Aeromonas stool isolates from individuals with or without diarrhea in southern Taiwan: Predominance of Aeromonas veronii

Background: Although aeromonads are important pathogens causing invasive infections in southern Taiwan, Aeromonas-associated intestinal infections have been rarely mentioned. Purpose: The aim of this study was to understand the frequency of isolation and clinical significance of aeromonads recovered from adult stool samples in southern Taiwan. Methods: During a 15-month study period, 514 adults with diarrhea and 167 asymptomatic controls were prospectively screened for the presence of aeromonads in stools. The identity of Aeromonas species was determined by the rpoD sequencing. Clinical information was retrieved from medical records, and in vitro cytotoxicity assay and polymerase chain reaction detection of putative virulent genes were performed. Results: Thirteen (2.5 %) of 514 diarrheal patients and six (3.6%) of 167 asymptomatic controls had Aeromonas isolates in their stools. Of 11 diarrheal patients with available clinical information, Aeromonas veronii, the predominant species, was noted in six patients, and another potential enteropathogen was present in four patients. The cytotoxicity of A. veronii isolates to the HT-29 cell line was more potent in the isolates from diarrheal patients than those from asymptomatic controls (p = 0.015). The cytotoxicity of A. veronii isolates was more potent than that of A. caviae from symptomatic patients (p = 0.001). Putative virulence markers, including AHCYTONE, ascV, ascF-ascG, and aexT, were detected exclusively in A. veronii. The presence of the ascV gene was associated with cytotoxicity in A. veronii isolates. All Aeromonas isolates were susceptible to varied antimicrobial agents, except ampicillin/sulbactam. Conclusion: A. veronii is the predominant species in stools from individuals with or without diarrhea in southern Taiwan.