[ study of sub-MIC ciprofloxacin effects on Shigella dysenteriae]

Shigella dysenteriae causes one of the most acute kinds of diarrhea which could be established as chronic infection with alternative periods of recurrence. Administration of normal doses of antibiotics will suppress microbial infections; however it is possible to control these infections by consumption of sub-MIC doses of certain antibiotics. In this basic study, a strain of Shigella dysenteriae [PTCC:1188] was used. After determination of MIC by microdilution method in Muller-Hinton Broth and MBC in Muller-Hinton Agar, the different dilutions [1/2,1/4,1/8] of MIC were prepared in order to study the sub-MIC effects of ciprofloxacin on some traits of Shigella dysenteriae. The results showed that different sub-MIC dilutions of ciprofloxacin could cause morphological changes in Shigella. The Shigella cells became filamentous in 1/2 MIC whereas this configuration was weaker in 1/4 MIC and 1/8 MIC. Meanwhile, the appearance of colonies was changed significantly due to the higher concentrations of sub-MIC. Some of the biochemical traits were affected by sub-inhibitory concentrations of ciprofloxacin. Ciprofloxacin is a drug of choice for shigellosis. According to the results of this study, treatment of Shigella infections would be possible by lower doses of ciprofloxacin

[Molecular characterization of a 70 kDa heat shock protein [HSP70] gene in dermatophyte pathogen T.verrucosum]

Trichophyton verrucosum [T.verrucosum] is one of the dermatophyte fungi which invades the skin of human and animals particularly cattle. Several properties of this fungus have been investigated so far. However a few studies were carried out in the field of molecular biology of this fungus. In the present study we tried to identify the chaperone proteins related to the 70 kDa heat shock proteins [HSP70] in this fungus and study of its gene regulation under heat-stress conditions. Pairs of 21 and 20 nt primers were designed from highly conserved regions of the similar genes in other fungi. Mentioned primers were utilized in PCR by using isolated genomic DNA and cDNA of T.verrucosum whereas the PCR fragments were then sequenced. Eventually, 2217 nucleotides have been sequenced from this new gene which has two introns and encodes a polypeptide with 654 amino acids. Sequences comparison in gene data banks [NCBI, NIH] for both the complete DNA and its deduced amino acid revealed significant homology with members of the eukaryotic 70 kDa HSP family. Further investigation revealed that the expression of this new gene increases under heat-stress conditions. This new gene has similarity with other genes of the same family in other organisms. This protein could efficiently protect the microorganism against heat stress