An isolated strain, multiple drug resistance gene island and application

Abstract

The application relates to the technical field of microbiology, in particular to an isolated strain, a multiple drug resistance gene island and application. Ectopseudomonas The strain is a Vibrio sp. strain, which is preserved in the Guangdong Microbial Culture Collection Center (GDMCC) and has a preservation number of GDMCC NO: 68272; the chromosome carries a multiple drug resistance gene island, which is first discovered. Ectopseudomonas The application solves the problems of incomplete drug resistance gene island sequence, missing data of aquatic source drug resistance and the like in the prior art, and has great application value in application methods such as aquatic breeding risk monitoring, drug resistance mechanism research and anti-drug resistant bacteria drug screening.

Description

Technical Field

[0001] This application relates to the field of microbiology technology, and in particular to an isolated strain, a multidrug-resistant gene island, and its applications. Background Technology

[0002] Antimicrobial resistance gene islands are large, mobile DNA segments integrated into bacterial chromosomes that carry multiple drug resistance genes. Their core danger lies in their ability to accelerate the rapid spread of multidrug resistance within and between bacterial species via horizontal gene transfer pathways. A typical resistance gene island usually contains an integrase gene, a specific attachment site, and multiple drug resistance gene cassettes arranged in tandem. These can form circular intermediates that are precisely excised from the chromosome and then transferred at high frequency through conjugation, transformation, or transduction. This genetic transmission of multidrug resistance traits allows previously antibiotic-sensitive strains to acquire resistance to multiple antibiotics with different structural types at once, greatly exacerbating the difficulty of controlling drug-resistant pollution in aquaculture waters.

[0003] Existing research indicates that in aquaculture ecosystems, various common pathogens and opportunistic pathogens, such as some members of the genera *Vibrio*, *Aeromonas*, and *Pseudomonas*, have been found to carry drug resistance gene islands with different structures and compositions. However, for… Ectopseudomonas Research on multidrug resistance gene islands in strains of the genus *Exopseudomonas* is almost nonexistent. Ectopseudomonas This genus comprises a group of Gram-negative bacteria belonging to the family Pseudomonasceae, primarily isolated from aquatic animals and their aquaculture environments. Several species within this genus, such as... Ectopseudomonas plecoglossicida This bacterium is a major pathogen causing serious infectious diseases such as visceral white spot disease in important farmed fish species like large yellow croaker and grouper, resulting in significant economic losses to the aquaculture industry every year. These bacteria experience continuous selective contact pressure with various antibiotics used in aquaculture, theoretically posing an extremely high risk of carrying and spreading multidrug-resistant gene islands.

[0004] However, as of now, there is no information regarding the source of aquatic products. Ectopseudomonas Reports on the isolation, identification, full-sequence structure analysis, and transmissibility assessment of drug-resistant gene islands in bacterial strains. Due to a lack of understanding of the mobile resistance elements carried by these bacteria, existing aquaculture drug resistance monitoring systems and risk assessment models suffer from data gaps regarding key pathogen groups, hindering effective prediction and early warning of drug resistance. Ectopseudomonas The risk of horizontal transfer of drug-resistant genes mediated by antibiotics also makes it difficult to develop targeted ecological control technologies to block the spread of drug resistance in these pathogens. Therefore, isolating aquatic sources carrying islands of novel multidrug-resistant genes is crucial. Ectopseudomonas The discovery of strains and the precise composition of their gene islands are of urgent scientific necessity and significant application value for filling the aforementioned gaps and comprehensively assessing the risk of drug-resistant gene transmission in aquaculture environments. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this application provides an isolated strain, a multidrug resistance gene island, and its applications.

[0006] To achieve the above objectives, the technical solution of this application is as follows: A first aspect of this application provides an isolated bacterial strain, which is Ectopseudomonas Genus strain, classified and named Pseudomonas khazarica The specimen was registered for deposit on May 14, 2026, at the Guangdong Microbial Culture Collection Center (GDMCC), located at 5th Floor, Building 59, No. 100 Xianlie Middle Road, Guangzhou, with accession number GDMCC NO:68272. It carries a multidrug resistance gene island on its chromosome, containing at least three of the following resistance genes: aac3_I_1, qnrVC1, floR, tetG, sul1, qacEdelta1, aadA8, cmlA1, and aac3_I_2.

