Background:Infections caused by strains with multi-drug resistance are difficult to treat with standard antibiotics. Garlic is a powerful remedy to protect against infections of many bacteria, fungi and viruses. However, little is known about the potentials of fresh garlic extract (FGE) to improve the sensitivity of multi-drug resistant strains to antibiotics.Objectives:In this study, we used the disk diffusion method to investigate the antimicrobial activities of FGE and the combination of antibiotics with FGE, on methicillin-resistant Staphylococcus aureus (MRSA), Pseudomonas aeruginosa and Candida albicans, to evaluate the interactions between antibiotics and FGE.Materials and Methods:Clinical isolates were isolated from clinical specimens obtained from the inpatients at the First Affiliated Hospital of Xi’an Jiaotong University Health Science Center. The isolates consisted of MRSA, (n = 30), C. albicans (n = 30) and P. aeruginosa (n = 30). Quality control for CLSI (Clinical and Laboratory Standards Institute) disk diffusion was performed using S. aureus ATCC®25923, C. albicans ATCC®90028 and P. aeruginosa ATCC®27853. The 93 microorganisms were divided into four groups in a factorial design: control (deionized water), FGE, antibiotics without FGE, and antibiotics with FGE. Next, antibacterial activity was evaluated by measuring the diameter of inhibition zones according to performance standards for antimicrobial susceptibility testing of the Clinical and Laboratory Standards Institute (CLSI, formerly NCCLS).Results:Fresh garlic extract displayed evident inhibition properties against C. albicans and MRSA, yet weak inhibition properties against P. aeruginosa. Additionally, FGE showed the potential to improve the effect of antibiotics on antibiotic resistant pathogens. The synergism of fluconazole and itraconazole with FGE on C. albicans yielded larger sized inhibition zones compared with fluconazole and itraconazole without FGE (P < 0.01). The factorial analysis represents intense positive interaction effects (P < 0.01). The synergism of cefotaxime and ceftriaxone with FGE on P. aeruginosa yielded larger sized inhibition zones than cefotaxime and ceftriaxone without FGE (P < 0.01). The factorial analysis represents intense positive interaction effects (P < 0.01).Conclusions:The results suggest that FGE can improve the antibiotic sensitivity of these pathogens to some antibiotics.

Spore surface display is the most desirable with enhanced effects, low cost, less time consuming and the most promising technology for environmental, medical, and industrial development. Spores have various applications in industry due to their ability to survive in harsh industrial processes including heat resistance, alkaline tolerance, chemical tolerance, easy recovery, and reusability. Yeast and bacteria, including gram-positive and -negative, are the most frequently used organisms for the display of various proteins (eukaryotic and prokaryotic), but unlike spores, they can rupture easily due to nutritive properties, susceptibility to heat, pH, and chemicals. Hence, spores are the best choice to avoid these problems, and they have various applications over nonspore formers due to amenability for laboratory purposes. Various strains of Clostridium and Bacillus are spore formers, but the most suitable choice for display is Bacillus subtilis because, according to the WHO, it is safe to humans and considered as “GRAS” (generally recognized as safe). This review focuses on the application of spore surface display towards industries, vaccine development, the environment, and peptide library construction, with cell surface display for enhanced protein expression and high enzymatic activity. Different vectors, coat proteins, and statistical analyses can be used for linker selection to obtain greater expression and high activity of the displayed protein.

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In fusion protein design strategies, the flexibility and length of linkers are important parameters affecting the bioactivity of multifunctional proteins. A series of fusion proteins with different linkers were constructed. The effect of temperature, pH, and organic solvents was investigated on the enzymatic activity. Fusion proteins with P1(PTPTPT) and P2((PTPTPT)) linkers remained highly active with wide temperature range. At pH 9.6, the relative activity of fusion proteins with (PTPTPT) and S2(EGKSSGSGSESKST) linkers was 70 and 62 % (1.75 and 1.5 times of that of non-linker ones). Fusion proteins with S3((GGGGS)) linker retained 55 % activity after 5 h of incubation at 80 °C (1.2-fold of that of non-linker fusion proteins and 1.9-fold of GGGGS-linker fusion proteins). Finally, the relative activity of fusion proteins having different linkers was increased with 20 % dimethyl sulfoxide (DMSO) and methanol; relative activity of fusion proteins with EGKSSGSGSESKST linkers was enhanced 1.5- and 2.2-fold, respectively. These results suggest that longer flexible linker can enhance the activity and stability of displayed esterase than shorter flexible linker. Optimizing peptide linkers with length, flexibility, and amino acid composition could improve the thermostability and activity of the displayed enzyme.