Isolation, Specification, Molecular Biology Assessment and Vaccine Development of Clostridium in Iran: A Review

Screening and Identification of DNA Nanostructure Aptamer Using the SELEX Method for ‎Detection of Epsilon Toxin

Background

Epsilon toxin (ETX), produced by Clostridium perfringens, is one of the most potent toxins known, with a lethal potency approaching that of botulinum neurotoxins. Epsilon toxin is responsible for enteritis. Therefore, the development of rapid and simple methods to detect ETX is imperative. Aptamers are single-stranded oligonucleotides that can bind tightly to specific target molecules with an affinity comparable to that of monoclonal antibodies (mAbs). DNA aptamers can serve as tools for the molecular identification of organisms, such as pathogen subspecies.

Objectives

This study aimed to isolate high-affinity single-stranded DNA (ssDNA) aptamers against ETX.

Methods

This study identified aptamers using the Systematic Evolution of Ligands by Exponential Enrichment (SELEX) method, enzyme-linked apta-sorbent assay (ELASA), and surface plasmon resonance (SPR) to determine the affinity and specificity of the newly obtained aptamers targeting ETX.

Results

Several aptamers obtained through the SELEX process were studied. Among them, 2 aptamers, ETX clone 3 (ETX3; dissociation constant (Kd = 8.4 ± 2.4E-9M) and ETX11 (Kd = 6.3 ± 1.3E-9M) had favorable specificity for ETX. The limits of detection were 0.21 and 0.08 μg/mL for ETX3 and ETX11, respectively.‎.

Conclusions

The discovered aptamers can be used in various aptamer-based rapid diagnostic tests for the detection of ETX.

First molecular evidence of Clostridium perfringens in adult Fasciola spp. isolates in cattle hosts

Fasciolosis is a parasitic disease caused by Fasciola spp. It is a prevalent helminth infection globally. Clostridial hepatitis is a general name refer to disorders caused by a few clostridial agents that most severely affect the liver. Migration of young parasite forms (mostly Fasciola hepatica) in the parenchymal tissue of the liver causes necrosis and anaerobic environment, stimulating the proliferation of C. novyi type B spores. This study investigated the occurrence of Clostridium spp in adult Fasciola spp isolates. Isolates (n = 100) were collected from the bile ducts of infected cattle after slaughter. Total genomic DNA was extracted from each sample. A multiplex-PCR based on the flagellin C (fliC) gene was used for quick identification of C. chauvoei, C. haemolyticum, C. novyi types A and B, and C. septicum. In addition, a pair of primers Cpa (F) and Cpa (R) were used for detection of the C. perfringens alpha toxin gene. The products were sequenced. No band was obtained after multiplex-PCR of the fliC gene. A 247 bp band was detected in two isolates using the Cpa primers. BLAST analysis of these two isolates characterized both as C. perfringens alpha toxin. This is the first description of the molecular detection of C. perfringens in flukes. Further studies are needed to investigate whether Clostridum species is also carried by other developmental forms (egg and larval stages) of Fasciola spp.

Enhanced expression of recombinant beta toxin of Clostridium perfringens type B using a commercially available Escherichia coli strain

Clostridium perfringens beta toxin is only produced by types B and C and plays an important role in many human and animal diseases, causing fatal conditions that originate in the intestines. We compared the expression of C. perfringens type B vaccine strain recombinant beta toxin gene in the Escherichia coli strains Rosetta^TM(DE3) and BL21(DE3). The beta toxin gene was extracted from pJETβ and ligated with pET22b(+). pET22β was transformed into E. coli strains BL21(DE3) and Rosetta^TM(DE3). Recombinant protein was expressed as a soluble protein after isopropyl β-D-1-thiogalactopyranoside (IPTG) induction in strain Rosetta^TM(DE3) but not in BL21(DE3). Expression was optimised by growing recombinant cells at 37 °C and at an induction of 0.5 mM, 1 mM, 1.5 mM IPTG. Expression was evaluated using sodium dodecyl sulfate Polyacrylamide gel electrophoresis (SDS-PAGE). The recombinant protein was purified via Ni-NTA and was analysed using western blot. We concluded that E. coli strain Rosetta^TM(DE3) can enhance the expression of C. perfringens recombinant beta toxin.