A proteomic approach of the different environmental conditions of Listeria monocytogenes

 

Listeria monocytogenes is the ubiquitous food-borne pathogen which causes listeriosis, a disease with a high mortality rate, mostly transmitted through contaminated ready-to-eat foods. To better understand the systemic response of L. monocytogenes exposed at 3 environmental factors (T, pH and NaCl), the proteome of L. monocytogenes strain NRG 1749-2016, isolated from a meat product, was investigated to identify differences in the protein patterns of such pathogen. Four different conditions were carried out as follows: A) T 37 °C, pH 7.0, NaCl 0.5%; B) T 37 °C, pH 5.5, NaCl 7%; C) T 12° pH 7, NaCl 0.5%; D) T 12 °C, pH 5.5, NaCl 7%. The proteins belonging to cytosol (C1) and vesicles (C2) were isolated and purified by CelLytic B Cell Lysis Reagent and CelLytic IB Inclusion Body Solubilization Reagent according manufacturer's instructions. The analysis were conducted by SDS PAGE and Immunoblotting techniques. The protein concentrations were evaluated by Pierce BCA Protein Assay Kit. From preliminary results, the protein banding patterns generated by 1D SDS PAGE were found to be different at visual observation for C1 and C2, in A, B, C and D conditions. The presence of specific antigen-antibody immunocomplexes (Ag-Ab ICs) was identified by Immunoblotting, in C1 at 100, 60, 55, 35 and 25 kDa for all incubated conditions with a positive serum to L. monocytogenes. As regards C2, Ag-Ab ICs at 110 kDa were observed in A and B, Ag-Ab ICs at 80 kDa in C and D, Ag-Ab ICs at 60 kDa in A and D, while Ag-Ab ICs at 40 and 30 kDa in all conditions. The analysis of the proteome profiles shows an intra-strain variation in the protein patterns produced by L. monocytogenes during the adaptation at different environmental conditions. Further analysis will be carried out to better understand the systemic response of L. monocytogenes, in particular in order to characterize the immunogenic proteins highlighted by Immunoblotting and their role in the virulence expression of such pathogen.

Key messages

Understand how L. monocytogenes adapts physiologically to different environmental factors. Development of new detection method of L. monocytogenes and prevention strategies for listeriosis outbreaks.

Shiga-toxin producing Escherichia coli detection in samples from Abruzzo and Molise regions, Italy

Background

Top five serogroups (O157, O111, O26, O103 and O145) of Shiga-toxin producing Escherichia coli (STEC) represent the third most important increasing zoonosis reported in European Union. The ISO methods of analysis, used in foods and environmental samples, quite often does not confirm the molecular detection of STEC genes (stx1 and stx2) in enrichment broth. The aim of this study was to summarize the results of the tests carried out at Istituto Zooprofilattico Sperimentale dell'Abruzzo e del Molise in the last six years (2016-2021), comparing genes detection in enrichment broth and in colonies grown on agar plates.

Methods

Along the 2016-2021, a total of 1716 foods and environmental samples from Abruzzo and Molise regions were tested, according to ISO/TS 13136:2012.

Results

Out of 1716 samples, 16 (0.9%) shown presumptive positive presence of STEC (stx1 and/or stx2) in broth. In spite of that, the presence of STEC (positive colonies for stx1 and/or stx2) was confirmed only in 4 out of 16 samples (one sample of cheese and 3 of minced meat). Then, eae gene was found in 54 samples in broth and only in 3 samples from colonies, during a foodborne outbreak investigation. Serogroup specific targets were detected in 6 broth samples (O26, O145 and O157) and confirmed in colonies only in 2 minced meat samples (O157).

Conclusions

STEC are a heavy hazard for the consumers and the number of cases is slightly increasing since 2015. Our results highlight a low number of presumptive positive samples and even lower number of STEC detection obtained with the ISO classical method. Furthermore, detection of the target genes in broth was rarely confirmed after plating, highlighting a weak point of the analytical method that needs to be investigated. Efforts are necessary to improve the method and the STEC confirmation from colonies. Immunomagnetic beads targeting the top five serogroups and digital PCR could help in increasing the recovery rate of cultivable STEC.

