Two colistin resistance-producing Aeromonas strains, isolated from coastal waters in Zhejiang, China: characteristics, multi-drug resistance and pathogenicity

Introduction Aeromonas spp. are ubiquitous inhabitants of ecosystems, and many species are opportunistically pathogenic to humans and animals. Multidrug-resistant (MDR) Aeromonas species have been widely detected in hospitals, urban rivers, livestock, and aquatic animals. Results In this study, we identified two Aeromonas isolates, namely Aeromonas veronii 0728Q8Av and Aeromonas caviae 1029Y16Ac, from coastal waters in Zhejiang, China. Both isolates exhibited typical biochemical characteristics and conferred MDR to 11 kinds of antibiotics, remaining susceptible to ceftazidime. Whole-genome sequencing revealed that both isolates harbored multiple antibiotic resistance genes (ARGs) and several mobile genetic elements (MGEs) on the chromosomes, each containing a resistance genomic island (GI), a typical class 1 integron, a transposon, and various insertion sequences (ISs). Most ARGs were situated within the multiple resistance GI, which contained a class 1 integron and a transposon in both Aeromonas isolates. Furthermore, a chromosomal mcr-3.16 gene was identified in A. veronii 0728Q8Av, while a chromosomal mcr-3.3 was found in A. caviae 1029Y16Ac. Both mcr-3 variants were not located within but were distanced from the multidrug resistance GI on the chromosome, flanking by multiple ISs. In addition, a mcr-3-like was found adjacent to mcr-3.16 to form a tandem mcr-3.16-mcr-3-like-dgkA structure; yet, Escherichia coli carrying the recombinants of mcr-3-like did not exhibit resistance to colistin. And an incomplete mcr-3-like was found adjacent to mcr-3.3 in A. caviae 1029Y16Ac, suggesting the possibility that mcr-3 variants originated from Aeromonas species. In vivo bacterial pathogenicity test indicated that A. veronii 0728Q8Av exhibited moderate pathogenicity towards infected ayu, while A. caviae 1029Y16Ac was non-virulent. Discussion Thus, both Aeromonas species deserve further attention regarding their antimicrobial resistance and pathogenicity.


Introduction
Antibiotic resistance genes (ARGs) are considered emerging environmental contaminants due to their potential risks to human and animal health (Zheng et al., 2021).Infections caused by multidrugresistant (MDR) Gram-negative bacteria (GNB) are increasingly common and pose a paramount therapeutic challenge, raising significant concerns worldwide (Osei Sekyere et al., 2016;Vivas et al., 2019).Colistin is considered one of the few "last-resort" antibiotics against MDR GNB infections (Osei Sekyere et al., 2016;Yin et al., 2017).The emergence and rapid dissemination of the mobile colistin resistance (mcr) genes further compound the challenges in antibiotic treatment of MDR bacteria (Vivas et al., 2019;Shen et al., 2020).
Aeromonas, a Gram-negative bacillus, is widely distributed in the environment, particularly in freshwater and estuarine ecosystems (Janda and Abbott, 2010).Currently, the Aeromonas genus encompasses 36 species, many of which are opportunistically pathogenic to both animals and humans (Janda and Abbott, 2010;Fernández-Bravo and Figueras, 2020).Aeromonas spp.infect humans, causing various gastroenteritis and extra-intestinal diseases (Fernández-Bravo and Figueras, 2020;Carusi et al., 2023).Long recognized as a significant pathogen in aquatic animals, Aeromonas instigates a broad spectrum of opportunistic infections, resulting in severe clinical manifestations such as sepsis, bleeding, ulcers, ascites, and high mortality (Janda and Abbott, 2010;Carusi et al., 2023).Many studies have demonstrated that Aeromonas serves as a MDR carrier and a reservoir of many ARGs like mar genes (Piotrowska and Popowska, 2015;Ling et al., 2017;Eichhorn et al., 2018;Shen et al., 2020).
The coastal waters, being significant areas of human activity, harbor a wealth of ARGs and antibiotic-resistant bacteria (ARB) (Zhu et al., 2017;Zheng et al., 2021).These genes and bacteria originate not only from coastal aquaculture but also from various human activities such as animal husbandry, freshwater aquaculture, clinical medicine, and industrial production (Zhu et al., 2017;Jang et al., 2018;Zheng et al., 2021).They are introduced into coastal water environments through mechanisms such as rainfall and sewage discharge (Shao et al., 2018).Exposure of environmental microorganisms to this mixture stimulates horizontal gene transfer (HGT) events, spreading genetic resistance elements across different microbial strains and increasing microbial abundance and penetration in new hosts (Juhas et al., 2009;Shao et al., 2018).Aeromonas spp. is ubiquitously distributed in coastal waters and mariculture animals, many of which harbors abundant ARGs and mobile genetic elements (MGEs) (Piotrowska and Popowska, 2014;Carusi et al., 2023).Although Aeromonas carrying mcr genes have been repeatedly detected in freshwater animals and water bodies (Eichhorn et al., 2018;Xu et al., 2020;Sakulworakan et al., 2021), the incidence of mobile colistin resistance determinants and their genetic environment in Aeromonas genomes from coastal waters and marine animals have largely been ignored.In this study, we investigated the antibiotic susceptibility of two MDR Aeromonas species isolated from the coastal waters near Wenzhou, Zhejiang Province, China.Through genome sequencing, we examined the genetic profiles for antimicrobial resistance, analyzed the structural characteristics of MDR gene islands on their chromosomes, and investigated the distribution of mcr variants.Additionally, we experimentally tested the ability of the mcr variants to mediate colistin resistance.Furthermore, we assessed the in vivo pathogenicity of the two MDR Aeromonas species in ayu (Plecoglossus altivelis), an important amphidromous economic fish species found in East Asia.

