Characterization and Antimicrobial Resistance of Environmental and Clinical Aeromonas Species Isolated from Fresh Water Ornamental Fish and Associated Farming Environment in Sri Lanka.

Pavithra M Dhanapala,D.P.H Wijesekera,Ayona Silva-Fletcher,Sanda A Kottawatta,S.S.S De S Jagoda,Ruwani S Kalupahana,Niromi K Jayasekera,Anil W Kalupahana

doi:10.3390/microorganisms9102106

Pavithra M Dhanapala, D.P.H Wijesekera + Show 6 more

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https://doi.org/10.3390/microorganisms9102106

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Abstract

The aims of this study were to characterize and investigate antimicrobial susceptibility and presence of integrons in 161 Aeromonas spp. isolated from ornamental freshwater fish farming environment, apparently healthy and diseased fish. Phylogenetic analyses of the gyrB gene sequences identified Aeromonas veronii as the most abundant species (75.8%) followed by Aeromonas hydrophila (9.3%), Aeromonas caviae (5%), Aeromonas jandaei (4.3%), Aeromonas dhakensis (3.7%), Aeromonas sobria (0.6%), Aeromonas media (0.6%), and Aeromonas popoffii (0.6%). Susceptibility to thirteen antimicrobials was determined and antimicrobial resistance frequencies were: amoxicillin (92.5%), enrofloxacin (67.1%), nalidixic acid (63.4%), erythromycin (26.1%), tetracycline (23.6%), imipenem (18%), trimethoprim-sulfamethoxazole (16.8%), and gentamicin (16.8%). Multi-drug resistance (MDR) was widespread among the isolates (51.6%, 83/161) with 51.6% (63/122) A. veronii isolates being MDR. In addition, 68.3% of isolates had multiple antibiotic resistance (MAR) indexes higher than 0.2, suggesting that they originated from a high-risk source of contamination where antimicrobials are often used. In all, 21.7% isolates carried class 1 integrons, with 97.1% having gene cassettes, while there were 12 isolates carrying class 2 integron gene cassettes. Our findings highlight that the aquatic environment and ornamental fish act as reservoirs of multidrug resistant Aeromonas spp. and underline the need for a judicious use of antimicrobials and timely surveillance of antimicrobial resistance (AMR) in aquaculture.

Highlights

IntroductionThe genus Aeromonas comprises 36 different species, among which mesophilic, motile Aeromonas spp. have long been recognized as important fish pathogens [3]
Considering that little is known about the role of aeromonads as a reservoir of antimicrobial resistance in the ornamental fish aquaculture environment of Sri Lanka, we evaluated the antimicrobial susceptibility profiles of Aeromonas spp. isolated from diseased fish, healthy fish and associated aquatic environments
Aeromonas spp. most frequently implicated in human infections, such as A. hydrophila, A. caviae, A. veronii and A. dhakensis [3,57] and their isolation from the ornamental fish culture environment and healthy fish in this study indicates that these sources serve as reservoirs of these pathogens

Summary

Introduction

The genus Aeromonas comprises 36 different species, among which mesophilic, motile Aeromonas spp. have long been recognized as important fish pathogens [3]. They cause a wide spectrum of opportunistic infections in fresh water and brackish water fish, which are collectively known as motile Aeromonas septicemia (MAS). The major clinical manifestation of this disease syndrome is hemorrhagic septicemia, characterized by fin rot, dropsy, hemorrhages, and ulcers. Mesophilic Aeromonas species have been linked to major disease outbreaks, leading to a high mortality in cultured freshwater food fish and ornamental fish [4,5,6], resulting in huge economic losses around the Microorganisms 2021, 9, 2106.

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