Background: Co-evolution of host and aeromonads has diversified their spectrums of diseases and antibiograms, while a paucity of data was concerning about this diversity in China. To fill this gap, this study was aimed to investigate and compare antimicrobial resistance (AMR) patterns of clinically important Aeromonas  spp. from various clinical sources.
Methods: A multicenter retrospective surveillance study was conducted in Chongqing from 2011 to 2017. Data of strains were retrieved from the database of China Antimicrobial Resistance Surveillance System (CARSS). Whonet 5.6 and Graphpad Prism 6 Software were adopted to determine and compare distribution and AMR patterns.
Results: Among 1135 Aeromonas  strains, Aeromonas hydrophila  complex (65.6%, 745/1135) was the most predominant species, followed by Aeromonas veronii  complex (16.7%, 190/1135) and Aeromonas caviae  complex (15.3%, 174/1135). Sputum was the most frequent source of strains (27.7%), followed by wound (20.8%), bloodstream (10.8%) and urine (8.8%). Urinary strains demonstrated the highest resistance rates to ceftriaxone (65.6%), ceftazidime (52.1%), cefepime (38.3%), ciprofloxacin (47.7%) and trimethoprim-sulfamethoxazole (56.6%). Similar AMR pattern was observed in intestinal strains, with corresponding resistance rates of 29.4%, 28.9%, 22.2%, 27.3% and 45%, respectively. However, respiratory, bloodstream and skin strains exhibited resistance rates of less than 20% to most of the antimicrobials tested. In terms of species, approximately 30% of Aeromonas hydrophila  complex and Aeromonas caviae  complex strains were resistant to ceftriaxone and trimethoprim-sulfamethoxazole, while Aeromonas veronii  complex strains harbored resistance rates of less than 20% to all tested antimicrobials. Although antibiograms of these species were distinct, they remained constant from 2011 to 2017.
Conclusions: Distinct AMR patterns between species and sources highlighted the predominance of Aeromonas hydrophila  complex and high resistance of strains in urine and intestine to extended-spectrum cephalosporins, ciprofloxacin and trimethoprim-sulfamethoxazole in Southwest China. Temporally constant AMR patterns should not relax the vigilance of antimicrobial resistance in clinically important Aeromonas  species.
Keywords: Aeromonas , human, antimicrobial resistance, distribution, time trend