Detection of expanded-spectrum cephalosporin hydrolysis by lateral flow immunoassay

Production of AmpC β-Lactamase and Development of a Competitive Array for Discriminative Determination of Cephalosporins in Milk

In this study, AmpC β-lactamase of Escherichia coli was expressed, and its intermolecular interaction mechanisms with 15 cephalosporins (CPs) were studied by using a molecular docking technique. Results showed that this enzyme mainly interacted with the β-lactam ring of these CPs, and the key contacting amino acids were Ser80 and Ser228. The AmpC β-lactamase was combined with 5 horseradish peroxidase-labeled conjugates to develop a direct competitive array on a microplate for determination of 15 drugs in milk. Due to the use of principal component analysis method to analyze the data, this method could discriminate the 15 drugs at the concentration as low as 10 ng/mL. The detection results for the unknown milk samples were consistent with those obtained by the liquid chromatography-mass spectrometry method. As a general comparison, this method is better than the previous antibody-based and receptor-based detection methods for CPs. This is the first paper reporting a competitive array for discriminative determination of a class of small-molecule substances.

Advances in the detection of β-lactamase: A review

β-lactamase, an enzyme secreted by bacteria, is the main resistant mechanism of Gram-negative bacteria to β-lactam antibiotics. The resistance of bacteria to β-lactam antibiotics can be evaluated by testing the activity of β-lactamase. Traditional phenotypic detection is a golden principle, but it is time-consuming. In recent years, many new methods have emerged, which improve the efficiency by virtue of their sensitivity, low cost, easy operation, and other advantages. In this paper, we systematically review these researches and emphasize their limits of detection, sample operation, and test duration. Noteworthily, some detection systems can identify the β-lactamase subtype conveniently. We mainly divide these tests into three categories to elaborate their characteristics and application status. Both advantages and disadvantages of these methods are discussed. Additionally, we analyze the recent 5 years published researches to predict the trend of development in this field.

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.

Rapid detection of CTX-M-type ESBLs and carbapenemases directly from biological samples using the BL-DetecTool

BACKGROUND

Lateral flow immunoassays (LFIA) have shown their usefulness for detecting CTX-M- and carbapenemase-producing Enterobacterales (CPEs) in bacterial cultures. Here, we have developed and validated the BL-DetecTool to detect CTX-M enzymes and carbapenemases directly from clinical samples.

METHODS

The BL-DetecTool is an LFIA that integrates an easy sample preparation device named SPID (Sampling, Processing, Incubation and Detection). It was evaluated in three University hospitals on urine, blood culture (BC) and rectal swab (RS) specimens either of clinical origin or on spiked samples. RS evaluation was done directly and after a 24 h enrichment step.

RESULTS

The CTX-M BL-DetecTool was tested on 485 samples (154 BC, 150 urines, and 181 RS) and revealed a sensitivity and specificity of 97.04% (95% CI 92.59%-99.19%) and 99.43% (95% CI 97.95%-99.93%), respectively. Similarly, the Carba5 BL-DetecTool was tested on 382 samples (145 BC, 116 urines, and 121 RS) and revealed a sensitivity and specificity of 95.3% (95% CI 89.43%-98.47%) and 100% (95% CI 98.67%-100%), respectively. While with the Carba5 BL-DetecTool five false negatives were observed, mostly in RS samples, with the CTX-M BL-DetecTool, in addition to four false-negatives, two false-positives were also observed. Direct testing of RS samples revealed a sensitivity of 78% and 86% for CTX-M and carbapenemase detection, respectively.

CONCLUSIONS

BL-DetecTool showed excellent biological performance, was easy-to-use, rapid, and could be implemented in any microbiology laboratory around the world, without additional equipment, no need for electricity, nor trained personnel. It offers an attractive alternative to costly molecular methods.

