Investigation of Salmonella, hepatitis E virus (HEV) and viral indicators of fecal contamination in four Italian pig slaughterhouses, 2021-2022

In the pork production chain, the control at slaughterhouse aims to ensure safe food thanks to proper hygienic conditions during all steps of the slaughtering. Salmonella is one of the main foodborne pathogens in the EU causing a great number of human cases, and pigs also contribute to its spreading. Pig is the main reservoir of the zoonotic hepatitis E virus (HEV) that can be present in liver, bile, feces and even rarely in blood and muscle. The aim of this study was to assess the presence of both Salmonella and HEV in several points of the slaughtering chain, including pig trucks. Other viruses hosted in the gut flora of pigs and shed in feces were also assayed (porcine adenovirus PAdV, rotavirus, norovirus, and mammalian orthoreovirus MRV). Torque teno sus virus (TTSuV) present in both feces, liver and blood was also considered. Four Italian pig abattoirs were sampled in 12 critical points, 5 of which were the outer surface of carcasses before processing. HEV and rotavirus (RVA) were not detected. Norovirus was detected once. Salmonella was detected in two of the 4 abattoirs: in the two lairage pens, in the site of evisceration and on one carcass, indicating the presence of Salmonella if carcass is improper handled. The sampling sites positive for Salmonella were also positive for PAdV. MRV was detected in 10 swabs, from only two abattoirs, mainly in outer surface of carcasses. TTSuV was also detected in all abattoirs. Our study has revealed a diverse group of viruses, each serving as indicator of either fecal (NoV, RVA, PAdV, MRV) or blood contamination (TTSuV). TTSuV could be relevant as blood contamination indicators, crucial for viruses with a viremic stage, such as HEV. The simultaneous presence of PAdV with Salmonella is relevant, suggesting PAdV as a promising indicator for fecal contamination for both bacterial and viruses. In conclusion, even in the absence of HEV, the widespread presence of Salmonella at various points in the chain, underscores the need for vigilant monitoring and mitigation strategies which could be achieved by testing not only bacteria indicators as expected by current regulation, but also some viruses (PAdV, TTSuV, MRV) which could represent other sources of fecal contamination.

Prevalence and Antimicrobial Resistance of Salmonella spp. From Irrigation Water in Two Major Sources in Jordan

Irrigation water could be a direct source of pathogenic microorganisms that contaminates fresh produce and causes human diseases. In this study, we evaluated the prevalence of Salmonella spp. and its serotypes Typhimurium and Enteritidis, antimicrobial susceptibility and multidrug resistance (MDR) status, and seasonal variation, of Salmonella spp. in irrigation water of King Abdullah Canal (KAC) and Wadi Shueib (WS) in Jordan. The study results demonstrated that 32.2% (29/90) of irrigation water was contaminated with Salmonella spp. and the irrigation water of WS was found highly contaminated (62.1%) with Salmonella spp. compared to KAC (37.9%). In addition, higher prevalence of Salmonella were recorded in spring (33.3%) and summer (36.3%) seasons, compared to winter seasons. Among the contaminated irrigation water samples, prevalence of Salmonella Typhimurium serotype was found in (37.9%) (11/29) samples, while S. Enteritidis was absent. The most common antimicrobial resistance of Salmonella isolates was observed as tetracycline (11/29, 37.9%) and 6 (20.7%) Salmonella Typhimurium isolates were found multidrug resistance (MDR). Thus, this study results confirmed that the irrigation water was contaminated with pathogenic MDR Salmonella spp.

Interaction between bacterial enteric pathogens and aquatic macrophytes. Can Salmonella be internalized in the plants used in phytoremediation processes?

The environment is considered a reservoir of pathogens and a possible source of infection for animals and humans. The association between enteric pathogens and food plants has been demonstrated in several studies, while few studies have addressed possible interactions between human pathogens and aquatic plants. This study, performed by setting mesocosms, evaluates the interaction between an enteric pathogen (Salmonella enterica serovar Napoli, S. Napoli) and a macrophyte (Phragmites australis (Cav.) Trin. ex Steudel) and the possible ability of the bacterium to internalize into the plant. The results show that S. Napoli concentration decreased gradually in growth solution without plants (control) while it was able to persist adhering to submerged parts of plants in treated mesocosms. The adhesion of the bacterium remained stable for 20 days, then decreased gradually until the end of the experiment. In addition, S. Napoli was able to internalize and colonize stems and leaves. In conclusion, the study suggests that macrophytes can represent an alternative environmental reservoir of pathogens for humans and animals. The adhesion to roots and rhizomes and the internalization could contribute to the bacterial persistence in the aquatic ecosystems by playing an important role in ecology and transmission of pathogens.

