Aeromonads are ubiquitous in aquatic environments and the genus consists of 36 species. Aeromonas hydrophila and A. caviae are commonly involved in causing human infections such as gastroenteritis, severe skin and soft tissue infection and bacteremia . Increasing usage of antimicrobial in humans, food fish and ornamental aquaculture can lead to antimicrobial resistance. In this study, we investigated the antimicrobial resistance patterns of A. hydrophila and A. caviae from clinical [2,3] and non-clinical sources [4,5,6] based on MICs using the dehydrated microdilution panel.
Thirty-six A. hydrophila (clinical=26, aquatic environments=10) and 70 A. caviae (clinical=40, aquatic environments=13, food fish =17) were subjected to antimicrobial susceptibility testing with 18 antimicrobial agents (Microscan NM44 plates). The plates were incubated at 35°C overnight and MIC values were determined according to CLSI .
Results and Discussion
Aeromonas hydrophila and A. caviae were resistant to eight antimicrobial agents (imipenem, meropenem, doripenem, trimethoprim-sulfamethoxazole, cefotaxime, ceftazidime, aztreonam and cefepime) ranging from 2.5% to 76.9%. A. hydrophila clinical strains were resistant at higher than that of water environmental strains towards imipenem (76.9% vs 70%) and meropenem (19.2% vs 10%) but in the opposite direction for doripenem (30.8% vs 50%). In contrast, A. caviae environmental strains primarily recovered from tank water of ornamental fish exhibited a higher resistance rate compared to clinical strains for imipenem (16.7% vs 10%), doripenem (16.7% vs 7.5%) and meropenem (16.7% vs 5%). Among imipenem resistant strains of both species, 83.3% (30/36) strains showed resistance with a MIC > 8 µg/mL which is two times above the CLSI breakpoint (> 4µg/mL). Overall, 2.8% of multidrug-resistant strains were observed in three A. hydrophila (urine, tissue and peritoneal fluid) and one A. caviae (stool).
Our findings highlight that imipenem should be used with caution when treating human Aeromonas infection, the aquatic environment and ornamental fish.
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