The Revolution of Lateral Flow Assay in the Field of AMR Detection

The global spread of antimicrobial resistant (AMR) bacteria represents a considerable public health concern, yet their detection and identification of their resistance mechanisms remain challenging. Optimal diagnostic tests should provide rapid results at low cost to enable implementation in any microbiology laboratory. Lateral flow assays (LFA) meet these requirements and have become essential tools to combat AMR. This review presents the versatility of LFA developed for the AMR detection field, with particular attention to those directly triggering β-lactamases, their performances, and specific limitations. It considers how LFA can be modified by detecting not only the enzyme, but also its β-lactamase activity for a broader clinical sensitivity. Moreover, although LFA allow a short time-to-result, they are generally only implemented after fastidious and time-consuming techniques. We present a sample processing device that shortens and simplifies the handling of clinical samples before the use of LFA. Finally, the capacity of LFA to detect amplified genetic determinants of AMR by isothermal PCR will be discussed. LFA are inexpensive, rapid, and efficient tools that are easy to implement in the routine workflow of laboratories as new first-line tests against AMR with bacterial colonies, and in the near future directly with biological media.

Comparison of Three Expanded-Spectrum Cephalosporin Hydrolysis Assays and the NG-Test CTX-M Multi Assay That Detects All CTX-M-Like Enzymes

Rapid detection of expanded-spectrum cephalosporins (ESC) hydrolysing enzymes is crucial to implement infection control measures and antibiotic stewardship. Here, we have evaluated three biochemical ESC hydrolysis assays (ESBL NDP test, β-LACTA™ test, LFIA-CTX assay) and the NG-Test^® CTX-M MULTI that detects CTX-M enzymes, on 93 well-characterized Gram-negative isolates, including 60 Enterobacterales, 21 Pseudomonas spp. and 12 Acinetobacter spp. The performances were good for all three hydrolysis assays, with the LFIA-CTX being slightly more sensitive and specific on the tested panel of isolates especially with Enterobacterales, without ambiguous results. This study showed that LFIA-CTX may be used for the detection of ESC hydrolysis as a competitive alternative to already available assays (β-LACTA™ test and ESBL NDP test) without any specific equipment and reduced hands-on-time. The lateral flow immunoassay NG-Test^® CTX-M MULTI has proven to be a useful, easy, rapid, and reliable confirmatory test in Enterobacterales for detection of CTX-M-type ESBLs, which account for most of the resistance mechanisms leading to ESC resistance in Enterobacterales, but it misses rare ESC hydrolysing β-lactamases (AmpC, minor ESBLs, and carbapenemases). Combining it with the LFIA-CTX assay would yield an assay detecting the most frequently-encountered ESBLs (CTX-M-like β-lactamases) together with ESC hydrolysis.

Multiplex Lateral Flow Immunoassay for the Detection of Expanded-Spectrum Hydrolysis and CTX-M Enzymes

Background: Early detection of expanded-spectrum cephalosporinase (ESC) hydrolyzing ß-lactamases is essential for antibiotic stewardship. Here we have developed a multiplex lateral flow immunoassay (LFIA) that detects cefotaxime-hydrolyzing activity as well as the most prevalent ESC-hydrolyzing ß-lactamases: the CTX-M-like. Methods: The Rapid LFIA ESC test was evaluated retrospectively on 188 (139 Enterobacterales, 30 Pseudomonas spp. and 14 Acinetobacter spp.) agar-grown bacterial isolates with well-characterized ß-lactamase content. One single colony was resuspended in 150 µL extraction buffer containing cefotaxime, incubated at room temperature for 30 min prior to loading on the LFIA for reading within 10 min. Results: Out of the 188 isolates, all 17 that did not express a β-lactamase hydrolyzing cefotaxime gave negative results, and all 171 isolates expressing a β-lactamase known to hydrolyze cefotaxime, gave a positive test result. In addition, all 86 isolates expressing a CTX-M-variant belonging to one of the five CTX-M-subgroups were correctly identified. The sensitivity and specificity was 100% for both tests. Conclusions: The results showed that the multiplex LFIA was efficient, fast, low cost and easy to implement in routine laboratory work for the confirmation of ESC hydrolyzing activity and the presence of CTX-M enzymes.