Investigate the immunogenic and protective effect of trivalent chimeric protein containing IpaD-StxB-TolC antigens as a vaccine candidate against S. dysenteri and S. flexneri

BACKGROUND

s: Shigella spp. causes bloody diarrhea and leads to death, especially in children. Chimeric proteins containing virulence factors can prevent Shigella infection. The purpose of this study is to investigate the immunogenic and protective effect of trivalent chimeric protein containing IpaD-StxB-TolC antigens against shiga toxin, S. dysenteri and S. flexneri in vitro and in vivo conditions.

METHODS

Recombinant vector was transferred to E. coli BL21. The expression of the chimeric protein was confirmed by SDS PAGE and purified using the Ni-NTA column. Mice were immunized with recombinant protein and antibody titer was evaluated by ELISA. 10, 25 and 50 LD₅₀ of Shiga toxin neutralization was evaluated in vitro (Vero cell line) and in vivo conditions. Also, the challenge of immunized mice with 10, 25 and 50 LD₅₀ of S. dysentery and S. flexneri was done.

RESULTS

The expression and purification of the recombinant protein with 60.6 kDa was done. ELISA showed increased antibody titer against the chimeric protein. MTT assay indicated that 1/8000 dilution of the sera had a 51% of cell viability against the toxin in Vero cell line. The challenge of mice immunized with toxin showed that the mice had complete protection against 10 and 25 LD₅₀ of toxin and had 40% survival against 50 LD₅₀. Mice receiving 10 and 25 LD₅₀ of S. dysenteri and S. flexneri had 100% protection and in 50 LD₅₀ the survival rate was 60 and 50%, respectively. Organ burden showed that the amount of bacterial colonization in immunized mice was 1 × 10⁴ CFU/mL, which was significantly different from the control group.

CONCLUSION

This study showed that chimeric proteins can create favorable immunogenicity in the host as vaccine candidates.

Using next-generation sequencing to develop a Shigella species threshold and profile faecal samples from suspected diarrhoea cases

Globally, it is estimated that there are 2 billion cases of diarrhoeal disease each year, with 525,000 children under the age of 5 years, dying from diarrhoea. This also affects 1 in 5 people in the UK each year. Rapid diagnosis, appropriate treatment and infection control measures are, therefore, particularly important. Currently, Public Health Wales and England Microbiology Division test for five key bacterial gastrointestinal pathogens, i.e. Escherichia coli O157 (VTEC), Shigella dysenteriae, Salmonella spp., Campylobacter spp. and Clostridioides difficile. There is, however, a poor success rate with identification of these pathogens, leaving the patient at risk from untreated infections. This study has developed effective and reliable tools with a high positive outcome for diagnosis of diarrhoeal infection. The study blindly analysed 592 samples, with the most abundant species being Shigella sonnei at 15%, and the top genus Bacteroides at 26%. Campylobacter spp. had an abundance of 4%, Clostridium difficile 3%, and Salmonella spp. 0.2%. There were also significant differences in abundance at genus level, between the Flemish Gut project and diarrhoea samples, with respect to Shigella (0.2%) and Campylobacter (0.1%). The project introduced a novel Shigella spp. (Escherichia) threshold of 5.32% to determine (Escherichia) a healthy or unhealthy community. A DMBiome model was developed to integrate the 5.32% threshold of Shigella spp., the Public Health laboratory tested pathogens, and two emerging enteropathogens. The overall positive outcome was that 89% of all samples were diagnosed with diarrhoea infections, leaving 11% unknown.

Determined by Label-Free Quantitative Proteomics

Escherichia coli and Shigella spp. causing illnesses in humans represent a genotypically and phenotypically diverse group of pathogens. Although E. coli diversity has been studied by comparative genomics, the intra-species variation at the proteome level is currently unknown. The proteomes of 16 pathogenic E. coli, 2 non-pathogenic E. coli, and 5 Shigella strains originating from 18 phylogenetic lineages are investigated. By applying label-free quantitative proteomics on trypsin-digested cell extracts from bacteria grown on blood agar, 4018 proteins are detected, 3285 of which arequantified, and 261 represented virulence factors. Of 753 proteins quantified in all strains, the levels of 153 vary substantially between strains and are functionally associated mostly with stress response and peripheral metabolism. The levels of proteins associated with the central metabolism vary considerably less than the levels of proteins from other metabolic pathways. Hierarchical clustering analysis based on the protein levels results in strains grouping that differ from that obtained by gene-based phylogenetic analysis. Finally, strains of some E. coli pathotypes have more similar protein profiles even when the strains are not genetically closely related. The results suggest that the degree of genetic relatedness may not necessarily be a good predictor of E. coli phenotypic characteristics.