Bacterial strains
In our previous study, we selected 25 sampling sites in the coaster waters near Wenzhou in the East China Sea and collected surface seawater samples (Jin et al., 2021).We isolated culturable bacteria resistant to sulfonamides, tetracyclines, and quinolones from the seawater samples using antibiotic resistance plates and detected the target ARGs in these isolates using polymerase chain reaction (PCR).We isolated 1,605 bacterial strain with antibiotic resistance phenotypes, among which 51 isolates tested positive for resistance genes related to sulfonamides, tetracyclines, and quinolones, with 43 of them belonging to the genus Aeromonas (Jin et al., 2021).Additionally, we identified 39 MDR strains (Jin et al., 2021).Using PCR primers for the mcr genes, we identified 2 Aeromonas isolates containing the mcr-3 variants (Jin et al., 2021;Xu et al., 2021) (Supplementary Table S1).Preliminary 16S rDNA sequencing suggested that both isolates likely belonged to Aeromonas veronii and Aeromonas caviae.In this study, further identification of both isolates was performed using multilocus phylogenetic analysis (MLPA) based on six genes (gyrB, rpoD, dnaJ, gyrA, dnaX, and atpD) (Martinez-Murcia et al., 2011).Phylogenetic trees were constructed based on the concatenated sequences containing these six genes using the maximum likelihood method in the MEGA 7.1 software package.Subsequently, biochemical tests were conducted on the isolates using biochemical test kits (Tiangen, Beijing, China).
The antibiotics that induced resistance in either of the tested bacterial strains were selected to calculate the minimum inhibitory concentrations (MICs) against both strains.This was achieved using

Whole-genome sequencing and sequence analysis
The genomic DNA of A. veronii 0728Q8Av and A. caviae 1029Y16Ac was extracted using cetyltrimethylammonium bromide method, following the manufacturer's protocol BGI-PB-TQ-DNA-003A0. Subsequently, a 20 kb fragment library was constructed for each isolate, utilizing high-quality genomic DNA that met the requirements for whole-genome sequencing.Sequencing was carried out on a Pacbio Sequel II platform (BGI, Shenzhen, China).The reads were assembled using Canu (version 1.5).After multiple adjustments to achieve the optimal assembly, base correction, circularization, and plasmid library alignment were performed on the assembled sequences to obtain the final assembly results.Gene prediction was performed with Glimmer (version 3.02).The annotation of genes was accomplished through in-house pipeline on the RAST server 2 (Ebu et al., 2023).Acquired antimicrobial resistance genes were predicted using ResFinder 4.1 3 with a threshold of percent identity set at 90% and a minimum coverage length of 60%.Genomic islands (GIs) were determined using IslandPath-DIMOB 4 (Bertelli and Brinkman, 2018).Insertion sequences (ISs) were identified through ISfinder 5 (Siguier et al., 2006).Transposons and integrons were predicted using TnCentral 6 and Integron Finder, 7 respectively (Damas et al., 2022).Comparative analysis of genome sequences was performed using Easyfig with a maximum e-value of 0.001 and identification threshold set at 98% and BRIG (with an identification threshold of 50%) (Tang et al., 2022).Virulence factors were predicted using the Virulence Factor Database (VFDB, http://www.mgc.ac.cn/VFs/) (Liu et al., 2022).

