Escherichia coli detection and identification in shellfish from southeastern Brazil

Abstract

The pathogenic Escherichia coli strain may be responsible for foodborne infections in humans. This study was carried out to evaluate the presence of Escherichia coli and verify the occurrence of virulence genes in mussels (Mytella falcata) and oysters (Crassostrea brasiliana) collected from natural banks of the Estuary Lagunar Complex of Cananéia in the State of São Paulo, southeastern Brazil. A total of 150 shellfish samples (75 mussels and 75 oysters) were collected from June 2016 to February 2017. Total coliforms and Escherichia coli were determined using the most probable number (MPN) procedure. Colonies of Escherichia coli were biochemically characterized. The positive samples were submitted to molecular identification of species and posterior genetic sequencing for identifying Escherichia coli pathotypes. Escherichia coli was detected in 48 samples (32%) in concentrations ranging from <3 to <927 MPN/g. From 240 colonies tested biochemically, ninety-three were positive and submitted to molecular analyses. Fourty-eight colonies were confirmed as Escherichia coli by presenting PhoA gene and six (12.5%) were identified as enteropathogenic Escherichia coli (EPEC) by presenting eaeA gene and by sequencing of positive amplicons. Phylogenetic analyses revealed that the Brazilian samples were grouped in clades along with other EPEC isolates. These results are the first to indicate the presence of EPEC in shellfish in Brazil.