Habitat Infection Analysis of Penaeid Shrimp with Enterovirulent Strains of Escherichia coli by Using PCR

Abstract

Escherichia coli is a harmless, gram negative bacterium that is commonly found in the lower intestine of warm-blooded animals. A number of E. coli strains are available in nature, only a few of them is pathogenic to human. In aquatic environment, the most commonly encountered are those belonging to the enterotoxigenic (ETEC), enterohaemorrhagic (EHEC) and enteropathogenic (EPEC) subtypes. The prospective shrimp sector is facing a threat of this disease. However, the study on the virulence of E. coli in shrimp habitat is still scarce. In order to better determine the health risks that are associated with the exposure to some of these specific subtypes, a PCR system was used for the quick and authentic detection and typing of ETEC, EHEC and EPEC groups of E. coli in the water, sediment and shrimp samples of fifteen different farms of Cox's Bazar region. Six pairs of oligonucleotide primers were used for the amplification and detection of target genes viz., the alkaline phophatase (Pho-A), heat-stable toxin1 (ST1), the heat-labile toxin1 (LT1) and heat-labile toxin2 (LT2) genes of ETEC, verotoxin (VT) genes of EHEC and attachment and effacement (EAE) genes of EPEC. The results revealed the presence of ETEC in sediment-farm-2 and water-farm-4 of cox's bazaar Sadar; sediment-farm-2, water-farm-4 and sediment-farm-5 of chakaria and sediment-farm-3 of moheshkhali and EPEC group in sediment-farm-5, water-farm-4 and sediment-farm-4 of cox's bazaar sadar; and water-farm-4 of chakaria region whereas no virulent strains was observed in shrimp samples. The water samples of one farm of both Cox's bazar sadar and Chakaria upazilla were found to be highly contaminated by ETEC and EPEC groups whereas, only ETEC group observed in the sediment sample farm-5 at Moheskhali upazilla. These findings of the study suggest that lack of enough sanitation system, polluted water source, unhygienic condition as well as poor management practices might be responsible for exposure of enterovirulent E. coli strains in this area.