Regulatory elements of stx2 gene and the expression level of Shiga-like toxin 2 in Escherichia coli O157:H7

One problem, multiple potential targets: Where are we now in the development of small molecule inhibitors against Shiga toxin?

Shiga toxin-producing Escherichia coli (STEC) are a group of enteric pathogens which carry phage-encoded Shiga toxins (Stx). STEC infections begin with severe abdominal pain and non-bloody diarrhoea, which can progress to bloody diarrhoea after approximately 4-days post-infection. In high-risk groups such as children and the elderly, patients may develop haemolytic uremic syndrome (HUS). HUS is characterised by microangiopathic haemolytic anaemia, thrombocytopenia, and in severe disease acute renal failure. Traditional antibiotics have been linked with increased toxin production due to the activation of recA-mediated bacterial stress response, resulting in poorer patient outcomes. Therefore, treatment relies on supportive therapies. Antivirulence strategies have been explored as an alternative treatment for bacterial infections and blockers of virulence factors such as the Type III Secretion System. Recent improvements in the mechanistic understanding of the Stx pathway have led to the design of inhibitors to disrupt the pathway, leading to toxin-mediated ribosome damage. However, compounds have yet to progress beyond Phase III clinical trials successfully. This review explores the progress in developing small molecule inhibitors by collating lead compounds derived from in-silico and experimental approaches.

Phenotype and genotype of Boerka goats raised in Bali

Background and Aim

Boerka goats are the new breed in Bali targeted at meeting the increasing demand for lamb. They are meat-type goats created by crossing male Boer and female Kacang breeds. This new breed is expected to have good adaptation in a poor environment, such as Kacang goats and produce good quality lamb as Boer goats. Therefore, this study aimed to examine phenotypic and genotypic characteristics of Boerka goats raised in Bali.

Materials and Methods

A total of 16 female Boerka goats at 2 years old collected from a group of livestock farmers in Sanda Village were used as samples. This observational study began with observations of qualitative characteristics and morphometric measurements of goats, followed by polymerase chain reaction (PCR) of the growth hormone (GH) gene using GH5F and GH5R primers. Polymerase chain reaction products were then sequenced and analyzed with the MEGA 11 program.

Results

The results showed that all Boerka goats had stuck-down ears, the heads were predominantly brown in color (62.5%), the body color pattern tends to be white (87.50%), and the tail color pattern was also dominated by white (62.5%). In morphometric terms, the samples were close to Kacang goats based on the body weight, head length, head width, chest width, depth, and circumference, left front leg circumference, ear length, ear width, tail length, tail width, and flank height except for head height, body length, horn length, and shoulder height. Analysis of the GH gene showed that Boerka goats had a nucleotide composition dominated by the purine base guanine (26.5%) and pyrimidine cytosine (31.8%). Furthermore, they formed a separate cluster with a genetic distance of 14.1% to the Anhui White breed from China, the Tibetan breed, and the Swiss Saanen breed.

Conclusion

Boerka goats raised in Bali have phenotypes, including qualitative characteristics and morphometric measurements close to Kacang goats. As meat-type goats, they also form a separate cluster distinct from similar types worldwide.

Molecular identification of lactic acid bacteria SR6 strain and evaluation of its activity as an anticancer in T47D cell line

Background and Aim: Breast cancer is the most common type of cancer in women because it attacks the productive age. Preliminary studies showed that lactic acid bacteria (LAB) strain SR6 from the Bali cattle colon has the potential to act as a superior probiotic. It is also assumed that its bacteriocin structure is specific and has a strong relationship with the specificity of the ligand and its biological activity at a receptor. Therefore, this study aims to assess the use of local LAB strains, which produce bacteriocins as anticancer agents, as well as to identify the bacteria as potent producers molecularly. Materials and Methods: The study was initiated by cultivating LAB SR6 strain from stock isolates on De Man, Rogosa, and Sharpe (Oxoid, CM 0369, England) broth media. It was then confirmed molecularly through analysis of the 16S ribosomal ribonucleic acid gene. Subsequently, its anticancer activity was tested by assessing the cytotoxic activity in T47D cell culture using the 3-(4, 5 dimetiltiazol-2-yl)-2.5-diphenyl tetrazolium bromide (Invitrogen M6494, US) method. Results: The results showed that the LAB strain SR6 was identified molecularly as Pediococcus pentosaceus. Furthermore, it had a toxic effect on T47D cells, which was indicated by the number of deaths after treatment with the extracellular protein of the strain, especially at the 50% total cell volume level. Conclusion: Based on the toxic effect of the strain on human T47D cells, the LAB SR6 isolate, which was identified as P. pentosaceus has the potential to be developed as a good anticancer drug against breast cancer. However, there is a need to carry out an integrated study to fully explore the suitability of bacteriocins as in vivo therapeutics against the disease completely.