[0007] Furthermore, the multidrug resistance gene island comprises aac3_I_1, qnrVC1, floR, tetG, sul1, qacEdelta1, aadA8, cmlA1, and aac3_I_2, which are arranged in sequence.

[0008] Furthermore, the nucleotide sequence of the multidrug resistance gene island is shown in SEQ ID NO: 2.

[0009] A second aspect of this application provides a multidrug resistance gene island comprising at least three of the following resistance genes: aac3_I_1, qnrVC1, floR, tetG, sul1, qacEdelta1, aadA8, cmlA1, and aac3_I_2.

[0010] Furthermore, it includes aac3_I_1, qnrVC1, floR, tetG, sul1, qacEdelta1, aadA8, cmlA1, and aac3_I_2, which are arranged in sequence.

[0011] Furthermore, its nucleotide sequence is shown in SEQ ID NO: 2.

[0012] A third aspect of this application provides a host cell comprising multidrug-resistant gene islands as described above, wherein the host cell is a bacterium.

[0013] Furthermore, the bacteria are Ectopseudomonas It belongs to the bacteria.

[0014] A fourth aspect of this application provides the use of the host cell as described above, wherein the use is one of the following: (a) Monitoring of drug resistance in aquaculture environments; (b) Research on multiple drug resistance mechanisms; (c) Horizontal transfer of drug resistance genes; (d) Screening for drugs against drug-resistant bacteria; (e) Early warning of ecological risks in shellfish farming.

[0015] A kit for detecting multidrug-resistant gene islands as described above contains a set of primers or probes that target one or more specific regions of the multidrug-resistant gene islands as described above.

[0016] The beneficial effects of this application are: This invention relates to an isolated aquatic strain carrying a novel multidrug-resistant gene island. Ectopseudomonas The strain was identified, and the full sequence composition of this novel multidrug resistance gene island was determined. Compared with the prior art, the inventive results of this invention produce the following outstanding beneficial effects: 1. First discovery and provision of aquatic resources Ectopseudomonas A novel multidrug resistance gene island in aquaculture strains. This invention is the first to discover such a gene island in aquaculture environments. Ectopseudomonas Complete and well-defined multidrug resistance gene islands were identified in the strain's chromosome, providing a basis for further analysis. Ectopseudomonas This provides a foundation for the molecular basis of drug resistance development and spread.

[0017] 2. This application clarifies that the gene island carries multiple drug resistance genes that have a significant impact on aquaculture, conferring on the host a phenotype of resistance to multiple antibiotics (including aminoglycosides, fluoroquinolones, phenylpropanols, tetracyclines, sulfonamides, β-lactams, and macrolides) and a class of disinfectants (such as benzalkonium chloride). This broad resistance spectrum means that the strain has a stronger competitive advantage in aquaculture environments, enabling it to survive and spread continuously even with the alternating or combined use of multiple antimicrobial drugs, thus making it highly representative as an indicator strain. The SH149 strain provided in this application is resistant to a variety of antibiotics: gentamicin (MIC ≥ 64 μg / mL), streptomycin (MIC ≥ 128 μg / mL), ciprofloxacin (MIC ≥ 16 μg / mL), florfenicol (MIC ≥ 128 μg / mL), tetracycline (MIC ≥ 64 μg / mL), sulfadiazine (MIC ≥ 512 μg / mL), and chloramphenicol (MIC ≥ 256 μg / mL).

[0018] 3. This application achieves complete verification of the correspondence between drug-resistant genotypes and drug-resistant phenotypes. All eight acquired resistance genes predicted through whole-genome sequencing were verified by minimum inhibitory concentration (MIC) experiments using the microbroth dilution method. Furthermore, gene knockout experiments confirmed that the floR gene is a key functional gene mediating florfenicol resistance. This three-tiered technical approach of "prediction-verification-knockout confirmation" ensures a clear and reliable causal relationship between the strain's genetic information and biological function.

