Characterization of blaAFM-1-positive carbapenem-resistant strains isolated in Guangzhou, China.

BACKGROUND: Carbapenemase-producing makes a great contribution to carbapenem resistance in Gram-negative bacilli. BlaAFM-1 gene was first discovered by us in Alcaligenes faecalis AN70 strain isolated in Guangzhou of China and, was submitted to NCBI on 16 November 2018. METHODS: Antimicrobial susceptibility testing was performed by broth microdilution assay using BD Phoenix 100. The phylogenetic tree of AFM and other B1 metallo-ß-lactamases was visualized by MEGA7.0. Whole-genome sequencing technology was used to sequence carbapenem-resistant strains including the blaAFM-1 gene. Cloning and expressing of blaAFM-1 were designed to verify the function of AFM-1 to hydrolyze carbapenems and common ß-lactamase substrates. Carba NP and Etest experiments were conducted to evaluate the activity of carbapenemase. Homology modeling was applied to predict the spatial structure of AFM-1. A conjugation assay was performed to test the ability of horizontal transfer of AFM-1 enzyme. The genetic context of blaAFM-1 was performed by Blast alignment. RESULTS: Alcaligenes faecalis strain AN70, Comamonas testosteroni strain NFYY023, Bordetella trematum strain E202, and Stenotrophomonas maltophilia strain NCTC10498 were identified as carrying the blaAFM-1 gene. All of these four strains were carbapenem-resistant strains. Phylogenetic analysis revealed that AFM-1 shares little nucleotide and amino acid identity with other class B carbapenemases (the highest identity (86%) with NDM-1 at the amino acid sequence level). The spatial structure of the AFM-1 enzyme was predicted to be αß/ßα sandwich structure, with two zinc atoms at its active site structure. Cloning and expressing of blaAFM-1 verified AFM-1 could hydrolyze carbapenems and common ß-lactamase substrates. Carba NP test presented that the AFM-1 enzyme possesses carbapenemase activity. The successful transfer of pAN70-1(plasmid of AN70) to E.coli J53 suggested that the blaAFM-1 gene could be disseminated by the plasmid. The genetic context of blaAFM indicated that the downstream of the blaAFM gene was always adjacent to trpF and bleMBL. Comparative genome analysis revealed that blaAFM appeared to have been mobilized by an ISCR27-related mediated event. CONCLUSIONS: The blaAFM-1 gene is derived from chromosome and plasmid, and the blaAFM-1 gene derived from the pAN70-1 plasmid can transfer carbapenem resistance to susceptible strains through horizontal transfer. Several blaAFM-1-positive species have been isolated from feces in Guangzhou, China.

NIR-II Responsive Nanohybrids Incorporating Thermosensitive Hydrogel as Sprayable Dressing for Multidrug-Resistant-Bacteria Infected Wound Management.

Developing an effective dressing against bacterial infection and synchronously addressing wound complications, such as bleeding, long-term inflammation, and reinfection, are highly desirable in clinical practice. In this work, a second near-infrared (NIR-II) responsive nanohybrid consisting of imipenem encapsulated liposome with gold-shell and lipopolysaccharide (LPS)-targeting aptamer, namely ILGA, is constructed for bacteria elimination. Benefiting from the delicate structure, ILGA exhibits strong affinity and a reliable photothermal/antibiotic therapeutic effect toward multidrug-resistant Pseudomonas aeruginosa (MDR-PA). Furthermore, by incorporating ILGA with a thermosensitive hydrogel poly(lactic-co-glycolic acid)-polyethylene glycol-poly(lactic-co-glycolic acid) (PLGA-PEG-PLGA), a sprayable dressing ILGA@Gel was prepared, which enables a quick on-demand gelation (10 s) for wound hemostasis and offers excellent photothermal/antibiotic efficacy to sterilize the infected wound. Additionally, ILGA@Gel provides satisfactory wound-healing environments by reeducating wound-associated macrophages for inflammation alleviation and forming a gel layer to block exogenous bacterial reinfection. This biomimetic hydrogel reveals excellent bacteria eradication and wound recovery effectiveness, demonstrating its promising potential for managing complicated infected wounds.