Prevalence and antimicrobial resistance of bacterial foodborne pathogens isolated from raw bivalve molluscs subjected to consumption in Poland during a ten-year period

Abstract

The aim of this study was to evaluate the microbiological contamination of raw bivalvemolluscan 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 inhibitoryconcentration (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 totalof 74.2% of the Salmonella isolates were sensitive to all antimicrobial agents, whereas three isolateswere multiresistant. L. monocytogenes was isolated from 18 (1.8%) BMS, and the isolates belonged toserogroups 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 withS. 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%) comparedto the samples analyzed in colder months (35.7%). The obtained results indicate that raw bivalvemolluscs from the Polish market are frequently contaminated with bacterial foodborne pathogens,which may be resistant to antimicrobials.