Fipronil (FPN), a widely used insecticide, poses health risks through environmental contamination. Although its toxicity is increasingly recognized, the impact of fipronil on glucose metabolism remains poorly understood. In this study, mice on a normal diet (ND) or high-fat diet (HFD) received a daily oral administration of fipronil (0, 0.25, 1, or 4 mg/kg) for 35 days. Blood glucose and insulin were measured, and glucose/insulin/pyruvate tolerance tests were performed. We found that fipronil compromised glucose tolerance in mice fed an ND. Gut microbiota composition was assessed by 16S rRNA sequencing and the expression of inflammatory factors was detected in the tissues. Serum fibroblast growth factor 15 (FGF15) and bile acid were determined. In HFD-fed mice, fipronil exacerbated glucose metabolic disorders and enhanced insulin resistance. These metabolic disturbances were associated with gut microbiota dysbiosis, particularly a marked reduction in Akkermansia muciniphila (A. muciniphila) abundance, and increased systemic inflammation. Fipronil exposure also decreased serum FGF15 and elevated serum bile acids. Our results suggest that fipronil disrupts glucose metabolism in association with gut microbiota alterations, impairment of the FGF15-bile acid axis, and induction of inflammation, highlighting its potential relevance to diabetes risk. Further studies are warranted to validate our findings.

Folpet is a nonspecific sulfonamide fungicide widely used to protect crops from mildew. However, the in vivo effects of folpet on glucose metabolism homeostasis, gut microbiota, and abundance of drug resistance genes remain unknown. The purpose of this study was to assess the effects of the pesticide, folpet, on glucose metabolism homeostasis, and folpet-induced changes in the intestinal microbiota and resistance genes in mice. Mice were orally administered folpet at 0, 1, 10, and 100 mg/kg body weight/day for 5 weeks. Blood sugar levels in mice were measured after 5 weeks of folpet administration. Metagenomic sequencing and drug resistance gene analyses were performed to explore changes in the abundance of gut microbiota members and drug resistance genes in mice after folpet administration. Correlation analysis was performed using metabolomics to explore the relationship between intestinal microbiota, drug resistance genes, and glucose metabolism. Mice in the folpet group had significantly lower blood glucose levels than those in the control group. The abundance of Atopobium, Libanicoccus, Collinsella, and Parabacteroides in the intestinal microbiota of folpet-treated mice was significantly higher than that in the control group. However, the abundance of Mailhella, Bilophila, Roseburia, and Bacteroides were reduced in folpet-treated mice. Compared with the control group, the abundance of APH6-Ic and AAC6-Ie-APH2-Ia resistance genes in mice treated with folpet significantly increased. The abundance of tetQ, ermE, and BahA resistance genes was significantly reduced after folpet treatment. Folpet is associated with changes in the abundance of gut microbiota in mice and may also affect the abundance of drug-resistance genes and the regulation of blood glucose levels.

Antimicrobial resistance (AMR) is a global health challenge. The gut microbiome, a major reservoir for AMR, is influenced by dietary habits. However, the specific impact of dietary patterns on gut resistome remains poorly understood. This study aimed to assess the effects of high-fat/low-fiber and high-fiber/low-fat diets on the development of AMR in the gut microbiome. The shift from a normal diet to a high-fat/low-fiber or a high-fiber/low-fat diet in mice resulted in corresponding increases and decreases in the relative abundance of the resistome (0.14 to 0.25, p < 0.001 vs. 0.14 to 0.09 p < 0.05), virulence genes (VGs) (0.56 to 0.91, p < 0.001 vs. 0.58 to 0.50, p < 0.05), and mobile genetic elements (MGEs) (0.20 to 1.66, p < 0.001 vs. 0.22 to 0.13, p < 0.05), respectively. Network analyses identified bacteria such as Bacteroides, Parabacteroides, and Alistipes as hosts of ARGs and VGs, with changes in their abundance closely associated with shifts in ARG and VG levels. Mobile genetic elements such as Tn916, ISBf10, IS91, and intl1 were linked to these variations, including genes conferring resistance to vancomycin and capsule-related VGs. In humans, a similar trend was observed, with high-fat diets correlating with higher resistome levels, while high-fiber diets were associated with lower resistome levels compared to a normal diet group. ARGs were more prevalent in pathogenic genera such as Enterococcus spp., Klebsiella spp., Pseudomonas spp., and Staphylococcus spp. The high-fat/low-fiber diet increased the bacterial resistome and VG abundance compared to a high-fiber/low-fat diet. Therefore, adopting a high-fiber/low-fat diet may be an effective strategy to reduce the AMR burden in the human gut, providing a valuable insight for public health recommendations.

