Rapid Identification and Classification of Pathogens That Produce Carbapenemases and Cephalosporinases with a Colorimetric Paper-Based Multisensor

Discovery of hydroxamate as a promising scaffold dually inhibiting metallo- and serine-β-lactamases

The bacterial infection mediated by β-lactamases MβLs and SβLs has grown into an emergent health threat, however, development of a molecule that dual inhibits both MβLs and SβLs is challenging. In this work, a series of hydroxamates 1a-g, 2a-e, 3a-c, 4a-c were synthesized, characterized by 1H and 13C NMR and confirmed by HRMS. Biochemical assays revealed that these molecules dually inhibited MβLs (NDM-1, IMP-1) and SβLs (KPC-2, OXA-48), with an IC50 value in the range of 0.64-41.08 and 1.01-41.91 μM (except 1a and 1d on SβLs, IC50 > 50 μM), and 1f was found to be the best inhibitor with an IC50 value in the range of 0.64-1.32 and 0.57-1.01 μM, respectively. Mechanism evaluation indicated that 1f noncompetitively and irreversibly inhibited NDM-1 and KPC-2, with Ki value of 2.5 and 0.55 μM, is a time- and dose-dependent inhibitor of both MβLs and SβLs. MIC tests shown that all hydroxamates increased the antimicrobial effect of MER on E. coli-NDM-1 and E. coli-IMP-1 (expect 1b, 1d, 1g and 2d), resulting in a 2-8-fold reduction in MICs of MER, 1e-g, 2b-d, 3a-c and 4b-c decreased 2-4-fold MICs of MER on E. coli-KPC-2, and 1c, 1f-g, 2a-c, 3b, 4a and 4c decreased 2-16-fold MICs of MER on E. coli-OXA-48. Most importantly, 1f-g, 2b-c, 3b and 4c exhibited the dual synergizing inhibition against both E. coli-MβLs and E. coli-SβLs tested, resulting in a 2-8-fold reduction in MICs of MER, and 1f was found to have the best effect on the drug-resistant bacteria tested. Also, 1f shown synergizing antimicrobial effect on five clinical isolates EC04, EC06, EC08, EC10 and EC24 that produce NDM-1, resulting in a 2-8-fold reduction in MIC of MER, but its effect on E. coli and K. pneumonia-KPC-NDM was not to be observed using the same dose of inhibitor. Mice tests shown that the monotherapy of 1f or 4a in combination with MER significantly reduced the bacterial load of E. coli-NDM-1 and E. coli-OXA-48 cells in liver and spleen, respectively. The discovery in this work offered a promising bifunctional scaffold for creating the specific molecules that dually inhibit MβLs and MβLs, in combating antibiotic-resistant bacteria.

Paper-based analytical device integrated with bacteriophage tail fiber protein for bacteria detection and antimicrobial susceptibility test

Severe antimicrobial resistance calls for developing rapid, sensitive and affordable methodological platform for clinical diagnosis of bacterial infection. Herein, a paper-based analytical device (PAD) for fluorescent (FL) detection and antimicrobial susceptibility test (AST) of Pseudomonas aeruginosa (P. aeruginosa) was fabricated by defining 96 hydrophilic microzones on a filter paper using a handheld stamp dipped with liquid wax. The size of microzones was designed to be consistent with traditional 96-well microplate, thus the FL signals can be collected by a commercialized microplate reader. Streptavidin was immobilized into the microzones by chitosan-glutaraldehyde crosslinking reaction, and then biotinylated bacteriophage tail fiber protein (TFP) was conjugated through biotin-streptavidin affinity system. TFP and fluorescein isothiocyanate (FITC) labeled antimicrobial peptide were used as capture agent and signal probe, respectively, for FL detection of P. aeruginosa on the PAD. The linear range for quantifying P. aeruginosa is 1.0 × 103 CFU/mL to 1.0 × 107 CFU/mL, with a detection limit of 137 CFU/mL. The PAD was also applied to conduct AST of P. aeruginosa for imipenem, meropenem, cefepime, amikacin, and gentamicin, and the results are consistent with the traditional broth dilution method. The PAD provides an affordable diagnosis platform for bacterial infection, especially in resource-limited institutes and countries.

Culture-Independent Multiplexed Detection of Drug-Resistant Bacteria Using Surface-Enhanced Raman Scattering

The rapid and accurate detection of bacteria resistance to β-lactam antibiotics is critical to inform optimal treatment and prevent overprescription of potent antibiotics. Here, we present a fast, culture-independent method for the detection of extended-spectrum β-lactamases (ESBLs) using surface-enhanced Raman scattering (SERS). The method uses Raman probes that release sulfur-based Raman active molecules in the presence of β-lactamases. The released thiol molecules can be captured by gold nanoparticles, leading to amplified Raman signals. A broad-spectrum cephalosporin probe R1G and an ESBL-specific probe R3G are designed to enable duplex detection of bacteria expressing broad-spectrum β-lactamases or ESBLs with a detection limit of 103 cfu/mL in 1 h incubation. Combined with a portable Raman microscope, our culturing-free SERS assay has reduced screening time to 1.5 h without compromising sensitivity and specificity.