Aeromonas Infections in Humans—Antibiotic Resistance and Treatment Options

The genus <i>Aeromonas</i> is widely distributed in aquatic environments, where it is a frequent fish pathogen. It has also been described in association with human infections, with most cases caused by <i>A. caviae</i>, <i>A. veronii</i> biovar <i>sobria</i>, and <i>A. hydrophila</i>. More recently, <i>A. dhakensis</i> has emerged as an increasingly important human pathogen. Transmission occurs primarily through ingestion or contacts with aquatic sources, or by consuming contaminated food, particularly from aquatic origins. Growing resistance in <i>Aeromonas</i> has been reported for penicillins (including their combinations with classical β-lactamase inhibitors), cephalosporins, and carbapenems. Among the β-lactam antibiotics, only fourth-generation cephalosporins remain almost uniformly active. Furthermore, the co-occurrence of resistance genes for third-generation cephalosporins and carbapenems within the same isolates is increasing. Recently, the presence of mobile genes conferring colistin resistance has also been documented, with resistance rates sometimes exceeding 30%. This evolution of colistin resistance is likely linked to its use in aquaculture, and together with the rise in β-lactam resistance, may be transforming <i>Aeromonas</i> into a significant reservoir of resistance genes that could potentially be transferred to species more commonly associated with human infections, such as the <i>Enterobacterales</i>.