[0019] 4. The SH149 strain provided in this application was isolated from the intestine of the blood clam, directly originating from the shellfish aquaculture ecosystem. Therefore, it has natural ecological relevance when applied to aquaculture environmental monitoring. Using this strain as a model organism, the colonization, persistence, and release of multidrug-resistant bacteria into the water body of shellfish under real-world conditions can be simulated.

[0020] 5. The SH149 strain provided in this application can be used as an indicator bacterium to assess the risk of horizontal transfer of multidrug resistance genes in aquaculture ecosystems. Because the resistance gene islands carried by this strain are structurally complete, have clear boundaries, and contain functional integrase, the efficiency of horizontal transfer between different bacteria can be quantified through conjugation experiments. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, obtaining other drawings based on these drawings without creative effort still falls within the scope of the present invention.

[0022] Figure 1 This is a schematic diagram of the drug resistance gene island structure of strain SH149; Captions: aac represents aminoglycoside acetyltransferase genes (aac3_I_1, aac3_I_2), with resistance to aminoglycosides; qnr represents fluoroquinolone resistance genes (qnrVC1), with resistance to fluoroquinolones; floR represents florfenicol / chloramphenicol resistance genes, with resistance to phenylpropanol / florfenicol; tet represents tetracycline resistance genes (tetG), with resistance to tetracyclines; sul represents sulfonamide resistance genes (sul1), with resistance to sulfonamides; qac represents quaternary ammonium disinfectant resistance genes (qacEdelta1), with resistance to quaternary ammonium disinfectants; aadA represents aminoglycoside adenylate transferase genes (aadA8), with resistance to aminoglycosides; cmlA The gene is cmlA1, which is a chloramphenicol resistance gene, and the resistance category is chloramphenicol; hypo is a putative protein gene with unknown function and no corresponding resistance category. Figure 2 A phylogenetic tree based on the 16S rRNA gene; Figure 3 This is a diagram showing the NCBI BLAST comparison results of drug resistance gene islands. Figure 4 A bar chart showing the MIC measurement results; Figure 5 Electrophoresis image for PCR verification of floR gene knockout; Figure 6 This is a comparison of the MICs of wild-type and knockout mutants. Detailed Implementation

[0023] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of this application and are not intended to limit this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application. The terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0025] This application provides an isolated strain, which was isolated from an aquaculture environment, specifically, from healthy blood clams (Clams) isolated in July 2025 from an aquaculture farm in Wenzhou City, Zhejiang Province. Tegillarca granosaThe sample was named SH149.

[0026] After inoculating SH149 strain onto LB medium and culturing at 28-37℃ for 18-24 hours, the colonies were round, raised, with neat edges, and milky white in color. 16S rRNA gene amplification and sequencing, and sequence alignment results showed similarity to the type strain. Ectopseudomonas khazarica The 16S rRNA gene sequence identity of TBZ2 was 99.93%, and it was identified as... Ectopseudomonas khazarica (Pseudomonas cristatus). Deposited on May 14, 2026 at Guangdong Provincial Microbial Culture Collection Center (GDMCC), accession number GDMCC NO:68272.

[0027] This application uses ABRicate software in conjunction with the NCBI drug resistance gene database for prediction. A multidrug resistance gene island of 13,609 bp (positions 21-13629 of NODE_12, sequence shown in SEQ ID NO:2) was found in NODE_12 (its sequence is shown in SEQ ID NO:1). NCBI BLAST alignment showed that the highest coverage of this sequence in the database was only 58% (compared to E. mendocina plasmid CP115818.1), demonstrating its novelty. This drug resistance gene island contains 10 complete drug resistance genes, as shown in the table below. Excluding the unknown functional gene hypothetical, the gene island contains 9 core functional drug resistance genes: aac3_I_1, qnrVC1, floR, tetG, sul1, qacEdelta1, aadA8, cmlA1, and aac3_I_2, arranged sequentially.

[0028] The SH149 strain provided in this application is a biological material with a clear genetic background and drug resistance characteristics, laying a material foundation for subsequent analysis of drug resistance mechanisms and application development. Specifically, the existence of this strain enables researchers to design detection probes, construct positive control systems, and assess the risk of drug resistance gene transmission in environmental samples based on its complete drug resistance gene island sequences, thereby overcoming the deficiency of traditional techniques that lack representative standard strains.

