Carba PBP: a novel penicillin-binding protein-based lateral flow assay for rapid phenotypic detection of carbapenemase-producing Enterobacterales.

Rapid phenotypic detection assays, including Carba NP and its variants, are widely applied for clinical diagnosis of carbapenemase-producing Enterobacterales (CPE). However, these tests are based on the acidification of the pH indicator during carbapenem hydrolysis, which limits test sensitivity and speed, especially for the detection of CPE producing low-activity carbapenem (e.g., OXA-48 variants). Herein, we developed a novel rapid and sensitive CPE detection method (Carba PBP) that could measure substrate (meropenem) consumption based on penicillin-binding protein (PBP). Meropenem-specific PBP was used to develop a competitive lateral flow assay (LFA) for meropenem identification. For the detection of carbapenemase activity, meropenem concentration was optimized using a checkerboard assay. The performance of Carba PBP was evaluated and compared with that of Carba NP using a panel of 94 clinical strains characterized by whole-genome sequencing and carbapenem susceptibility test. The limit of detection of PBP-based LFA for meropenem identification was 7 ng mL-1. Using 10 ng mL-1 meropenem as the substrate, Carba PBP and Carba NP could detect 10 ng mL-1 carbapenemase within 25 min and 1,280 ng mL-1 CPE in 2 h, respectively. The sensitivity and specificity were 100% (75/75) and 100% (19/19) for Carba PBP and 85.3% (64/75) and 100% (19/19) for Carba NP, respectively. When compared with Carba NP, Carba PBP showed superior performance in detecting all the tested CPE strains (including OXA-48-like variants) within 25 min and presented two orders of magnitude higher analytical sensitivity, demonstrating potential for clinical diagnosis of CPE. IMPORTANCE This study successfully achieved the goal of carbapenemase activity detection with both high sensitivity and convenience, offering a convenient lateral flow assay for clinical diagnosis of carbapenemase-producing Enterobacterales.

Molecular Recognition Mechanism of an Anti-Amatoxins mAb and Its Application in Centrifugal Disk-Based Immunoassay.

Amatoxins are polypeptides that cause 90% of fatalities from accidental ingestion of poisonous mushrooms. Unfortunately, there are no specific antidotes against amatoxins poisoning, hence preparation of high-affinity antibodies, understanding the receptor (amatoxins) and ligand (antibody) mechanism, and establishing a straightforward screening approach are of great significance for confirming poison agents and clinical diagnosis. Here, anti-amatoxins monoclonal antibody (mAb) 9B2 was prepared and the recognition mechanism was investigated. The approach is useful for designing desirable immunogens, developing new antibodies with improved performance, and constructing effective immunoassays. Based on the mAb, we designed a centrifugal disk-like microfluidics chip and developed a fully automated immunoassay capable of detecting amatoxins poisoning in various samples including serum, urine, and mushrooms. The whole detection process could be automatically accomplished within 30 min, with a limit of detection of 0.08 to 0.12 µg/L for real samples, ∼30-fold more sensitive than conventional enzyme-linked immunosorbent assay (ELISA). Our platform not only provided a practical approach for performing poison agent confirmation and clinical diagnosis but also had important implications for improving the survival of patients with mushroom poisoning.

Quantitative Determination of Nitrofurazone Metabolites in Animal-Derived Foods Based on a Background Fluorescence Quenching Immunochromatographic Assay.

Due to their facile synthesis and friendly functionalization, gold nanoparticles (AuNPs) have been applied in all kinds of biosensors. More importantly, these biosensors, with the combination of AuNPs and immunoassay, are expected to be used for the detection of different compounds with low concentrations in complex samples. In this study, a AuNPs-labeled antibody immunoprobe was prepared and combined with a fluorescence-quenching principle and a background fluorescence-quenching immunochromatographic assay (bFQICA), achieving rapid on-site detection. By using a portable fluorescence immunoquantitative analyzer and a QR code with a built-in standard curve, the rapid quantitative determination for nitrofurazone metabolite of semicarbazide (SEM) in animal-derived foods was realized. The limits of detection (LODs) for bFQICA in egg, chicken, fish, and shrimp were 0.09, 0.10, 0.12, and 0.15 µg kg-1 for SEM, respectively, with the linear range of 0.08-0.41 µg L-1, the recoveries ranging from 73.5% to 109.2%, and the coefficient of variation <15%, only taking 13 min for the SEM detection. The analysis of animal-derived foods by bFQICA complied with that of liquid chromatography-tandem mass spectrometry (LC-MS/MS).

Application of biofertilizers increases fluoroquinolone resistance in Vibrio parahaemolyticus isolated from aquaculture environments.

