Introduction The eradication rates for Helicobacter pylori have decreased in Korea although the prevalence of this bacterium has also decreased. Antibiotic resistance is likely to be a crucial factor in H. pylori eradication success, and we therefore mapped these resistance patterns nationwide in Korea. Materials and Methods Five hundred and ninety adult subjects were prospectively enrolled from 2017 to 2018 from 15 centers across six geographic areas of Korea. A total of 580 biopsy tissues had been sampled from these patients during an upper endoscopy and were frozen at −80°C and delivered to a central laboratory. The agar dilution method was used to determine the minimum inhibitory concentration of amoxicillin, clarithromycin, metronidazole, tetracycline, ciprofloxacin, and levofloxacin for each H. pylori isolate. Results The culture success rate was 60.2% (349/580). Resistance rates against clarithromycin, metronidazole, amoxicillin, tetracycline, levofloxacin, and ciprofloxacin were 17.8%, 29.5%, 9.5%, 0%, 37.0%, and 37.0%, respectively. The geographic distribution of metronidazole and quinolone resistance was highly variable. Some subjects had multiple H. pylori strains in the antrum and body of the stomach and showed a heterogeneous resistance profile between these anatomic areas. The H. pylori multidrug resistance (MDR) rate was 25.2% (88/349) among amoxicillin, clarithromycin, metronidazole, tetracycline, and quinolone and 11.2% (39/349) among four of these major antibiotics except for quinolone. The Seoul and Chungcheong areas showed a relatively lower MDR rate. Conclusion The antibiotic resistance of H. pylori differs by drug and geographic area in Korea. Detailed nationwide antibiotic resistance mapping is needed to develop an effective H. pylori eradication strategy.

The diterpene cyclase CotB2 catalyzes the cyclization of geranylgeranyl diphosphate (GGPP) to the tricyclic cyclooctat-9-en-7-ol, which is characterized by a 5-8-5-fused ring skeleton. We have previously proposed a cyclization cascade involving a unique carbon-carbon bond rearrangement combined with multiple hydride shifts, all occurring at a single active site. Here, we report the first high-resolution X-ray crystal structure of CotB2 with bound substrate analog geranylgeranyl thiodiphosphate (GGSPP). In the GGSPP-bound form, GGSPP folds into a unique S-shaped conformation that probably reflects the substrate-bound state prior to ionization of the substrate GGPP. The folded framework of GGSPP is surrounded by hydrophobic residues and several aromatic and asparagine residues that are well-positioned to stabilize a series of reactive carbocation intermediates through a combination of cation-π and dipole charge interactions. The combined crystal structures and mutagenesis-based biochemical assays provide a structural basis for exquisite control of ring formation and stereochemistry during CotB2 catalysis.

cFosfomycin is a wide-spectrum antibiotic that is used clinically to treat acute cystitis in the United States. The compound is produced by several strains of streptomycetes and pseudomonads. We sequenced the biosynthetic gene cluster responsible for fosfomycin production in Pseudomonas syringae PB-5123. Surprisingly, the biosynthetic pathway in this organism is very different from that in Streptomyces fradiae and Streptomyces wedmorensis. The pathways share the first and last steps, involving conversion of phosphoenolpyruvate to phosphonopyruvate (PnPy) and 2-hydroxypropylphosphonate (2-HPP) to fosfomycin, respectively, but the enzymes converting PnPy to 2-HPP are different. The genome of P. syringae PB-5123 lacks a gene encoding the PnPy decarboxylase found in the Streptomyces strains. Instead, it contains a gene coding for a citrate synthase-like enzyme, Psf2, homologous to the proteins that add an acetyl group to PnPy in the biosynthesis of FR-900098 and phosphinothricin. Heterologous expression and purification of Psf2 followed by activity assays confirmed the proposed activity of Psf2. Furthermore, heterologous production of fosfomycin in Pseudomonas aeruginosa from a fosmid encoding the fosfomycin biosynthetic cluster from P. syringae PB-5123 confirmed that the gene cluster is functional. Therefore, two different pathways have evolved to produce this highly potent antimicrobial agent.

Antimicrobial-resistant and novel pathogens continue to emerge, outpacing efforts to contain and treat them. Therefore, there is a crucial need for safe and effective therapies. Ultraviolet-A (UVA) phototherapy is FDA-approved for several dermatological diseases but not for internal applications. We investigated UVA effects on human cells in vitro, mouse colonic tissue in vivo, and UVA efficacy against bacteria, yeast, coxsackievirus group B and coronavirus-229E. Several pathogens and virally transfected human cells were exposed to a series of specific UVA exposure regimens. HeLa, alveolar and primary human tracheal epithelial cell viability was assessed after UVA exposure, and 8-Oxo-2'-deoxyguanosine was measured as an oxidative DNA damage marker. Furthermore, wild-type mice were exposed to intracolonic UVA as an in vivo model to assess safety of internal UVA exposure. Controlled UVA exposure yielded significant reductions in Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Enterococcus faecalis, Clostridioides difficile, Streptococcus pyogenes, Staphylococcus epidermidis, Proteus mirabilis and Candida albicans. UVA-treated coxsackievirus-transfected HeLa cells exhibited significantly increased cell survival compared to controls. UVA-treated coronavirus-229E-transfected tracheal cells exhibited significant coronavirus spike protein reduction, increased mitochondrial antiviral-signaling protein and decreased coronavirus-229E-induced cell death. Specific controlled UVA exposure had no significant effect on growth or 8-Oxo-2'-deoxyguanosine levels in three types of human cells. Single or repeated in vivo intraluminal UVA exposure produced no discernible endoscopic, histologic or dysplastic changes in mice. These findings suggest that, under specific conditions, UVA reduces various pathogens including coronavirus-229E, and may provide a safe and effective treatment for infectious diseases of internal viscera. Clinical studies are warranted to further elucidate the safety and efficacy of UVA in humans.