Microbial quality and antibiotic sensitivity of bacterial isolates in "Tuo-Zaafi" vended in the central business district of tamale

INTRODUCTION

Food safety concerns remain a challenge across nations and among citizens. Microbial contamination of foods and antibiotic resistance constitutes a global threat to food security. The present study assessed microbial quality of "Tuo-Zaafi" sold in the Tamale metropolis as well as antibiotic resistance of isolates from these products.

RESULTS

Samples were collected aseptically and transported to the Spanish laboratory complex of the University for Development Studies, Ghana, for microbial analysis. E. coli which recorded the highest occurrence was detected in 50% of the T.Z samples with bacterial loads ranging from < 100 to 2.3 × 106 cfu/g (4.49 × 105 ± 5.72 × 104 cfu/g). Salmonella spp and Staphylococcus aureus recorded the least occurrence representing 33.3%. There were significant differences in the levels of E. coli, Shigella spp, Salmonella spp, and Staphylococcus aureus (p < .001) across the four zones demarcated. Results of the antibiotic test revealed higher resistance to the antibiotics employed in the present study (81%). Susceptibility of microbes to ciprofloxacin (100%) was the highest, and higher resistance to gentamycin (100%) was observed in this study.

CONCLUSION

The study revealed that T.Z sold in the business district of Tamale could constitute a likely health risk to consumers especially when it is consumed in a cold state. It is hereby recommended that the Food and Drugs Authority (FDA) should enforce food hygiene laws and ensure strict adherence.

Virulence gene profiles of Shigella species isolated from stool specimens in India: its association with clinical manifestation and antimicrobial resistance

Shigella is the major cause of bacillary dysentery worldwide, especially in developing countries. There are several virulence factors essential for the organism to be virulent which are generally present in the virulence plasmid and on chromosomal pathogenicity islands. The present study was undertaken to determine the virulence gene profile of Shigella spp isolated from a clinical specimen and to study their significant association with common clinical symptoms and antimicrobial resistance. Sixty Shigella whole genome sequences, including 22 S. flexneri, 14 S. sonnei, 17 S. boydii and 7 S. dysenteriae were analyzed for the presence of virulence genes. The gene found predominantly in this study were ipaH (90%) followed by sigA (83%), and lpfA (78%) respectively. The virulence genes were significantly higher in S. flexneri, particularly in serotype 2 compared to S. sonnei. Interestingly, a significant association was observed between sigA gene and fever whereas sepA and sigA were found to be associated with diarrhea. Among the studied Shigella isolates, the presence of virulence genes was found higher in isolates resistant to more than three antibiotic classes. The present work revealed the varying incidence of virulence determinants among different Shigella serogroups and shows their contribution to disease severity.

Antibiotic resistance and molecular characterization of shigella isolates recovered from children aged less than 5 years in Manhiça, Southern Mozambique

The objective of this study was to assess antibiotic resistance and the molecular epidemiology of shigella isolates from a case-control study of diarrhoea, conducted from 2007 to 2012 in children aged less than 5 years in Manhiça district, southern Mozambique. All isolates were tested for antimicrobial susceptibility using the disc diffusion method. Polymerase chain reaction was used to detect different molecular mechanisms of antibiotic resistance. Serotyping was performed using specific antisera. The clonal relationship of Shigella flexneri and Shigella sonnei was assessed by pulsed-field gel electrophoresis (PFGE). Of the 67 shigella isolates analysed, 59 were diarrhoeal cases and eight were controls. S. flexneri (70.1%; 47/67) was the most common species, followed by S. sonnei (23.9%; 16/67). The most prevalent S. flexneri serotypes were 2a (38.3%; 18/47), 6 (19.2%; 9/47) and 1b (14.9%; 7/47). High rates of antimicrobial resistance were observed for trimethoprim-sulfametoxazole (92.5%; 62/67), tetracycline (68.7%; 46/67), chloramphenicol (53.7%; 36/67) and ampicillin (50.7%; 34/67). Multi-drug resistance (MDR) was present in 55.2% (37/67) of the isolates and was associated with a case fatality rate of 8.1% (3/37). PFGE revealed 22 clones (16 S. flexneri and 6 S. sonnei), among which P1 (31.9%; 15/47), P9 (17%; 8/47) and P2 (10.6%; 5/47) were the most prevalent clones of S. flexneri. In conclusion, S. flexneri was the most prevalent species, with MDR isolates mainly belonging to three specific clones (P1, P9 and P2). The case fatality rate observed among MDR isolates is a matter of concern, indicating the need for appropriate treatment.

outbreaks

BACKGROUND

Shigellosis remains a serious public health problem and an important cause of morbidity and mortality worldwide. The aim of this study was to characterize fliC and the genetic relatedness of Shigella spp. isolated during a one-year period from children in a suspected outbreak in Tehran, Iran.