[0029] The multidrug-resistant gene island (SEQ ID NO:2) provided in this application embodiment was isolated and identified from the chromosome of the aforementioned SH149 strain. This gene island, as an independent functional element, can exist independently of the original host strain, for example, by being cloned into a plasmid vector and replicating and maintaining itself in a heterologous host.

[0030] Furthermore, this application also provides a host cell containing any of the aforementioned multidrug resistance gene islands, and the host cell is a bacterium. Specifically, the bacterium may be an original isolation. Ectopseudomonas The bacterial strain can also be a recipient bacterium into which isolated multidrug resistance gene islands are introduced via conjugation transformation, electroporation, or chemical transformation. Recipient bacteria include, but are not limited to, *Escherichia coli*, *Salmonella*, *Aeromonas hydrophila*, or *Pseudomonas fluorescens*. In the host cell, the multidrug resistance gene islands can be integrated onto the chromosome or exist in a free circular form. The stably integrated host cells can grow normally in a culture medium containing the corresponding antibiotic. The host cell model carrying clearly defined drug resistance gene islands provided in this application allows researchers to simulate horizontal transfer events of drug resistance genes in nature under controlled laboratory conditions, without relying on the uncertainties of environmental samples. By comparing the expression differences of the same gene islands in different host backgrounds, the regulatory role of host factors on drug resistance gene expression can be revealed.

[0031] Furthermore, this application also provides multiple applications of the host cell, including but not limited to the following types: (a) Monitoring of drug resistance in aquaculture environment; Some specific implementation schemes of this application are as follows: collect water samples or sediment samples from aquaculture ponds, filter and enrich them and extract DNA, use the specific sequence of multidrug resistance gene islands carried by host cells as targets, set up fluorescent probes to perform real-time quantitative PCR detection, and combine antibiotic residue detection data to assess the multidrug resistance risk level of the aquaculture area. (b) Study on multiple drug resistance mechanisms; Some specific implementation schemes of this application are as follows: using the host cell as a model strain, the expression of integrase gene is regulated by a tetracycline-inducible expression system, and the complete molecular process of drug resistance gene islands looping out of the chromosome, forming a circular intermediate, and transferring to plasmids or recipient bacteria is mapped by time gradient sampling combined with whole genome sequencing.

[0032] (c) Study on horizontal transfer of drug resistance genes; Some specific implementation schemes of this application are as follows: the host cell marker streptomycin resistance marker is used as the donor bacteria, and Escherichia coli that does not naturally carry drug resistance gene islands is used as the recipient bacteria. A filter membrane conjugation experiment is carried out in a culture medium that simulates the composition of aquaculture water. The transfer frequency of gene islands is determined under different temperature, pH and salinity conditions, and a multiple regression model is established.

[0033] (d) Screening for drugs against drug-resistant bacteria; Some specific implementations of this application are as follows: The host cells are evenly spread on MH agar plates, and drug sensitivity test discs containing natural product extracts or chemically synthesized compounds to be screened are placed on them. After incubation at 35°C for 18 hours, the diameter of the inhibition zone is measured. At the same time, a solvent control without the compound and a positive control of known effective antibiotics are set up to preliminarily screen out candidate compounds that can inhibit the growth of the multidrug-resistant bacteria.

[0034] (e) Ecological risk warning for shellfish farming; Specific implementation methods of some embodiments of this application are as follows: regularly collect digestive gland tissues of farmed shellfish (such as oysters and mussels), homogenize them, isolate bacteria, and screen them using selective culture media. Ectopseudomonas Similar bacterial colonies were identified, and multiplex PCR was used to detect the three core drug-resistant genes on the gene island. A risk warning threshold was established based on the changing trend of the detection positive rate.

[0035] Furthermore, this application also provides a kit for detecting the aforementioned multidrug resistance gene islands, comprising a primer set or probes targeting one or more specific regions of the aforementioned multidrug resistance gene islands.

[0036] The following are some specific implementation processes of this application.

