In vivo exposure–response relationship of meropenem against metallo-β-lactamase-harbouring Pseudomonas aeruginosa: an assessment using MICs from conventional and zinc-limited broth

Abstract

Objectives Previous investigations into metallo-β-lactamase (MBL)-harbouring Enterobacterales suggest that susceptibility testing in zinc-limited media may be more appropriate in predicting β-lactam in vivo activity. There are limited data with MBL-harbouring Pseudomonas aeruginosa. Methods Forty-three MBL-harbouring P. aeruginosa isolates (IMP, n = 11; VIM, n = 12; NDM, n = 10; SPM, n = 10) and two P. aeruginosa control isolates (KPC, n = 1; WT, n = 1) were evaluated. Meropenem activity was evaluated in the murine neutropenic thigh model using humanized exposures. Susceptibility testing was conducted in conventional CAMHB, EDTA-supplemented CAMHB (3–300 mg/L EDTA) and Chelex-treated CAMHB (0–1.0 mg/L re-supplemented zinc), resulting in a range of meropenem MIC values for each isolate. A sigmoidal Emax model was fitted to fT>MIC versus change in log10 cfu/thigh to estimate the goodness of fit (R2). Results Increasing EDTA concentrations or limiting the amount of zinc in broth resulted in several-fold reductions in MIC among the majority of the MBL-harbouring P. aeruginosa while the MICs for the KPC and WT isolates were unchanged. Bacterial killing in vivo was variable, with the range of killing spanning −3.29 to +4.81 log10 change in cfu/thigh. Addition of 30 mg/L EDTA and Chelex-treated CAMHB (with no zinc supplementation) provided broth conditions for susceptibility testing that best predicted in vivo efficacy (R2 > 0.7). Conclusions Among MBL-harbouring P. aeruginosa, meropenem in vivo efficacy is best represented by the pharmacodynamic profile generated using MICs determined in EDTA-supplemented or zinc-limited broth. In addition to previous data with Enterobacterales, antibiotic susceptibility testing in media that approximates physiological conditions makes it possible to uncover potential and existing therapeutic agents.

The Intersection between Bacterial Metabolism and Innate Immunity

“…Moreover, these results suggest that the cultivation methods often fail to align with the actual antibiotic susceptibility in vivo because they do not replicate the nutritional conditions in the host [113]. For example, MDR Gram-negative bacteria, such as E. coli , Pseudomonas aeruginosa , and Klebsiella pneumoniae , show high resistance to carbapenems due to the presence of excess zinc in Mueller-Hinton media as Zinc is a metal cofactor required for carbapenemase activity [142–144]. In validation studies, it was found that K. pneumoniae , E. coli , and P. aeruginosa were also highly resistant to carbapenems when grown in Mueller-Hinton broth [142, 143].…”

“…For example, MDR Gram-negative bacteria, such as E. coli , Pseudomonas aeruginosa , and Klebsiella pneumoniae , show high resistance to carbapenems due to the presence of excess zinc in Mueller-Hinton media as Zinc is a metal cofactor required for carbapenemase activity [142–144]. In validation studies, it was found that K. pneumoniae , E. coli , and P. aeruginosa were also highly resistant to carbapenems when grown in Mueller-Hinton broth [142, 143]. However, when the Mueller-Hinton broth was supplemented with a metal chelator, the bacteria had significantly increased carbapenem sensitivity.…”

“…In validation studies, it was found that K. pneumoniae, E. coli, and P. aeruginosa were also highly resistant to carbapenems when grown in Mueller-Hinton broth [142,143]. However, when the Mueller-Hinton broth was supplemented with a metal chelator, the bacteria had significantly increased carbapenem sensitivity.…”