Correlation Between the Crude Extracellular Secretion by Shigella dysenteriae and Destruction of RD and L20B Cell Lines, A Simple Sign as Alternative Treatments for Cancer Tumors through Cytotoxicity

Abstract

The clinical pathogenic strains of S. dysenteriae in this study were initially diagnosed as enteroinvasive E. coli due to the high similarity in characterization and pathogenic mechanism. The clinical samples were collected previously from patients of diarrheic stool. Confirmation was done by API 20 NE and API 20 E systems in central public health laboratory in Baghdad. The three clinical strains of S. dysenteriae had shown weakness in their ability to produce serine protease autotransporters (Sat), showing small clear zone (about 1-1.4 mm in diameter) around the colonies. No clear hemolysis pattern on blood agar was shown but, the lysis of human Erythrocytes was observed by hemagglutination test in twofold dilution 1/10-1/320 for non-heated bacterial supernatant. When treated with heated supernatant however, agglutination appeared, which indicates that RBCs did not lyse. The biofilm formation was evaluated in this study by Congo red plate Method which had shown weak strength in formation. The clinical strains of S. dysenteriae have different antibiogram analyses; it was strong sensitive against ceftriaxone, ciprofloxacin, and co-trimoxazole; while, resistant to Tetracycline, ampicillin and chloramphenicol and finally, Nalidixic acids shown intermediate susceptibility. Both non-heated and heated (at boiling temperature for 60 min) supernatants had cytotoxic effect on shape and vitality of RD and L20B cell lines. Several changes in morphology include: size, shrinkage, segregation, rounding were noted as cytopathic effect. Cell death was shown, which caused either failure of cells in suspension to attach (to a surface to form a monolayer) or detachment of cells from established monolayers within 120 hr. compared with non- treated cells as a control. There is a poor relation between cytotoxicity effect and Sat protease and hemolysin secretion of S. dysenteriae. But, other heat-stable toxins may involve in infectivity of S. dysenteriae on human cells. Also, the destruction and damage of above mentioned cell lines by extracellular production of clinical pathogens may effect cancer cells when infected with S. dysenteriae and become weaker. Cytotoxicity of cancer cells may leave them vulnerable and exposed to active immune cells leading to rapid death. Although the toxins of S. dysenteriae are dangerous, they can be employed in treatment of cancer cells or developing anti-tumor drug through destruction of tumor mass.

Keywords

• shigella dysenteriae
• rd and l20b cell lines
• sat
• cytotoxicity
• heated and non-heated supernatant