An enzyme-free homogenous electrochemical assay for sensitive detection of the plasmid-mediated colistin resistance gene mcr-1

A "Turn-on" fluorescence sensing strategy based on DNA-templated silver nanoclusters for the detection of antibiotic resistance genes

BACKGROUND

Antibiotic resistance genes (ARGs) are emerging environmental contaminants that pose serious threats to human health and ecological security due to their rapid migration and transformation in the environment. Thus, developing a sensitive and rapid method to detect ARGs is significant.

RESULTS

In this study, the neighborhood-dependent fluorescent sensor was established with DNA templated silver nanoclusters (AgNCs) and multi-branched linear structure to detect the typical macrolide resistance gene ermB. A DNA fluorescent probe with a specific recognition fragment for AgNCs and a tuning enhancement sequence were designed. The probe and the target resistance genes were complementary hybridized to form a linear multi-branch DNA structure of bright yellow silver nanocluster beacon that realized fluorescence signal amplification and transduction.

SIGNIFICANCE

This method has the advantages of being enzyme-free, label-free and amplification-free for being applied to the rapid detection of specific ARGs and successfully detected macrolide resistance gene ermB with the LOD as low as 0.37 nM in environmental samples with complex composition.

Rapid and sensitive parallel on-site detection of antibiotics and resistance genes in aquatic environments using evanescent wave dual-color fluorescence fiber-embedded optofluidic nanochip

Environmental antibiotics and antibiotic resistance genes (ARGs) pose considerable threat to humans and animals; thus, the rapid and sensitive parallel detection of these pollutants from a single sample is urgently required. However, traditional multiplexed analytic technologies detect only one type of target (e.g., small molecules or nucleic acids) per assay. To address this issue, Evanescent wave Dual-color fluorescence Fiber-embedded Optofluidic Nanochip (EDFON) was fabricated by integrating a fiber-embedded optofluidic nanochip with evanescent wave dual-color fluorescence technology. The EDFON was used for the parallel quantitative detection of sulfamerazine (SMR) and MCR-1 with high sensitivity and specificity by combining a heterogeneous immunoassay with a homogenous hybridization chain reaction based on time-resolved effects. LODs of 0.032 μg/L and 35 pM was obtained for SMR and MCR-1, respectively, within 20 min. To our best knowledge, the EDFON is the first device for the simultaneous detection of two type of targets in each test, which is highly valuable to prevent the global threats of antibiotics and ARGs. Comparison with liquid chromatography-mass spectrometry showed a strong linear relationship (R2 = 0.998) for SMR pollution in the Qinghe River, with spiked SMR and MCR-1 negative surface and wastewater samples showing recovery rates of 91.8-113.4%. These results demonstrate the excellent accuracy and reliability of the EDFON, with features such as multi-analyte detection, field-deployment, and minimal-equipment, rendering it revolutionary for environmental monitoring, food safety, and medical diagnostics.

Mobile colistin resistance (mcr) genes and recent developments in colistin resistance detection

The peptide antibiotic colistin has been reserved as a last resort antibiotic treatment option for cases where other antibiotics including carbapenems have failed. Recent emergence of colistin resistance and discovery of mobile colistin resistance (mcr) genes, which encode the cell wall modifying phosphoethanolamine transferase enzyme, complicates the issue. The mcr genes have been associated with conjugative plasmids and can be horizontally transferred between different bacterial species. The global spread of mcr genes has been extensively documented and this warrants surveillance of the resistance genes in the community. However, susceptibility testing of colistin is fraught with practical challenges owing to the chemical nature of the drug and multiple mechanisms of resistance. Although broth microdilution is the current gold standard for colistin susceptibility testing, the method poses technical challenges. Hence, alternative detection methods for screening colistin resistance are the need of the hour. Several methods have been studied in the recent times to address this issue. In this review, we discuss some of the recent developments in the detection of colistin resistance.

Dual-channel fluorescence detection of antibiotic resistance genes based on DNA-templated silver nanoclusters

The aqueous environment is an ideal site for the generation and transmission of antibiotic resistance genes (ARGs), and has become a sink for multiple ARGs. Detection of multiple ARGs in one-pot by a simple method is essential to control the spread of antibiotic resistance. Herein, we developed a novel fluorescence sensing strategy based on chameleon DNA-templated silver nanoclusters (AgNCs) to achieve simultaneous detection of two ARGs (tet-A and sul-1). A DNA fluorescent probe with AgNCs stabilized at both termini and another DNA probe carried enhancer sequences were designed. The hybridization of the target ARGs and probes can form an infinitely extended linear DNA structure containing multi-branched AgNCs beacons, and the chameleon AgNCs approach the fluorescence enhancer sequence, thereby realizing the transduction and amplification of green and red fluorescence signals. Through this strategy, we successfully achieved highly specific detection of two ARGs with the LOD of 0.45 nM for tet-A and 0.32 nM for sul-1. In addition, the strategy still had good applicability in the detection of actual samples containing complex components. In this study, fluorescent DNA-AgNCs were applied to the rapid, enzyme-free and reliable detection of ARGs for the first time. The excellent performance of the simultaneous detection of two ARGs displayed that this method can be used to simultaneously analyze different types of ARGs, indicating its great potential in rapid screening and quantitative detection of ARGs in various environmental medias.

How to: screening for mcr-mediated resistance to colistin

BACKGROUND

Colistin belongs to the last-resort antibiotics. The discovery of plasmid-bound colistin resistance mediated by the mcr-gene(s) is of great concern because, given its biological potential, there is a risk of its rapid spread.