mcr-3 variant functionality assay
According to Jin et al. (2021), the prevalence of Aeromonas spp. with mcr genes in coastal waters is low (2 out of 51). A. veronii 0728Q8Av and A. caviae 1029Y16Ac show different levels of resistance to colistin and harbor different mcr-3 variants.To assess whether these mcr-3 variants affect resistance to colistin, we conducted functionality assays.To in silico verify mcr-3 variants in both A. veronii 0728Q8Av and A. caviae 1029Y16Ac, the sequences of mcr-3.16, mcr-3.3, and mcr-3-like, was aligned, respectively, referred to sequences of mcr-3 variants downloaded from NCBI. 8 And a phylogenetic tree was constructed based on mcr-3 variants' sequences using the Maximum likelihood method in the MEGA 7.1 software package.
To determine whether the mcr-3 variants in A. veronii 0728Q8Av and A. caviae 1029Y16Ac are located on the chromosome or plasmid, conjugation assays were conducted as described previously (Sun et al., 2016;Tang et al., 2024).The E. coli J53 was used as the recipient strain, and A. veronii 0728Q8Av or A. caviae 1029Y16Ac was the donor strain.The E. coli ECCNB20-2 carrying mcr-1 was used as a positive control donor (Chang et al., 2020).All bacterial strains were cultured to be in the logarithmic growth phase in LB broth at 37°C.Each of the donor bacteria, that is A. veronii 0728Q8Av, A. caviae 1029Y16Ac, and E. coli ECCNB20-2, was mixed with E. coli J53 in suitable proportion, and the bacterial mixture was transferred to filter paper on the LB agar and cultured for 8 h.Then the filter paper was suspended into a centrifuge tube containing LB broth and serially diluted.Each diluted bacterial solution (10 μL) was cultured onto screening LB agar supplemented with 2 μg/mL colistin and 100 μg/mL NaN 3 , and with 100 μg/mL NaN 3 , respectively.Conjugation transfer was determined as described by Tang et al. (2022).

Bacterial pathogenicity assessment
Healthy ayu, weighing 20-25 g, were purchased from a commercial farm in Ningbo, China.Fish were raised in a recirculating system with filtered water at 20-22°C (Zhou et al., 2020).The fish were fed with pelleted dry food once a day and acclimatized to laboratory conditions for 2 weeks before experiments.Then, randomly allocate the fish into 21 tanks, each containing 10 individuals.The fish in each three tanks were intraperitoneally administered 100 μL of bacterial suspension of A. veronii 0728Q8Av and A. caviae 1029Y16Ac, at concentrations of 1 × 10 7 , 1 × 10 8 , and 1 × 10 9 CFU/mL.Additionally, three tanks of fish were injected sterile PBS in volumes matching those of the experimental groups, serving as negative controls.All fish were kept at 20-22°C for 7 days to observe and record the morbidity and mortality rates.The degree of virulence, expressed as the 50% mean lethal dose (LD 50 ), was calculated using the Bliss method (Finney, 1985).All intervention measures are strictly carried out in accordance with the guiding principles of the Animal Experiment Ethics Committee of Ningbo University (No. 11102).

Nucleotide sequence accession numbers
The complete genome sequences of A. veronii 0728Q8Av and A. caviae 1029Y16Ac were submitted to GenBank under Bioproject accession numbers PRJNA1070378 and PRJNA1070380, respectively.

