenzymatic ELISA and xMap Luminex flow fluorimetry to determine TFF3 in serum and urine. There was a significant difference in TFF3 levels in the serum of patients collected on the first one or two days after kidney transplantation compared to the control group (determined by ELISA and Luminex) and six months and one year after kidney transplantation (ELISA). We observed a correlation between creatinine concentration and urinary TFF3 concentration (ELISA and Luminex) and a negative association between eGFR and urinary (ELISA) and serum (Luminex) TFF3 concentration in patients on the first and second days after kidney transplantation. We noted significant correlations between eGFR and TFF3 levels in the serum and urine of patients determined by the two methods six months and one year after transplantation. In women, we observed that urinary TFF3 concentration increased significantly with increasing creatinine and that with increasing eGFR, urinary TFF3 concentration determined by two methods decreased significantly. In the present study, the choice of diagnostic method for the determination of TFF3 in serum and urine significantly affected the concentration of this biomarker. The values of this parameter determined by ELISA were higher than those assessed using the Luminex assay. Based on the presented results, we can conclude that TFF3 has great potential to monitor renal transplant patients. Determination of this protein in parallel with creatinine and eGFR levels in serum and urine may provide helpful diagnostic information.