Listeria monocytogenes Isolated from Illegally Imported Food Products into the European Union Harbor Different Virulence Factor Variants

Unregulated international flow of foods poses a danger to human health, as it may be contaminated with pathogens. Recent studies have investigated neglected routes of pathogen transmission and reported the occurrence of Listeria monocytogenes in food illegally imported into the European Union (EU), either confiscated at four international airports or sold illegally on the Romanian black market. In this study we investigated the genotype diversity and the amino acid sequence variability of three main virulence factors of 57 L. monocytogenes isolates. These isolates were derived from 1474 food samples illegally imported into the EU and originated from 17 different countries. Multilocus sequence typing revealed 16 different sequence types (STs) indicating moderate genotype diversity. The most prevalent STs were ST2, ST9, and ST121. The pulsed-field gel electrophoresis (PFGE) analysis resulted in 34 unique pulsotypes. PFGE types assigned to the most prevalent STs (ST2, ST9, and ST121) were highly related in their genetic fingerprint. Internalin A (InlA) was present in 20 variants, including six truncated InlA variants, all harbored by isolates of ST9 and ST121. We detected eight ST-specific listeriolysin O (LLO) variants, and among them, one truncated form. The actin-assembly-inducing protein ActA was present in 15 different ST-specific variants, including four ActA variants with an internal truncation. In conclusion, this study shows that L. monocytogenes, isolated from illegally imported food, have moderate genotype diversity, but diverse virulence factors variants, mainly of InlA.

Prevalence of major foodborne pathogens in food confiscated from air passenger luggage

The EU has issued several directives and regulations pertaining to the importation of animals and products of animal origin (POAO) and veterinary controls on importation. Unfortunately, little information is available concerning associated risks and no attempts have been made to collect baseline data on the actual prevalence of zoonotic agents in POAO carried by travellers. To meet these challenges the EU recently introduced and financed a research project "PROMISE". Its main objectives were to assess the risks involved when foodborne pathogens are introduced to the EU via uncontrolled imports. With special permission of the Austrian health authorities, spot-checks were made of the luggage of 61,355 passengers from 240 flights from non-EU countries arriving at the Vienna International Airport (VIE airport). Over a period of eight months (August 2012 through March 2013) 1473 POAO items were confiscated. A total of 600 samples were suitable for Salmonella spp., Campylobacter spp., verotoxigenic Escherichia coli and Listeria monocytogenes prevalence analysis. Foodborne pathogens could be detected in 5% (30/600) of all samples. The highest prevalence was attributed to L. monocytogenes, at 2.5%, followed by VTEC and Salmonella spp. at 1.3% and 1.2%, respectively. Campylobacter spp. was not present in any of the 600 samples. Multi-locus sequence typing (MLST) of L. monocytogenes revealed that current sequence types (ST) corresponded to the worldwide most present clonal complexes 1, 2, 3, 5, 9, and 121. Generally, L. monocytogenes ST9 was the predominant allelic profile, which was mainly isolated from Turkish meat products.