Fosfomycin has been proven to be a vital choice to treat infection caused by multidrug resistance bacteria, especially carbapenem-resistant Klebsiella pneumoniae (CRKP). However, fosfomycin resistant cases has been reported gradually. In this study, we reported the fosfomycin-resistant rate in CRKP strains and further revealed the molecular mechanisms in resistance gene dissemination. A total of 294 non-duplicated CRKP strains were collected. And 55 fosfomyin-resistant strains were detected, 94.5% of which were clustered to sequence type (ST) 11 by PCR followed up sequencing. PFGE further revealed two major groups and four singletons. The positive rates of genes responsible to fosfomycin and carbapenem resistance were 81.8% (fosA3), 12.7% (fosA5) and 94.5% (blaKPC-2), respectively. Genomic analysis confirmed insertion sequence (IS) 26 was the predominant structure surrounding fosA3. The fosA3 genes in six isolates were located on plasmids which were able to transfer to E. coli J53 recipient cells by means of conjugation. Although the resistant rate of CRKP to fosfomycin is relatively low in our area, considering its gene is located on transferrable plasmid and inserted in IS structure, continuous monitoring is still needed.

The aim was to determine the potential association of the gut microbiota composition, especially the abundance of Actinobacteria, as well as the differentiation of functional and resistance genes with age (young adults vs elderly subjects) in China. The patterns of relative abundance of all bacteria isolated from fecal samples differed between young adults and elderly subjects, but the alpha diversity (Chao1 P = 0.370, Shannon P = 0.560 and Simpson P = 0.270) and beta diversity (ANOSIM R = 0.031, P = 0.226) were not significantly different. There were 3 Kyoto Encyclopedia of Genes and Genomes (KEGG) metabolic pathways (carbon metabolism, inositol phosphate metabolism, and sesquiterpenoid and triterpenoid biosynthesis) and 7 antibiotic resistant genes (ARGs) (macrolide lincosamide-streptogramin B (MLSB), tetracycline, aminoglycoside, sulfonamide, fosmidomycin, lincomycin, and vancomycin) that showed significant differences between the 2 groups (all P  0.05). Only the Bifidobacterium_dentium species showed significant differences between the 2 groups (P = 0.013), with a higher abundance in elderly subjects but absent in young adults. The present study revealed that there were 3 KEGG metabolic pathways and 7 ARGs as well as enhanced Bifidobacterium_dentium species abundance in elderly compared to young subjects.