Comparative genomic analysis of toxin-negative strains of Clostridium difficile from humans and animals with symptoms of gastrointestinal disease

Background: Clostridium difficile infections (CDI) are a significant health problem to humans and food animals. Clostridial toxins ToxA and ToxB encoded by genes tcdA and tcdB are located on a pathogenicity locus known as the PaLoc and are the major virulence factors of C. difficile. While toxin-negative strains of C. difficile are often isolated from faeces of animals and patients suffering from CDI, they are not considered to play a role in disease. Toxin-negative strains of C. difficile have been used successfully to treat recurring CDI but their propensity to acquire the PaLoc via lateral gene transfer and express clinically relevant levels of toxins has reinforced the need to characterise them genetically. In addition, further studies that examine the pathogenic potential of toxin-negative strains of C. difficile and the frequency by which toxin-negative strains may acquire the PaLoc are needed. Results: We undertook a comparative genomic analysis of five Australian toxin-negative isolates of C. difficile that lack tcdA, tcdB and both binary toxin genes cdtA and cdtB that were recovered from humans and farm animals with symptoms of gastrointestinal disease. Our analyses show that the five C. difficile isolates cluster closely with virulent toxigenic strains of C. difficile belonging to the same sequence type (ST) and have virulence gene profiles akin to those in toxigenic strains. Furthermore, phage acquisition appears to have played a key role in the evolution of C. difficile. Conclusions: Our results are consistent with the C. difficile global population structure comprising six clades each containing both toxin-positive and toxin-negative strains. Our data also suggests that toxin-negative strains of C. difficile encode a repertoire of putative virulence factors that are similar to those found in toxigenic strains of C. difficile, raising the possibility that acquisition of PaLoc by toxin-negative strains poses a threat to human health. Studies in appropriate animal models are needed to examine the pathogenic potential of toxin-negative strains of C. difficile and to determine the frequency by which toxin-negative strains may acquire the PaLoc

Deep proteomic analysis of microglia reveals fundamental biological differences between model systems

Using high-resolution quantitative mass spectrometry, we present comprehensive human and mouse microglia proteomic datasets consisting of over 11,000 proteins across six microglia groups. Microglia share a core protein signature of over 5,600 proteins, yet fundamental differences are observed between species and culture conditions. Mouse microglia demonstrate proteome differences in inflammation- and Alzheimer's disease-associated proteins. We identify differences in the protein content of ex vivo and in vitro cells and significant proteome differences associated with protein synthesis, metabolism, microglia marker expression, and environmental sensors. Culturing microglia induces rapidly increased growth, protein content, and inflammatory protein expression. These changes are restored by engrafting in vitro cells into the brain, with xenografted human embryonic stem cell (hESC)-derived microglia closely resembling microglia from the human brain. These data provide an important resource for the field and highlight important considerations needed when using model systems to study human physiology and pathology of microglia

Variations in TcdB Activity and the Hypervirulence of Emerging Strains of Clostridium difficile

Hypervirulent strains of Clostridium difficile have emerged over the past decade, increasing the morbidity and mortality of patients infected by this opportunistic pathogen. Recent work suggested the major C. difficile virulence factor, TcdB, from hypervirulent strains (TcdBHV) was more cytotoxic in vitro than TcdB from historical strains (TcdBHIST). The current study investigated the in vivo impact of altered TcdB tropism, and the underlying mechanism responsible for the differences in activity between the two forms of this toxin. A combination of protein sequence analyses, in vivo studies using a Danio rerio model system, and cell entry combined with fluorescence assays were used to define the critical differences between TcdBHV and TcdBHIST. Sequence analysis found that TcdB was the most variable protein expressed from the pathogenicity locus of C. difficile. In line with these sequence differences, the in vivo effects of TcdBHV were found to be substantially broader and more pronounced than those caused by TcdBHIST. The increased toxicity of TcdBHV was related to the toxin's ability to enter cells more rapidly and at an earlier stage in endocytosis than TcdBHIST. The underlying biochemical mechanism for more rapid cell entry was identified in experiments demonstrating that TcdBHV undergoes acid-induced conformational changes at a pH much higher than that of TcdBHIST. Such pH-related conformational changes are known to be the inciting step in membrane insertion and translocation for TcdB. These data provide insight into a critical change in TcdB activity that contributes to the emerging hypervirulence of C. difficile

WSES guidelines for management of Clostridium difficile infection in surgical patients