Salmonella serovar distribution from non-human sources in Italy; results from the IT-Enter-Vet network

The study summarises the results obtained over the period 2002-2013 by the Italian IT-Enter-Vet network, aimed at collecting data on Salmonella isolates from non-human sources. A total of 42,491 Salmonella isolates were reported with a progressive decrease over the years. S. Typhimurium was the most frequent serovar up to 2011, but then, it was overtaken by S. 4,[5],12,:i:-, S. Derby, S. Livingstone and S. Enteritidis alternated as the third most commonly isolated serovars. With regard to the sources of isolation, S. Typhimurium was distributed ubiquitously among the animal species. On the contrary, S. 4,[5],12,:i:- and S. Derby were strictly associated with pigs, whereas S. Livingstone, S. Enteritidis and S. Infantis were clearly related to poultry. Intriguingly, when the frequency of serovar distribution along the food chain was considered, it was evident that S. Typhimurium and S. Derby tended to persist along the chain, as they were isolated even more frequently from foods than from animals. A similar distribution was found for S. Enteritidis and S. Hadar. Despite limitations related to non-mandatory participation of laboratories in the network, the data presented are valuable to obtain a picture of the evolution of Salmonella from non-human sources over time in Italy.

Salmonella enterica Serotype Napoli is the First Cause of Invasive Nontyphoidal Salmonellosis in Lombardy, Italy (2010-2014), and Belongs to Typhi Subclade

Salmonella enterica serotype Napoli (S. Napoli) is currently emerging in Europe and particularly in Italy, where in 2014 it caused a large outbreak associated with elevated rates of bacteremia. However, no study has yet investigated its invasive ability and phylogenetic classification. Here, we show that between 2010 and 2014, S. Napoli was the first cause of invasive salmonellosis affecting 40 cases out of 687 (invasive index: 5.8%), which is significantly higher than the invasive index of all the other nontyphoidal serotypes (2.0%, p < 0.05). Genomic and phylogenetic analyses of an invasive isolate revealed that S. Napoli belongs to Typhi subclade in clade A, Paratyphi A being the most related serotype and carrying almost identical pattern of typhoid-associated genes. This work presents evidence of invasive capacity of S. Napoli and argues for reconsideration of its nontyphoidal category.

A novel group of IncQ1 plasmids conferring multidrug resistance

The IncQ is a group of non-conjugative but mobilisable plasmids that are found and stably maintained in a wide range of bacteria contributing to the spread of antimicrobial resistance genes and to the insurgence of multidrug resistant bacteria. Here we report the identification, in clinical Salmonella Typhimurium strains, of an IncQ1 plasmid (pNUC) which confers resistance to sulfamethoxazole, streptomycin and tetracycline through the presence of sul2, strAB and tetA genes, respectively. pNUC was detected in five multidrug resistant S. Typhimurium strains collected in Southern Italy from various hospitals and years of isolation. Bioinformatics analyses highlighted the presence of pNUC-like plasmids in pathogenic bacteria of various Enterobacteriaceae genera or species. Taken as a whole, these plasmids constitute a novel group of IncQ1 plasmids that might have originated through recombination events between a tetR-tetA gene cluster (possibly derived from a Tn1721) and a recipient IncQ1 plasmid related to RSF1010. Our findings raise concerns regarding the possible contribution of the newly identified group of IncQ1 plasmids to the spread of tetracycline resistance.

Pediatric Epidemic of Salmonella enterica Serovar Typhimurium in the Area of L'Aquila, Italy, Four Years after a Catastrophic Earthquake

