الفهرس 
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Abstract
In order to preserve the characters of the highly toxigenic C. tetani (Harvard strain) as long as possible, a combined approach of pre-lyophilization treatment of microorganisms and subsequent storage was developed in order to improve cell survival and toxin production capability. Different stabilizers have been tried in combination with different storage temperatures. The study revealed that -20 c° is the best temperature for storing C. tetani (Harvard strain) and that stabilizer III (modified Pivnick ) is the best stabilizer for lyophilization of C. tetani (Harvard strain)as it preserve the strain toxigenic capability till the 19th month post lyophilization with minimum reduction in toxin titer. By PCR assay, the samples were found to be positive for tetX gene, thus confirming their potential to produce the tetanus toxin.
In conclusion: preserving C. tetani by lyophilization using stabilizer III (modified Pivnick) retain its toxigenic power than other stabilizers for longer periods. Also, the optimum temperature for storing lyophilized C. tetani (Harvard strain) is at -20 ᵒ c.