Key messages

The presumptive positive samples for STEC genes in foodstuffs from the Abruzzo and Molise regions are quite rare, even lower is the number of confirmed colonies by agar plate isolation. Specific immunomagnetic beads for the top five STEC serogroups could improve the method and the STEC colonies detection, increasing the recovery rate of cultivable strains.

Genomic persistence of Listeria monocytogenes strains in dairy and meat processing plants in Italy

Background

Persistence of Listeria monocytogenes (Lm) in food processing plants (FPP) is still considered the major source of food contamination during processing. Correlations among different Lm strains and evaluation of the isolates persistence in FPP environments is an essential tool to improve food safety. The aim of this study was to investigate the genomic characteristics of persistent Lm strains (e.g. Metal and Detergent Resistance, SSIs and genomic island).

Methods

Totally 221 strains isolated from 10 FPP in the Abruzzo and Molise regions, Italy, were enrolled (4 of dairy products FPP - DP - and 6 of meat products FPP - MP). Sampling was performed in 6 sessions, from March 2017 to May 2018. Strains were sequenced using Illumina platform. The CCs, cgMLST analysis and Metal and Detergent Resistance, SSIs and genomic island (GI) detection was carried using the Pasteur scheme.

Results

Results returned 13 CCs and 2 singletons. cgMLST clustering showed two persistent clusters DP and 9 clusters in MP. In DP CC3 and CC9 were persistent. While in MP CC5, CC8, CC9, CC37, CC121 and CC155. The presence of SSI-1, was detected in 100% of the persistent strains from DP and 80% from MP, in particular in all strains of CC155, CC5, CC8 and CC9. In CC121 and CC37 it was absent. The presence of loci of Lm GI3, was in 100% of persistent strains of DP and in 52.3% of MP plant, in particular in 100% of CC121, CC8, CC5 and 16.3% of CC9. The 100% of CC121 in DP and MP plant harboured Tn6188 and SSI-2. The inlA PMSC mutations were detected in 100% of CC9 and CC121 strains.

Conclusions

The persistence of strains inside FPP was confirmed using NGS data, most of the strains were characterised by the presence of genes involved in resistance and adaptation. NGS is confirmed to be a powerful tool to study Lm persistence in FPP, looking also at strains' ecology.

Key messages

Most of persistent strains showed genes involved in resistance and adaptation in the food processing environment. NGS could help in facing Lm persistence in food producing plants giving new insights on the genomic characteristics of persistent strains.

Foodborne outbreaks surveillance in hospitals and nursery homes: investigation on catering data

Background

Healthcare associated foodborne outbreaks (HA-FBO) can result from exposure to contaminated food in premises where highly vulnerable patients are cared, including hospitals and nursery homes. The probability of developing severe foodborne diseases such as invasive listeriosis is much higher for susceptible populations. There is limited knowledge on the data on food exposures that could be used to investigate HA-FBOs. There is also lack of data relating to specific policies in the health facilities aimed to prevent the administration of potentially risky foods, possibly bringing them from home.

Methods

This study was in the framework of One Health EJP Project NOVA. A semistructured questionnaire was administered to 4 general hospitals, 1 specialist clinic and 3 nursing homes located in the Abruzzo and Molise regions, Italy. The questionnaire included 25 questions in 3 sections (I. General organization of the catering service; II. Food menu data; III. Food from home).

Results

In most facilities (75%) external catering companies used in-house kitchens. Trace-back of food to individual patients was possible in 5 premises out of 8 (62.5%), but only in 1 nursery home out of 3 (33.3%). Data were collected in electronic format (hospitals) or paper (nursery homes) and stored 1-12 months. Food at risk of Listeria monocytogenes were not excluded from the menus, such as pre-sliced cooked meat products (served in 4 out of 8 premises, 50%), smoked fish (20%), soft cheese (20%). The consumption of food brought from home was possible in “special occasions”, mostly in the nursery homes (66.6%).

Conclusions

In case of HA-FBO it could be difficult to trace back the food particularly in the nursery homes where food data are not individually collected and usually on paper. More studies are needed in order to understand the effective exposure to foodborne pathogens, given that some types of foods considered by EFSA as at high risk of microbial contamination are commonly served.

