| Summary: | 碩士 === 慈濟大學 === 醫學生物技術研究所 === 99 === The improper use of antibiotics nowadays has caused bacteria to resist frequently used antibiotics. These antibiotic-resistant bacteria are called multiple drug-resistant bacteria, particularly Acinetobacter baumannii, has been turning up one after another in a lot of hospitals in Taiwan. When in-patients are infected with multiple drug-resistant Acinetobacter baumannii, MDRAB, it often leads to a situation where no antibiotics can be used to treat the infection. Therefore, it is our aim to develop a new antibacterial agent that can effectively destroy MDRAB. Previous studies show that the endolysin produced after the bacteriophage has infected the bacteria can hydrolyze the peptidoglycan of bacterial cell wall. This suggests that endolysin can perhaps act as an effective antibacterial agent. This study initially used a bioinformatic analysis to find a possible endolysin gene in the A. bumannii phage chromosome. We isolated and characterized a novel phage lysozyme (endolysin) from ?淲B2 and named it LysAB2 To analyze antibacterial activity of LysAB2, the complete LysAB2 and two deletion derivatives were constructed, purified and characterized. Zymographic assays showed that only the intact LysAB2 could lyse the peptidoglycan of A. baumannii and the Staphylococcus aureus cell wall. The bactericidal test results show that LysAB2 can effectively restrain parts of Gram positive and negative bacteria. Under the Scanning Electron Microscope, it was observed that LysAB2 can directly destroy A. baumannii, E. coli, S. aureus. Thermostability assays indicated that LysAB2 was stable at 20~40 ℃. Its optimal pH was 6.0, and it was active from pH 4 to 8. These results indicate that LysAB2 is an effective lysozyme against bacteria, and they suggest that it is a good candidate for a therapeutic/disinfectant agent to control nosocomial infections caused by multiple drug-resistant bacteria.
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