Glucose metabolic disorders, prevalent in numerous metabolic diseases, have become a pressing global public health concern. Artemisinin (ART) and its derivatives, including artesunate (ARTs) and artemether (ARTe), have shown potential as metabolic regulators. However, the specific effects of ART and its derivatives on glucose metabolism under varying nutritional conditions and the associated molecular mechanisms remain largely unexplored. In this study, we examined the impact of ART, ARTs, and ARTe on glucose homeostasis using a mouse model subjected to different dietary regimens. Our findings revealed that ART, ARTs, and ARTe increased blood glucose levels in mice on a normal-chow diet (ND) while mitigating glucose imbalances in high-fat diet (HFD) mice. Notably, treatment with ART, ARTs, and ARTe had contrasting effects on in vivo insulin signaling, impairing it in ND mice and enhancing it in HFD mice. Moreover, the composition of gut microbiota underwent significant alterations following administration of ART and its derivatives. In ND mice, these treatments reduced the populations of bacteria beneficial for improving glucose homeostasis, including Parasutterella, Alloprevotella, Bifidobacterium, Ileibacterium, and Alistipes. In HFD mice, there was an increase in the abundance of beneficial bacteria (Alistipes, Akkermanisia) and a decrease in bacteria known to negatively impact glucose metabolism (Coprobacillus, Helicobacter, Mucispirillum, Enterorhabdus). Altogether, ART, ARTs, and ARTe exhibited distinct effects on the regulation of glucose metabolism, depending on the nutritional context, and these effects were closely associated with modifications in gut microbiota composition.

BackgroundThe emergence of optrA, which can confer resistance to phenicols and oxazolidinones in Enterococcus spp., poses a growing public health threat.Methods102 optrA-positive enterococci (OPEs) including various species were isolated from feces of 719 healthy volunteers in a Shenzhen community, China. Antimicrobial susceptibility of these isolates was tested. Whole-genome sequencing and bioinformatics analysis were performed to characterize molecular epidemiology of OPEs.ResultsCompared to optrA-negative enterococci (ONEs), antimicrobial resistance (linezolid, florfenicol, doxycycline, erythromycin and ciprofloxacin) and presence of antimicrobial resistance genes (ARGs) (fexA, cat, tet(M), erm(A), erm(B) and etc) were higher in OPEs. Phylogenetic analysis revealed that high similarly (19–338 SNPs) was observed between the optrA-positive E. faecalis from community and the strains from patients, animals, and environment. In 102 OPEs, the optrA gene was detected on the chromosome (n = 36), on plasmids (n = 62), or both (n = 4). A diverse range of optrA-carrying plasmid types was identified. The rep9-plasmid replicons were widely detected in E. faecalis (44/66), whereas repUS1-plasmid replicons were widely identified in other enterococcal species (7/66). Most of all ARGs harbored by isolates were co-existed on optrA-carrying plasmids, suggesting that the acquisition of optrA-carrying plasmids will pose a greater threat to public health. Notably, the pAD1 (rep9 family) + DOp1-type plasmids should receive more attention for the transfer of optrA given their high prevalence (36.36%), high number of co-located ARGs with optrA (83.87% of total ARGs) and presence in multiple sources. Tn6674, IS1216E, ISEnfa1 and ISEnfa5 are related to the transfer of chromosomal and plasmids-derived optrA, respectively. The bcrABDR gene cluster, fexA, and erm(A) were frequently identified surrounding optrA and may be transferred with optrA via IS1216E or ISEnfa1.ConclusionThe transfer of optrA gene is related to a variety of mobile elements (including plasmids, insertion sequences, transposons), which will promote the horizontal transfer of optrA. Moreover, many ARGs co-exist with optrA and could co-transfer with optrA. The acquisition of OPEs and optrA-carrying plasmids will pose a greater threat to public health and should be obtained more attention, especially optrA-positive E. faecalis and pAD1 + DOp1-type plasmids.

