Research – New details behind how the Shigella pathogen delivers bacterial proteins into our cells

Science Daily

Shigella - kswfoodworld

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Shigella, a bacterial pathogen that causes dysentery and is the leading cause of childhood diarrheal diseases, inserts a pore called a translocon into an infected person’s intestinal cells and then injects bacterial proteins into the cells. There, the proteins hijack the cells’ machinery to help Shigella multiply. In a study published in mBio, a team at Massachusetts General Hospital (MGH) has uncovered important details about Shigella‘s translocon, which may help researchers develop an effective strategy to block this critical component of infection.

Shigella infects our gut by manipulating our intestinal cells and tricking them into letting the Shigella inside. In fact, there are many bacterial pathogens that use this same, or similar, mechanism to infect us,” says lead author Poyin Chen, PhD, a postdoctoral fellow at MGH. “This translocon pore is essentially the gateway through which bacterial proteins get pumped into our cells. We know that this structure is made of two proteins — IpaB and IpaC — but what we don’t know is how these proteins fit together to make this pore.”

When the investigators used protein mapping techniques to look closely at translocons when they were embedded in cell membranes, they were able to see which of the two proteins — specifically IpaB — makes up the inner ring of the pore. “If you think of the translocon pore as a donut, this would be the walls of the donut hole. This finding is important because this is the part of the translocon pore that directly interacts with bacterial proteins as they are injected into our cells,” explains Chen. “With the findings from this study, we can begin to understand if this pore acts as a slippery tube that bacterial proteins travel through or if the translocon pore can control the flow of bacterial proteins into our cells.”

Such details may help investigators target the translocon and block the entry of Shigella proteins into cells. “For something that is so essential to establishing infection, we know terribly little of how it’s made and how it works,” says Chen. “As we gain a better understanding of its parts, we will be able to approach the structure as a whole and maybe even find ways to neutralize the function of this structure to prevent infection before it can begin.”

Co-authors include Brian C. Russo, Jeffrey K. Duncan-Lowey, Natasha Bitar, Keith Egger and Marcia B. Goldberg.

This work has been supported by the National Institutes of Health, the Massachusetts General Hospital Executive Committee on Research Tosteson Award, and the Charles A. King Trust Postdoctoral Research Fellowship Program.

Research – Editorial: Vibrio Species in the Food Processing Chain

Frontiers in Microbiology

Food Illness

Editorial on the Research Topic
Vibrio Species in the Food Processing Chain

Rising concern about the foodborne illnesses caused by pathogenic Vibrio species (mainly V. parahaemolyticus, V. cholera, and V. vulnificus) has led to a strengthening of research on the characterization of the presence of the genus in food matrices, virulence genes, pandemic markers, and the correlation between clinical and environmental isolates from different ecosystems. The emergence of antimicrobial resistance strains (AMR) in Vibrio spp. may produce a decrease in the effectiveness of commonly used antibiotics, thus posing a threat to public health. Progress in genomic studies has identified motile elements implied in gene transfer that may give birth to developing surveillance strategies for risk mitigation. The development of new infection models that can predict the pathogenesis of Vibrio spp. and the use of high-throughput sequencing techniques for serogroup genes may be useful tools for understanding molecular pathways and the infectivity of Vibrio spp. food isolates. In this Research Topic, different approaches, aiming at characterizing Vibrio spp. from aquaculture, marine, and vegetable ecosystems, together with the evaluation of microbial behavior and the development of new infection and serogroup models, are shown.

A mini-review by Dutta et al. discusses the role and antimicrobial resistance of pathogenic Vibrio spp. They present potential sources of antibiotic resistance genes for Vibrio spp., including the horizontal gene transmission from other pathogens as the main route. This has shown the genetic basis of the emergence of multidrug and extensively multidrug resistant Vibrio spp. through different types of highly mobile elements that can be extensively propagated among bacteria. The use of phage or probiotic therapies as alternative treatments for the inactivation of antibiotic resistant species of Vibrio may be helped by the maintenance of good hygiene practices and processing technologies to protect public health.

