Antimicrobial Resistance analysis of Pathogenic Bacteria Isolated from Freshwater Nile Tilapia ( Oreochromis niloticus )
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Antimicrobial Resistance analysis of Pathogenic Bacteria Isolated from Freshwater Nile Tilapia (Oreochromis niloticus) Cultured in Kerala, India P. G. Preena1 · Arathi Dharmaratnam1 · T. Raja Swaminathan1 Received: 6 February 2020 / Accepted: 30 July 2020 © Springer Science+Business Media, LLC, part of Springer Nature 2020
Abstract Aquaculture of popular freshwater species, Nile tilapia (Oreochromis niloticus), accounts for around 71% of the total global tilapia production. Frequent use of antibiotics for treating bacterial infections in tilapia leads to the emergence of antimicrobial resistance. To mitigate the issue, proper evaluation methods and control strategies have to be implemented. This study was aimed to analyze the antimicrobial resistance of bacterial isolates from the infected Nile tilapia cultured in freshwater. The recovered isolates were identified as Pseudomonas entomophila, Edwardsiella tarda, Comamonas sp, Delftia tsuruhatensis, Aeromonas dhakensis, A. sobria, A. hydrophila, A. lacus, Plesiomonas shigelloides and Vogesella perlucida through phenotypic and genotypic analyses. Using Primer-E software, Shannon Wiener diversity index of the isolates was determined as H’ (loge) = 2.58. Antibiotic susceptibility test of the recovered strains through disk diffusion using 47 antibiotics, showed an elevated resistance pattern for Aeromonas hydrophila, Pseudomonas entomophila and Comamonas with higher multiple antibiotic resistance indexes (MAR index > 0.3). The minimum inhibitory concentration of antibiotics was > 256 mcg/ml for most of the resistant isolates. Meanwhile, all the recovered isolates were susceptible to amikacin, aztreonam, kanamycin, cefalexin, cefotaxime, levofloxacin, norfloxacin, piperacillin, and polymyxin-B.
Introduction Tilapia is one of the most popular farmed fish worldwide and around 100 countries are commercially culturing this fish [1]. Reports confirm that among the finfish, tilapia is the second most cultured fish next to carps [2]. Nile tilapia, Oreochromis niloticus holds the sixth position in cultured species worldwide and contributes to around 71% of total global tilapia production [1]. Diseases are of great concern in freshwater aquaculture. Aeromonas, Edwardsiella, Vibrio, Pseudomonas, and Pasteurella are the most important Gram negative pathogens reported in freshwater fishes [3]. Bacterial infections are also common in tilapia and Aeromonas, Streptococcus and Edwardsiella infections cause severe economic losses in tilapia culture [4]. Various species of Aeromonas such as A. sobria, A. dhakensis, A. hydrophila, and
* P. G. Preena [email protected] 1
Peninsular and Marine Fish Genetic Resources Centre of ICAR-NBFGR, CMFRI Campus, P.O. Number 1603, Kochi 682018, India
A. jandaei prevail in cultured tilapia infections [5]. Edwardsiella is also a predominant causative agent of mortality in cultured Nile tilapia [6]. Recent studies consider Francisella noatunensis as an emerging pathogen in cultured red tilapia in Thailand [7]. Currently, most of the antimicrobial
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