Occurrence of Listeria monocytogenes in Artisanal Cheeses from Poland and Its Identification by MALDI-TOF MS.

Listeria monocytogenes is a foodborne pathogen. A source of infection can be artisanal cheeses. Identification of the Listeria species is important for the protection of public health and the food industry. This study aimed to examine artisanal cheeses for the presence of L. monocytogenes and the effectiveness of the MALDI-TOF MS method in the identification of the L. monocytogenes isolates. A total of 370 samples of artisanal cheeses were examined. L. monocytogenes was found in 23 cheese samples (6.2%). The reliability of L. monocytogenes identification achieved by MALDI-TOF MS was varied, and the vast majority of the isolates (27/32) were identified only to the secure genus, probable species level. This study showed that (i) the occurrence of L. monocytogenes in the artisanal cheeses was at a higher level than that in the other EU countries, (ii) the standard of species identification of L. monocytogenes isolates from artisanal cheeses achieved by MALDI-TOF MS was not satisfactory and (iii) the presence of L. monocytogenes in artisanal cheeses remains a problem with regard to the food safety criterion and a potential public health risk.

Occurrence of Alaria alata in wild boars (Sus scrofa) in Poland and detection of genetic variability between isolates.

Alaria alata is a trematode included among several emerging zoonotic parasites. The mesocercarial larval stage of A. alata named Distomum musculorum suis (DMS) may potentially be infective for humans. In the past, DMS was often observed in wild boar meat during the official Trichinella inspection by artificial digestion before a more specific and effective detection method, the A. alata mesocercariae migration technique (AMT), was introduced. In the present study, the AMT method was used to screen 3589 tissue samples collected from wild boars hunted in Poland during the 2015-2019 period. The survey mainly focused on the southern part of Poland with the majority of samples coming from Malopolskie, Swietokrzyskie, and Dolnoslaskie provinces; samples from ten additional provinces were also included. The total prevalence was 4.2% with mean abundance of 4.7 DMS. Occurrence was dependent upon environmental conditions (i.e., wetland habitats and water reservoirs) rather than on sex of the host or season in which they were hunted. The recovered trematodes were identified as Alaria spp. according to their morphological features. Molecular analysis of 18S rDNA and COI genes confirmed the species identification to be A. alata and documented genetic variability among the isolates.