Antibiotic resistance genes can also originate from the environment, such as wastewater effluents or sediments in marine or aquaculture habitats. In this regard, Siddique et al. studied the characterization of pathogenic V. parahaemolyticus in a fish farm ecosystem (tilapia, rui, and shrimp). Among the 216 samples, 60.2% were positive for the pathogen, including 323 isolates of which 17 harboured the trh virulence gene gene. They confirm the presence of resistant strains to amoxicillin, ampicillin, and penicillin. Pathogenicity was further confirmed by the fluid accumulation in the ileal loop of rabbits being O8: KUT, the most predominant pathogenic serotype.

The presence and characterization of V. parahaemolyticus and V. vulnificus in marine and estuarine environments was studied by da Silva et al. They found 150 isolates of V. parahaemolyticus, including 52 positives for trh gene, and 129 of V. vulnificus from water and blue crab samples. PFGE and agglutination tests were used for molecular subtyping and determination of antibiotic resistance. The study showed the high presence of the O5 pathogenic serotype, together with the multidrug resistant isolates (41%) and the high genetic diversity of both Vibrio species, as no correlations were found among the sampling sites, antimicrobial resistance profiles, and pathogenicity.

The associated presence of Vibrio spp. in water ecosystems may underestimate their origin from other environmental and food sources. Ready-To-Eat vegetables can harbor pathogenic Vibrio spp. if poor manufacturing, hygiene, and storage practices are followed. Igbinosa et al. evaluated the presence of V. parahaemolyticus in minimally processed vegetables. Among the 63 isolates, they found microbial counts from 1.5 to 1,000 MPN/g and drug resistant isolates to ampicillin and cefotaxime mainly (>60%). They studied the biofilm formation finding that 23.8% of the isolates were strong biofilm producers. Regarding the presence of virulence genes, 100, 14.3, and 31.8% of the isolates harbored the toxR gene, trh, and tdh determinants, respectively.

The microbial behavior of Vibrio spp. can be quantified with predictive models. Posada-Izquierdo et al. investigated the fate of a Vibrio spp. cocktail inoculated in lye-treated table olives for 22 days. A predictive growth model was developed as a function of salt concentration (2–12%) and pH (4–9) using a synthetic medium and table olive brines. They found a higher effect of salt concentration than of pH for the growth inhibition of Vibrio spp. However, they were not able to proliferate in the table olives during fermentation, highlighting that phenolics compounds could exert a clear antimicrobial effect.

The disposal of reliable models to predict the pathogenesis of Vibrio spp. are increasingly needed since the use of virulence markers could not fully elucidate the presence of long-standing virulence indicators. This was demonstrated by Santos et al. using clinical and environmental V. parahaemolyticus isolates in two systemic infection models, namely mice and Galleria mellonella larvae. Interestingly, non-pathogenic environmental isolates produced lethal infections regardless of their source, serotype, and genotype (tdh, orf8, toxRSnew, and vpadF). A high correlation was found in the assayed models, supporting that G. mellonella larvae can be used as an alternative model to study the pathogenesis of V. parahaemolyticus.

Recently, the use of high-throughput sequencing technologies has aided researchers in deciphering the genome of different species. This was essential to provide complete knowledge of the molecular and metabolic pathways of microorganisms and the identification of virulence gene clusters. Bian et al. have developed VPsero, a rapid serotyping tool for V. parahaemolyticus using serogroup specific genes obtained from whole-genome sequencing data. The algorithm, based on the comparison of lipopolysaccharide and capsular polysaccharide gene clusters covered 43 K and 12 O serogroups. The authors showed the high sensitivity and specificity of the tool (>0.91), though limitations could be faced in future studies, such as the addition of new serogroups, the verification of the quality of assembled genomes and the availability of short reads.

This Research Topic presents a collection of manuscripts highlighting relevant findings in the pathogenesis of Vibrio spp. in the food chain and suggests future directions for research, enabling progress in the development of novel analytical methods and surveillance actions to mitigate the emerging risk posed by these human pathogens.