[0037] Example 1: Isolation and Purification of Strains In July 2025, healthy blood clams were collected from an aquaculture farm in Wenzhou City, Zhejiang Province. Tegillarca granosa Samples were collected by dissecting the intestines under aseptic conditions and inoculating them onto LB agar (10 g / L tryptone, 5 g / L yeast extract, 10 g / L NaCl, pH 7.2) and incubating at 37°C for 24 hours. Single colonies were picked; the colonies were round, raised, with neat edges, and milky white in color, and the strain was named SH149.

[0038] Example 2: 16S rRNA gene identification and phylogenetic analysis 1. Using genomic DNA from strain SH149 as a template, PCR amplification was performed using primers 27F / 1492R, yielding an amplification product of approximately 1,500 bp. Sequencing yielded a 1,532 bp 16S rRNA gene sequence (SEQ ID NO:13). The specific process is as follows: (1) Genomic DNA extraction Genomic DNA was extracted from strain SH149 using a bacterial genomic DNA extraction kit (such as TIANGEN DP302), following the manufacturer's instructions. The extracted DNA was quality-checked by 1% agarose gel electrophoresis and NanoDrop 2000.

[0039] (2) PCR amplification Using universal primers for bacterial 16S rRNA gene: PCR reaction system (50 μL): PCR amplification procedure: (3) Sequencing and sequence analysis After purification, the PCR product was bidirectionally sequenced using upstream primer 27F and downstream primer 1492R. The spliced ​​sequence yielded the 16S rRNA gene sequence of strain SH149, which is 1,532 bp in length (SEQ ID NO:13).

[0040] The BLAST alignment results are as follows: (4) Phylogenetic analysis The 16S rRNA gene sequence of strain SH149 was BLAST-aligned in the NCBI database. Sequences from type strains with high homology were selected, and phylogenetic analysis was performed using MEGA 11 software. Comparison tool: Clustal W Tree construction method: Neighbor-Joining Evolutionary distance model: Kimura 2-parameter Confidence test: Bootstrap (1,000 repetitions) like Figure 2 As shown in the phylogenetic tree, strain SH149 clusters with Ectopseudomonas khazarica TBZ2 in the same evolutionary branch, with a Bootstrap support rate of 99%.

[0041] Conclusion: Strain SH149 was identified as... Ectopseudomonas khazarica .

[0042] Example 3: Whole Genome Sequencing and Assembly The whole genome of strain SH149 was sequenced and assembled using the following methods: (1) Sequencing Paired-end sequencing (150 bp × 2) was performed using the Illumina NovaSeq 6000 platform, yielding 5,565,919 read pairs. The total raw data volume was approximately 1.5 Gb (approximately 750 MB after compression), with a genome coverage of approximately 300×.

[0043] (2) Quality control and assembly Quality control: Data quality control was performed using FastP v0.23.0 to remove connectors and low-quality reads. Assembly: Use SPAdes v3.15.5 for assembly, parameters: --isolate --careful -k 21,33,55,77,99,127 Evaluation: Assembly quality was evaluated using QUAST v5.0.2 and BUSCO v5.4.5. The results are as follows: Example 4: Identification and Sequence Analysis of Drug Resistance Gene Islands Using ABRicate software in conjunction with the NCBI drug resistance gene database, a multidrug resistance gene island of 13,609 bp in length (positions 21-13629) was found in NODE_12, containing 10 complete drug resistance genes (SEQ ID NO:3-12).

[0044] The target region sequence was extracted using seqkit v2.13.0, and its structure is as follows: Figure 1 As shown. After comparison using NCBI BLAST, as... Figure 3 As shown, the highest coverage of this sequence in the database is only 58% (compared with E. mendocina plasmid CP115818.1), proving its novelty.

