The presence of V. parahaemolyticus 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 V. parahaemolyticus 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 V. parahaemolyticus . The monitoring of antimicrobial resistance of isolates is important to ensure the high efficacy in the treatment of human infections. Most of V. parahaemolyticus strains possessed new sequence types (STs), which showed the high genetic diversity of the isolates tested.

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.

Introduction: The prevalence of potentially pathogenic microorganisms in different foods is widely researched. The aim of this study was to investigate the prevalence and antimicrobial resistance of selected Enterobacterales species isolated from retail food of animal origin in Poland. Material and Methods: Cold cuts, cold-smoked fish and cheeses making 194 samples were tested with the ISO horizontal method for the detection of Enterobacteriaceae , and then Enterobacterales isolates were identified using matrix-assisted laser desorption/ionisation–time of flight mass spectrometry (MALDI-TOF). The isolates’ antimicrobial susceptibility was determined using the minimal inhibitory concentration method. Results: Enterobacterales were detected in 159 (82.0%) samples, from which 226 bacterial isolates were recovered. Six bacterial species accounted for 65.9% of Enterobacterales isolates: Escherichia coli (n = 41), Enterobacter cloacae (n = 26), Hafnia alvei (n = 25), Citrobacter spp. (n = 20), Serratia liquefaciens (n = 20) and Klebsiella oxytoca (n = 17). The isolated E. coli strains showed low resistance to seven antimicrobials. E. cloacae isolates were mostly resistant to ampicillin (76.9%) and azithromycin (38.5%), S. liquefaciens to colistin (100%) and H. alvei strains to colistin (96.0%) and ampicillin (60.0%). The majority of K. oxytoca isolates (70.6%) were resistant to ampicillin, whereas only five Citrobacter isolates were. Twenty of the total pool of isolates (8.8%) were defined as multidrug resistant. Conclusion: Retail food of animal origin can be contaminated with various species of Enterobacterales, including microorganisms pathogenic to humans as well as others resistant to commonly used antimicrobials.