Aeromonas caviae subsp. aquatica subsp. nov., a New Multidrug-Resistant Subspecies Isolated from a Drinking Water Storage Tank

The increasing prevalence and dissemination of multidrug-resistant bacteria represent a serious concern for public health. <i>Aeromonas caviae</i> is a pathogenic microorganism that causes a wide spectrum of diseases in fish and humans and is often associated with aquatic environments and isolated from foods and animals. Here, we present the isolation and characterization of the V15^T strain isolated from a drinking water storage tank in Rio de Janeiro, Brazil. The V15^T strain has a genome length of 4,443,347 bp with an average G + C content of 61.78% and a total of 4028 open reading frames. Its genome harbors eight types of antibiotic resistance genes (ARGs) involving resistance to beta-lactamases, macrolides, and quinolones. The presence of <i>bla_MOX-6</i>, <i>bla_OXA-427/bla_OXA-504</i>, and mutations in <i>parC</i> were detected. In addition, other ARGs (<i>macA</i>, <i>macB</i>, <i>opmH</i>, and <i>qnrA</i>) and multidrug efflux pumps (such as <i>MdtL</i>), along with several resistance determinants and 106 genes encoding virulence factors, including adherence (polar and lateral flagella), secretion (T2SS, T6SS), toxin (<i>hlyA</i>), and stress adaptation (<i>katG</i>) systems, were observed. The genome sequence reported here provides insights into antibiotic resistance, biofilm formation, evolution, and virulence in <i>Aeromonas</i> strains, highlighting the need for more public health attention and the further monitoring of drinking water systems. Also, the results of physiological and phylogenetic data, average nucleotide identity (ANI) calculation, and digital DNA-DNA hybridization (dDDH) analysis support the inclusion of the strain V15^T in the genus <i>Aeromonas</i> as a new subspecies with the proposed name <i>Aeromonas caviae</i> subsp. <i>aquatica</i> subsp. nov. (V15^T = P53320^T). This study highlights the genomic plasticity and pathogenic potential of <i>Aeromonas</i> within household drinking water systems, calling for the revision of water treatment protocols to address biofilm-mediated resistance and the implementation of routine genomic surveillance to mitigate public health risks.