Antimicrobial resistance genes in aquaculture environments have attracted wide interest, since these genes pose a severe threat to human health. This study aimed to explore the possible mechanisms of the ciprofloxacin resistance of Vibrio parahaemolyticus (V. parahaemolytiucs) in aquaculture environments, which may have been affected by the biofertilizer utilization in China. Plasmid-mediate quinolone resistance (PMQR) genes, representative (fluoro)quinolones (FNQs), and ciprofloxacin-resistance isolates in biofertilizer samples were analyzed. The significantly higher abundance of oqxB was alarming. The transferable experiments and Southern blot analysis indicated that oqxB could spread horizontally from biofertilizers to V. parahaemolyticus, and two (16.7%) trans-conjugants harboring oqxB were provided by 12 isolates that successfully produced OqxB. To the best of our knowledge, this study is the first to report PMQR genes dissipation from biofertilizers to V. parahaemolyticus in aquaculture environments. The surveillance, monitoring and control of PMQR genes in biofertilizers are warranted for seafood safety and human health.

Antimicrobial resistance and pulsed-field gel electrophoresis typing of Vibrio parahaemolyticus isolated from shrimp mariculture environment along the east coast of China.

Environmental antimicrobial resistance (AMR) has drawn increasing attention due to its great risk to human health. The aim of this study was to investigate AMR and genotyping of Vibrio parahaemolyticus isolates (n = 114) recovered from shrimp mariculture environment in China. The isolates exhibited a high rate of resistance to streptomycin (78.9%), ampicillin (64.9%) and gentamicin (53.5%). Furthermore, multi-drug resistance was highly prevalent (61.4%), in which 95.9% of these ampicillin-resistant isolates were primarily mediated by blaCARB-17. Surprisingly, doxycylcine, florfenicol, and trimethoprim/sulfamethoxazole (TMP/SMZ) resistance genes occurred in susceptible isolates. Moreover, 114 isolates were grouped into unique pulsed field gel electrophoresis patterns. These findings suggest the need for the prudent use of antimicrobial agents on mariculture farms, in order to control the dissemination of antimicrobial resistant V. parahaemolyticus.

Preparation of high affinity antibody for ribavirin with new haptens and residue analysis in chicken muscle, eggs and duck muscle.

In this work, high affinity polyclonal antibodies for ribavirin (RBV) from new haptens were prepared and were used to analyse RBV residues in chicken muscle, eggs and duck muscle. The new haptens were synthesised with different spacers, and the best antibody was obtained with an IC50 value as low as 0.61 ng/mL in indirect competitive enzyme-linked immunosorbent assay (ELISA). The cross-reactivities with another five antiviral drugs including amantadine, rimantadine, moroxydine, zanamivir and oseltamivir were less than 0.1%, which indicated the good specificity of the antibody. An ELISA was developed based on the antibody and applied to detect RBV in multi-food matrices. The sample preparation prior to detection only needed simple dilution after trichloroacetic acid extraction. The limits of detection were 1.07, 1.18 and 1.03 µg/kg in chicken muscle, eggs and duck muscle, respectively. Recoveries ranged from 89.0% to 112.7% with coefficients of variation below 13.0%. Ten blind samples of chicken muscle were analysed simultaneously by ELISA and liquid chromatography-tandem mass spectrometry, and a good correlation between the methods was observed. The results indicated that the high affinity antibody could be applied for the simple and fast detection of RBV in multi-food matrices.

Antimicrobial Resistance of Campylobacter Species Isolated from Broilers in Live Bird Markets in Shanghai, China.

This study was conducted to determine the prevalence of antimicrobial resistance in Campylobacter spp. isolates from broilers in live bird markets (LBMs). A total of 209 Campylobacter spp. isolates (84 Campylobacter jejuni; 125 Campylobacter coli) were recovered from 364 broiler cecum samples collected from five LBMs in Shanghai, China. Minimum inhibitory concentrations of 13 antimicrobials were determined using agar dilution method. More than 96% of the Campylobacter spp. isolates were resistant to quinolones and tetracyclines. A high prevalence of macrolide resistance (erythromycin, 84.0%; azithromycin, 80.8%) was observed in C. coli, but not in C. jejuni (erythromycin, 6.0%; azithromycin, 2.4%). C. coli also showed significantly higher resistance than C. jejuni to clindamycin, gentamicin, and kanamycin. In contrast, C. coli isolates had lower resistance to florfenicol than the C. jejuni isolates. The majority of the C. jejuni (88.1%) and C. coli (97.6%) isolates exhibited multidrug resistance (MDR) to three or more classes of antimicrobials. All of the 208 ciprofloxacin-resistant Campylobacter spp. isolates were positive for the C257T mutation of the gyrA gene. In addition, the tet(O) gene was identified in all of the 202 doxycycline-resistant Campylobacter spp. isolates. Furthermore, 75.7% and 20.4% of the 103 azithromycin-resistant Campylobacter spp. isolates were positive for the A2075G mutation of the 23S rRNA gene and the presence of the erm(B) gene, respectively. Moreover, the cat gene was found in 14.3% (8/56) and 76.8% (73/95) of the chloramphenicol-resistant C. jejuni and C. coli isolates, respectively. To the best of our knowledge, this is the first report of the prevalence of antimicrobial resistance among Campylobacter spp. isolates originating from LBMs. The high prevalence of MDR Campylobacter spp. isolates in LBMs highlights the need to implement efficient intervention measures to control not only Campylobacter contamination in LBMs but also dissemination of antimicrobial resistance among Campylobacter spp. in poultry production.

