Antimicrobial resistance of Listeria monocytogenes serogroups IIa and IVb from food and food-production environments in Poland.

Introduction: Listeria monocytogenes is an important foodborne pathogen responsible for human listeriosis, which is a disease with high hospitalisation and mortality rates. The bacteria are usually susceptible to most antibacterial substances, but resistance to some of them has been recently observed. The present study introduces the evidence on the emergence of antibiotic resistance among L. monocytogenes strains isolated from food and food-production environments in Poland.

Material and methods: A total of 283 L. monocytogenes isolates classified into serogroups IIa and IVb which had been recovered from food and food production environments were tested with 17 antimicrobials. These included those that are recommended for treatment of severe listeriosis cases in humans. A multiplex PCR was used to identify serogroups, and a microbroth dilution method was applied for the determination of antibiotic resistance among the isolates tested.

Results: Only 34 (12.0%) strains were susceptible to all the antimicrobials used in the study. The remaining 249 (88.0%) strains displayed different instances of resistance to the antimicrobials tested, from insusceptibility to one (112 strains; 39.6%) to resistance to four antibacterial substances (6 strains; 2.1%). Among them, there were 38 strains (13.4%) with multiresistance patterns.

Conclusion: Polish food and its processing environments may be a potential source of antimicrobial-resistant L. monocytogenes, which may pose a potential health risk to consumers in the country.