Characteristics of Aeromonas veronii 0728Q8Av and Aeromonas caviae 1029Y16Ac
Jin et al. ( 2021) identified both mcr-3.16and mcr-3-like in strain 0728Q8Av and mcr-3.3 in strain 1029Y16Ac by DNA sequencing of PCR products.In this study, MLPA based on six house-keeping genes demonstrated that strain 0728Q8Av clustered together with selected A. veronii strains and strain 1029Y16Ac clustered together with A. caviae strains, which indicated that the two isolates belonged to A. veronii and A. caviae, respectively (Figure 1).
Regarding the biochemical characteristics, both A. veronii 0728Q8Av and A. caviae 1029Y16Ac exhibited numerous identical traits.For example, both isolates demonstrated growth at a concentration of 1-3% sodium chloride (NaCl) (w/v) but were unable to be maintained at >6% NaCl.They were both positive for acid formation when provided with glucose, sucrose, mannose, maltose, OPNG, mannitol, and saligenin, while showing negativity towards xylose, raffinose, and sorbose.Additionally, both bacterial isolates demonstrated the ability to produce oxidase, indole, and arginine dihydrolase (Table 1).However, the two bacterial isolates presented some differing characteristics.Specifically, A. veronii 0728Q8Av, unlike A. caviae 1029Y16Ac, tested positive in the Voges-Proskauer test and exhibited urea hydrolysis. A. caviae 1029Y16Ac could utilize arabinose and lactose, producing acid, whereas A. veronii 0728Q8Av could not (Table 1).

Genomic analysis of
The virulence factors' prediction suggested that virulence factors were significantly different between A. veronii 0728Q8Av and A. caviae 1029Y16Ac (Table 3).The Tap type IV pili of both strains exhibited similar structural features.However, A. veronii 0728Q8Av possessed 16 genes related to MSHA type IV pili, whereas A. caviae 1029Y16Ac had only 3.And A. veronii 0728Q8Av had type I and Flp type IV pili, whereas A. caviae1029Y16Ac did not.Flagella analysis revealed that both strains had polar flagella.However, A. veronii 0728Q8Av possessed 54 genes related to polar flagella, whereas A. caviae 1029Y16Ac had only 7. Both stains had a type II secretion system (T2SS) containing 14 genes.Toxin analysis revealed that both strains contained Hemolysin and Thermostable hemolysin (TH).Interestingly, A. veronii 0728Q8Av had Aerolysin, but A. caviae 1029Y16Ac did not.

Functional identification in mediating colistin resistance of mcr-3 variants
Blast analysis revealed that both mcr-3.16(1623-bp of ORF) of A. veronii 0728Q8Av and mcr-3.3(1623-bp of ORF) of A. caviae 1029Y16Ac exhibited 100% identity to previous reported mcr-3.16(WP-111273845.1) and mcr-3.3(WP-099982814.1).MCR-3-like of A. veronii 0728Q8Av provided a 145-aa substitution by 29 amino acids at the carbon terminus, while a single amino acid difference occurred at the 273rd residue within the 396 amino acid residues at the Nitrogen terminus, compared to reported MCR-3-like (MF495680) (Figure 2).The phylogenetic tree unveiled a close clustering of both MCR-3.16 and MCR-3.3 with other predetermined MCR-3 variants.Additionally, the MCR-3-like variant in this study exhibited clustering alongside the one reported in A. veronii isolated from retail chicken (MF495680) (Supplementary Figure S2).
Transformants containing pUC19-mcr-3-like had a colistin MIC of The multilocus phylogenetic tree analysis based on the sequences of six house-keeping genes (gyrB, rpoD, dnaJ, gyrA, dnaX, and atpD) from Aeromonas spp.using the maximum likelihood method.The values at the forks indicate the percentage of bootstrap values (1,000 replicates; shown only when >60%).Scale bar shows the number of substitutions per base.Accession numbers of the sequences used are listed in Supplementary Table S2.
A segment consisting of mcr-3.3-mcr-3-likewas discovered in A. caviae 1029Y16Ac.But the mcr-3-like gene was incomplete and only had 116 amino acids, which showed 100% identity to the Nitrogen terminus of the MCR-3-like (MF495680).Compared to other Aeromonas spp., it seemed that the 3′ end of the mcr-3-like and its downstream dgkA gene were completely absent in A. caviae 1029Y16Ac.None ORFs but 10 ISs, namely ISAs12, ISAs15, ISAs2, ISAs29, IS5D, IS50R, and ISAeme2, were observed at the flanking regions of the segment mcr-3.3-mcr-3-like in A. caviae 1029Y16Ac (Figure 3).No transconjugants were observed on the colistincontaining screening LB agar plates coated with bacterial culture from the conjugation assay using A. veronii 0728Q8Av or A. caviae 1029Y16Ac.This indicated that the mcr-3 variants, that is mcr-3.16and mcr-3-like in A. veronii 0728Q8Av and mcr-3.3 in A. caviae 1029Y16Ac, were not transferred into E. coli J53 through conjugation, suggesting that these mcr-3 variants were located on the chromosomes of both A. veronii 0728Q8Av and A. caviae 1029Y16Ac (Supplementary Figure S3).