Background: A Salmonella enterica epidemic occurred in children of the area of L’Aquila (Central Italy, Abruzzo region) between June 2013 and October 2014, four years after the catastrophic earthquake of 6 April 2009. Methods: Clinical and laboratory data were collected from hospitalized and ambulatory children. Routine investigations for Salmonella infection were carried out on numerous alimentary matrices of animal origin and sampling sources for drinking water of the L’Aquila district, including pickup points of the two main aqueducts. Results: Salmonella infection occurred in 155 children (83 females: 53%), aged 1 to 15 years (mean 2.10). Of these, 44 children (28.4%) were hospitalized because of severe dehydration, electrolyte abnormalities, and fever resistant to oral antipyretic and antibiotic drugs. Three children (1.9%) were reinfected within four months after primary infection by the same Salmonella strain. Four children (2.6%), aged one to two years, were coinfected by rotavirus. A seven-year old child had a concomitant right hip joint arthritis. The isolated strains, as confirmed in about the half of cases or probable/possible in the remaining ones, were identified as S. enterica serovar Typhimurium [4,5:i:-], monophasic variant. Aterno river, bordering the L’Aquila district, was recognized as the main responsible source for the contamination of local crops and vegetables derived from polluted crops. Conclusions: The high rate of hospitalized children underlines the emergence of a highly pathogenic S. enterica strain probably subsequent to the contamination of the spring water sources after geological changes occurred during the catastrophic earthquake.

Occurrence and antimicrobial resistance of Salmonella strains from food of animal origin in southern Italy

Six hundred fourteen strains of Salmonella enterica were isolated from 16,926 samples of food of animal origin collected in southern Italy from 2003 to 2012. The isolates were identified, serotyped, and challenged against 15 antibiotics according to the protocol defined at national level for veterinary isolates of Salmonella (EnterVet surveillance network). Salmonella serotypes Typhimurium, Hadar, Enteritidis, Derby, and 4,[5],12:i:- were those most frequently isolated. The widest resistances were recorded towards sulfonamides (69 % of the isolates), trimethoprim-sulfamethoxazole (52 % of the isolates), and tetracycline (51 % of the isolates). The rate of multidrug resistance of the isolates decreased significantly from the first 5 years of the study period (82.6 %) to the last 5 years (54.3 %).

Serotypes and Antimicrobial Resistance of Human Nontyphoidal Isolates of Salmonella enterica from Crete, Greece

We report on the serotype distribution and the antimicrobial resistance patterns to 20 different antimicrobials of 150 Salmonella enterica strains isolated from stools of diarrhoeal patients on the island of Crete over the period January 2011-December 2012. Among the S. enterica serotypes recovered, Enteritidis was the most prevalent (37.3%), followed by Typhimurium (28.7%) and Newport (8.7%). No resistance was detected to extended-spectrum cephalosporins and carbapenems. Rates of resistance to ampicillin, amoxicillin/clavulanic acid, chloramphenicol, tetracycline, and cotrimoxazole were 9.3%, 4%, 2%, 15.3%, and 8.7%, respectively. Resistance to ≥4 antibiotics was primarily observed for serotypes Typhimurium and Hadar. Enteritidis remains the predominant serotype in Crete. Although low resistance to most antimicrobials was detected, continued surveillance of susceptibility is needed due to the risk of resistance.

Salmonella enterica serovar enteritidis modulates intestinal epithelial miR-128 levels to decrease macrophage recruitment via macrophage colony-stimulating factor

BACKGROUND

The mechanism underlying the ability of virulent Salmonella organisms to escape clearance by macrophages is incompletely understood. Here, we report a novel mechanism by which Salmonella escapes macrophages.

METHODS

Microarray and quantitative real-time polymerase chain reaction analyses were used to screen key microRNAs regulating Salmonella-host cell interactions. Target gene was tested using luciferase reporter and Western blot assays. The role of microRNA 128 (miR-128) was assayed using intestinal epithelial cells and a mouse infection model.

RESULTS

The miR-128 level in human intestinal epithelial HT29 cells was strongly increased by infection with strain SE2472, and the elevation in miR-128 levels in mouse intestine and colon tissues correlated with the level of Salmonella infection in mice. Macrophage colony-stimulating factor (M-CSF) was identified as a target of miR-128, and increased miR-128 levels in epithelial cells due to infection with strain SE2472 significantly decreased the level of cell-secreted M-CSF, leading to impaired M-CSF-mediated macrophage recruitment. The secreted proteins from Salmonella were identified as possible effectors to induce miR-128 expression via the p53 signaling pathway. Moreover, intragastric delivery of anti-miR-128 antagomir into mice significantly increased M-CSF-mediated macrophage recruitment and suppressed Salmonella infection.

CONCLUSIONS

Salmonella can upregulate intestinal epithelial miR-128 expression, which, in turn, decreases levels of epithelial cell-secreted M-CSF and M-CSF-induced macrophage recruitment.