Effects of inducers of cytochrome P450s on enrofloxacin N-deethylation in crucian carp Carassius auratus gibelio.

In this study with crucian carp (Carassius auratus gibelio), the effect on enrofloxacin (EF) and its metabolite ciprofloxacin (CF) and on the activity of cytochrome P450 1A (CYP1A) and cytochrome P450 3A (CYP3A) was estimated following the oral administration of rifampicin (RIF) (12mg/kg) and ß-naphthoflavone (BNF) (12mg/kg), respectively. First, reversed-phase high-performance liquid chromatography (RP-HPLC) was used to detect the pharmacokinetics of EF with continual blood sampling. In RIF-treated, BNF-treated and control groups, the value of the CmaxCF/CmaxEF ratio was 4.41, 0.81 and 0.95, and the corresponding value of the AUC0-t-CF/AUC0-t-EF ratio was 3.69, 1.84 and 1.76, respectively. In the RIF-treated, BNF-treated and control groups, the MRT values of EF were 26.57, 27.45 and 30.88h, and the corresponding values for CF were 5.79, 35.18 and 38.11h, respectively. Based on these results for crucian carp, the accumulation and elimination of EF and CF in the RIF-treated group were more rapid than in BNF-treated and control groups. Second, liver microsomes were pretreated with the inducer of CYP1A for BNF and that of CYP3A for RIF, and then the enzymatic activities of CYP1A and CYP3A were measured, respectively. The activities of ethoxyresorufin-O-deethylation (EROD) and erythromycin-N-demethylation (ERND) increased significantly (P<0.05) for CYP1A and CYP3A, respectively. However, in further experiments on the formation of CF, the level of EF N-deethylation was significantly induced by RIF and inhibited by ketoconazole (KTZ) for CYP3A but had no influence for CYP1A, BNF and berberine chloride (BER). We concluded that CYP3A might be responsible for the N-deethylation of EF and because of this activity, could also serve as a toxicity biomarker in crucian carp.

Tracking Campylobacter contamination along a broiler chicken production chain from the farm level to retail in China.

This study was conducted to determine the prevalence and distribution of Campylobacter species along a broiler production chain from farm to retail, and to evaluate the antimicrobial resistance profile of Campylobacter isolates. A total of 259 Campylobacter isolates (C. jejuni n=106, C. coli n=153) were isolated from broiler ceca samples (72.5%, 103/142), broiler carcasses (34.1%, 46/135), and retail broiler meat (31.3%, 40/128) samples collected in Shanghai, China. Minimal inhibitory concentrations of six antimicrobials were determined using the agar dilution method. High prevalence of resistance to ciprofloxacin (C. jejuni: 99.1%;C. coli: 100%) and tetracycline (C. jejuni: 100%;C. coli: 98.7%) was detected among the C. jejuni and C. coli isolates. The vast majority of C. coli were resistant to clindamycin (92.2%), gentamicin (95.4%), and erythromycin (94.1%), but only 25.5%, 53.8%, and 16.0% of C. jejuni exhibited resistance to these three antimicrobials, respectively. In contrast, the prevalence of florfenicol resistance in C. jejuni (37.7%) was significantly higher than that in C. coli (7.8%) (P<0.05). It is noteworthy that all Campylobacter isolates were resistant to one or more antimicrobials, and 71.7% of C. jejuni and 98.0% of C. coli isolates exhibited multi-drug resistance (resistant to three or more antimicrobials). Fifty-five C. jejuni and sixty C. coli isolates, selected from different production stages, species, and antimicrobial resistance patterns, were analyzed by pulsed field gel electrophoresis (PFGE), among which 15 unique PFGE patterns (PFGE patterns represented by a single strain) and 31 clusters (PFGE patterns represented by multiple strains) were detected. Furthermore, nearly all of the PFGE patterns of the Campylobacter strains isolated from retail broiler meats overlapped with those of the strains from ceca and slaughterhouse carcasses. Together, these findings revealed the high prevalence of Campylobacter species in a broiler chicken production chain, and the concerning situation of antimicrobial resistance in Campylobacter species. The findings also indicated that Campylobacter isolates from retail broiler meats were associated with fecal contamination in the slaughterhouse, underlying the need for improved measures for reducing carcass contamination in slaughter plants.