In the last two decades there have been dramatic changes in the epidemiology of Clostridium difficile infection (CDI), with increases in incidence and severity of disease in many countries worldwide. The incidence of CDI has also increased in surgical patients. Optimization of management of C difficile, has therefore become increasingly urgent. An international multidisciplinary panel of experts prepared evidenced-based World Society of Emergency Surgery (WSES) guidelines for management of CDI in surgical patients.Peer reviewe

Possibility of partial replacement of sodium chloride with potassium chloride and ammonium chloride in chicken ćevapčići (kebabs)

Abstract The goal of this study was to investigate the influence of reducing sodium chloride content in chicken ćevapčići (kebabs) by partial replacement of sodium chloride with potassium chloride and ammonium chloride, with the target of achieving the optimal salty taste. The trial consisted of five groups. In the control group of chicken ćevapčići, only sodium chloride was added. In group 1, one third of sodium chloride was replaced with potassium chloride; in group 2 one half of the sodium chloride was replaced with potassium chloride; in group 3, one third of sodium chloride was replaced with ammonium chloride. In group 4, sodium chloride was half reduced and one quarter of ammonium chloride in the relation to control group was added. Sensory evaluation was performed by ten trained assessors using numeric scales. Evaluations of colour acceptability and consistency showed there were no statistical differences (P&gt;0.05) between the ćevapčići. The most expressed saltiness was evaluated in the control ćevapčići group due to it having the largest amount of added sodium chloride, as well in group 3 ćevapčići, wherein one third of the sodium chloride was replaced with ammonium chloride.</jats:p

Impact of COVID-19 pandemic on food supply chain: An overview

Abstract Since 2020, the rapid spread of the SARS-CoV-2 virus has caused the global pandemic COVID-19, generating health, economic and social impacts. The rapid spread of the infection in the human population required an accelerated adaptation to the new circumstances to protect human health and mitigate financial losses. As the ongoing pandemic has caused reported cases in the multi-millions, all stakeholders need to prevent further outbreaks and mitigate associated risks. Hence, besides government, health care systems, business stakeholders, public authorities, non-governmental organizations, and other socially responsible associations, the food sector has a crucial role in combating COVID-19. The food sector in this context is referred to as every actor in the food supply chain. This paper explores the difficulties in the entire food supply chain’s reactions to the pandemic crisis and underlines the meat sector’s response.</jats:p

Nitrite content in meat products from the Serbian market and estimated intake

Abstract The aim of this study was to determine levels of nitrites in some meat products sold on the Serbian market over a period of 3 years (2018-2020) and to compare results with maximum residue levels as well to discuss dietary exposure of the Serbian adult population to nitrites.A total of 1291 meat product samples, produced by the Serbian meat industry or imported (509 dry fermented sausages, 37 semi-dry fermented sausages, 451 finely minced cooked sausages and 294 coarsely minced cooked sausages), were obtained from the Serbian retail market during 2018-2020.Higher mean levels of nitrite content, expressed as NaNO2, were found in cooked sausages (40.35 mg kg-1, finely minced and 33.75 mg kg-1, coarsely minced) compared to fermented sausages (1.86 mg kg-1 dry fermented and 1.83 mg kg-1, semi-dry fermented).The average dietary exposure to nitrites, expressed as nitrite ion, for the Serbian adult population varies from 0.001 to 0.015 mg kg-1body weight (BW) day-1 and was far below the European acceptable daily intake (0.07 mg kg-1 BW day-1). In conclusion, the concentrations of nitrite in all meat products were below established maximum permitted levels (national and European), indicating that the use of nitrite as a food additive in Serbia is generally in line with existing regulations.</jats:p

Food contact surfaces and food handler’s hygiene in one Serbian retail chain–estimation and trend

Abstract This research aimed to investigate the efficiency of sanitary procedures (cleaning, washing, disinfection) applied on food contact surfaces and food handlers’ hands in one retail chain in Serbia. For that reason, a total of 364 swabs of food contact surfaces and 86 food handlers’ hand swabs were investigated for microbiological parameters of process hygiene. The results showed that 15.66% (57 of 365) swabs of food contact surfaces, and 5.81% (5 of 86) swabs from the food handlers’ hands, failed to meet the criteria laid down in the self-control plans of the food business operators. Therefore, continuous training of employees on the proper application of sanitation procedures is essential for efficient GHP and HACCP.</jats:p