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Wild boar (Sus scrofa) is the most widely distributed large wildlife mammal worldwide. To investigate the transmission of Salmonella enterica amongst wild boars (Sus scrofa), humans, and livestock, we compared via pulsed-field gel electrophoresis and whole genome sequences the isolates of S. enterica serovar Typhimurium (biphasic and monophasic variants) and Enteritidis collected from wild boars, food-producing animals, and human patients in Emilia-Romagna region (Northern Italy) between 2017 and 2020. Specifically, we analysed 2175 isolates originated from human (1832), swine (117), bovine (128), poultry (76), and wild boar (22). The genomic analyses showed that wild boars shared most of their lineages of biphasic Typhimurium with bovines and most of Enteritidis with poultry, whilst we did not find any lineage shared with swine. Moreover, almost 17% of human biphasic Typhimurium and Enteritidis belonged to genomic clusters including wild boar isolates, but the inclusion of bovine and poultry isolates in the same clusters and the peculiar spatial distribution of the isolates suggested that human cases (and wild boar infections) likely originated from bovines and poultry. Consequently, wild boars appear not to play a significant role in infecting humans with these serovars, but seem to get infected themselves from livestock, probably through the environment., (© 2023. EcoHealth Alliance.)

Background: To date, whole genome sequencing has been performed mainly for isolates of Chlamydia trachomatis, C. pneumoniae, C. psittaci and C. abortus, but only a few isolates of C. pecorum have been entirely sequenced and this makes it difficult to understand its diversity and population structure. In this study the genome of two C. pecorum strains isolated from the lung of an Alpine chamois affected with pneumonia (isolate PV7855) and the brain of a water buffalo affected with meningoencephalomyelitis (isolate PV6959), were completely sequenced with MiSeq system (Illumina) and analyzed in their most polymorphic regions., Results: The genome length and GC content of the two isolates were found to be consistent with other C. pecorum isolates and the gene content of polymorphic membrane proteins and plasticity zone was found to be very similar. Some differences were observed in the phospholipase genes for both isolates and in the number of genes in the plasticity zone, such as the presence of some hypothetical proteins in PV6959, not present in any other genomes analyzed in this study. Interestingly, PV6959 possesses an extra pmp and has an incomplete tryptophan biosynthesis operon. Plasmids were detected in both isolates., Conclusions: Genome sequencing of the two C. pecorum strains did not reveal differences in length and GC content despite the origin from different animal species with different clinical disease. In the plasticity zone, the differences in the genes pattern might be related to the onset of specific symptoms or infection of specific hosts. The absence of a tryptophan biosynthesis pathway in PV6959 may suggest a strict relationship between C. pecorum and its host., (© 2022. The Author(s).)

The study assessed Salmonella carriage in wild boars (Sus scrofa) and compared their isolates with those recovered from the domestic swine population of the same area of northern Italy (Emilia-Romagna), characterized by intensive pig farming and rather high density of wild boars. A total of 189 wild boars hunted during twelve months (2017-2018) were tested for Salmonella in mesenteric lymph nodes (MLN) and faecal samples. Antimicrobial resistance of recovered strains was tested against 14 antimicrobials. Salmonella was detected in 33/189 wild boars (17.5%), specifically from 30/189 MLN (15.9%) and 6/189 faecal samples (3.2%). Three animals were positive in both samples. Thirteen Salmonella serovars were identified, i.e. Typhimurium (the most common), Bovismorbificans, Coeln, Derby, Enteritidis, Gaminara, Hessarek, Houtenae IV, Kottbus, Napoli, Stanleyville, Thompson and Veneziana. Salmonella carriage was higher in warm than in cold months (P = 0.0013). Pregnancy status was never associated with Salmonella carriage, with significant difference in the recovery of the pathogen between non-pregnant and pregnant females (P = 0.003). Only one resistance pattern to streptomycin and tetracycline was found in 15 isolates (41.7%) belonging to Typhimurium (14/14; 100%) and Kottbus (1/3; 33.3%) serovars. Overlap with isolates from farmed pigs was limited at serotype level (Typhimurium, Derby, Enteritis, Bovismorbificans, Kottbus) and absent at PFGE level, and also antimicrobial resistance patterns were substantially different. This evidence indicates a substantial segregation of the two animal populations with regard to infectious contacts, possibly suggesting that biosecurity measures in place at industrial farm level limit the exchange of Salmonella.

Salmonella enterica serovar Napoli (serovar Napoli) is an emerging cause of human salmonellosis in Northern Italy. No specific reservoirs of serovar Napoli have been identified in Italy, so far. However, the environment, especially surface waters, has been hypothesized as an important source of infection based on the observation that genotypically different clusters of serovar Napoli are detected in different geographical macro-areas. To further support the hypothesis of a spatially-restricted pattern of serovar Napoli diffusion, a spatial segregation of serovar Napoli lineages should be observed also at smaller geographical scale. However, classical genotyping techniques used for Salmonella, such as pulsed-field gel electrophoresis (PFGE), did not possess enough discriminatory power to highlight spatial clustering of serovar Napoli within the macro-areas. To this purpose, we performed phylogeographical analyses based on genome-wide single nucleotide polymorphisms to test whether spatio-temporal evolution patterns of serovar Napoli in Northern Italy could be recognized with high geographical resolution, i.e. at local level. Specifically, we analyzed the local spread of the main PFGE clonal group, responsible for more than 60% of human infections in the study area, that did not show any geographical differentiation by PFGE within Northern Italy, i.e. the macro-area considered in the study. Both discrete and continuous phylogeography highlighted the existence of two main geographically-restricted clades: a Southern clade corresponding to the Po Valley and a Northern clade corresponding to the Pre-Alps area. Furthermore, the phylogeographical analyses suggested that the most probable site of origin of the clone was in an area of the Po Valley at the confluence of the Po and Ticino rivers, one of the most important Italian wetlands. These findings provide further support to the hypothesis that environmental transmission may play an important role in the ecology of serovar Napoli., Competing Interests: The authors have declared that no competing interests exist.

The aim of the study was the comparative evaluation of an isothermal amplification and bioluminescence detection of DNA (IMBD) method and method ISO 6579:2002 for detection of Salmonella in retail meat products of unknown contamination status. A total of 200 meat samples were tested: 116 minced meat and meat preparations to be eaten cooked (52 chicken, 48 pork, and 16 beef samples) and 84 fresh meat samples (68 poultry and 16 pork). With one or both methods, 21 samples (10.5%) were positive for Salmonella enterica. Fifteen samples were positive with both methods (71.4% of all positive samples), two more samples (9.5%) were positive with the IMBD method only, and four samples (19.1%) were positive with the ISO method only. One ISO-positive sample was inhibited with the IMBD method. For the IMBD method, relative accuracy was 97.0% (95% confidence interval [CI], 93.6 to 98.9%), relative sensitivity was 78.9% (95% CI, 54.4 to 93.9%), and relative specificity was 98.9% (95% CI, 96.1 to 99.7%). Time to negative results was shorter with the IMBD method (20 to 24 h). Also, positive results were available in 20 to 24 h but should be confirmed using other methods (presumptive-positive results). Rapidity of response of the IMBD method gave us the opportunity to test the presumptive-positive samples by the most-probable-number (MPN) method, which was not performed for samples that were positive only with the ISO method because of likely microbial changes during the long storage period (5 to 7 days) at refrigeration temperature. Salmonella MPN values in naturally contaminated meat were low, at <0.3 to 2.1 MPN/g.