Detection of Vibrio parahaemolyticus (tlh) and virulence factors in Oyster Crassostrea virginica in the Gulf of Mexico

Abstract

Vibrio parahaemolyticus is a pathogenic species to humans, known for its ability to cause disease. Thermostable direct hemolysin (TDH) and related TLH (TRH), are very important virulence factors of Vibrio parahaemolyticus. Consuming raw or undercooked bivalve molluscs increases the likelihood of getting a disease. The objective of this study was to identify and quantify the gene tlh of V. parahaemolyticus and the hemolysins TDH and TRH as virulence factors. This to assess risks to public health by eating oysters from coastal lagoons of the state of Veracruz, Mexico. Analysis of each sample was performed in triplicate. Initially they were enriched with alkaline peptone water (APW) and processed by applying the combination of the technique More Probable Number and the Polymerase chain reaction (MPN-PCR). A standardization of PCR to amplify the genes encoding the hemolysins was performed. The results of the oyster samples analysis of lagoons such as, Pueblo Viejo (<22 MPN/g), Tamiahua (0.7 MPN/g), La Mancha (5.8 MPN/g) and Mandinga (> 22 MPN/g), were found below the maximum permissible limit set by NOM-242-SSA1-2009. Molecular tests were negative for the genes of tdh and trh hemolysins, which are associated with toxicity. Even though, the analysis for the presence of pathogenicity hemolysins, TDH and TRH were negative in this study, it is reported that pathogenic strains may not produce TDH hemolysin. Therefore, they should be considered as potential carriers of virulence genes as they represent a risk to human health.