The COVID-19 pandemic has severely affected healthcare worldwide and has led to the excessive use of disinfectants and antimicrobial agents. However, the impact of excessive disinfection measures and specific medication prescriptions on the development and dissemination of bacterial drug resistance during the pandemic remains unclear. This study investigated the influence of the pandemic on the composition of antibiotics, antibiotic resistance genes (ARGs), and pathogenic communities in hospital wastewater using ultra-performance liquid chromatography-tandem mass spectrometry and metagenome sequencing. The overall level of antibiotics decreased after the COVID-19 outbreak, whereas the abundance of various ARGs increased in hospital wastewater. After COVID-19 outbreak, blaOXA, sul2, tetX, and qnrS had higher concentrations in winter than in summer. Seasonal factors and the COVID-19 pandemic have affected the microbial structure in wastewater, especially of Klebsiella, Escherichia, Aeromonas, and Acinetobacter. Further analysis revealed the co-existence of qnrS, blaNDM, and blaKPC during the pandemic. Various ARGs significantly correlated with mobile genetic elements, implying their potential mobility. A network analysis revealed that many pathogenic bacteria (Klebsiella, Escherichia, and Vibrio) were correlated with ARGs, indicating the existence of multi-drug resistant pathogens. Although the calculated resistome risk score did not change significantly, our results suggest that the COVID-19 pandemic shifted the composition of residual antibiotics and ARGs in hospital wastewater and contributed to the dissemination of bacterial drug resistance.

Bisphenol F (BPF) is a widely used bisphenol A (BPA) substitute plastic additive that has attracted increasing public concerns due to its potential toxic effects on animal and human health. Although previous studies have indicated that BPF might have harmful effects on metabolic homeostasis, the systematic effects of BPF on glucose disorders remain controversial. In this study, mice fed a normal chow diet (ND) and high-fat diet (HFD) were administered BPF at a dose of 100 μg/kg of body weight, and glucose metabolism was monitored after both short- and long-term treatment. Little change in glucose metabolism was observed in BPF-treated ND mice, but improved glucose metabolism was observed in BPF-treated HFD mice. Consistently, BPF treatment led to increased insulin signalling in the skeletal muscle of HFD mice. Additionally, liver metabolite levels also revealed increased carbohydrate digestion and improved TCA cycle progression in BPF-treated HFD mice. Our results demonstrate that sustained BPF exposure at an environmentally relevant dosage may substantially improve glucose metabolism and enhance insulin sensitivity in mice fed a high-fat diet.

Humans are at risk of exogenous exposure to exogenous chemicals. Challenges exist for the comprehensive monitoring of residues with different physical and chemical properties in serum. Here, an on-line two-dimensional liquid chromatography (2D-LC) - high resolution mass spectrometry system (HRMS) was developed, expanding the range of the partition coefficient in octanol/water of the residue analysis from -8 to 12. A high-coverage serum residue screening strategy was further designed by integrating 2D-LC system with HRMS full MS/data independent acquisition and automatic spectral library searching. This strategy enables to simultaneously screen 1210 pesticides, veterinary/human drugs, other chemical pollutants and their metabolites in serum with a single analysis. Method validation showed 92% and 81% of 1022 residues spiked in serum could be detected at 50 ng/mL and 5 ng/mL, respectively. The developed method was applied to the analysis of 24 separately pooled serum samples, 58 suspect residues were found, some of them were detected at high frequencies over than 50%. Among them, 4,6-Dinitro-O-cresol and probable carcinogenic folpet are highly toxic, and cimaterol is banned in China. Collectively, this study developed a 2D-LC-HRMS -based screening strategy for screening pesticides, veterinary/human drugs, and other chemical pollutants in serum, it is helpful for studying the effect of exogenous exposures on human health.