OBJECTIVES

To discuss the current literature on the methods for the screening for mcr-mediated resistance to colistin.

SOURCES

Literature was drawn from a search of PubMed from 1 January 2016 to 26 April 2021.

CONTENT

The selective culture-based or culture-independent approach can be used for the screening of mcr-mediated resistance to colistin in clinical samples. Rapid Polymyxin NP, Colistin Drop or Colistin Agar Spot tests are applicable for the selection of isolates with a suspected resistance to colistin that has to be confirmed by broth microdilution. The mcr-mediated resistance to colistin can be confirmed by the detection of the causal gene(s) or by phenotype using EDTA-colistin broth disc elution; production of the MCR-1 enzyme can be confirmed with lateral flow immunoassay, using matrix-assisted laser desorption/ionization time-of flight or liquid chromatography-based mass spectrometry. Whole-genome sequencing (WGS) is the ultimate typing method. When a WGS platform is not available at a healthcare facility, a WGS-outsourced service, in combination with freely available bioinformatics tools, allows for the characterization of the mcr-gene(s) carrying isolates.

IMPLICATIONS

mcr-mediated colistin resistance should be monitored through active targeted screening. The broth microdilution method is required for colistin susceptibility testing but as only a selected number of clinical isolates are tested, colistin resistance, including mcr-mediated, may remain undetected. In mcr-1-positive Escherichia coli isolates, the MIC to colistin can range from 2 to 8 mg/L, so it is proposed that Enterobacterales with a colistin MIC of 2 mg/L should also be included in the mcr-mediated colistin resistance screening and those with a confirmed mcr-genotype and/or MCR-phenotype should be considered to be colistin-resistant.

Current and emerging polymyxin resistance diagnostics: A systematic review of established and novel detection methods

The emergence of polymyxin resistance, due to transferable mcr genes, threatens public and animal health as there are limited therapeutic options. As polymyxin is one of the last-line antibiotics, there is a need to contain the spread of its resistance to conserve its efficacy. Herein, we describe current and emerging polymyxin resistance diagnostics to inform faster clinical diagnostic choices. A literature search in diverse databases for studies published between 2016 and 2020 was performed. English articles evaluating colistin resistance methods/diagnostics were included. Screening resulted in the inclusion of 93 journal articles. Current colistin resistance diagnostics are either phenotypic or molecular. Broth microdilution is currently the only gold standard for determining colistin MICs (minimum inhibitory concentration). Phenotypic methods comprise of agar-based methods such as CHROMagar™ Col-APSE, SuperPolymyxin, ChromID^® Colistin R, LBJMR and LB medium; manual MIC-determiners viz., UMIC, MICRONAUT MIC-Strip and ComASP Colistin; automated antimicrobial susceptibility testing systems such as BD Phoenix, MICRONAUT-S, MicroScan, Sensititre and Vitek 2; MCR-detectors such as lateral flow immunoassay (LFI) and chelator-based assays including EDTA- and DPA-based tests, that is, combined disk test, modified colistin broth-disk elution (CBDE), Colispot, and Colistin MAC test as well as biochemical colorimetric tests, that is, Rapid Polymyxin NP test and Rapid ResaPolymyxin NP test. Molecular methods only characterize mobile colistin resistance; they include PCR, LAMP and whole-genome sequencing. Due to the faster turnaround time (≤3 h), improved sensitivity (84%-100%) and specificity (93.3%-100%) of the Rapid ResaPolymyxin NP test and Fastinov^® , we recommend this test for initial screening of colistin-resistant isolates. This can be followed by CBDE with EDTA or the LFI as they both have 100% sensitivity and a specificity of ≥94.3% for the rapid screening of mcr genes. However, molecular assays such as LAMP and PCR may be considered in well-equipped clinical laboratories.

Geospatial Spread of Antimicrobial Resistance, Bacterial and Fungal Threats to Coronavirus Infectious Disease 2019 (COVID-19) Survival, and Point-of-Care Solutions

CONTEXT.—

Point-of-care testing (POCT) is inherently spatial, that is, performed where needed, and intrinsically temporal, because it accelerates decision-making. POCT efficiency and effectiveness have the potential to facilitate antimicrobial resistance (AMR) detection, decrease risks of coinfections for critically ill patients with coronavirus infectious disease 2019 (COVID-19), and improve the cost-effectiveness of health care.

OBJECTIVES.—

To assess AMR identification by using POCT, describe the United States AMR Diagnostic Challenge, and improve global standards of care for infectious diseases.

DATA SOURCES.—

PubMed, World Wide Web, and other sources were searched for papers focusing on AMR and POCT. EndNote X9.1 (Clarivate Analytics) consolidated abstracts, URLs, and PDFs representing approximately 500 articles were assessed for relevance. Panelist insights at Tri•Con 2020 in San Francisco and finalist POC technologies competing for a US $20,000,000 AMR prize are summarized.

CONCLUSIONS.—

Coinfections represent high risks for COVID-19 patients. POCT potentially will help target specific pathogens, refine choices for antimicrobial drugs, and prevent excess morbidity and mortality. POC assays that identify patterns of pathogen resistance can help tell us how infected individuals spread AMR, where geospatial hotspots are located, when delays cause death, and how to deploy preventative resources. Shared AMR data "clouds" could help reduce critical care burden during pandemics and optimize therapeutic options, similar to use of antibiograms in individual hospitals. Multidisciplinary health care personnel should learn the principles and practice of POCT, so they can meet needs with rapid diagnostic testing. The stakes are high. Antimicrobial resistance is projected to cause millions of deaths annually and cumulative financial loses in the trillions by 2050.