Essack, S. | Search bioRxiv

bioRxiv2023

Metal Ions and their Effects on Antimicrobial Resistance Development in Wastewater

Antimicrobial resistance (AMR) is a global health challenge and there is increasing recognition of the role of the environment, particularly wastewater, in the development and spread of AMR. Although trace metals are common contaminants in wastewater, the quantitative effects of trace metals on AMR in wastewater settings remain understudied. We experimentally determined the interactions between common antibiotic residues and metal ions found in wastewater and investigated their effects on the development of antibiotic resistance in Escherichia coli over time. These data were then used to expand on a previously developed computational model of antibiotic resistance development in continuous flow settings to incorporate the effects of trace metals acting in combination with multiple antibiotic residues. We found that the common metal ions, copper and iron, interact with both ciprofloxacin and doxycycline at wastewater relevant concentrations. This can significantly affect resistance development due to antibiotic chelation of the metal ions causing a reduction in the antibiotics bioactivity. Furthermore, modeling the effect of these interactions in wastewater systems showed the potential for metal ions in wastewater to significantly increase the development of antibiotic resistant E. coli populations. These results demonstrate the need to quantitatively understand the effects of trace metal-antibiotic interactions on AMR development in wastewater.

bioengineering↗

bioRxiv2018

Evaluation of 1, 4, 7-Triazacyclononane (TACN) as a potential Metallo-B-Lactamase inhibitor in Enterobacteriaceae: Restoring the Activity of B-lactams

Metallo-{beta}-lactamase producing Enterobacteriaceae are of grave clinical concern particularly as there are no Metallo-{beta}-lactamase (MBL) inhibitors approved for clinical use. The discovery and development of MBL inhibitors to restore the efficacy of available {beta}-lactams are thus imperative. We investigated a zinc-chelating moiety, 1, 4, 7-triazacyclononane (TACN) for its inhibitory activity against clinical carbapenem-resistant Enterobacteriaceae. Minimum inhibitory concentrations (MICs), minimum bactericidal concentrations (MBCs), serum effect, fractional inhibitory concentrations index and time-kill kinetics were performed using broth microdilution techniques according to the Clinical Laboratory Standard Institute (CSLI) guidelines. Enzyme kinetic parameters and cytotoxicity effects of TACN were determined using spectrophotometric assays. The interactions of the enzyme-TACN complex were investigated by computational studies. Meropenem regained its activity against carbapenemase-producing Enterobacteriaceae, with the MIC decreasing to 0.03 mg/L in the presence of TACN. TACN-Meropenem combinations showed bactericidal effects with MIC/MBC ratio of [≤]4, and synergistic activity was observed. Human serum effects on the MICs were insignificant, and TACN was found to be non-cytotoxic at concentrations above the MIC values. Computational studies predicted that TACN inhibits MBLs by targeting their catalytic active site pockets. This was supported by its inhibition constant Ki = 0.044 {micro}M and inactivation constant kinact= 0.0406 (min-1) demonstrating that TACN inhibits MBLs efficiently and holds promise as a potential inhibitor.\n\nImportanceCarbapenem-resistant Enterobacteriaceae (CRE)-mediated infections remain a significant public health concern and have been reported as critical in the World Health Organizations Priority Pathogens List for the Research and Development of New Antibiotics. CRE produce enzymes such as Metallo-{beta}-lactamases (MBLs), which inactivate {beta}-lactam antibiotics. Combination therapies involving a {beta}-lactam antibiotic and a {beta}-lactamase inhibitor remain a major treatment option for infections caused by {beta}-lactamase-producing organisms. Currently, no MBL inhibitor-{beta}-lactam combination therapy is clinically available for MBL-positive bacterial infections. Hence, developing efficient molecules capable of inhibiting these enzymes could be a promising way to overcome this phenomenon. TACN played a significant role in the inhibitory activity of the tested molecules against CREs by potentiating the carbapenem. This study demonstrated that TACN inhibits MBLs efficiently and holds promises as a potential MBLs inhibitor to help curb the global health threat posed by MBL-producing CREs.

microbiology↗