Clinical Presentation, Antimicrobial Resistance, and Treatment Outcomes of Aeromonas Human Infections: A 14-Year Retrospective Study and Comparative Genomics of 2 Isolates From Fatal Cases

Abstract

Background: Aeromonas virulence may not be entirely dependent on the host's immune status. Pathophysiologic determinants of disease progression and severity remain unclear.

Methods: One hundred five patients with Aeromonas infections and 112 isolates were identified, their clinical presentations and outcomes were analyzed, and their antimicrobial resistance (AMR) patterns were assessed. Two isolates (A and B) from fatal cases of Aeromonas dhakensis bacteremia were characterized using whole-genome sequencing. Virulence factor- and AMR-encoding genes from these isolates were compared with a well-characterized diarrheal isolate A. dhakensis SSU and environmental isolate Aeromonas hydrophila American Type Culture Collection_7966T.

Results: Skin and soft tissue infections, traumatic wound infections, sepsis, burns, and intraabdominal infections were common. Diabetes, malignancy, and cirrhosis were frequent comorbidities. Male sex, age ≥ 65 years, hospitalization, burns, and intensive care admission were associated with complicated disease. High rates of AMR to carbapenems and piperacillin-tazobactam were found. Treatment failure was observed in 25.7% of cases. Septic shock and hospital-acquired infections were predictors of treatment failure. All 4 isolates harbored assorted broad-spectrum AMR genes including blaOXA, ampC, cphA, and efflux pumps. Only clinical isolates possessed both polar and lateral flagellar genes, genes for various surface adhesion proteins, type 3 and 6 secretion systems and their effectors, and toxin genes, including exotoxin A. Both isolates A and B were resistant to colistin and harbored the mobile colistin resistance-3 (mcr-3) gene.

Conclusions: Empirical therapy tailored to local antibiograms may facilitate favorable outcomes, while advanced diagnostic methods may aid in identifying correct Aeromonas spp. of significant clinical importance.

Keywords: Aeromonas; antimicrobial resistance; genomics; retrospective study.

Figure 1.

A, Number of Aeromonas isolates per year of study period (long bars, n = 112) and the mean number of antibiotics that were affected by resistance per isolate during each year (short bars). B, Antimicrobial susceptibilities to commonly used antibiotics during the study period. Abbreviations: I, intermediate; R, resistant; numbers indicate percentage values; S, susceptible; TMP-SMX, trimethoprim-sulfamethoxazole .