Identification of a novel G2073A mutation in 23S rRNA in amphenicol-selected mutants of Campylobacter jejuni.

OBJECTIVES: This study was conducted to examine the development and molecular mechanisms of amphenicol resistance in Campylobacter jejuni by using in vitro selection with chloramphenicol and florfenicol. The impact of the resistance development on growth rates was also determined using in vitro culture. METHODS: Chloramphenicol and florfenicol were used as selection agents to perform in vitro stepwise selection. Mutants resistant to the selective agents were obtained from the selection process. The mutant strains were compared with the parent strain for changes in MICs and growth rates. The 23S rRNA gene and the L4 and L22 ribosomal protein genes in the mutant strains and the parent strain were amplified and sequenced to identify potential resistance-associated mutations. RESULTS: C. jejuni strains that were highly resistant to chloramphenicol and florfenicol were obtained from in vitro selection. A novel G2073A mutation in all three copies of the 23S rRNA gene was identified in all the resistant mutants examined, which showed resistance to both chloramphenicol and florfenicol. In addition, all the mutants selected by chloramphenicol also exhibited the G74D modification in ribosomal protein L4, which was previously shown to confer a low-level erythromycin resistance in Campylobacter species. The mutants selected by florfenicol did not have the G74D mutation in L4. Notably, the amphenicol-resistant mutants also exhibited reduced susceptibility to erythromycin, suggesting that the selection resulted in cross resistance to macrolides. CONCLUSIONS: This study identifies a novel point mutation (G2073A) in 23S rRNA in amphenicol-selected mutants of C. jejuni. Development of amphenicol resistance in Campylobacter likely incurs a fitness cost as the mutant strains showed slower growth rates in antibiotic-free media.

Identification of New Delhi metallo-ß-lactamase 1 in Acinetobacter lwoffii of food animal origin.

BACKGROUND: To investigate the presence of metallo-ß-lactamase (MBL) genes and the genetic environment of the New Delhi metallo-ß-lactamase gene bla(NDM-1) in bacteria of food animal origin. METHODOLOGY/PRINCIPAL FINDINGS: Gram-negative bacteria with low susceptibility to imipenem (MIC>8 µg/mL) were isolated from swab samples collected from 15 animal farms and one slaughterhouse in eastern China. These bacteria were selected for phenotypic and molecular detection of known MBL genes and antimicrobial susceptibility testing. For the bla(NDM-1) positive isolate, conjugation and transformation experiments were carried out to assess plasmid transfer. Southern blotting was conducted to localize the bla(NDM-1) genes, and DNA sequencing was performed to determine the sequences of bla(NDM-1) and the flanking genes. In total, nine gram-negative bacteria of four different species presented a MBL phenotype. bla(NDM-1) was identified on a mobile plasmid named pAL-01 in an Acinetobacter lwoffii isolate of chicken origin. Transfer of pAL-01 from this isolate to E. coli J53 and JM109 resulted in resistance to multiple ß-lactams. Sequence analysis revealed that the bla(NDM-1) gene is attached to an intact insertion element ISAba125, whose right inverted repeat (IR-R) overlaps with the promoter sequence of bla(NDM-1). Thus, insertion of ISAba125 likely enhances the expression of bla(NDM-1). CONCLUSION: The identification of a bla(NDM-1)- carrying strain of A. lwoffii in chickens suggests the potential for zoonotic transmission of bla(NDM-1) and has important implications for food safety.

Detection of the staphylococcal multiresistance gene cfr in Escherichia coli of domestic-animal origin.

OBJECTIVES: To investigate the presence and the genetic environment of the multiresistance gene cfr in Escherichia coli found in domestic animals. METHODS: A total of 1230 E. coli isolates, collected from pigs, chickens and ducks, were screened by PCR for the cfr gene. The location of the cfr gene was determined by Southern blotting, the transferability of cfr gene was tested by conjugation and transformation, and the regions flanking the cfr gene were sequenced by a modified random primer walking strategy. The location of the cfr promoter sequence was analysed by mapping the cfr transcription start site using rapid amplification of 5' cDNA ends (5' RACE). RESULTS: Only a single strain from the nasal swab of a pig harboured the cfr gene. Southern blotting indicated that the cfr gene was located on a ~110 kb plasmid, designated pEC-01. A cfr-carrying segment of 1545 bp with a sequence identical to that of the cfr-harbouring plasmid pSCFS1 was flanked by two IS26 elements in the same orientation. The IS26 transposition created a new hybrid promoter in which the -35 region was part of the left inverted repeat of IS26 while the -10-like sequence was part of the original cfr upstream region. CONCLUSIONS: To the best of our knowledge, this is the first report of the cfr gene in a naturally occurring E. coli strain. Continued surveillance of the presence of the cfr gene in Gram-negative bacteria of domestic-animal origin is warranted.