The occurrence of antibiotics in the feces of elderly individuals in Shenzhen, China, was investigated by monitoring 78 compounds to understand the adverse effects and its association with antibiotic residues in animal products collected from local markets. In total, 18 compounds belonging to 5 classes of antibiotics were identified in 74 of 140 fecal samples. Furthermore, 17.9

Considering processing concerns regarding emerging food safety incidents and large-scale food testing, efficient and straightforward screening tools are urgently needed. The requirements for this technology include effective sample pretreatment, sensitive assay, and sample-to-answer solution that enable the detection of trace amounts of contaminants in complex food matrices. Here, we developed a chemiluminescence- and optical fiber-based fully automated immunosensing (COFFAI) system that conducts chemical contaminant food screening in a truly "sample-to-result" manner. Instead of utilizing laborious benchtop sample purification techniques followed by a time-consuming manual ELISA procedure, the user simply injects the sample of interest, and the whole procedure is automatically processed. We demonstrated that the utility of our COFFAI system can be used to detect trace amounts of chemical contamination in various milk samples within approximately 75 min. This method showed an ultrahigh sensitivity with a quinolone detection limit in the 0.022-0.065 mu g/L range for skim milk, whole milk, and raw milk samples. The integration of pretreatment and assay into one automated system is an effective method for food testing. We believe that this platform provides a general method for efficient contaminant screening in foodstuffs.

Background: The association between serum vitamin A and non-alcoholic fatty liver disease (NAFLD) remains uncertain due to inconsistent results and scarce longitudinal data. We examined the prospective associations between serum vitamin A and the evolution of the NAFLD severity score as well as the potential mediating effects in middle-aged and older Chinese adults. Method: A total of 2658 adults (between 40-75 years of age) were included in the analysis. We determined the serum concentrations of vitamin A at the onset of the study (the baseline), and the degree of NAFLD after years 3 and 6. Results: Subjects were classified into stable, progressed, and improved groups according to the changes in their severity score (0-3) of NAFLD between two visits. Analyses of covariance showed that the serum VA concentrations were positively associated with NAFLD progression (all p-trend < 0.05). After adjusting for potential confounders, the mean differences in the serum vitamin A were 7.7% lower in the improved group than those in the progressed group among the total population. Path analyses showed that vitamin A was positively associated with the serum retinol-binding protein 4, triglycerides, insulin resistance, and body mass index (standardized β 0.065-0.304, all p < 0.001), and all of these factors positively correlated with the prevalence and progression of NAFLD (standardized β 0.045-0.384, all p < 0.01). Conclusions: A higher serum vitamin A concentration was associated with NAFLD progression, which might be mediated by increases in the serum retinol-binding protein 4, triglycerides, insulin resistance, and body mass index.

Although carbapenem use is prohibited in animals in China, carbapenem-resistant Escherichia coli (CREC), especially New Delhi metallo-β-lactamase (NDM)-producing strains, are widely prevalent in food-producing animals. At present, the impact of livestock-associated CREC strains on human populations at the national level is unknown. Here, we conduct a retrospective cross-sectional study to investigate the prevalence of CREC from clinical settings across 22 Chinese provinces or municipalities and analyze anthropogenic factors associated with their presence. We also ascertain the blaNDM and blaKPC abundance among pig and chicken farms and present a detailed genomic framework for CREC of animal and human origin. Overall, 631/29 799 (2.1%) clinical Escherichia coli (E. coli) isolates were identified as CREC. Multivariable analysis revealed that being male, an age below 1, an age between 13 and 18, provinces with greater chicken production, and provinces with higher pig production were associated with higher odds of CREC infection. In general, 73.8% (n = 45/61) of pig farms and 62.2% (n = 28/45) of chicken farms had a blaNDM abundance of 1 × 10−5 to 1 × 10−3 and 1 × 10−3 to 1 × 10−2, respectively. Among all the Chinese NDM-positive E. coli (n = 463) available at the National Center for Biotechnology Information (NCBI), the genomic analysis revealed that blaNDM-5 and IncX3 were the predominant carbapenemase gene-plasmid combination, while a highly homogeneous relationship between NDM-positive isolates from humans and animals was demonstrated at the plasmid and core genome levels. All the findings suggest frequent CREC transmission between humans and animals, indicating that further discussions on the use of antibiotics in animals and humans are needed, both in China and across the globe.

