Abstract
Abstract Pakistan is an agricultural country and fisheries play a very important role in the economic development of the country. Different diseases are prevalent in Pakistani fish but information related to the causative agents is not well-known. Keeping in view the significance of bacterial pathogens as the causative agents of multiple fish diseases, the present study was conducted for identification, characterization and analysis of virulence genes of Aeromonas spp. isolated from diseased fishes. A total of fifty fish samples having multiple clinical indications were collected from different fish farms of district Kasur, Punjab Pakistan. For isolation of Aeromonas spp. samples were enriched and inoculated on Aeromonas isolation medium. Isolates were identified and characterized by different biochemical tests, Analytical Profile Index (API) 20E kit and Polymerase Chain Reaction (PCR) assays. All isolates were screened for three putative virulence genes including aerolysin (aer), haemolysin (hyl) and heat labile cytotonic enterotoxin (alt). Seven isolates of Aeromonas (A.) hydrophila were retrieved and identified based on API 20E. These isolates were further confirmed as A. hydrophila on the basis of PCR assays. Three isolates were detected positive for the presence of virulence genes (alt and hyl). Whereas aerolysin (aer) gene was not present in any of A. hydrophila isolates. The present study confirmed A. hydrophila as the causative agent of epizootic ulcerative syndrome and motile Aeromonas septicemia in fish farms of district Kasur, Punjab Pakistan. Moreover, detection of two virulence genes (alt and hyl) in A. hydrophila isolates is a threat for fish consumers of study area.
Highlights
As a result of population explosion, satisfying safe, sufficient and nutritious diet have become a global issue
On the basis of conventional biochemical tests and Analytical Profile Index (API) 20E, all isolates were characterized as A. hydrophila
Despite the fact that the aquaculture sector is facing many challenges with respect to bacterial diseases all around the world and these diseases have a negative impact on the economic affluence of aquaculture fields; still very less determination is observed towards focusing on this aspect of the field (Elsheshtawy et al, 2019)
Summary
As a result of population explosion, satisfying safe, sufficient and nutritious diet have become a global issue. Fish is a delicious and nutritious part of human diet but of animal feed as well. To meet the growing demand of fish and its products, the freshwater fish culture sector is developing using various modern techniques (Govind et al, 2012; Mert and Bulut, 2014). Substantial financial losses in terms of infections play an essential part. Freshwater fishes are spoiled with various infections of bacterial, viral, fungal and parasitic origins. One of the most critical fish illnesses are bacterial infections, responsible for huge loss in the form of fish mortality (Dias et al, 2012) such as dropsy, tuberculosis, gill spoil, tail decay, fin rot, scale oedema and furunculosis
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