Clinical presentation, antimicrobial resistance, and treatment outcomes of Aeromonas human infections: A 14-year retrospective study and comparative genomics of two isolates from fatal cases

In a 14-year retrospective study from 2008 to 2021, 105 culture-proven Aeromonas infected subjects were identified and their demographic and clinical syndromes and outcomes analyzed. 112 Aeromonas cultures from 105 patients were assessed for antimicrobial resistance (AMR). The most common clinical syndromes were skin and soft tissue infections (SSTIs), traumatic wound infections, sepsis, burns, and intraabdominal infections. Diabetes, malignancies, and cirrhosis were frequent comorbidities. One-third of cases were complicated by bacteremia, necrotizing fasciitis, or sepsis. Factors associated with complications included male sex, age over 65 years, hospitalization, burns, and ICU care. A high percentage of SSTI and traumatic wound infected patients had exposure to water sources. High rates of AMR to carbapenems and piperacillin-tazobactam were found associated with treatment failure. Two isolates (A and B) from fatal cases of Aeromonas dhakensis bacteremia were characterized using whole genome sequence (WGS) analysis. Virulence factor and AMR encoding genes from these isolates were compared with a well characterized diarrheal isolate A. dhakensis SSU, and environmental isolate A. hydrophila ATCC 7966T. All isolates harbored assorted broad-spectrum AMR genes including blaOXA, ampC, cphA, and efflux pumps. Only clinical isolates possessed polar and lateral flagellar genes, genes for an array of surface adhesion proteins, type 3- and -6 secretion systems, and a variety of toxin genes, including exotoxin A. Both isolates A and B were resistant to colistin and harbored the mcr-3 gene. Antibiotic treatment tailored to local Aeromonas antibiograms may lead to more favorable outcomes, while advanced diagnostic methods may aid in identifying correct Aeromonas spp. of significant clinical importance.