Food products confiscated from air passengers travelling from third countries into the European Union: Microbiological analyses and genomic characterization of zoonotic and multiresistant bacteria

Illegal imports of food of animal origin from third countries into the EU are a potential transmission route for zoonotic and multiresistant bacterial pathogens. Here, we collected illegally imported food products that were confiscated from passengers arriving from non-EU countries at Frankfurt International Airport (FRA), Germany. A total of 100 food samples were microbiologically tested for the presence of foodborne and multiresistant pathogens and hygiene parameters were determined. For this, samples were qualitatively examined for Salmonella spp., Listeria monocytogenes, Staphylococcus aureus, Shiga toxin-producing Escherichia coli (STEC), methicillin-resistant S. aureus (MRSA), and extended-spectrum β-lactamase (ESBL)-/AmpC-producing Enterobacterales. Quantitative microbiological analyses included aerobic mesophilic colony counts, L. monocytogenes, coagulase-positive staphylococci, Enterobacterales and E. coli counts. Overall, Enterobacterales and E. coli were detected in 36 % and 23 % of the samples, respectively, indicating hygiene deficiencies, while foodborne pathogens were observed in 17 % of the samples. Selected isolates were subjected to a comprehensive genotypic analysis, for which they were whole genome sequenced. It was demonstrated that the S. aureus isolates (n = 11) revealed a wide variety of genotypic profiles, with one isolate belonging to a newly assigned sequence type ST8323. Three S. aureus isolates were classified as multiresistant, including one MRSA. The Salmonella enterica isolates (n = 3) belonged to three serovars (Uganda, Altona, Rauform) and were susceptible to all antimicrobial agents tested. Further, no resistance was detected in the obtained L. monocytogenes isolates (n = 3; ST8, ST121, ST425). In three of the 23 presumed commensal E. coli isolates multiresistance was observed, whereas the single STEC isolate (O43:H2) was susceptible. In addition, we obtained five ESBL-producing Enterobacterales isolates, of which one isolate carried a rarely described bla_SHV-168 subtype. Overall, the data show that illegal imports in the baggage of airline passengers can facilitate the spread of zoonotic and multiresistant bacterial isolates, including those resistant to third-generation cephalosporins and quinolones. This contributes to the transmission of newly described or uncommon lineages.