Nontoxigenic Vibrio parahaemolyticus Strains Causing Acute Gastroenteritis

Abstract

We investigated the virulence properties of four Vibrio parahaemolyticus strains causing acute gastroenteritis following consumption of indigenous mussels in Italy. The isolated strains were cytotoxic and adhesive but, surprisingly, lacked tdh, trh, and type three secretion system 2 (T3SS2) genes. We emphasize that nontoxigenic V. parahaemolyticus can induce acute gastroenteritis, highlighting the need for more investigation of the pathogenicity of this microorganism. Vibrio parahaemolyticus infections cause acute, self-limiting gastroenteritis, typically characterized by diarrhea, abdominal cramps, nausea, vomiting, fever, and chills, lasting 1 to 3 days. The onset usually occurs within 24 h of eating contaminated food. Cases are most commonly reported during the warmer months and are often associated with eating raw or undercooked shellfish or other cooked foods that have been cross-contaminated with raw shellfish (22). Pathogenicity of this microorganism is attributed to the production of a thermostable direct hemolysin (TDH) and the TDH-related hemolysin (TRH) (13). Recently, type three secretion system 2 (T3SS2) of V. parahaemolyticus has been investigated as an additional potential indicator of strain virulence (2,8,17). Together, the tdh, trh, and T3SS2 genes are widely considered the predominant indicators of strain virulence for this microorganism (8). This is substantiated by the prevalence of these genetic markers in clinical V. parahaemolyticus isolates, as opposed to their infrequent detection in food and environmental samples (8).For this report, we characterized four V. parahaemolyticus strains lacking tdh, trh, and T3SS2 genes isolated as the sole pathogen from patients affected by acute gastroenteritis with indigenous mussels as the most probable source of infection. On 20 September 2010 in Torino (northern Italy), 4 people were hospitalized with acute gastroenteritis. The first case involved a healthy 47-year-old man (patient A), while a family group outbreak involved another three healthy individuals: a 55-year-old woman (patient B), a 59-year-old man (patient C), and a 58-year-old man (patient D). Epidemiological information reported that none of the patients had recently traveled to other countries and that on 19 September they had eaten home-cooked mussels, probably undercooked. Mussels involved in both the sporadic case and the outbreak came from the same Italian growing area (North Adriatic), but it was not possible to trace the specific lots. Patient A and patients B, C, and D developed diarrhea, fever, abdominal cramps, nausea, and vomiting about 13 h and about 18 h after mussel consumption, respectively. On admission, the patients were treated with intravenous hydration, and the symptoms ceased within 48 h without the need for antibiotic therapy.Stool specimens of patients were cultured on MacConkey agar, Salmonella-Shigella agar, Columbia blood agar, Hektoen agar, 5% sheep blood agar supplemented with ampicillin (30 g/ml) (ASBA 30), Yersinia cefsulodin-irgasan-novobiocin (CIN) agar (a...

Complete genome of Vibrio parahaemolyticus FORC014 isolated from the toothfish

“…The test result supported that FORC_014 strain has pathogenesis activity. Based on these results, we suggest that FORC_014 is pathogenic, even though it is tdh and trh negative [5, 6, 27, 28]. …”

“…While environmental strains rarely contain pathogenic genes thermostable direct hemolysin ( tdh ) and thermostable direct hemolysin-related hemolysin ( trh ), clinical strains which create foodborne illness, possess virulence factor including tdh , and trh . Therefore, tdh , and trh have been considered as the indicators of V. parahaemolyticus pathogenicity, which has an enterotoxic effect on the intestinal cells of the affected mammal [4, 5]. Recent studies, however, announced that some clinical strains identified negative for tdh and trh genes [4, 5].…”

“…Therefore, tdh , and trh have been considered as the indicators of V. parahaemolyticus pathogenicity, which has an enterotoxic effect on the intestinal cells of the affected mammal [4, 5]. Recent studies, however, announced that some clinical strains identified negative for tdh and trh genes [4, 5]. In addition to the two previously mentioned pathogenicity indicators, T3SS2, which is required for intestinal colonization, has been speculated to be a possible indicator of V. parahaemolyticus pathogenicity [5–8].…”

“…Recent studies, however, announced that some clinical strains identified negative for tdh and trh genes [4, 5]. In addition to the two previously mentioned pathogenicity indicators, T3SS2, which is required for intestinal colonization, has been speculated to be a possible indicator of V. parahaemolyticus pathogenicity [5–8]. However, major virulence indicators of V. parahaemolyticus at the genomic level are still unclear despite the many studies which have been performed which attempted to identify them.…”

Effects of Intertidal Harvest Practices on Levels of Vibrio parahaemolyticus and Vibrio vulnificus Bacteria in Oysters

“…Although recent evidence suggests that there may be additional factors responsible for differential virulence of this organism (10,11), the tdh and trh genes remain the most reliable indicators of virulence currently available. Therefore, understanding the growth and survival of strains carrying these genes, in addition to total V. parahaemolyticus populations, is important for evaluating the potential risk of illness from shellfish consumption.…”