An extensive investigation into the prevalence and the genetic and serological diversity of toxigenic Vibrio parahaemolyticus in Italian marine coastal waters

Abstract

Summary The relationship between Vibrio parahaemolyticus strains isolated from the aquatic environment and those isolated from cases of infection in humans is poorly understood due to the low prevalence of tdh‐ and/or trh‐positive strains in the environment. To address this concern, it would be useful to analyse the genetic relationships among environmental and food strains and with reference to clinical isolates, also applying molecular typing methods. The aim of this study was to evaluate the prevalence of toxigenic V. parahaemolyticus in Italian coastal waters and seafood, to examine intra‐species variability and to identify, using serotyping and pulsed‐field gel electrophoresis (PFGE), relationships among strains from different sources, geographical origin and period of isolation. Of the 192 V. parahaemolyticus strains isolated in different Italian areas and examined in this study, 25 (13.0%) proved to carry the trh gene while none of the strains proved positive to the search by PCR for tdh and Group‐Specific‐toxRS genes. The prevalence of toxigenic strains in the Tyrrhenian Sea was significantly lower than that calculated for the Ligurian coasts. Regarding the sources of isolation, the higher prevalence of trh‐positive V. parahaemolyticus was revealed in fish, followed by clams, plankton, oysters, mussels and lastly seawater. Within the toxigenic strains, 16 serotypes and 20 distinct PFGE patterns were identified. Two clusters, which included a total of 8 V. parahaemolyticus strains, were specifically associated with the North Adriatic Sea area and were stable over time. Our results demonstrate that trh‐positive V. parahaemolyticus strains circulated in Italy in the period 2002–2009 with a prevalence higher than that reported from other European and extra‐European countries, confirming that toxigenic V. parahaemolyticus is an emerging public health concern in Italy, regardless of its pandemic potential.

Epidemiological Evidence of Lesser Role of Thermostable Direct Hemolysin (TDH)–Related Hemolysin (TRH) Than TDH onVibrio parahaemolyticusPathogenicity

“…There are few reports of foodborne infections caused by trh-positive strains, but infections caused by tdh-positive V. parahaemolyticus are common. Therefore, information regarding seafood contaminated with trh-positive strains is limited in the world ( Johnson et al, 2010;Nakaguchi, 2013;Ottaviani et al, 2013).…”

Bile Sensing: The Activation of Vibrio parahaemolyticus Virulence

“…This is of concern as approximately half the reported foodborne cases in Asian countries are caused by V. parahaemolyticus (Alam et al, 2002; Bhuiyan et al, 2002). Frequent outbreaks of V. parahaemolyticus cases have also been reported in the United States and coastal countries of Europe such as Spain, Italy, and Norway (Caburlotto et al, 2008; Scallan et al, 2011; Ottaviani et al, 2013). …”

Characterization of a novel zinc transporter ZnuA acquired by Vibrio parahaemolyticus through horizontal gene transfer

“…T3SS1 is prevalent in all V. parahaemolyticus strains, whereas T3SS2 is more popular among clinical isolates (Meador et al, 2007). Comparative genomic analysis of pre-pandemic and pandemic V. parahaemolyticus strains, as well as molecular profiling studies, revealed that the organization of mobile gene cassettes and pathogenicity islands were divergent in these V. parahaemolyticus strains and that the emergence of pandemic strain could be associated with the recombination events and novel gene acquisition (Hurley et al, 2006; Gonzalez-Escalona et al, 2008; Han et al, 2008; Caburlotto et al, 2011; Chen et al, 2011; Yan et al, 2011; Garcia et al, 2012; Gennari et al, 2012; Gavilan et al, 2013; Ottaviani et al, 2013; Theethakaew et al, 2013; Turner et al, 2013). The genetic divergence of V. parahaemolyticus strongly correlates with their diverse virulence potentials (Vongxay et al, 2008; Caburlotto et al, 2010).…”