pneumoniae chromosome, Citation14, Citation23 and have high similarity of nucleic acid sequence with fosA10, with difference in only four or seven nucleotides. The other two plasmid-located fosA genes, fosA5 and fosA6, also originated from K. However, the size of the spacer region between the 3ʹ end of fosA10 and IS 10 was longer than that in pHNPK9-FOS (1663 bp vs 1060 bp), indicating occurrence of a different mobilization event of fosA10 from K. pneumoniae strains mentioned above ( Figure 3). coli strain AUH_IMP168 was also 100% identical to the chromosome sequences of 18 K. The fragment containing fosA10 surrounded by IS 10 in E. coli strain AUH_IMP168 collected in 2013 from Lebanon also contained fosA10 and two incomplete IS 10 elements caused by short-read DNA sequencing. In addition, a WGS contig (GenBank accession number MUJB01000052) of an E. pneumoniae strains belong to ST644 except one that belongs to ST3821 ( Table S1). pneumoniae strains from Austria, USA, UK, Morocco, and Japan ( Figure 3 and Table S1), suggesting its mobilization from the chromosome of one K. BLAST homology analysis demonstrated that the sequence of the 1670 bp region surrounded by IS 10 had 100% nucleotide identity with chromosome sequences of 18 K. ![]() In addition to fosA10 gene, the region surrounded by IS 10 includes a truncated transcriptional regulator gene lysR (190 bp) and a 1060 bp sequence (containing a truncated hypothetical gene) located upstream and downstream of fosA10, respectively. The insertion was surrounded by a 9-bp direct repeat sequences (DRs) (TACCTGGTG) suggesting mobilization of this fosA10 gene by composite transposon formed by IS10 ( Figure 3). A variable region of 4328 bp consisting of fosA10 and two copies of IS 10 element was inserted into a hypothetical gene of the plasmid backbone. It possessed a typical IncF-type backbone, encoding genes for replication, transfer, maintenance, and stability functions ( Figure 2). pHNPK9-FOS was a 53,736 bp plasmid containing 69 predicted ORFs, and belonged to IncFII (F35:A-:B-). One plasmid, designated pHNPK9-FOS, carries fosA10. Hybrid assembly of the MinION long reads and HiSeq short reads revealed that PK9 had a circular 5,423,354 bp chromosome and three plasmids ( Table 2). Genetic Context and Origin of the fosA10 Gene coli isolate, and characterized the genetic context of fosA10 to identify its origin. In this study, we reported a novel plasmid-encoded fosA variant, fosA10, in an ESBL-producing E. Citation14, Citation16, Citation17, Citation21-23 ![]() Citation12, Citation18-20 All fosA subtypes, except fosA2 and fosA7, are identified in plasmids, and they are usually originated from the chromosomal gene of Enterobacteriaceae species. coli, has been detected in human and animal isolates from more than 12 countries, especially in food-producing animal-associated isolates from China. Citation10, Citation12, Citation14-17 fosA3, the most widespread fosA gene in E. Citation13 Until now, nine subtypes of fosA genes have been identified. Citation12, Citation13 As a glutathione S-transferase, FosA inactivates fosfomycin by catalyzing the addition of glutathione to fosfomycin. Citation10 – Citation12 FosA is the most frequently reported group of enzymes in Enterobacteriaceae. Citation9 A variety of fosfomycin-modifying enzymes, such as FosA, FosB, FosC, FosL, have been described. coli, including modification or overexpression of MurA, inactivation of transporters and their regulatory genes (such as uhpA, cyaA, and ptsI), and acquisition of fosfomycin-modifying enzymes. Citation7, Citation8 Several mechanisms underlying fosfomycin resistance have been identified in E. ![]() Citation6 Besides, fosfomycin enters the bacterial cell via two transporters, glycerol-3-phosphate transporter (GlpT) and hexose phosphate transporter (UhpT). Citation4, Citation5įosfomycin interferes with the biosynthesis of cell wall by inhibiting production of UDP-N-acetylglucosamine enolpyruvyl transferase (MurA). Citation1 – Citation3 Fosfomycin exhibits broad-spectrum bactericidal activity against Gram-positive and Gram-negative bacteria, and is listed as one of the first-line options for the treatment of uncomplicated lower urinary tract infections caused by ESBL-producing Escherichia coli. ![]() In recent years, the widespread occurrence of extended-spectrum β-lactamases (ESBLs)-producing and carbapenem-resistant Enterobacteriaceae (CRE) in human clinic has renewed interest in the use of old antimicrobial agents, such as colistin and fosfomycin in the treatment of infections caused by multidrug-resistant pathogens.
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