Background: As several vaccines for SARS-CoV-2 have been developed, a large proportion of individuals have been vaccinated worldwide so far. The rapid and accurate immunoassays are urgently needed for detecting the specific virus-neutralizing antibody (NAb), which reflect the protective effect of the vaccines among different populations. Methods: In this study, we designed a quantum dot lateral flow immunoassay strip (QD-LFIA) for smartphones for the detection of specific IgG or neutralizing antibodies in SARS-CoV-2 in human serum or whole blood samples. The recombinant receptor binding domain of the SARS-CoV-2 spike protein was used as the antigen to combine with NAb or angiotensin-converting enzyme 2. Results: Among 81 patients who recovered from COVID-19 who were diagnosed using the nucleic acid test initially, 98.8% (80/81) were positive for IgG and 88.9% (72/81) were positive for NAb by QD-LFIA. Among 64 individuals inoculated with inactivated vaccines and six subunit vaccines, 90% (63/70) were positive for IgG and 82.9% (58/70) were positive for NAb by QD-LFIA, whereas no cross-reaction was found in 150 healthy blood donors, two patients with influenza B, and three patients with common cold. Conclusion: The established platform could achieve a rapid and accurate detection of NAb specific to SARS-CoV-2, which could be used for detecting the protective effect of the vaccines in areas of world that currently affected by the pandemic. (C) 2022 The Authors. Published by Elsevier Ltd on behalf of International Society for Infectious Diseases.

Abstract Background Mobile colistin-resistance gene mcr-1 is prevalent among various bacteria, hosts and countries, especially in the guts of humans and animals. However, the biological basis for mcr-1 colonization and transmission in the intestines is largely unknown. Methods We used mouse models to mimic exposure to mcr-1-positive Escherichia coli (MCRPEC, harboring an IncI2 plasmid positive for mcr-1) in human intestines without and with antibiotic pretreatment, respectively. We used cultivation and qPCR method to determine the presence and quantity of MCRPEC. We also used Fluorescence in situ hybridization (FISH) method to locate mcr-1-positive bacteria in situ and confocal laser scanning microscopy method to examine the interaction between MCRPEC and Caco-2 cell in vitro. Finally, we used mouse model to investigate the transmission of MCRPEC among individuals. Results We found two approaches of MCRPEC colonization in the mouse intestines after exposure. In mice with intestinal microbiota homeostasis, MCRPEC was transient in the large intestines, while mcr-1 was detected at lower abundances (10-4–10-5) for at least 21 days as relic DNA or mcr-1-positive uncommon bacteria (MCRPUB). In mice with intestinal microbiota dysbiosis, MCRPEC colonized the intestines directly with a high shedding load (~108 CFU/g feces) and high mcr-1 abundance (~10-2). The transmission model confirmed that both MCRPEC and MCRPUB could cryptically transfer among individuals and persist for long periods. Conclusions These results demonstrate two approaches of MCRPEC colonization and a long persistence of MCRPUB or an antetype in mouse intestines as well as their transmission among mice, which partially explains the widespread prevalence of mcr-1-positive IncI2 plasmid among hosts and its long persistence in the gut even without antibiotic pressure. Contaminated food enables exposure to pathogens that can colonize human intestines; thus, reducing MCRPEC/MCRPUB in livestock and animal-derived food and preventing MCRPEC/MCRPUB transmission in ecosystems under the "One Health" perspective are crucial.

