We report a general strategy for diverse synthesis of ten disaccharide aminoglycosides including natural 2-trehalosamine (1), 3-trehalosamine (2), 4-trehalosamine (3), 6-trehalosamine (4), and neotrehalosyl 3,3'-diamine (8), and synthetic aminoglycosides (4-7, 9, and 10). The aminoglycoside compounds feature different anomeric configurations and numbers of the amino groups. The key step for the synthesis is the 1,1'-glycosylation coupling of a stereo-directing donor and a configuration stable TMS glycoside acceptor with or without azido group substitution in high stereoselectivity. The compounds obtained in present study are fully characterized with the 1D and 2D NMR spectroscopy.

The intestinal microbiota plays an important role in the pathogenesis of acute graft-versus-host disease (aGVHD). During the course of hematopoietic stem cell transplantation (HSCT), the intestinal microbiota is influenced by the use of broad-spectrum antibiotics. However, the impact of the use and type of antibiotics on the microbiota composition and, subsequently, the onset of aGVHD remain poorly understood. We hypothesized that the use and type of antibiotics had an impact on the occurrence of aGVHD. We assessed 275 patients who underwent their first allogeneic HSCT between January 2005 and June 2015 at Kyoto University Hospital. We monitored the 6 most frequently administered antibiotics (fourth-generation cephalosporins, glycopeptides, piperacillin-tazobactam, carbapenems, aminoglycosides, and quinolones) administered between days -14 and +14 relative to HSCT and its duration. The primary endpoint was the cumulative incidence of grades II to IV aGVHD. The cumulative incidence of aGVHD was significantly higher in patients administered fourth-generation cephalosporins than in patients not receiving fourth-generation cephalosporins (grades II to IV: hazard ratio, 1.98; 95% confidence interval, 1.19 to 3.29; P = .0087; grades III to IV: hazard ratio, 8.03; 95% confidence interval, 1.07 to 60.51; P = .043). In contrast, there was no significant association between administration of other antibiotics and aGVHD incidence. As for organ-specific aGVHD, the cumulative incidence of gut aGVHD was significantly higher in patients who received fourth-generation cephalosporins than in those who did not (31% versus 16%, P = .018). In conclusion, we demonstrated that the administration of fourth-generation cephalosporins had a strong impact on the development of aGVHD.

Aminoglycosides containing a 2-deoxystreptamine core (AGs) represent a large family of antibiotics that target the ribosome. These compounds promote miscoding, inhibit translocation, and inhibit ribosome recycling. AG binding to helix h44 of the small subunit induces rearrangement of A-site nucleotides (nt) A1492 and A1493, which promotes a key open-to-closed conformational change of the subunit and thereby increases miscoding. Mechanisms by which AGs inhibit translocation and recycling remain less clear. Structural studies have revealed a secondary AG binding site in H69 of the large subunit, and it has been proposed that interaction at this site is crucial for inhibition of translocation and recycling. Here, we analyze ribosomes with mutations targeting either or both AG binding sites. Assaying translocation, we find that ablation of the h44 site increases the IC50 values for AGs dramatically, while removal of the H69 site increases these values modestly. This suggests that AG-h44 interaction is primarily responsible for inhibition, with H69 playing a minor role. Assaying recycling, we find that mutation of h44 has no effect on AG inhibition, consistent with a primary role for AG-H69 interaction. Collectively, these findings help clarify the roles of the two AG binding sites in mechanisms of inhibition by these compounds.