METHODS AND RESULTS

Fifty Shigella spp. were isolated from 3779 stool samples of children with diarrhea (prevalence rate: 1.32%). Among the isolates, 92% were characterized as Shigella sonnei, while 6% and 2% were identified as S. flexneri and S. boydii, respectively. S. dysenteriae was not recovered from the patients. All isolates were negative for fliC except for Shigella standard strains. The enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR) profiles allowed differentiating the 50 isolates into 5 ERIC types, which were grouped into five clusters (ET1-ET5). Computer-assisted clustering of the strains showed a high degree of similarity among the isolates.

CONCLUSION

In conclusion, given the clonal correlation of the Shigella strains isolated in this study and the lack of fliC among them, we propose that probably a single or limited fliC-defected Shigella clone spread and caused the outbreak.

CTX-M extended-spectrum β-lactamase-producing Klebsiella spp, Salmonella spp, Shigella spp and Escherichia coli isolates in Iranian hospitals

This study was conducted in Iran in order to assess the distribution of CTX-M type ESBLs producing Enterobacteriaceae. From January 2012 to December 2013, totally 198 E. coli, 139 Klebsiella spp, 54 Salmonella spp and 52 Shigella spp from seven hospitals of six provinces in Iran were screened for resistance to extended-spectrum cephalosporins. After identification and susceptibility testing, isolates presenting multiple-drug resistance (MDR) were evaluated for ESBL production by the disk combination method and by Etest using (cefotaxime and cefotaxime plus clavulanic acid). All isolates were also screened for bla_CTX-M using conventional PCR. A total of 42.92%, 33.81%, 14.81% and 7.69% of the E. coli, Klebsiella spp, Salmonella spp and Shigella spp isolates were MDR, respectively. The presence of CTX-M enzyme among ESBL-producing isolates was 85.18%, 77.7%, 50%, and 66.7%, in E. coli, Klebsiella spp, Salmonella spp and Shigella spp respectively. The overall presence of CTX-M genes in Enterobacteriaceae was 15.4% and among the resistant isolates was 47.6%. This study indicated that resistance to β-lactams mediated by CTX-M enzymes in Iran had similar pattern as in other parts of the world. In order to control the spread of resistance, comprehensive studies and programs are needed.

isolated from stool cultures in two different populations in Southern Israel

Southern Israel is inhabited by Bedouins, living in conditions similar to developing countries and Jews, living in conditions similar to developed countries. We determined the epidemiology of Shigella spp. in these populations. We retrospectively reviewed Shigella spp. stool isolations between 2005-2009. Overall, 3295 isolates were analyzed. S. sonnei was isolated in 2057/3295 (62.4%) and S. flexneri in 1058 (32.1%). S. sonnei was isolated in 1567/1707 (91.8%) from Jewish patients and S. flexneri in 931/1542 (60.4%) from Bedouin patients. Ampicillin resistance increased linearly from 217/373 (58.2%) in 2005 to 186/256 (72.7%) in 2009, (P < 0.001). Trimethoprim-sulfamethoxazole resistance decreased linearly from 328/373 (87.9%) in 2005 to 133/256 (51.9%) in 2009 (P < 0.001). Higher resistance of Shigella spp. to ampicilin and trimethoprim-sulfamethoxazole were found in Jewish patients: 1527/1706 (89.5%) versus 977/1542 (63.4%) (P < 0.0001), 1635/1706 (95.8%) versus 1026/1542 (66.5%) (P < 0.0001). The epidemiology of Shigella spp. infections can differ in populations residing in the same geographical area.

in Tehran, Iran

BACKGROUND AND OBJECTIVES

The emergence of extended-spectrum β-lactamase (ESBL)-producing Shigella spp. is of increasing clinical concern specially in children worldwide. The aim of this study was to investigate the occurrence of extended-spectrum β-lactamase producing Shigella spp. in Tehran, Iran.

MATERIALS AND METHODS

The study included all Shigella isolates recovered from pediatric patients aged less than 12 years admitted to a major pediatric hospital in Tehran, Iran, from 2008 to 2010. Bacterial identification, antimicrobial susceptibility testing, extended spectrum β-lactamases (ESBLs) screening and confirmatory tests were performed according to the standard guidelines. Conjugal transfer experiments and plasmid analysis were also carried out. Polymerase chain reaction and sequencing were used to identify the genetic determinants responsible for ESBL production.

RESULTS

Four out of 55 Shigella isolates, including three S. sonnei and one S. flexneri, showed an ESBL-positive phenotype. Plasmid transfer of the ESBL phenotype was successful for the S. flexneri isolate only. By PCR and sequencing, one S. sonnei isolate tested positive for the CMY-59 gene, while the other two S. sonnei and the S. flexneri isolates tested positive for the bla TEM-1 and bla CTX-M-15 genes.

CONCLUSION

We found the prevalence of ESBL producing Shigella isolates was higher than detection rates observed in many other countries. Our finding raise concerns about the dissemination of ESBL among the strains of endemic S. sonnei throughout the country, because this species is now the most frequently isolated Shigella species in Iran and shigellosis by such strains in the community can pose a significant threat to patients and presents a challenge for disease management.