Antibacterial and Antimutagenic Effects of Synthetic Histidine

This study was accomplished to determine the Histidine behaviors toward two pathogenic bacteria (Staphylococcus aureus and Escherichia coli) toward exposed to various conditions, as well as to test their susceptibility toward related antibiotics. The method of His measurement in colostrum and natural Iraqi breast milk was modified  by transferring the separation column of  Amino Acid Analyzer (AAA) to a High Performance Liquid Chromatography (HPLC) that contains a fluorescent detector. Results of analysis showed high concentrations rate of free His which reached two folds (222 mg/l)  in the colostrum compared with the combined (94 mg /l).No noticeable differences were detected between the concentration rates of the free and combined His in milk; they were  51 and 88 mg/l,  respectively. It was found that the free His in the colostrum was about four times than that of the free histidine in natural milk.Results of determining the  effect of exposure to ultraviolet light at (254 nm) and high frequencies of microwave  on the structure of histidine by using the FTIR analysis have not  shown  any  effect on  the structure of histidine and its active groups. Where polymerization and condensation  were not available in these methods. Results  showed that the His used as an antibacterial agent,sensitivity of S. aureus and E. coli was not effected at concentrations up to  10 mg/ml. It was found that presence of His in the solidified  medium led to a significant change in the sensitivity of the isolates toward the antibiotic used.Histidine led to increase the sensitivity of the isolates against the Rifampicin(Rp) and reducing  it toward Levofloxacine (Lev), Ciprofloxacin (Cp), Gentamicin(Gm) without change toward Streptomycin (S), Metronidazole (Mz), Cloxacillin (Cx), Tetracycline (T), Nalidixic acid (Na), Penicillin (P) Clarithromycin (Cla), Vancomycine (Va) and  Chloramphenicol (C). Results of the genomic profile indicated the presence of small    plasmids  in E. coli but absent in Staph. aureus. The use of chemical  and physical curing agents caused changes in the sensitivity of S. aureus against  the three selected antibiotics ( Rp, Lev and Cx) regard less to the presence or absence of Histidine in the plasmids. The change also includes E. coli at different levels. Histidine   reflected  a  large heterogeneous behaviors,  after mixing with the    suspension of isolates and exposed  to  the physical  mutagenesis  (UV250 nm ),as compared with the three selected antibiotics. These  interactions were restricted   between the histidine and the microorganism. The results also showed that  E. coli isolate was turned  into a sensitive against  Rp, Cx and resistant against  Lev. While  S. aureus was  turned  to be more sensitive against Rp and  Cx, but did not change against the Lev. The role of Histidine was investigated by examing the sensitive  and resistant isolates of  Mycobacterium tuberculosis (TB) against  Rp was studied, results exhibited that presence of Histidine in the concentrations 5 and 10 mg/ml which  turned   the  resistant TB isolates against  Rp (40 µg / ml) into sensitive. These results  had  a significant effect to avoid patients from exposure subsequent levels of high risk   antibiotics.