In vivo bacterial pathogenicity determination
The mortality of fish infected with the A. veronii 0728Q8Av and A. caviae 1029Y16Ac isolate are summarized in Table 5.Using the calculated method reported by Mittal et al. (1980), the LD 50 value in a

Discussion
Aeromonas species isolated from coastal waters are prone to developing MDR, contributing to the interchange of ARGs between land-derived and marine environments (Zhu et al., 2017;Jang et al., 2018;Zheng et al., 2021).In this study, we pinpointed two MDR Aeromonas species, that is A. veronii 0728Q8Av and A. caviae 1029Y16Ac, which exhibited distinct biochemical characteristics as previously documented (Abbott et al., 2003).Both isolates exhibited resistance to colistin and harbored different mcr-3 variants.All resistance elements, including ARGs and MGEs, were located on their chromosomes, irrespective of the presence of plasmids.The mcr-3 variants were not clustered with other ARGs but were independently located on the chromosomal DNA, flanked by several ISs.In addition, A. veronii 0728Q8Av, but not A. caviae 1029Y16Ac, exhibits significant pathogenicity to ayu (Plecoglossus altivelis).
Antimicrobial resistance in Aeromonas is rapidly escalating worldwide, and resistance elements have become increasingly complex.For example, Aeromonas spp.resistance to 3rd-generation cephalosporin and producing broad-spectrum carbapenemase KPC-24 have been isolated globally (Bhaskar et al., 2015;Yang et al., 2022).Aeromonas demonstrates notable activity in MDR, exhibiting widespread resistance to various classes of antibiotics including β-lactam, aminoglycosides, fluoroquinolones, tetracyclines, macrolides, sulfonamides, polymyxins, and phenicols, particularly in wastewater (Figueira et al., 2011;Carusi et al., 2023;Neil et al., 2024).However, few reports have highlighted the contribution of Aeromonas to the development and dissemination of antimicrobial resistance elements in coastal aquatic environments (Gambino et al., 2022;Liang et al., 2024).In the present study, the two Aeromonas species exhibited broad MDR profiles, with sulfamethoxazole, oxytetracycline, ampicillin and florfenicol being the least effective to A. veronii 0728Q8Av and sulfamethoxazole and trimethoprim being the least effective to A. caviae 1029Y16Ac.Correspondingly, various ARGs could be found in the chromosomal genomes of both Aeromonas strains, such as mcr-3.16,qnrVC4,sul1,dfrA14,ampS,cphA4,tet(E),floR,and cmlA1 in A. veronii 0728Q8Av,sul1, , bla MOX-6 , bla OXA-10 , tet(E), and catB3 in A. caviae 1029Y16Ac.If only considering ARGs as determinants of antibiotic resistance, sul1 exhibits highly potent resistance to sulfamethoxazole (with an MIC value of 256 μg/mL).No ARGs coding for trimethoprim-resistant dihydrofolate reductases (DHFRs) was found in the genome of A. caviae 1029Y16Ac, indicating other resistance mechanisms probably responsible for trimethoprim.Interestingly, both strains remained susceptible to ceftazidime, which is supported by their resistance gene profiles.
After the ban on colistin as a growth promoter in several countries for example China, Japan, and Thailand, both the colistin residue concentrations and mcr variants (especially mcr-1) in different environments have reportedly decreased (Wang et al., 2020;Rhouma 10.3389/fmicb.2024.1401802Frontiers in Microbiology 13 frontiersin.orget al., 2023).This has alleviated the predicament of Aeromonas in the spread of mcr genes.However, the emergence of MDR in treating Aeromonas infections remains a concern.In this study, the two Aeromonas strains exhibited similar resistance profiles, showing resistance to commonly used antibiotics such as tetracycline, oxytetracycline, florfenicol, ampicillin, sulfamethoxazole, and trimethoprim (Table 2).Both strains remained sensitive to ceftazidime and lacked common ARGs for other antibiotics, such as the tetX family conferring resistance to tetracycline and bla NDM conferring resistance to carbapenem, indicating that therapeutic options are still available.Nevertheless, both strains were found to carry the bla OXA-10 gene encoding ESBL, and A. caviae 1029Y16Ac harbored the bla VEB-3 gene, highlighting the need to monitor the spread of these strains.
A. caviae and A. veronii, along with A. dhakensis, A. hydrophila and A. salmonicida, are the most frequently detected Aeromonas species causing diseases in both humans and animals (Janda and Abbott, 2010;Fernández-Bravo and Figueras, 2020).As opportunistic pathogens, their pathogenicity is restricted by various factors, including genetic virulence factors, temperature, and host immune status (Fernández-Bravo and Figueras, 2020;Carusi et al., 2023).In this study, according to a virulence assessment method (Mittal et al., 1980), A. veronii 0728Q8Av demonstrated moderate virulence towards tested ayu, while A. caviae 1029Y16Ac showed no virulence.Additionally, a 100% mortality rate was observed within 2 days post-infection when fish were injected with A. veronii 0728Q8Av at concentrations ranging from 10 8 to 10 9 CFU/mL, indicating a short incubation period for A. veronii 0728Q8Av infection (Chen F. et al., 2019).Compared to A. caviae 1029Y16Ac, more virulence factors related to pili (such as Type I, Flp type IV, and MSHA type IV) and polar flagella were identified in A. veronii 0728Q8Av, which probably enhanced the bacteria adhesion and persistence thus to promote its pathogenicity (Kirov et al., 2004;Boyd et al., 2008;Dacanay et al., 2010).Moreover, although the genomes of both A. veronii 0728Q8Av and A. caviae 1029Y16Ac contained genes encoding toxins hemolysin and thermostable hemolysin, only A. veronii 0728Q8Av additionally harbored aerolysin, a pore-forming toxin (Ran et al., 2018).This may be associated with the pathogenicity observed in A. veronii 0728Q8Av.