Despite causing permanent hearing loss by damaging inner ear sensory cells, aminoglycosides (AGs) remain one of the most widely used classes of antibiotics in the world. Although the mechanisms of cochlear sensory cell damage are not fully known, reactive oxygen species (ROS) are clearly implicated. Mitochondrial-specific ROS formation was evaluated in acutely cultured murine cochlear explants exposed to gentamicin (GM), a representative ototoxic AG antibiotic. Superoxide (O2·-) and hydrogen peroxide (H2O2) were measured using MitoSOX Red and Dihydrorhodamine 123, respectively, in sensory and supporting cells. A 1-h GM exposure significantly increased O2·- formation in IHCs and increased H2O2 formation in all cell types. At the same time point, GM significantly increased manganese superoxide dismutase (MnSOD) levels while significantly decreasing copper/zinc superoxide dismutase (CuZnSOD) in cochlear sensory cells. This suggests (1) a rapid conversion of highly reactive O2·- to H2O2 during the acute stage of ototoxic antibiotic exposure and (2) that the endogenous antioxidant system is significantly altered by AGs. Fluorescence intensity-based measurements of reduced nicotinamide adenine dinucleotide (phosphate) [NAD(P)H] and mitochondrial membrane potential were measured to determine if increases in GM-induced ROS production were correlated with changes in mitochondrial metabolism. This project provides a basis for understanding the mechanisms of mitochondrial ROS production in cochlear cells exposed to ototoxic antibiotics. Understanding the nature of ototoxic antibiotic-induced changes in mitochondrial metabolism is critical for developing hearing loss treatment and prevention strategies.

Salmonella enterica is a leading cause of human gastroenteritis in both developed and developing countries, causing significant economic losses on humans and animals worldwide. There are several routes for contracting salmonellosis, but the consumption of contaminated foods is by far the most frequent cause of human infections. This study aimed to assess the prevalence and resistance determinants of S. enterica isolates obtained from meat. Swab samples from meat were cultured for the identification of Salmonella spp., and 239 presumptive S. enterica isolates were recovered, purified and kept in glycerol stocks. The S. enterica. confirmed by polymerase chain reaction (PCR) were further tested against 15 antimicrobials using the disc-diffusion method on Muller-Hinton agar and the genotypic antimicrobial resistance determinants by PCR. Resistance among tetracyclines, bêta-lactams, and 3rd generation cephalosporins was found to be most frequent with a noticeable rise in the number of multi-drug resistance ranging from two to seven antimicrobials. A total of 20 resistance determinants were assessed with their prevalence and distributions obtained as follows; [aminoglycosides: aadA (89%), aacC2 (100%), aphA1 (38%), aphA2 (0%) and strA (7%)], [β-lactams: (ampC 100%), blaTEM, (33 %), blaZ (17 %) and blaOXA (10%)], [Chloramphenicol: catI (9%), catII (7 %), and cmIA1 (10 %)] and [tetracyclines: tetA (57%), tetB (30%), tetC (11 %), tetD (73 %), tetK (20%) and tetM, (43 %)], and [sulfonamides: sulI (82 %), sulII (7%)]. The findings signify a high prevalence of multidrug-resistant (MDR) S. enterica isolates and resistance determinants indicating increased public health risks associated with the consumption of contaminated meat.