[0045] Example 5: Determination of Minimum Inhibitory Concentration (MIC) The MIC values ​​of SH149 strain against multiple antibiotics were determined using the microbroth dilution method according to CLSI M07-A11 standards. The specific procedure is as follows: (1) Preparation of bacterial culture The SH149 strain was inoculated onto MHA plates and activated by incubation at 37°C for 18-24 hours. Single colonies were picked and inoculated into MHB broth, and cultured at 37°C with shaking until the logarithmic growth phase (OD200). 600 ≈ 0.5) Dilute the bacterial suspension to 0.5 McFarland standard (approximately 1-2 × 10⁻⁶) using sterile 0.9% NaCl. 8 CFU / mL Dilute with MHB broth 100 times to obtain approximately 1-2 × 10⁻⁶. 6 CFU / mL inoculated bacterial solution (2) Preparation of antibiotic gradients Prepare serially diluted antibiotic solutions in wells 1-11 of a 96-well plate. Well 12 is a positive control (without antibiotics), and well 13 is a negative control (sterile MHB).

[0046] (3) Sample addition and incubation Add 100 μL of the above bacterial culture to each well (except for the negative control), cover with sealing film, and incubate at 37°C for 16-20 hours.

[0047] (4) Result Interpretation The MIC value is defined as the lowest antibiotic concentration that completely inhibits bacterial growth, as observed by the naked eye. Escherichia coli ATCC 25922 is the quality control strain, and the quality control results must be within the CLSI allowable range.

[0048] The results are as follows: S = Sensitive, R = Resistant; the results of the quality control strain E. coli ATCC 25922 are within the CLSI acceptable range.

[0049] Conclusion: SH149 strain exhibits multidrug resistance phenotypes to 5 classes of antibiotics and 1 class of disinfectant, with 100% genotypic and phenotypic similarity.

[0050] Example 6: Validation of floR gene knockout The specific process for constructing the floR gene knockout mutant SH149-ΔfloR is as follows: (1) Knockout vector construction Primer design: step: Using SH149 genomic DNA as a template, the upstream and downstream homologous arms (approximately 500 bp each) of the floR gene were amplified. The upstream and downstream homologous arms were cleaved with enzymes and then ligated into the pK18mobsacB suicide plasmid. The ligation product was transformed into E. coli S17-1 (λpir) competent cells and plated on LB agar plates containing kanamycin (50 μg / mL). The positive clone was verified by PCR and named pK18-ΔfloR (2) Joining transfer (single exchange) (3) Double exchange screening Select single-colony crossovers and inoculate them onto LB liquid medium (antibiotic-free). Incubate at 37°C with shaking for 6-8 h, then plate them onto LB agar plates containing 10% sucrose (NaCl-free) and incubate at 30°C for 24-48 h. Select single colonies and copy them onto LB agar plates containing / without kanamycin to screen for kanamycin-sensitive clones.

[0051] (4) PCR verification PCR was performed using validation primers floR-VF (5′-TGCTGGCTCTTCCTTTCCAG-3′) and floR-VR (5′-CCAGCGTATCGTCCAGGTAG-3′): (5) Sequencing verification The PCR product was purified and sent for sequencing, which confirmed that the floR gene was precisely deleted.

[0052] (6) MIC determination of knockout mutant Referring to the minimum inhibitory concentration (MIC) determination method in Example 5, the MICs of wild-type and knockout mutants against florfenicol were compared.

[0053] The results are as follows: (1) Validation of knockout mutants (2) MIC measurement results Conclusion: Knockout of the floR gene reduced the MIC value of the strain against florfenicol by 32-fold, confirming that the floR gene is the main determinant of florfenicol resistance.

[0054] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An isolated bacterial strain, characterized in that, It is Ectopseudomonas The strain, classified as Pseudomonas khazarica, is deposited at the Guangdong Provincial Microbial Culture Collection Center (GDMCC) with accession number GDMCCNO:68272. It carries a multidrug resistance gene island on its chromosome, and the nucleotide sequence of the multidrug resistance gene island is shown in SEQ ID NO:

2.

2. A multidrug-resistant gene island, characterized in that, Its nucleotide sequence is shown in SEQ ID NO:

2.

3. A host cell comprising the multidrug resistance gene island as described in claim 2, characterized in that, The host cell is bacteria.

4. The host cell according to claim 3, characterized in that: The bacteria are Ectopseudomonas It belongs to the bacteria.

5. The application of the host cell as described in claim 4, characterized in that, The application is one of the following: (a) Monitoring of drug resistance in aquaculture environments; (b) Screening for drugs against drug-resistant bacteria; (c) Early warning of ecological risks in shellfish farming.

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