High-throughput DNA sequencing technologies have facilitated the in silico forensic analysis of human microbiome. Specific microbial species or communities obtained from the crime scene provide evidence of human contacts and their body fluids. The microbial community is influenced by geographic, ethnic, lifestyle, and environmental factors such as urbanization. An understanding of the effects of these external stressors on the human microbiome and determination of stable and changing elements are important in selecting appropriate targets for investigation. In this study, the Forensic Microbiome Database (FMD) (http://www.fmd.jcvi.org) containing the microbiome data of various locations in the human body in 35 countries was used. We focused on skin, saliva, vaginal fluid, and stool and found that the microbiome distribution differed according to the body part as well as the geographic location. In the case of skin samples, Staphylococcus species were higher than Corynebacterium species among Asians compared with Americans. Holdemanella and Fusobacterium were specific in the saliva of Koreans and Japanese populations. Lactobacillus was found in the vaginal fluids of individuals in all countries, whereas Serratia and Enterobacter were endemic to Bolivia and Congo, respectively. This study is the first attempt to collate and describe the observed variation in microbiomes from the forensic microbiome database. As additional microbiome databases are reported by studies worldwide, the diversity of the applications may exceed and expand beyond the initial identification of the host.

The rapid increase in antibiotic resistance has prompted the discovery of drugs that reduce antibiotic resistance or new drugs that are an alternative to antibiotics. Plant extracts have health benefits and may also exhibit antibacterial and antibiofilm activities against pathogens. This study determined the antibacterial and antibiofilm effects of α-humulene extracted from plants against enterotoxigenic Bacteroides fragilis, which causes inflammatory bowel disease. The minimum inhibitory concentration and biofilm inhibitory concentration of α-humulene for B. fragilis were 2 μg/mL, and the biofilm eradication concentration was in the range of 8–32 μg/mL. The XTT reduction assay confirmed that the cellular metabolic activity in biofilm rarely occurred at the concentration of 8–16 μg/mL. In addition, biofilm inhibition by α-humulene was also detected via confocal laser scanning microcopy. Quantitative real-time polymerase chain reaction (qPCR) was also used to investigate the effect of α-humulene on the expression of resistance–nodulation–cell division type multidrug efflux pump genes (bmeB1 and bmeB3). According to the results of qPCR, α-humulene significantly reduced the expression of bmeB1 and bmeB3 genes. This study demonstrates the potential therapeutic application of α-humulene for inhibiting the growth of B. fragilis cells and biofilms, and it expands the knowledge about biofilm medicine.

Stenotrophomonas maltophilia is a multi-drug resistant opportunistic pathogen that causes nosocomial infections in immunocompromised patients. This pathogen is difficult to treat owing to its intrinsic multidrug resistance and ability to form antimicrobial-tolerant biofilms. In the present study, we aimed to assess the potential use of celastrol as a novel anti-biofilm and/or anti-virulence agent against S. maltophilia. Results showed that celastrol at its sub-inhibitory doses decreased biofilm formation and disrupt the established biofilms produced by S. maltophilia. Celastrol-induced decrease in biofilm formation was dose-dependent based on the results of the microtiter plate biofilm assays and confocal laser scanning microscopy. In addition, our data validated the anti-virulence efficacy of celastrol, wherein it significantly interfered with the production of protease and motility of S. maltophilia. To support these phenotypic results, transcriptional analysis revealed that celastrol down-regulated the expression of biofilm- and virulence- associated genes (smeYZ, fsnR, and bfmAK) in S. maltophilia. Interestingly, celastrol significantly inhibited the expression of smeYZ gene, which encodes the resistance-nodulation-division (RND)-type efflux pump, SmeYZ. Overall, our findings suggested that celastrol might be a promising bioactive agent for treatment of biofilm- and virulence-related infections caused by the multi-drug resistant S. maltophilia.

The azoxymethane (AOM)/dextran sulfate sodium (DSS) murine model is commonly used to study colitis-associated cancer. The human commensal bacterium, enterotoxigenic Bacteroides fragilis (ETBF) secretes the Bacteroides fragilis toxin (BFT) which is necessary and sufficient to cause colitis. We report that BALB/c mice infected with WT-ETBF and administered three cycles of AOM/DSS developed numerous, large-sized polyps predominantly in the colorectal region. In addition, AOM/DSS-treated BALB/c mice orally inoculated with wild-type nontoxigenic Bacteroides fragilis (WT-NTBF) overexpressing bft (rETBF) developed numerous polyps whereas mice infected with WT-NTBF overexpressing a biologically inactive bft (rNTBF) did not promote polyp formation. Unexpectedly, the combination of AOM+ETBF did not induce polyp formation whereas ETBF+DSS did induce polyp development in a subset of BALB/c mice. In conclusion, WT-ETBF promoted polyp development in AOM/DSS murine model with increased colitis in BALB/c mice. The model described herein provides an experimental platform for understanding ETBF-induced colonic tumorigenesis and studying colorectal cancer in wild-type mice.

Anthocyanins have been studied as potential antimicrobial agents against Helicobacter pylori. We investigated whether the biosynthesis and secretion of cytotoxin-associated protein A (CagA) and vacuolating cytotoxin A (VacA) could be suppressed by anthocyanin treatment in vitro. H. pylori reference strain 60190 (CagA+/VacA+) was used in this study to investigate the inhibitory effects of anthocyanins; cyanidin 3-O-glucoside (C3G), peonidin 3-O-glucoside (Peo3G), pelargonidin 3-O-glucoside (Pel3G), and malvidin 3-O-glucoside (M3G) on expression and secretion of H. pylori toxins. Anthocyanins were added to bacterial cultures and Western blotting was used to determine secretion of CagA and VacA. Among them, we found that C3G inhibited secretion of CagA and VacA resulting in intracellular accumulation of CagA and VacA. C3G had no effect on cagA and vacA expression but suppressed secA transcription. As SecA is involved in translocation of bacterial proteins, the down-regulation of secA expression by C3G offers a mechanistic explanation for the inhibition of toxin secretion. To our knowledge, this is the first report suggesting that C3G inhibits secretion of the H. pylori toxins CagA and VacA via suppression of secA transcription.

So-Yeon Lee, and Yong-Bin Eom. BSL 2016;22:150-9. https://doi.org/10.15616/BSL.2016.22.4.150