Enterobacteriaceae cause different types of community- and hospital-acquired infections. Moreover, the spread of multidrug-resistant Enterobacteriaceae is a public health problem and the World Health Organization pointed them among the pathogens in which the search of new antibiotics is critical. The objective of this study was to analyze the in vitro activity of pentamidine alone and in combination with gentamicin, tobramycin, amikacin, tigecycline, rifampicin, or doripenem against eight clinical strains of carbapenemase-producing and/or colistin-resistant Enterobacteriaceae: five carbapenemase-producing Klebsiella pneumoniae, one carbapenemase-producing Escherichia coli, and two colistin-resistant Enterobacter cloacae. MIC and MBC were determined following standard protocols. MIC results were interpreted for all the antibiotics according to the EUCAST breakpoints but for rifampicin in which the French FSM breakpoint was used. Bactericidal and synergistic activity of pentamidine alone and in combination with antibiotics at concentrations of 1xMIC was measured by time-kill curves. For one selected strain, K. pneumoniae OXA-48/CTX-M-15 time-kill curves were performed also at 1/2xMIC of pentamidine. All studies were performed in triplicate. Pentamidine MIC range was 200-800 μg/mL. The 50, 12.5, 62.5, 87.5, and 62.5% of the strains were susceptible to gentamicin, tobramycin, amikacin, tigecycline, and doripenem, respectively. Only the two E. cloacae strains were susceptible to rifampicin. Pentamidine alone at 1xMIC showed bactericidal activity against all strains, except for the E. cloacae 32 strain. The bactericidal activity of pentamidine alone was also observed in combination. The combinations of pentamidine were synergistic against E. cloacae 32 with amikacin and tobramycin at 24 h and with tigecycline at 8 h. Pentamidine plus rifampicin was the combination that showed synergistic activity against more strains (five out of eight). Pentamidine plus doripenem did not show synergy against any strain. At 1/2xMIC, pentamidine was synergistic with all the studied combinations against the K. pneumoniae OXA-48/CTX-M-15 strain. In summary, pentamidine alone and in combination shows in vitro activity against carbapenemase-producing and/or colistin-resistant Enterobacteriaceae. Pentamidine appears to be a promising option to treat infections caused by these pathogens.

Thermotolerant Campylobacter species C. jejuni and C. coli are actually recognized as the major bacterial agent responsible for food-transmitted gastroenteritis. The most effective antimicrobials against Campylobacter are macrolides and some, but not all aminoglycosides. Among these, susceptibility to streptomycin is reduced by mutations in the ribosomal RPSL protein or by expression of ANT(6)-I aminoglycoside O-nucleotidyltransferases. The presence of streptomycin resistance genes was evaluated among streptomycin-resistant Campylobacter isolated from humans and animals by using PCR with degenerated primers devised to distinguish ant(6)-Ia, ant(6)-Ib and other ant-like genes. Genes encoding ANT(6)-I enzymes were found in all possible combinations with a major fraction of the isolates carrying a previously described ant-like gene, distantly related and belonging to the new ant(6)-I sub-family ant(6)-Ie. Among Campylobacter isolates, ant(6)-Ie was uniquely found functional in C. coli, as shown by gene transfer and phenotype expression in Escherichia coli, unlike detected coding sequences in C. jejuni that were truncated by an internal frame shift associated to RPSL mutations in streptomycin resistant strains. The genetic relationships of C. coli isolates with ANT(6)-Ie revealed one cluster of strains presented in bovine and humans, suggesting a circulation pathway of Campylobacter strains by consuming contaminated calf meat by bacteria expressing this streptomycin resistance element.

Infections due to New Delhi metallo-beta lactamase (NDM)-7-producing Escherichia coli are infrequent and sporadic. In this study, we report one case of recurrent urinary tract infection caused by blaNDM-7-producing E. coli belonging to phylogenetic group A, sequence type (ST) 167. In this study, we aimed to describe the genotype and phenotype of blaNDM-7-producing E. coli in China. The isolate exhibited resistance to β-lactam antimicrobials, trimethoprim-sulfamethoxazole, quinolones, and aminoglycosides. blaNDM-7 is located on a conjugative plasmid designated pJN05NDM-7 belonging to type IncX3. pJN05NDM-7 was fully sequenced and compared with all publicly available blaNDM-7-harboring plasmids. pJN05NDM-7 is almost identical to pKpN01-NDM7 and pKW53T, although the plasmids are geographically unrelated. The comparison of IncX3 plasmids harboring blaNDM in China showed high similarity, with genetic differences within insertion fragments. Notably, the differences in plasmids of animal and human origin were insignificant, because only one plasmid showed deletion inside the ISAba125 region compared with pJN05NDM7. Our study demonstrates that E. coli carrying IncX3 plasmids play an important role as a reservoir and in the spread of blaNDM. Further studies should be performed to control the dissemination of blaNDM among food animals.