Scalable Reporter Assays to Analyze the Regulation of stx2 Expression in Shiga Toxin-Producing Enteropathogens

Stx2 is the major virulence factor of EHEC and is associated with an increased risk for HUS in infected patients. The conditions influencing its expression in the intestinal tract are largely unknown. For optimal management and treatment of infected patients, the identification of environmental conditions modulating Stx2 levels in the human gut is of central importance. In this study, we established a set of chromosomal stx2 reporter assays. One system is based on superfolder GFP (sfGFP) using a T7 polymerase/T7 promoter-based amplification loop. This reporter can be used to analyze stx2 expression at the single-cell level using FACSs and fluorescence microscopy. The other system is based on the cytosolic release of the Gaussia princeps luciferase (gluc). This latter reporter proves to be a highly sensitive and scalable reporter assay that can be used to quantify reporter protein in the culture supernatant. We envision that this new set of reporter tools will be highly useful to comprehensively analyze the influence of environmental and host factors, including drugs, small metabolites and the microbiota, on Stx2 release and thereby serve the identification of risk factors and new therapies in Stx-mediated pathologies.

Shiga toxin-producing Escherichia coli isolated from pasteurized dairy products from Bahia, Brazil

The presence of pathogenic Shiga toxin-producing Escherichia coli (STEC) in dairy products represents a public health concern because of its ability to produce the toxins Stx1 and Stx2, which cause intestinal diseases. Monitoring the stages of milk production and checking dairy products for contamination are crucial steps to ensure dairy safety. This study aimed to report the occurrence of thermotolerant coliforms, E. coli, and STEC strains in pasteurized dairy products and to evaluate the antibiotic resistance profiles, serotypes, and characterizations of the STEC isolates by pulsed-field gel electrophoresis. We obtained a total of 138 pasteurized dairy products from 15 processing plants in Bahia, Brazil, to examine coliforms, E. coli, and STEC strains. We found that 43% of samples (59/138) contained thermotolerant coliforms, and 30% (42/138) did not comply with Brazilian regulations. Overall, 6% (9/138) were positive for E. coli and 4% (5/138) were positive for STEC. We recovered 9 STEC isolates from pasteurized cream (2/9), Minas Padrão cheese (2/9), Minas Frescal cheese (4/9), and ricotta (1/9). All isolates were stx2-positive, and 2 were eae-positive. All isolates were negative for the "big 6" STEC serogroups, belonging instead to serotypes ONT:HNT, ONT:H12, O148:H-, OR:H40, OR:HNT, and O148:HNT. Pulsed-field gel electrophoresis revealed 100% genetic similarity among 3 isolates from 2 different samples produced in the same production facility, which may suggest cross-contamination. As well, we found isolates that were 98% similar but in samples produced in different production facilities, suggesting a mutual source of contamination or a circulating strain. Two STEC strains exhibited resistance to streptomycin. Although the isolates presented a low resistance profile and no strain belonged to the "big 6" pathogenic group, the circulation of stx2-positive STEC strains in ready-to-eat products highlights the importance of epidemiological surveillance inside the Brazilian dairy chain.

Shiga-Like Toxin Produced by Local Isolates of Escherichia coli O157:H7 Induces Apoptosis of the T47 Breast Cancer Cell Line

Purpose:

It has been suggested that Shiga-like toxins produced by Escherichia coli O157:H7 could be used as novel therapeutic agents against malignant tumors. In addition, the antitumor potency of local isolates from Indonesia, which are known to be less toxic than the control isolate ATCC 43894, has not yet been tested. The study aimed to analyze local strains of E. coli O157:H7 as a proapoptosis agent on the T47 breast cancer cell line.