Conclusion
The MDR Aeromonas are ubiquitously distributed among humans, animals, and their environments.Numerous Aeromonas species carrying various mcr variants, which confer resistance to colistin, have been detected in hospitals, urban rivers, livestock, and aquatic animals.However, their presence in coastal waters remains relatively underreported.In this study, we identified two MDR Aeromonas strains, namely A. veronii 0728Q8Av and A. caviae 1029Y16Ac, from coastal waters in Zhejiang, China.Both Aeromonas isolates exhibited significant resistance to 11 kinds of antibiotics and remained susceptible to ceftazidime, a 3rd-generation cephalosporin antibiotic.And both isolates harbored multiple ARGs located on their chromosomes, with the majority concentrated within in a resistance GI, respectively.Both islands harbored typical class 1 integrons.Notably, both isolates carried ARGs mediating colistin resistance, namely mcr-3.16 on A. veronii 0728Q8Av and mcr-3.3 on A. caviae 1029Y16Ac.Both mcr-3 variants were located on the chromosome, distanced from the multidrug resistance GIs, flanking by multiple ISs.Additionally, a mcr-3-like was identified in the genome of A. veronii 0728Q8Av, forming a tandem mcr-3.16-mcr-3-like-dgkAstructure.However, the mcr-3-like recombinants did not confer colistin resistance in E. coli.Furthermore, an incomplete mcr-3-like was found adjacent to mcr-3.3 in the genome of A. caviae 1029Y16Ac, suggesting the likelihood that mcr-3 originated from Aeromonas species.Additionally, we demonstrated that A. veronii 0728Q8Av exhibited pathogenicity towards infected ayu.These findings indicated the presence of terrestrial MDR Aeromonas species in the coastal waters of China, posing a potential threat to the aquaculture, necessitating the development of more effective strategies to mitigate the spread of antibiotic resistance.

FIGURE 3
FIGURE 3 The genetic context of mcr-3.16 and mcr-3.3 in the A. veronii 0728Q8Av and A. caviae 1029Y16Ac, respectively.The arrows indicate the direction of gene transcription.The grayscale intensity indicates the sequence similarity between two linked regions.The black box indicates the identical insertion sequence ISAS29.*Representing incomplete sequences.

FIGURE 5
FIGURE 5 analysis of genetic environments of AvGI1.The arrows indicate the direction of gene transcription.The grayscale intensity indicates the sequence similarity between two linked regions.*Representing incomplete sequences.

TABLE 1
Biochemical characteristics of both A. veronii 0728Q8Av and A. caviae 1029Y16Ac.

TABLE 2
Antibiotic resistance phenotype and antibiotic resistance genotypes of both A. veronii 0728Q8Av and A. caviae 1029Y16Ac.

TABLE 3
Main virulence factors for A. veronii 0728Q8Av and A. caviae 1029Y16A.