| Summary: | 碩士 === 長庚大學 === 醫學生物技術研究所 === 96 === Both vancomycin-resistant enterococci (VRE) and methicillin- resistant Staphylococcus aureus (MRSA) are widespread in hospitals, which are leading pathogens for hospital-acquired infections. Vancomycin is currently the first choice for treating infections caused by MRSA. However, only few cases of vancomycin-resistant S. aureus (VRSA) had been isolated from clinical specimens since 2002. VRSA strains have been proposed to acquire vancomycin resistant determinants such as vanA cluster from VRE. We hypothesize that type I restriction-modification (RM) system in S. aureus may be involved in the transfer of vanA cluster from VRE to S. aureus. In the present study, RM system had been mutated by inserting a spectinomycin cassette in which the capacity of external DNA intake should be increased as S. aureus RN4220. However, the ability of such mutant to acquire foreign DNA is very similar to its parental strain, indicating that RM system itself is not the only factor to acquire external DNA. On the other hand, the slower growth rate of VRSA strains suggests that some factors are lacked in fighting vancomycin pressure in VRSA. VanK-like protein, which is first characterized in Streptomyces coelicolor, may be related to vancomycin resistance during cell wall remodeling. Thus, vanK will be inserted into genomic DNA to investigate the role in vancomycin resistance.
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