Identification of Antimicrobial Resistance Determinants in Aeromonas veronii Strain MS-17-88 Recovered From Channel Catfish (Ictalurus punctatus)

Abstract

<i>Aeromonas veronii</i> is a Gram-negative species ubiquitous in different aquatic environments and capable of causing a variety of diseases to a broad host range. <i>Aeromonas</i> species have the capability to carry and acquire antimicrobial resistance (AMR) elements, and currently multi-drug resistant (MDR) <i>Aeromonas</i> isolates are commonly found across the world. <i>A. veronii</i> strain MS-17-88 is a MDR strain isolated from catfish in the southeastern United States. The present study was undertaken to uncover the mechanism of resistance in MDR <i>A. veronii</i> strain MS-17-88 through the detection of genomic features. To achieve this, genomic DNA was extracted, sequenced, and assembled. The <i>A. veronii</i> strain MS-17-88 genome comprised 5,178,226-bp with 58.6% G+C, and it encoded several AMR elements, including <i>imiS, ampS, mcr-7.1, mcr-3, catB2, catB7, catB1, floR, vat(F), tet(34), tet(35), tet(E), dfrA3</i>, and <i>tetR</i>. The phylogeny and resistance profile of a large collection of <i>A. veronii</i> strains, including MS-17-88, were evaluated. Phylogenetic analysis showed a close relationship between MS-17-88 and strain Ae5 isolated from fish in China and ARB3 strain isolated from pond water in Japan, indicating a common ancestor of these strains. Analysis of phage elements revealed 58 intact, 63 incomplete, and 15 questionable phage elements among the 53 <i>A. veronii</i> genomes. The average phage element number is 2.56 per genome, and strain MS-17-88 is one of two strains having the maximum number of identified prophage elements (6 elements each). The profile of resistance against various antibiotics across the 53 <i>A. veronii</i> genomes revealed the presence of <i>tet(34), mcr-7.1, mcr-3</i>, and <i>dfrA3</i> in all genomes (100%). By comparison, <i>sul1</i> and <i>sul2</i> were detected in 7.5% and 1.8% of <i>A. veronii</i> genomes. Nearly 77% of strains carried <i>tet(E)</i>, and 7.5% of strains carried <i>floR</i>. This result suggested a low abundance and prevalence of sulfonamide and florfenicol resistance genes compared with tetracycline resistance among <i>A. veronii</i> strains. Overall, the present study provides insights into the resistance patterns among 53 <i>A. veronii</i> genomes, which can inform therapeutic options for fish affected by <i>A. veronii</i>.