Methods:

As many as 30 culture cells of T47D breast cancer cell line were subjected to purified extracts of Shiga-like toxin originating from 5 local isolates of E. coli O157:H7: KL-48(2), SM-25(1), SM-7(1), DS-21(4), and 1 isolate ATCC 43894 which was used as a control. Toxin production of each isolate was detected using a sandwich enzyme-linked immunosorbent assay, and the treatment of cell lines was observed for 24 hours, with 2 replications; 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide tests and acridine orange/ethidium bromide double staining assays were used for detection and analyses of apoptosis.

Results:

The study showed 2 local strains of E. coli O157:H7 (codes KL-48(2) and SM-25(1)) had toxins positive at titer 5 and 10 μg/100 μL. These titers were lower than the control isolate ATCC 43894, but they had a necrosis effect higher (P < .05), ie, 80.3%, than control isolate, ie, 63.3%. Other local strain SM-25(1) also had a good necrosis effect. It has a nondifferent necrosis effect (P > .05) with the control isolate ATCC 43894, ie, 13.0% from 13.3%.

Conclusion:

This study concludes that the Shiga toxin produced by E. coli O157:H7 local isolate (Indonesia) has potential as a proapoptotic and/or necrotic agent for treating T47 breast cancer cell lines, as effectively as ATCC 43894 control isolates.

Molecular characteristic of Pasteurella multocida isolates from Sumba Island at East Nusa Tenggara Province, Indonesia

AIM

This study aimed to determine the molecular characteristics of Pasteurella multocida isolates originated from Sumba Island, East Nusa Tenggara Province.

MATERIALS AND METHODS

The isolates of P. multocida stored in frozen storage were cultured in blood agar as a selective medium and identified conventionally. Molecular tests were initiated by DNA isolation and then followed by polymerase chain reaction tests with specific primers for the determination of P. multocida serotype A or B. Positive strain of serotype B was then confirmed molecularly using 16S rRNA gene primer and followed by the sequencing of nucleotides.

RESULTS

The study showed that both P. multocida isolates from Sumba island, i.e. PM1 is isolated from East Sumba district, while PM2 isolated from West Sumba district have 99.6% homology. Both isolates also known have 99% similarities with P. multocida originated from India, Britain, and Japan, respectively. The isolates share the same clade in the phylogenetic tree.

CONCLUSION

The 16S rRNA sequencing revealed a high similarity of P. multocida serotype B:2 isolated from Sumba island with the Indian isolates although the sample size is very small. Therefore, further molecular studies like multilocus sequence typing, VNTR need to be performed using a larger number of samples to establish the genetic relatedness observed in this study.

Overexpressed Proteins in Hypervirulent Clade 8 and Clade 6 Strains of Escherichia coli O157:H7 Compared to E. coli O157:H7 EDL933 Clade 3 Strain

Escherichia coli O157:H7 is responsible for severe diarrhea and hemolytic uremic syndrome (HUS), and predominantly affects children under 5 years. The major virulence traits are Shiga toxins, necessary to develop HUS and the Type III Secretion System (T3SS) through which bacteria translocate effector proteins directly into the host cell. By SNPs typing, E. coli O157:H7 was separated into nine different clades. Clade 8 and clade 6 strains were more frequently associated with severe disease and HUS. In this study, we aimed to identify differentially expressed proteins in two strains of E. coli O157:H7 (clade 8 and clade 6), obtained from cattle and compared them with the well characterized reference EDL933 strain (clade 3). Clade 8 and clade 6 strains show enhanced pathogenicity in a mouse model and virulence-related properties. Proteins were extracted and analyzed using the TMT-6plex labeling strategy associated with two dimensional liquid chromatography and mass spectrometry in tandem. We detected 2241 proteins in the cell extract and 1787 proteins in the culture supernatants. Attention was focused on the proteins related to virulence, overexpressed in clade 6 and 8 strains compared to EDL933 strain. The proteins relevant overexpressed in clade 8 strain were the curli protein CsgC, a transcriptional activator (PchE), phage proteins, Stx2, FlgM and FlgD, a dienelactone hydrolase, CheW and CheY, and the SPATE protease EspP. For clade 6 strain, a high overexpression of phage proteins was detected, mostly from Stx2 encoding phage, including Stx2, flagellin and the protease TagA, EDL933_p0016, dienelactone hydrolase, and Haemolysin A, amongst others with unknown function. Some of these proteins were analyzed by RT-qPCR to corroborate the proteomic data. Clade 6 and clade 8 strains showed enhanced transcription of 10 out of 12 genes compared to EDL933. These results may provide new insights in E. coli O157:H7 mechanisms of pathogenesis.