Background and Objectives: The most common problems limiting the medical use of aminoglycosides have been the nephro- and oto-toxicities as well as the increasing bacterial resistance.Encapsulation of drugs into liposomes enhances their efficacy while reducing their toxicities. The aim of this study was to evaluate the antimicrobial activity of free and liposomal amikacin.Material and Methods: Encapsulated amikacin into liposome was prepared by sonication. The drug contained in the liposome was measured by HPLC after lysis of vesicles by 0.2% Triton X-100. The amikacin kinetic released from liposomes in the presence of normal human pooled plasma was also evaluated. The MICs of this drug for Pseudomonas. aeruginosa (ATCC 27853), Escherichia. Coli (ATCC 25922), Streptococcus. faecalis (ATCC 29212) and Staphylococcus. aureus (ATCC 29213) were determined and compared to those of the respective free drug using a broth dilution method.Results: In the presence of plasma, liposomal retention of amikacin was 80.25 ± 0.55% (P £ 0.05) after 1 h of incubation and then remained nearly constant over a 24 h period of the study. The encapsulation efficiency of liposomal preparation was 24.36% ± 0.14 (P£0.05) of the initial amount of the drug in solution. The MICs of liposomal amikacin against all bacterial strains tested were lower than MICs of free amikacin.Conclusion: The amikacin appears a promising approach in the management of bacterial infections and should be further evaluated in vivo experiments.

Background and Objectives: The great potential of bacteriophage for removing pathogen bacteria via targeting the cell wall is highly concerned. With a priority for overcoming drug-resistance, we screened against endolysins targeting Gram-negative bacteria to introduce a new antibacterial agent. This study was aimed to identify endolysins from the lysogenic phage of the Siphoviridea family in Bacillus subtilis. Materials and Methods: The Bacillus subtilis strain DDBCC46 was isolated from a preliminary antibacterial screening pro-gram. The endolysin (s) was extracted, concentrated with ammonium sulfate saturation, and their activity evaluated against the indicator bacteria. The phage particles were extracted from the bacteria using the minimum inhibition concentration of mitomycin C, followed by testing the phage inhibitory effect on the growth of indicator bacteria. The NCBI, Virus-Host DB, and EXPASY databases were used to obtain and confirm the sequences of the genes encoding PG hydrolases in Siphoviridea phages hosted in B. subtilis. Results: An 816 bp gene encoding an endolysin enzyme, was approved in the B. subtilis DDBCC 46, with specific primers of Bacillus phage SPP1. The purified-endolysin indicated antibacterial activity against Klebsiella pneumoniae, Salmonella typhimurium, Proteus (sp), and Escherichia coli. SDS-PAGE profiling followed by silica gel purification, led to introduce Lys46 as a therapeutic product and food preservative. Conclusion: lys46 showed antibacterial effects on the common Gram-negative pathogens in clinics and food industries; E. coli, P. aeruginosa and Salmonella (sp).

Background: Helicobacter pylori (H. pylori) is a spiral Gram negative bacteria that can transform to the coccoid form in adverse conditions.Objectives: The aim of this study was to determine the in vitro morphological and Bactericidal effects of metronidazole, amoxicillin and clarithromycin on H. pylori.Materials and Methods: The standard strain 26695 of H. pylori was cultured on Brucella agar (BA) and the minimum inhibitory concentrations (MICs) of three antibiotics were determined by E-test method. The bacteria were exposed to antibiotics at 1/2 MIC, MIC and 2X MIC concentrations in Brucella broth (BB). Induced coccoid forms were confirmed by Gram staining and light microscopy. The viability of cells as well as the susceptibility of viable coccoids to antibiotics were examined using the flow cytometry method.Results: All of the three antibiotics at sub-MIC induced coccoid forms. The highest rates of coccoids (>90%) were induced at 0.008 mg/ mL concentration (1/2 MIC) of amoxicillin, 72 hours postexposure. Metronidazole and clarithromycin with 1/2 MIC (0.5 and 0.125 mg/mL respectively) induced lower rates of coccoid forms (60% and 40% respectively). Potent Bactericidal effects on coccoids were observed with Metronidazole at 2X MIC and clarithromycin at MIC (0.25 mg/mL) (80-90%). Amoxicillin with MIC and 2X MIC had no Bactericidal effect on coccoid forms.Conclusions: Despite the good in vitro Bactericidal effect of amoxicillin on spiral forms of H. pylori, this antibiotic has little effect on induced coccoids that may develop after the inappropriatein vivo antibacterial treatment. Hence, for successful therapy, it is essential not only to eradicate the spiral forms, but to eliminate the viable coccoids.