Whole-Genome Sequencing Analysis of the Multidrug-Resistant

Purpose: The Gram-negative bacterium Aeromonas caviae is an important opportunistic facultative anaerobic pathogen. In the present study, we aimed to elucidate the whole-genome sequence of the multidrug-resistant (MDR) A. caviae strain AC1520, detailing its acquired antibiotic resistance genes (ARGs) and their genetic elements. Patients and Methods: The A. caviae strain AC1520 was isolated from a urine sample taken from a patient with urinary tract infection. Whole-genome sequencing was performed following strain identification and antimicrobial susceptibility testing. Overall, we identified ARGs, integrons, insertion sequences (IS), and transposons acquired by strain AC1520, systematically analyzing the genetic elements associated with these ARGs. Results: The A. caviae strain AC1520 contained a circular chromosome and a plasmid. Multilocus sequence typing revealed that this strain belonged to ST-1056. All ARGs within this strain were distributed on the circular chromosome. We identified two MDR regions: (1) IS common region 1 (ISCR1) and class 1 integron (IntI1) elements associated with aadA16, aac(6')-Ib-cr, catB3, qacE (two copies), sul1 (two copies), and blaPER-3; one gene cluster structure (IS6100-mphR(A)-mph(A)-mrx(A)-IS26); (2) Two IntI1 elements, linked to ant(2'')-Ia, blaOXA-10, aadA2b, aph(3'')-Ib, aph(6)-Id, ARR-2, aac(6')-Ib3, dfrA1, qacE, and sul1. Notably, these two MDR regions were not only present in A. caviae but also in other bacteria, such as Aeromonas hydrophila, Aeromonas media, and Edwardsiella tarda. Conclusion: The A. caviae strain AC1520 with two separate MDR regions and 20 ARGs, conferring resistance to aminoglycoside, fluoroquinolone, phenicol, sulfonamide, beta-lactam, macrolide, rifampicin, and trimethoprim, was identified in a hospital in China. Mobile genetic elements including TnAs1, ISCR1, ISAs25, IS6100, IS26, TnAs3, ISAs1, and Tn3, were found within the MDR region, which could play important roles in the global dissemination of these resistance genes.