RASFF Alerts – Salmonella – Polish Chicken Products- Sesame Seeds – Black Beef – Okok Herb -Rabbit Thighs – Frozen Duck –

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Salmonela en pimienta negra de Brasil. Salmonela in black pepper from Brazil in Spain

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Salmonella Enteritidis in chilled chicken legs from Poland in Latvia

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Salmonella typhimurium in fresh okok-herb from Cameroon in Finland

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Salmonella spp. in sesame seeds from India in Poland

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Salmonella Enteritidis in rabbit thighs from China in Germany and Czech Republic

RASFF

Salmonella typhimurium in frozen duck from Hungary in Slovenia

RASFF

Salmonella spp. in Chicken meat portion used in chicken skewers from Germany in Belgium, France, Germany

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Salmonella in sesame snack from India, via the Netherlands

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Salmonella Newport in poultry meat from Poland in Slovakia and Poland

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Salmonella enteritidis in frozen hen filet breast, origin Poland in Romania

RASFF Alerts – E.coli – Mussels – Clams

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Escherichia coli oltre i limiti in vongole (Camelea gallina) dall’Italia //too high count of Escherichia coli in clams (Camelea gallina) from Italy in Italy and Spain

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Escherichia coli in mussels from Netherlands in Belgium

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Escherichia coli in live mussels (Mytilus galloprovincialis) from Spain in Italy

RASFF Alerts – STEC E.coli – Boneless Beef – Dough for Cookies

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STEC stx2 in Chilled boneless beef from Brazil in Belgium and Netherlands

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VTEC/STEC in ready dough for cookies from Germany in Austria

RASFF Alerts – Listeria monocytogenes – Cheese – Smoked and Oiled Salted Herring – Salmon Pate

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Saint-Nectaire Cheese – from France  Listeria monocytogenes – in Germany, Italy and Luxembourg

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Listeria monocytogenes in smoked and oiled salted herring fillets from Poland in France

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Listeria Monocytogenes in salmon paté from Great Britain in France, Netherlands and Spain

RASFF Alert- Bacillus cereus – Organic Barley Grass Powder

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Bacillus cereus in organic barley grass powder from Hungary in Germany

RASFF Alerts – Aflatoxin – Dried Figs – Pistachios – Hazelnuts – Peanuts –

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High Aflatoxin values in shell hazelnuts from Georgia in Italy

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Aflatoxins in pistachios in shell from Iran in Poland

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Aflatoxin B1 in hazelnuts from Turkey in Germany

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Aflatoxins in dried organic figs from Turkey in Germany

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Aflatoxins in pistachios from Turkey in Germany

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Aflatossine in fichi secchi/aflatoxins above legal limit in dried figs from Turkey in Italy

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AFLATOSSINE OLTRE I LIMITI MASSIMI CONSENTITI IN ARACHIDI IN GUSCIO DA EGITTO/ Peanuts in Italy

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Aflatossine in fichi secchi dalla Turchia in Italy

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Aflatoxinas en cacahuete molido de Paraguay/ Afltatoxins in peanuts from Paraguay in Spain

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Alto contenuto di aflatossine in fichi secchi dalla Turchia//high content of aflatoxins in dried figs from Turkey in Italy

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Excessive levels of aflatoxin B1 and total aflatoxin in unshelled peanuts from Egypt in Germany and Italy

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Aflatoxin and clothianidin in californian pistachio meal in France

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Alto contenuto di aflatossine in fichi secchi dalla Turchia/ aflatoxins above legal limit in dried figs from Turkey in Italy

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AFLATOXINS IN RAW PISTACHIO FROM TURCIA in Romania

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Aflatoxins in hazelnut kernels from Azerbaijan

RASFF Alerts – Animal Feed – Enterobacteriaceae – Dog Chews

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High content of Enterobacteriaceae in dog chews from China in Spain

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Enterobacteriaceae in dog chews from India in Spain

RASFF Alerts – Animal Feed -Salmonella – Yeast – Rapeseed Meal

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Salmonella Tennessee in rapeseed meal from Czech Republic in Germany

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Salmonella in yeast from Poland in Austria