Real-time monitoring of New Delhi metallo-β-lactamase activity in living bacterial cells by 1H NMR spectroscopy.
Bottom Line: Disconnections between in vitro responses and those observed in whole cells confound many attempts to design drugs in areas of serious medical need.NDM-1 activity in cells was also shown to be inhibited by spermine, a porin inhibitor, although in an in vitro assay, the influence of spermine on the activity of isolated NDM-1 protein is minimal.This new approach may have generic utility for monitoring reactions involving diffusible metabolites in other complex biological matrices and whole-cell settings, including mammalian cells.
Affiliation: Discovery Sciences, AstraZeneca Boston, Waltham, MA 02451 (USA).Show MeSH
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Mentions: The stability of a few selected antibiotics (Figure S6) that display broad-spectrum antibacterial activities was compared in the presence of NDM-1 E. coli cells (Figure 2). It is known that NDM-1-positive strains are no longer susceptible to carbapenems such as meropenem and imipenem.13 These were readily hydrolyzed by the NDM-1 E. coli cells within an hour or so under our experimental conditions. Aztreonam, an exception among β-lactams, is not inactivated by metallo-β-lactamases.16, 17 Our results are consistent with this observation: no reduction in the NMR signals of aztreonam is seen in NDM-1 E. coli cells (Figure 2). It is reported that NDM-1-producing Klebsiella pneumoniae and E. coli are still susceptible to tigecycline.16, 18 Indeed, our data confirm that tigecycline is stable in the NDM-1 E. coli cells. Despite the fact that when using in vitro enzymatic assays, isolated NDM-1 enzyme shows moderate hydrolysis activity against cephalosporins such as cefotaxime and ceftazidime,17 no detectable change was observed within an hour when either drug was incubated with NDM-1 E. coli cells.
Affiliation: Discovery Sciences, AstraZeneca Boston, Waltham, MA 02451 (USA).