A First Report of Molecular Typing, Virulence Traits, and Phenotypic and Genotypic Resistance Patterns of Newly Emerging XDR and MDR Aeromonas veronii in Mugil seheli

Abstract

Aeromonas veronii is associated with substantial economic losses in the fish industry and with food-borne illness in humans. This study aimed to determine the prevalence, antibiogram profiles, sequence analysis, virulence and antimicrobial resistance genes, and pathogenicity of A. veronii recovered from Mugil seheli. A total of 80 fish were randomly gathered from various private farms in Suez Province, Egypt. Subsequently, samples were subjected to clinical, post-mortem, and bacteriological examinations. The retrieved isolates were tested for sequence analysis, antibiogram profile, pathogenicity, and PCR detection of virulence and resistance genes. The prevalence of A. veronii in the examined M. seheli was 22.5 % (18/80). The phylogenetic analyses revealed that the tested A. veronii strains shared high genetic similarity with other A. veronii strains from India, UK, and China. Using PCR it was revealed that the retrieved A. veronii isolates harbored the aerA, alt, ser, ompAII, act, ahp, and nuc virulence genes with prevalence of 100%, 82.9%, 61.7%, 55.3%, 44.7%, 36.17%, and 29.8%, respectively. Our findings revealed that 29.8% (14/47) of the retrieved A. veronii strains were XDR to nine antimicrobial classes and carried bla_TEM, bla_CTX-M, bla_SHV,tetA, aadA1, and sul1 resistance genes. Likewise, 19.1% (9/47) of the obtained A. veronii strains were MDR to eight classes and possessed bla_TEM, bla_CTX-M, bla_SHV,tetA, aadA1, and sul1 genes. The pathogenicity testing indicated that the mortality rates positively correlated with the prevalence of virulence-determinant genes. To our knowledge, this is the first report to reveal the occurrence of XDR and MDR A. veronii in M. seheli, an emergence that represents a risk to public health. Emerging XDR and MDR A. veronii in M. seheli frequently harbored aerA, alt, ser, ompAII, and act virulence genes, and bla_TEM, sul1, tetA, bla_CTX-M, bla_SHV, and aadA1 resistance genes.

Keywords: A. veronii; XDR; antimicrobial resistance genes; pathogenicity; sequence analysis; virulence.

Figure 1

M. seheli showing (A): Erosion of gill cover and skin hemorrhages, (B): Erosion and hemorrhages in the opercular region, anus, and base of the fins, (C): Friable pale liver and congested kidney, (D): Congested kidney.

Figure 2

The distribution of A. veronii among different internal organs of naturally infected M. seheli.

Figure 3

Phylogenetic tree based on 16S rRNA gene sequencing. The tree clarifies the genetic relatedness of the tested A. veronii strains and other strains deposited in the GenBank database. The tested strains in the present study are indicated with red circles.

Figure 4

Antimicrobial susceptibility patterns of A. veronii isolates retrieved from examined M. seheli samples.

Figure 5

The correlation coefficient (r) between various tested antibiotics in the disc diffusion test.

Figure 6

Distribution of virulence and antimicrobial resistance genes among A. veronii strains retrieved from the examined M. seheli.

Figure 7

Distribution of XDR and MDR patterns among A. veronni strains isolated from the examined M. seheli. The horizontal axis indicates MDR and XDR patterns, while the vertical axis indicates the antimicrobial resistance genes.

Figure 8

The correlation coefficient (r) between the tested antibiotics and the identified antimicrobial resistance genes.

Figure 9

Cumulative mortality of T. zillii experimentally challenged with different virulent strains of A. veronii (G1-G5: Fish groups received a bacterial dose of 3 × 10⁸ cfu/mL of various A. veronii strains S1–S5, respectively), data were analyzed 14 days after challenge.