MAJOR VIRULENCE FACTORS AND PATHOGENICITY ISLANDS IN PATHOGENIC CLOSTRIDIUM SPECIES

Abstract

Clostridia are obligately anaerobic, spore-forming bacilli that, at least in the early stages of growth, stain gramme positive. Clostridia produce greater toxins than any other bacterium genus, and pathogenic clostridia are typically diagnosed by their unique toxins. Clostridium spp. has been found to have more than 20 toxins and other extracellular proteins that contribute to virulence, such as spread factors and proteolytic enzymes. Botulinum and tetanus toxins are the most potent poisons ever discovered. Clostridium botulinum neurotoxins are the most potent acute toxins identified, and they are the cause of the neuroparalytic illness botulism. Such toxins work by inhibiting presynaptic nerve terminal neurotransmission in the peripheral and central nervous systems. Other clostridia toxins have different modes of action, such as tissue destruction, hemolysis, diarrhoea, or generating an overactive immunological response in the recipient. On non-integrative lysogenic bacteriophages or plasmids, the genes coding for numerous clostridial toxins are found. Protein secretory processes in Clostridia are poorly understood. It has remained a mystery as to how the tetanus toxin, which lacks a normal N-terminal signal peptide, is exported until today. Typical PAI are DNA segments that are found in pathogenic bacteria's genomes but not in nonpathogenic strains of the same or similar species.