Statistical analysis.
Statistical analyses of the results relating to the seasonal prevalence of V.parahaemolyticus in the shellfish and to antimicrobial resistance by shellfish type or country of origin were performed using a 2 ×2 contingency table and Fisher’s exact test (Statistica, Krako, Poland ). P values were two-tailed, and groups were considered significantly different at P < 0.05.
Results and discussion
Prevalence of V.parahaemolyticus. During the study period, a total of 400 shellfish samples were tested for the presence of V.parahaemolyticus. With the ISO method,these bacteria were identified in 70 (17.5%) of the 400 samples (Table 1). However, the PCR assay for the toxR gene confirmed only 64 (91.4%) of these isolates as V.parahaemolyticus. Of the four kinds of shellfish tested,clams were most commonly contaminated (48.4% of samples positive) followed by mussels(26.6%) and oysters (18.8%). In a similar study conducted between 2006 and 2008 by Roque et al.(26), V.parahaemolyticus was mainly isolated from oysters (65{42.2% } of 154 total samples were positive)
Followed mussels (51 {33.1%}) and clams (38 {24.7%}). In the present study, most of the contaminated moluscs originated from the Netherlands (29 {45.3%} of 64 samples) and Italy (23