Fecal contaminants are a major public concern that directly affect human health in the fish production industry. In this study, we aimed to determine the fecal coliform, spoilage bacteria, and antimicrobial-resistant bacterial contamination in rainbow trout (Oncorhynchus mykiss) farms. Fish were sampled from rainbow trout farms that have a high production capacity and are established on spring water, stream water, and dammed lakes in six different regions of Turkey. A total of seven Enterobacter subspecies, two strains of Pseudomonas spp., and one isolate each of Morganella and Stenotrophomonas were characterized based on biochemical and molecular methods, including the 16S rRNA and gyrB housekeeping gene regions. The sequencing results obtained from the 16S rRNA and gyrB gene regions were deposited in the GenBank database and compared with isolates from different countries, which were registered in the database. Resistance to 10 different antimicrobial compounds was determined using the broth microdilution method, and molecular resistance genes against florfenicol, tetracycline, and sulfamethoxazole were identified by PCR. All detected resistance genes were confirmed by sequencing analyses. E. cloacae, E. asburiae, Pseudomonas spp., S. maltophilia, and M. psychrotolerans were identified using the gyrB housekeeping gene, while isolates showed different biochemical characteristics. All isolates were found to be phenotypically resistant to sulfamethoxazole, and some isolates were resistant to tetracycline, florfenicol, amoxicillin, and doxycycline; the resistance genes of these isolates included floR, tetC, tetD, and tetE. We showed that fecal coliforms, spoilage bacteria, and antimicrobial resistant bacteria were present in farmed rainbow trout, and they pose a threat for human health and must be controlled in the farming stage of fish production.

Constipation, a functional disorder of the digestive system, is common in children and adults and may compromise patient quality of life. Because many patients are not satisfied with the efficacy of existing therapies, in this study, we investigated the efficacy of the probiotic Bifidobacterium bifidum G9-1 (BBG9-1) in constipation induced by a low-fiber diet. After inducing constipation in rats by feeding a low-fiber diet, rats were fed a low-fiber diet mixed with BBG9-1 in 14 days to determine the efficacy of BBG9-1 for alleviating constipation. BBG9-1 significantly alleviated the dysbiosis induced by a low-fiber diet and improved the fecal counts, fecal weights, and fecal water contents. Moreover, it also improved organic acid concentrations in the cecal contents. These results suggested that in low-fiber diet-induced constipation, BBG9-1 could alleviate dysbiosis and constipation and may improve the intestinal environment, supporting its potential application in the treatment of constipation.

Excessive fat intake is associated with changes in gut microbiota composition. In the present study, we focused on the secretory immunoglobulin A (SIgA) coating of gut microbiota as a mucosal immune response affecting the gut microbiota following a high-fat diet (HFD). The level of SIgA coating of gut microbiota was evaluated in normal-fat diet (NFD)- and HFD-fed mice. HFD significantly decreased the level of SIgA coating the gut microbiota compared with NFD. Of note, substitution of HFD with NFD resulted in a complete recovery of the level of SIgA coating. These findings suggest that dietary fat influences the SIgA coating of the gut microbiota. Furthermore, we analyzed the composition of the gut microbiota and the concentration of cecal short-chain fatty acids. HFD feeding changed the gut microbiota composition at the phylum and family levels. Pearson correlation analysis between the level of SIgA coating of gut microbiota and the relative abundance of gut microbiota showed that the relative abundances of Clostridiaceae, Mogibacteriaceae, Turicibacteraceae, and Bifidobacteriaceae were negatively correlated with the level of SIgA coating of gut microbiota. Conversely, the relative abundances of Desulfovibrionaceae, S24-7, and Lactobacillaceae were positively correlated with the level of SIgA coating. The concentrations of cecal acetate and butyrate were lower in HFD-fed mice and positively correlated with the level of SIgA coating of gut microbiota. Our observations suggest that a decrease in the level of SIgA coating of the gut microbiota through a HFD might relate to HFD-induced changes in microbial composition and microbial metabolites production.

Six species and one group of Clostridium cluster XI, Clostridium sordellii, Clostridium bifermentans, Clostridium difficile, Clostridium hiranonis, Intestinibacter bartlettii, and Romboutsia lituseburensis and the Terrisporobacter glycolicus group, respectively, in human feces collected from 18 healthy adults were analyzed with real-time PCR. Although individual differences were recognized, the predominant colonization of C. sordellii and I. bartlettii in the human large intestine was identified.

To investigate the prebiotic effect of lactulose at low dosages, we assessed changes in defaecation frequency following ingestion of 1, 2, or 3 g/day of lactulose for 2 weeks. Each test was carried out after a 2-week washout period. This was an open-label, before-after trial that enrolled 26 healthy Japanese women. The defaecation frequency, number of defaecation days, and number of faecal bifidobacteria increased significantly compared with before ingestion of 1, 2, and 3 g/day of lactulose. These results suggest that even 1 g/day of lactulose could have a prebiotic effect.