Key messages

Served food could not be traced back to the patient mostly in nursery homes. Foods at risk of Listeria monocytogenes contamination are commonly served to patients and residents.

Antibiotic-free farming for poultry meat production: impact on animal welfare

Background

Multidrug-resistant zoonotic pathogens represent a risk for human health. The irrational use of antibiotics in production animals has contributed to the spread of antibiotic resistance (AMR) also in humans. The search for alternative systems to the use of antibiotics, including the study of ‘animal welfare-friendly' management tools, should be encouraged. The reduction of the use of antibiotics should be a controlled process, as their absence could have a negative impact on animal welfare, if not accompanied by adequate structural and managerial interventions.

Methods

Welfare Quality® protocol was used to measure the level of welfare in 14 batches of broiler chickens from 6 farms of an integrated poultry company and the results were compared (antibiotic-free vs conventional). The number of animals per batch ranged from 9,000 to 41,700. Assessments were made throughout a 9-month period, from 2018 to 2019, at-farm the day before slaughtering (age from 42 to 48 days old).

Results

No statistically significant differences between antibiotic-free and conventional in the general ‘welfare score' were reported. Stocking density was higher in antibiotic-free batches, and the ‘good feeding' principle was averagely higher in conventional batches (74.7 vs 63), with statistical significance (t=-2.45; p < 0.05). Other welfare principles (good housing, good health and appropriate behaviour) were slightly higher for antibiotic-free batches, without statistical significance. The absence of antibiotics did not affect the ‘good health' principle, ranging from 24.1 to 44.7, with the minimum in a conventional batch and the maximum detected in an antibiotic-free batch. The highest mortality (3.9%) was found in a conventional batch.

Conclusions

The absence of antibiotics in broiler farming doesn't affect animal health and welfare if associated with good management practices. Antibiotic-free farming should be standardized in order to protect both animal welfare and consumers' health.

Key messages

The absence of antibiotic use does not impact on broiler chicken general welfare score. High stocking density due to the high demand of antibiotic-free meat should be avoided and specific guidelines for antibiotic-free farming should be produced.

The impact of calcification patterns in transcatheter aortic valve performance: a fluid-structure interaction analysis

Transcatheter aortic valve replacement (TAVR) strongly depends on the calcification patterns, which may lead to a malapposition of the stented valve and complication onsets in terms of structure kinematics and paravalvular leakage (PVL). From one anatomical-resembling model of the aortic root, six configurations with different calcific deposits were built. TAVR fluid-structure interaction simulations predicted different outcomes for the different calcifications patterns in terms of the final valve configuration in the implantation site and the PVL estimations. In particular models with deposits along the cups coaptation resulted in mild PVL, while those with deposits along the attachment line in moderate PVL.

Distributed and Lumped Parameter Models for the Characterization of High Throughput Bioreactors

Next generation bioreactors are being developed to generate multiple human cell-based tissue analogs within the same fluidic system, to better recapitulate the complexity and interconnection of human physiology [1, 2]. The effective development of these devices requires a solid understanding of their interconnected fluidics, to predict the transport of nutrients and waste through the constructs and improve the design accordingly. In this work, we focus on a specific model of bioreactor, with multiple input/outputs, aimed at generating osteochondral constructs, i.e., a biphasic construct in which one side is cartilaginous in nature, while the other is osseous. We next develop a general computational approach to model the microfluidics of a multi-chamber, interconnected system that may be applied to human-on-chip devices. This objective requires overcoming several challenges at the level of computational modeling. The main one consists of addressing the multi-physics nature of the problem that combines free flow in channels with hindered flow in porous media. Fluid dynamics is also coupled with advection-diffusion-reaction equations that model the transport of biomolecules throughout the system and their interaction with living tissues and C constructs. Ultimately, we aim at providing a predictive approach useful for the general organ-on-chip community. To this end, we have developed a lumped parameter approach that allows us to analyze the behavior of multi-unit bioreactor systems with modest computational effort, provided that the behavior of a single unit can be fully characterized.

