Literature Review On Clostridium Bacteria And Its Therapeutic Applications

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Abstract

Clostridium is a gram-positive bacillus bacterium. Any disturbance to healthy microbes of GI tract due to antibiotics activates the cytotoxins release by Clostridium, resulting in adverse effects. The toxins released by Clostridium are known as botulinum toxin. Its toxins are potent poisons but have several therapeutic qualities. It can block neuromuscular transmission, and this ability transformed it into a therapeutic tool. Botulinum toxin blocks acetylcholine release at the neuromuscular junction as well as in the sympathetic and parasympathetic neurons. It is used in vaccines to weaken overactive muscles and regulate hypersecretion of glands connected with neurons.

Introduction

Clostridium is a genus of gram-positive bacteria that is rod-shaped and mostly residing in water, soil and GI tract of human, as well as other animals. Most of them are anaerobic, spore-bearing bacillus (Aktories & Wilkins, 2000) but several species are microaerophilic. Inactive cells of this bacteria show high resistance to heat, aridity, and toxins. The cytotoxins released by C. botulinum causes botulism, which is a potent poison known (Aktories, 2008). C. tetani is responsible for tetanus while C. novyi, C. perfringens, and C. septicum contribute to the development of gangrene. There are several other species that cause acute infections in cattle and waterfowl. The most dangerous species is C. difficile that releases its toxins in the intestines and develop the condition known as C. difficile colitis (Aktories & Wilkins, 2000). Though, it is rare but a severe reason of infectious diarrhea, with watery stools and abdominal cramps. The human GI tract is the home of many beneficial microbes that maintain the environment of the tract. Due to any disturbance to this balance the harmful bacteria starts growing releasing its cytotoxins in the absence of competitive microbes. Clostridium belongs to such group that exerts detrimental effects on human beings in such condition. C. difficile was believed to be the reason of pseudomembranous colitis (Salminen & Von Wright, 2004). The isolation of Clostridium difficile from a healthy newborn baby in 1935 changes the perception regarding this organism. In 1974, it came to lime light that PMC was caused post administration of antibiotics (Aktories, 2008). This discovery led to the further researches on Clostridium. Its toxins show unique capabilities of protein shuttling through entering target cells that made it ideal for the drug delivery application. It is a highly significant genus with striking features and become an interest of pharma experts (Aktories & Wilkins, 2000).

Discussion

The toxins released by Clostridium are known as botulinum toxin. Research suggests that it can block neuromuscular transmission, and this ability transformed it into a therapeutic tool (Münchau & Bhatia, 2000). Botulinum toxin hinders acetylcholine release at the neuromuscular junction as well as in the sympathetic and parasympathetic neurons. It is used in vaccines to weaken overactive muscles and regulate hypersecretion of glands associated with neurons. It is used for chronic anal fissure, ocular motility, achalasia, and hyperhidrosis (Munchau & Bhatia, 2000). The reason is unknown for the toxin production by C. difficile after disruption of normal gut flora by antibiotics. A likely cause is the overgrowth of organisms results in the production of toxins as well (Moncrief, Barroso, & Wilkins, 1997). Several diseases in animals, insects and humans are linked to the toxins produced by pathogenic class of Bacillus and Clostridium that employ “A-B” enzyme paradigm for protein toxin production. The components that produce toxins include B. anthracis, B.botulinum, B. cereus, C.perfringens, C. difficile and C. spiroforme. In recent times, B. anthracis has also been associated with an agent for biowarfare and bioterrorism (Barth et al., 2004). One of the most potent natural toxins is Botulinum neurotoxins. These toxins are poisonous enough to cause death and paralysis. The bacterium responsible for their growth is Clostridium. Although there are also derived, benefits from the family of these toxins like botulinum neurotoxin type-A is known for its use in beauty clinics and neurology (Davletov, Bajohrs & Binz, 2005). A comparatively new therapy called gene-therapy uses virus and liposome vectors for the treatment of cancer. In this therapy, the bacteria thrive amongst the tumor cell producing therapeutic protein (Nakamura et al., 2002).
Clostridial neurotoxins are the generic term for Botulinum (BoNT, serotypes A-G) and tetanus (TeNT) neurotoxins. These neurotoxins are responsible for two deadly disease called botulism and tetanus (Poulain et al., 1997).
The single chain exotoxin A of C. diphtheria has grabbed attention due to its capability to translocate the heterologous proteins (Wilkins & Lyerly, 2003). The Clostridium binary toxins exhibited excellence in carrying heterologous proteins, including DNAs inside the cell. This uniqueness of protein shuttling has provided a striking alternative for the application of viral vectors as a part of gene therapy (Salminen & Von Wright, 2004). According to Barth and co-workers, various experiments and studies have been performed on its lethal toxins to understand the concept of shuttling to introduce a novel approach to application for Clostridium and Bacillus binary toxins in therapeutics (Barth et al, 2004).
Though, in this field various queries are still unanswered which is regarding the fusion products of binary toxins and the size of heterologous protein shuttled. The capability to open, thread and rebuild in the cytosol is sufficient to prove the shuttling ability of protein as a biologically active form. Application of Clostridium binary toxin for receiving heterologous proteins into targeted cells is still under research. On using Clostridium or Bacillus binary toxin for shuttling process, any particular antibodies production is not observed in vivo (Barth et al., 2004).
Barth explained the biochemistry of Clostridium toxins. A crystal structure of C. botulinum C3 exoenzyme exhibited very weak entry into the cells via an ineffective pinocytosis that is a cytolysin-mediated transportation. It does not facilitate binding, or any production of transport components is noticed by host bacteria (Salminen & Von Wright, 2004). Due to its inefficient penetration and poor adherence these toxins are have become the perfect model for shuttle experiments (Barth et al., 2004). Numerous antibody studies of C. perfringens and C. botulinum toxins exhibited that they contain toxin-neutralizing epitopes at C termini (Barth et al., 2004). The toxicity of C3 is low on Rho proteins, in comparison of other toxins because it lacks cell binding and transport subunits. But it has exhibited strong cytotoxicity in the cytosol. Moreover, it is found that several C3 isoforms are proficient to enter the culture cells. It has shown its impact on the low concentration of transferase (Aktories, 2008). Thus, it requires more thorough studies to identify the reason of variation in the frequency whether it depends on the C3 isoforms and or the conditions of the cell culture (Aktories, 2008).

Conclusion

The literature based research concludes that the binary toxins of Clostridium have specific features and versatile characteristics that are advantageous in drug-protein delivery inside the cell. It elaborates the function of actin in cellular functions and present suitable alternatives for vaccine targets. It has changed the perception of binary toxins and led to the development of recombinantly customized therapeutics.

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