Uncovering the hidden threat: The widespread presence of chromosome-borne accessory genetic elements and novel antibiotic resistance genetic environments in <i>Aeromonas</i>

Abstract

The emergence of antibiotic-resistant <i>Aeromonas</i> strains in clinical settings has presented an escalating burden on human and public health. The dissemination of antibiotic resistance in <i>Aeromonas</i> is predominantly facilitated by chromosome-borne accessory genetic elements, although the existing literature on this subject remains limited. Hence, the primary objective of this study is to comprehensively investigate the genomic characteristics of chromosome-borne accessory genetic elements in <i>Aeromonas</i>. Moreover, the study aims to uncover novel genetic environments associated with antibiotic resistance on these elements. <i>Aeromonas</i> were screened from nonduplicated strains collected from two tertiary hospitals in China. Complete sequencing and population genetics analysis were performed. BLAST analysis was employed to identify related elements. All newly identified elements were subjected to detailed sequence annotation, dissection, and comparison. We identified and newly designated 19 chromosomal elements, including 18 integrative and mobilizable elements (IMEs) that could be classified into four categories: Tn<i>6737</i>-related, Tn<i>6836</i>-related, Tn<i>6840</i>-related, and Tn<i>6844a</i>-related IMEs. Each class exhibited a distinct pattern in the types of resistance genes carried by the IMEs. Several novel antibiotic resistance genetic environments were uncovered in these elements. Notably, we report the first identification of the <i>bla</i>_OXA-10 gene and <i>bla</i>_VEB-1 gene in clinical <i>A. veronii</i> genome, the first presence of a <i>tetA</i>(E)-<i>tetR</i>(E) resistance gene environment within the backbone region in IMEs, and a new <i>mcr-3.15</i> resistance gene environment. The implications of these findings are substantial, as they provide new insights into the evolution, structure, and dissemination of chromosomal-borne accessory elements.