Evaluation of the efficacy of selamectin spot-on in cats infested with Aelurostrongylus abstrusus (Strongylida, Filariodidae) in a Central Italy cat shelter

In recent years Aelurostrongylus abstrusus has often been reported in Italy. This lungworm is very common in cat colonies due to its route of transmission. Deciding a therapeutic approach can be difficult in such colonies, because there is no certainty whether oral medicines administered with food, or with what dose, will be taken. In this field study, stool samples were taken from 42 cats and analysed for A. abstrusus L1 larvae with Baermann technique. Ten cats testing positive were treated with a spot-on formulation of selamectin 45 mg. Clinical examinations and laboratory tests, repeated four times in two months, demonstrated the success of the treatment in 9 of the 10 cats. Improvements in respiratory signs and general clinical condition were reported after treatment.

Free-roaming dog control among OIE-member countries

A questionnaire was distributed to the state veterinary services of all 172 OIE countries to collect data on the different national approaches to dog population control. We used all 81 completed questionnaires with ≥80% of the question answered to identify the different national approaches to the issue. The intensity of the free-roaming dog (FRD) problem was negatively correlated with the value of the UN's human development index recognized for each country. Dog bites/attacks and rabies were the main problems associated with FRDs, and these problems were reported disproportionately by less-developed countries. Dog-control programs (DCP) were more widely used among the more-developed countries. In less-developed countries, DCPs (when they existed at all) tended to employ killing methods (including poisoned baits), that are not recommended on animal-welfare grounds.

[Osteo-odonto-kerato-prosthesis. Radiographic, CT and MR features]

PURPOSE

Osteo-odonto-keratoprosthesis, a complex eye surgery technique devised by Strampelli, provides a valuable opportunity to restore vision in patients with severe corneal opacification (chemical or thermal burns, bullous keratopathy, severe keratitis, consequences of perforating injuries) in whom corneal transplant or the insertion of synthetic prostheses is contraindicated because of the high risk of rejection. Successful implantation of corneal prostheses in these patients was clearly dependent on the use of perfectly biocompatible materials to support the optic. Strampelli demonstrated that thin autologous tooth sections, complete with alveolar-dental ligament fulfilled these requirements, and integrated perfectly with the eye tissues without any risk of rejection. This study aims to present the radiological aspects and postoperative outcome of 13 patients who received osteo-odonto-keratoprosthesis (bilateral in 11 cases and monolateral in 2) evaluated by plain radiography, CT and MRI.

MATERIAL AND METHODS

Between 1993 and 2001 we evaluated 13 patients who had undergone Strampelli's osteo-odonto-keratoprosthesis, using CT, plain radiography and MRI. All patients were examined by plain radiography; 11 patients were also examined by CT and 8 also by MRI. The time interval between surgery and the radiological evaluation ranged from 3 to 13 years with a mean follow-up of 5 years and 9 months.

RESULTS

All patients underwent periodic clinical and imaging examinations in the post-operative period to evaluate the osteo-dental implant and to study trophism of the transplant. No post-operative complications, either cicatricial, inflammatory or of any other nature, were clinically suspected. Only two patients showed partial reabsorption of the osteo-dental lamina - evident both on plain film and CT - 10 and 12 years after surgery. Vision was restored in all the patients, with visual acuity of 10/10 in 7 cases.

DISCUSSION AND CONCLUSIONS

Plain radiography allows to correctly evaluate the position of the prosthesis and detect possible displacements or variations in thickness, but it fails to visualize intraocular soft tissues. Besides allowing visualization and study of the prosthesis, CT also allows optimal evaluation of the intra-orbital structures and early detection of the presence and extension of inflammatory complications that may undermine outcome of the procedure. MRI is similar to CT in its capacity to evaluate intra-orbital tissues, but has the advantage of allowing greater contrast resolution thanks to the use of different types of sequences. However, because of the long image acquisition times, this method is subject to movement artifacts that are less evident in the CT examination which, especially if performed using the spiral technique, has very short image acquisition times.

Intrauterine device for contraception in dogs

A new intrauterine device for contraception was tested on nine bitches. After it had been implanted, the bitches were mated but none of them became pregnant. Over a two-year period no side effects were observed, except in a bulldog bitch in which signs of oestrus persisted until the device had been removed.