| Vancomycin is an important antibiotic used in treating gram-positive bacteria caused infection. Because the frequently use of vancomycin, there're more and more vancomycin -resistant Enterococci and staphylococci which do great harm to people's health. It is reported that the occurrence ratio of vancomycin resistant enterococci among enterococci caused infection was 19% in American while in China the occurrence ratio is 4%.To isolation antibiotic substances against vancomycin-resistant enterococci and vancomycin-intermediate Staphylococcus aureus, it is very necessary to construct screening models. Some models have been constructed based a specific drug-resistant mechanism. The resistance of bacteria to one kind of antibiotic is the combination of different mechanisms. So the screening models constructed by this study are based on the whole cells.Ultraviolet radiation is an effective way to mutate microorganisms. To obtain vancomycin resistant strains, the clinical isolates of Enterococcus faecalis 458 and Staphylococcus aureus 9918 were treated by ultraviolet. The optimal treating time was determined. Using this treatment, vancomycin-intermediate strains of Enterococcus faecalis and Staphylococcus aureus were obtained, designated 458 V20 and 9918 V16 respectively. Susceptibilities of the two strains to antibiotics indicated that 458 V20 was resistant to benzylpenicillin and ervthromycin and 9918 V16 was resistant to benzylpenicillin, erythromycin and sodium oxacillin. After ten generation of passes on drug-free plate, the resistance of 458 V20 and 9918 VI6 to vancomycin decreased slightly. The resistant pattern of 458 V20 to glycopeptides indicate that it was VanB type vancomycin resistant Enterococci. This was further confirmed by the SDS-PAGE profiles of 458 V20's membrane protein. Coagulase production studies show that 9918 V16 produces coagulase slowly than 9918. There is some difference of the post antibiotic effect of vancomycin and teicoplanin against 9918 V16 and 9918.The optimal condition for preparation protoplasts from Staphylococcus aureus ATCC 25923 were established and were summarized as follows: bacteria cells were mixed with lysozyme at 20mg/ml and lysostapbin 0.4mg/ml respectively, incubating at 37℃ for 2h. Plasmid from clinical virulent strain 293 was isolated and transformed into avirulent strain ATCC 25923. Resistance of the obtained strain 25923T to tienem was increased from 0.032mg/ml to 0.5mg/ml,Ferment broths of 1200 strains soil microorganisms were examined use the vanconmycin resistant 458 V20. Among which 48 strains' ferment broths show inhibitory activity. Those strains' broths were further examined by more drug resistant gram-positive and gram-negative strains. But those strains showed no inhibitory activity to gram-negative strains. Finally, four strains were selected. Their ferment broths showed very high inhibitory activity to gram-positive drug resistant bacteria.The metabolites of SIPI2001-542, SIPI2001-270 and SIPI2001-1140 were studied. Five pure active compounds, SIPI2001-542, SIPI2001-270- I and SIPI2001-270- II, SIPI2001-1140-8 and SIPI2001-1140-10 were obtained. Their structures were deduced as actinomycin D, actinomycin C2, actinomycin C3, quinomycin A and quinomycin C respectively by means of IR, UV, 1H-NMR and 13C-NMR methods and physical and chemical analysis. Those five compounds have higher inhibitory activity to drug-resistant gram-positive bacteria than vancomycin and teicoplanin.It was found in this study that the anti-tumor agents actinomycin D and quinomycin had higher activity against drug-resistant gram-positive bacteria than vancomycin. The inhibitory activity of actinomycin D against drug resistant gram-positive bacteria was compared with other anti-tumor agents on different medium. Those anti-tumor agents include mitomycin C, bleomycin, adriamycin, 5-fluorouracil and etoposide. The results indicate that the MIC of actinomycin D and mitomycin C to 458 V20 and 9918 VI6 is 80 times and 64 times higher than vancomycin, while bleomycin, ad...
|
PDF Full Text Request