Study On The Effect Of Static And Flow On The Interaction Of NDM-1 And Aztreonam

New Delhi metal-β-lactamase 1(New Delhi metallo-beta-lactamase-1;NDM-1)is a metal ion-dependent β-lactamase(metal-lactamase,MBL)which can hydrolyze almost all β-lactam antibiotics but is extremely difficult to hydrolysis aztreonam(ATM).Good treatment outcomes were observed from combined treatment of infection by serine-β-lactamase(SBL)and metallo-β-lactamase(MBL)co-expressing Gram-negative bacteria with Aztreonam and Ceftazidime-Avibactam.However,the detailed role of aztreonam in the good treatment outcome remains not clear.On the other hand,data from a recent study show that NDM-1 in high concentrations can hydrolyzed aztreonam.Thus far,it remains largely unknown whether antibiotic resistance(AR)of NDM-1 to aztreonam is condition-dependent as well as what conditions will lead NDM-1 to resist ammonia.In the present study,we investigated the effect of reciprocal interaction between NDM-1 and aztreonam on AR activity of the NDM-1 in condition of static and continuous-flow reactions using soluble NDM-1,NDM-1 immobilized glass beads(NDM-1 beads)and a NDM-1 thermal sensor preloaded with NDM-1 beads.Firstly,when hydrolytic reaction of NDM-1 to antibiotics occurred in microcentrifuge tube(termed as a static condition),it was observed that cotreatment of Aztreonam significantly inhibited hydrolysis of Nitrocefin and Meropenem by soluble NDM-1.The NDM-1 bead NDs efficiently hydrolyze penicillin G and meropenem,but not Aztreonam.Moreover,co-treatment of Aztreonam significantly inhibits the NDM-1 beads to hydrolyze penicillin G.In spite of extensive washing for multiple times,activity to hydrolyze Penicillin G by the Aztreoman pre-treated NDM-1 beads was just partially recovered.These data indicate that Aztreonam can covalently and stably bind on NDM-1,thus efficiently inhibiting hydrolysis of other kinds of β-lactam antibiotics by NDM-1 in a competitive way.On the other hand,effect of continuous-flow condition on hydrolytic activity of the NDM-1 beads to antibiotics was investigated using a NDM-1 thermal sensor.It was observed that Aztreonam couldn’t inhibit hydrolysis of penicillin G by the NDM-1 beads when the mixture of Aztreonam and penicillin G was loaded into the NDM-1 thermal sensor.In addition,Aztreonam itself was hydrolyzed by the NDM-1 beads in the meanwhile.Approximate 40% Aztreonam was hydrolyzed by analyzing the amount of Aztreonam in the flow-through from the NDM-1 thermal sensor loaded with Aztreonam.These data indicate that continuous flow promotes NDM-1 to hydrolyze Aztreonam.In conclusion,the data of current study indicate that the relative motion between NDM-1 and Aztreonam functions as a switch to turn on or turn off the hydrolytic activity of NDM-1.This finding facilitates to understand the role of Aztreonam in effective treatment of MBL/SBL co-producing gram negative bacteria,but also enhance understanding of the mechanism behind AR of NDM-1.