Prevalence of mobile colistin resistance (mcr) genes in extended-spectrum ß-lactamase-producing Escherichia coli isolated from retail raw foods in Nha Trang, Vietnam.

The aim of the study was to assess the presence of genes in ESBL-producing E. coli (ESBL-Ec) isolated from retail raw food in Nha Trang, Vietnam. A total of 452 food samples comprising chicken (n = 116), pork (n = 112), fish (n = 112) and shrimp (n = 112) collected between 2015 and 2017 were examined for the prevalence of ESBL-Ec. ESBL-Ec were detected in 46.0% (208/452) of retail food samples, particularly in 66.4% (77/116), 55.4% (62/112), 42.0% (47/112) 19.6% (22/112) of chicken, pork, fish and shrimp, respectively. Sixty-five out of the 208 (31.3%) ESBL-Ec isolates were positive for mcr genes including mcr-1, mcr-3 and both mcr-1 and mcr-3 genes in 56/208 (26.9%), 1/208 (0.5%) and 8/208 (3.9%) isolates, respectively. Particularly, there was higher prevalence of mcr-1 in ESBL-Ec isolates from chicken (53.2%, 41/77) in comparison to shrimp (22.7%, 5/22), pork (11.3%, 7/62) and fish (6.4%, 3/47). mcr-3 gene was detected in co-existence with mcr-1 in ESBL-Ec isolates from shrimp (9.1%, 2/22), pork (8.1%, 5/62) and fish (2.1%, 1/47) but not chicken. The 65 mcr-positive ESBL-Ec (mcr-ESBL-Ec) were colistin-resistant with the MICs of 4-8 µg/mL. All mcr-3 gene-positive isolates belonged to group A, whereas phylogenetic group distribution of isolates harboring only mcr-1 was B1 (44.6%), A (28.6%) and D (26.8%). PFGE analysis showed diverse genotypes, although some isolates demonstrated nearly clonal relationships. S1-PFGE and Southern hybridization illustrated that the mcr-1 and mcr-3 genes were located either on chromosomes or on plasmids. However, the types of mcr genes were harbored on different plasmids with varied sizes of 30-390 kb. Besides, the ESBL genes of CTX-M-1 or CTX-M-9 were also detected to be located on plasmids. Noteworthy, co-location of CTX-M-1 with mcr-1 or mcr-3 genes on the same plasmid was identified. The conjugation experiment indicated that the mcr-1 or mcr-3 was horizontally transferable. All mcr-ESBL-Ec isolates were multidrug resistance (resistance to ≥3 antimicrobial classes). Moreover, ß-Lactamase-encoding genes of the CTX-M-1 (78.5%), CTX-M-9 (21.5%), TEM (61.5%) groups were found in mcr-ESBL-Ec. The astA gene was detected in 27 (41.5%) mcr-ESBL-Ec isolates demonstrating their potential virulence. In conclusion, mcr-1 and mcr-3 genes existed individually or concurrently in ESBL-Ec isolates recovered from retail raw food in Nha Trang city, which might further complicate the antimicrobial-resistant situation in Vietnam, and is a possible health risk for human.

Improving silymarin oral bioavailability using silica-installed redox nanoparticle to suppress inflammatory bowel disease.

Chronic inflammatory diseases such as inflammatory bowel diseases (IBD), which are strongly related to the overproduction of reactive oxygen species (ROS), have become more threatening to health. Silymarin is an active compound with the effect of expressing anti-inflammatory activity; however, it exhibits poor bioavailability due to the rapid metabolism and secretion, low permeability across the intestinal epithelial cells, and poor water solubility. In this study, we developed silica-containing redox nanoparticles (siRNP) with 50-60 nm in diameter to improve the bioavailability of silymarin by improving its uptake into the bloodstream and delivery to the targeted tissues of the colon. Silymarin-loaded siRNP (SM@siRNP) significantly increased the antioxidant capacity and anti-inflammatory efficacy in vitro by scavenging 2,2-diphenyl-1-picrylhydrazyl free radical and suppressing nitric oxide and pro-inflammatory cytokines as compared to the other treatments such as free silymarin, siRNP, and silymarin-loaded si-nRNP (the control nanoparticle without ROS scavenging property). Orally administered SM@siRNP significantly improved the bioavailability of silymarin and its retention in the colonic mucosa. The anti-inflammatory effects of SM@siRNP were also investigated in dextran sodium sulfate (DSS)-induced colitis in mice and it was observed that SM@siRNP treatment significantly improved the damage in the colonic mucosa of DSS colitis mice as compared to the other treatments. The results in this study indicate that SM@siRNP is a promising nanomedicine for enhancing the anti-inflammatory activity of silymarin and has a high potential for the treatment of IBD.