Quinolones (QNs), used extensively as therapeutic agents and growth promoters worldwide, have significantly residued in food and environment, causing serious threat to human health through food chain. There is a high and urgent demand for easy, rapid, sensitive, and economical analytical methods for QNs residues monitoring. Immunoassays are recommended as the first-rate choice in the rapid screening of QNs residues in food and environmental samples due to various advantages. Great progress has been achieved in recent researches of immunoassays for screening QNs. This comprehensive review systematically presents specific recognition elements production, immunoassay format construction and improvement, outlook and challenges of immunoassays for QNs. The review provides new information and insightful commentary, critically important to the development and innovation of further immunoassay for QNs detection.

Hybridoma technology is widely used for monoclonal antibody (mAb) discovery, whereas the generation and identification of single hybridomas by the limiting dilution method (LDM) are tedious, inefficient, and time- and cost-consuming, especially for hapten molecules. Here, we describe a single transgenic hybridoma selection method (STHSM) that employs a transgenic Sp2/0 with an artificial and stable on-cell-surface anchor. The anchor was designed by combining the truncated variant transmembrane domain of EGFR with a biotin acceptor peptide AVI-tag, which was stably integrated into the genome of Sp2/0 via a piggyBac transposon. To ensure the subsequent precise selection of the hybridoma, the number of on-cell-surface anchors of the transfected Sp2/0 for fusion with immunized splenocytes was further normalized by flow cytometry at the single cell level. Then the single antigen-specific transgenic hybridomas were precisely identified and automatically selected using a CellenONE platform based on the fluorescence assay of the on-cellsurface anchor with the corresponding secreted antigen-specific mAb. The STHSM produced 579 single chloramphenicol (CAP)specific transgenic hybridomas with a positive rate of 62.7% in 10 plates within 2 h by one-step selection, while only 12 single CAPspecific hybridomas with a positive rate of 6.3% in 40 plates required at least 32 days using the LDM with multiple subcloning steps. The best affinity of mAbs from the STHSM was more than 2-fold higher than that of those from the LDM, and this was mainly due to the preaffinity selection based on the on-cell-surface anchors and more interactions between the mAb and CAP. Then the mAbs from the STHSM and LDM were used to develop an immunoassay for CAP in spiked and natural biological samples. The method displayed satisfactory sensitivity, accuracy, and precision, demonstrating that the STHSM we developed is a versatile, practical, and efficient method for mAb discovery.

BACKGROUND:Mobile tigecycline-resistance gene tet(X) variants have emerged as diverse pathogens from animal, human as well as their associated environments, which could potentially threaten public health. The insertion sequence, ISCR2, carries tet(X4) for horizontal transfer by rolling-cycle (RC) transposition. However, the diversity of ISCR2 and tet(X4) isolated from different sources is largely unknown.METHODS:The tet(X4)-carrying isolates were collected from human and livestock in several multiple regions of China. The whole genomic sequences of these isolates were either obtained from NCBI GenBank or determined by Illumina Hiseq 2500 and the MinION platform. The intact transposon region, ISCR2-tet(X4)-ISCR2, observed in a small number of isolates as the reference sequence to construct the transposon phylogeny. The diversity of the genetic environments of all ISCR2-tet(X4) elements were analyzed.RESULTS:A 2760-bp element encompassing the tet(X4)-hydrolase-encoding gene, catD, located between two ISCR2 elements was highly conserved in all isolates and could form an RC transposable unit (RC-TU). ISCR2 could also capture more resistance genes and formed a larger RC-TU base on RC transposition. However, the ISCR2-mediated RC-TUs were constantly truncated and inserted by other IS elements, indicating frequent recombination events. Of these elements, IS26 disrupted both the upstream and downstream ISCR2-mediated RC-TUs, indicating that IS26 captured tet(X4), thus leading to a wider spread of tet(X4).CONCLUSIONS:These results confirmed the critical role of ISCR2 for dissemination and co-transmission of tet(X4) and other resistance genes. More effort is needed to monitor the variation tendencies of tet(X4)-carrying mobile elements and determine the driving factors for disseminating transferable tigecycline resistance.

