is a widespread bacterium in the marine environment and is responsible for gastroenteritis in humans. Foodborne infections are mainly associated with the consumption of contaminated raw or undercooked fish and shellfish. The aim of this study was to determine the antimicrobial resistance, virulence factors, and genetic profiles of isolates from seafood originating from different countries. A total of 104 (17.5%) isolates were recovered from 595 analyzed samples. The isolates were tested for the presence of the and genes, involved in the pathogenesis of infections in humans, and these genes were detected in 3 (2.9%) and 11 (10.6%) isolates, respectively. The -positive isolates also possessed the gene, which is responsible for urease production. Moreover, the activity of protease A was identified in all strains. Antimicrobial resistance revealed that most isolates were resistant to ampicillin (75.0%) and streptomycin (68.3%), whereas all strains were sensitive to chloramphenicol and tetracyclines. Most of the isolates (55.8%) showed resistance against two classes of antimicrobials, mainly to ampicillin and streptomycin (46.2%). Only one isolate displayed a multiresistant pattern. Genotypic analysis of revealed a high degree of diversity among the isolates tested. The pulsed-field gel electrophoresis (PFGE) method distinguished 73 clonal groups, and the most numerous group consisted of 7 strains. Sequencing by the multilocus sequence typing (MLST) method showed 76 sequence types (STs), of which ST481 and ST1361 were most frequently identified. In addition, 51 (67.1%) new sequence types were discovered and added to the PubMLST international database. The presence of in seafood may pose a risk for consumers, especially in countries where shellfish are eaten raw. In recent years, a significant increase of food poisoning caused by these bacteria has been also observed in Europe. Our results highlight the high level of contamination of seafood, along with the isolates being potentially pathogenic for humans. However, the first-line antimicrobials, such as tetracyclines and fluoroquinolones, remained highly effective against The monitoring of antimicrobial resistance of isolates is important to ensure the high efficacy in the treatment of human infections. Most of strains possessed new sequence types (STs), which showed the high genetic diversity of the isolates tested.

Vibrio parahaemolyticus is a marine bacterium recognized as an important cause of gastroenteritis in humans consuming contaminated shellfish. In recent years, increasing resistance to ampicillin and aminoglycosides has been observed among V. parahaemolyticus isolates. However, the first-line antimicrobials such as tetracyclines and fluoroquinolones remained highly effective against these bacteria. The aim of this study was to evaluate the occurrence of V. parahaemolyticus in live bivalve molluscs available on the Polish market and to determine the antimicrobial resistance of the recovered isolates. A total of 400 shellfish samples (mussels, oysters, clams, and scallops) from 2009 to 2012 were tested using the International Organization for Standardization standard 21872-1 method and PCR for the species-specific toxR gene. Antimicrobial susceptibility of the isolates was determined using a microbroth dilution method. V. parahaemolyticus was identified in 70 (17.5%) of the 400 samples, and the toxR gene was confirmed in 64 (91.4%) of these isolates. Most of the isolates were recovered from clams (31 isolates; 48.4% prevalence) followed by mussels (17 isolates; 26.6% prevalence). More V. parahaemolyticus-positive samples were found between May and September (22.7% prevalence) than between October and April (11.4% prevalence). Antibiotic profiling revealed that most isolates were resistant to ampicillin (56 isolates; 87.5%) and to streptomycin (45 isolates; 70.3%), but all of them were susceptible to tetracycline and chloramphenicol. Forty-one isolates (64.1%) were resistant to two or more antimicrobials; however, only one isolate (1.6%) was resistant to three antimicrobial classes. The antimicrobials used in treatment of human V. parahaemolyticus infection had high efficacy against the bacterial isolates tested. This study is the first concerning antibiotic resistance of V. parahaemolyticus isolates in Poland, and the results obtained indicate that these bacteria may pose a health risk to consumers.

Globally, vibrios represent an important and well-established group of bacterial foodborne pathogens. The European Commission (EC) mandated the Comite de European Normalisation (CEN) to undertake work to provide validation data for 15 methods in microbiology to support EC legislation. As part of this mandated work programme, merging of ISO/TS 21872-1:2007, which specifies a horizontal method for the detection of V. parahaemolyticus and V. cholerae, and ISO/TS 21872-2:2007, a similar horizontal method for the detection of potentially pathogenic vibrios other than V. cholerae and V. parahaemolyticus was proposed. Both parts of ISO/TS 21872 utilized classical culture-based isolation techniques coupled with biochemical confirmation steps. The work also considered simplification of the biochemical confirmation steps. In addition, because of advances in molecular based methods for identification of human pathogenic Vibrio spp. classical and real-time PCR options were also included within the scope of the validation. These considerations formed the basis of a multi-laboratory validation study with the aim of improving the precision of this ISO technical specification and providing a single ISO standard method to enable detection of these important foodborne Vibrio spp.. To achieve this aim, an international validation study involving 13 laboratories from 9 countries in Europe was conducted in 2013. The results of this validation have enabled integration of the two existing technical specifications targeting the detection of the major foodborne Vibrio spp., simplification of the suite of recommended biochemical identification tests and the introduction of molecular procedures that provide both species level identification and discrimination of putatively pathogenic strains of V. parahaemolyticus by the determination of the presence of theromostable direct and direct related haemolysins. The method performance characteristics generated in this have been included in revised international standard, ISO 21872:2017, published in July 2017.

The aim of this study was to evaluate the microbiological contamination of raw bivalve molluscan shellfish (BMS) available on the Polish market and determinate the antimicrobial resistance of the obtained isolates. A total of 1000 mollusc samples were tested for the presence of Salmonella spp., L. monocytogenes, V. parahaemolyticus, and S. aureus using the ISO standard methods. Additionally, the bacterial isolates’ susceptibility to antimicrobials was determined using the minimum inhibitory concentration (MIC) method. The obtained results showed that Salmonella spp. was detected in 31 (3.1%) samples, and 51.6% of the bacterial isolates were classified as Salmonella Typhimurium. A total of 74.2% of the Salmonella isolates were sensitive to all antimicrobial agents, whereas three isolates were multiresistant. L. monocytogenes was isolated from 18 (1.8%) BMS, and the isolates belonged to serogroups IIa, IIb, and IVb. Most of them were resistant to ceftriaxone (77.8%) and oxacillin (55.6%). V. parahaemolyticus was present in 24.2% BMS. These isolates were mainly resistant to ampicillin (77.3%) and streptomycin (64.0%). Moreover, 15.2% of the bivalve molluscs were contaminated with S. aureus. Most isolates belonging to this species were resistant to penicillin (84.9%). A total of 60 (6.0%) bivalve molluscs were contaminated with more than one pathogen simultaneously. In addition, the tested bacteria were more likely to be identified during the warmer period (53.9%) compared to the samples analyzed in colder months (35.7%). The obtained results indicate that raw bivalve molluscs from the Polish market are frequently contaminated with bacterial foodborne pathogens, which may be resistant to antimicrobials.