A rare antibody that is able to tolerate physio-chemical factors is preferred and highly demanded in diagnosis and therapy. Rabbit monoclonal antibodies (RmAbs) are distinguished owing to their high affinity and stability. However, the efficiency and availability of traditional methods for RmAb discovery are limited, particularly for small molecules. Here, we present an indirect competitive screening method in nanowells, named CSMN, for single rabbit antibody-secreting cells (ASCs) selection with 20.6 h and propose an efficient platform for RmAb production against small molecules within 5.8 days for the first time. Chloramphenicol (CAP) as an antibacterial agent poses a great threat to public health. We applied CSMN to select CAP-specific ASCs and produced one high-affinity RmAb, surprisingly showed extremely halophilic properties with an IC50 of 0.08 ng mL-1 in the saturated salt solution, which has not yet been seen for other antibodies. The molecular dynamic simulation showed that the negatively charged surface improved the stability of the RmAb structure with additional disulfide bonds compared with mouse antibodies. Moreover, the reduced solvent accessible surface area of the binding pocket increased the interactions of RmAb with CAP in a saturated salt solution. Furthermore, RmAb was used to develop an immunoassay for the detection of CAP in real biological samples with simple pretreatment, shorter assay time, and higher sensitivity. The results demonstrated that the practical and efficient CSMN is suitable for rare RmAb discovery against small molecules.

Intrinsic fluorescence of tryptophan (Trp) in antibody is of particular interest in label-free fluorescence resonance energy transfer (FRET) immunoassay. However, the relationship between the effective Trp proportion of antibody fragment and energy transfer efficiency and the behind structural basis are still unclear. Herein, we constructed three label-free FRET-immunoassays for detecting sulfonamides (SAs) based on intact IgG, fragment of antigen binding (Fab), and single-chain variable fragment (scFv) of antibody 4C7 as donors, respectively. By analyzing the amino acid sequence of three antibody fragments and the interaction between antibody fragments and SAs, the results that the higher effective Trp proportions of antibody fragments lead to higher energy transfer efficiencies can be obtained. Then, the higher detection sensitivity for detecting sulfathiazole (STZ) was achieved, while the limits of detection (LODs) were 1.27, 0.58, and 0.29 ng/mL of IgG, Fab, and scFv-based label-free FRET-immunoassays, respectively. Furthermore, the conclusion derived from 4C7 has been proved by another combination of IgG, Fab, and scFv of 4D11 against sulfamethazine (SMZ) with the LODs of 0.97, 0.32, and 0.15 ng/mL, respectively. In conclusion, apart from the first demonstration of label-free FRET immunoassays for detecting SAs, we have clarified the structural basis of label-free FRET immunoassays, which gives useful clues to other analytes that require rapid screening by label-free FRET platform.

目的 研究深圳市健康人群肠道携带optrA阳性肠球菌流行率及其风险因素.方法 共调取2018-2019年社区健康体检者粪便样本565份,采用肠球菌选择培养基筛选耐氟苯尼考肠球菌,使用MALDI-TOF MS(MALDI Biotyper,Bruker,Germany)进行种属鉴定及PCR鉴定optrA基因.以optrA阳性肠球菌的携带者作为病例,以年龄为匹配条件,按1:4匹配未携带者作为对照.采用多因素logistic回归分析模型分析optrA阳性肠球菌定植于健康人群肠道的风险因素.结果 2018-2019年深圳市健康人群肠道中optrA基因的流行率为18.10％(102/565,95％CI:14.90％～21.20％),从基因阳性人群粪便中共分离447株optrA阳性肠球菌,粪肠球菌为最主要流行种属(76.06％).猪肉日摄入量＞50.0g(0R=1.615,95％CI:1.017-2.565,P=0.042)、3 个月内住院治疗(OR=11.551,95％CI:2.153-61.963,P=0.004)是optrA阳性肠球菌在健康人群肠道中定植的危险因素.结论 optrA阳性肠球菌在深圳市健康人群肠道中已广泛流行,其可能通过食物链传播至人类,同时住院治疗将增加optrA阳性肠球菌在健康人群肠道中定植的风险.