| Summary: | 碩士 === 中華醫事科技大學 === 醫學檢驗生物技術系碩士班 === 101 === This study explores the ability of pan-drug resistant Acinetobacter baumannii (PDR-AB) to form biofilms and investigates the tolerance of PDR-AB when in the biofilms and planktonic state to desiccation, temperature, and alcohol. Experiments were conducted to test 236 clinically isolated strains of PDR-AB, which were verified to be diverse genotypes using pulsed field gel electrophoresis. The strains were cultured in media containing 1% glucose, and the strength of the formed biofilms was analyzed after 1, 3, and 5 d of culture. An optical density value measured at 570 nm (OD570) greater than 0.17 and smaller than 1 was defined as a very low level of biofilm formation; an OD570 value greater than 1 and smaller than 2 denoted a very low level of biofilm formation; an OD570 value greater than 2 and smaller than 3 denoted an intermediate level; and an OD570 value exceeding 3 signified a high level. In this study, all 11 PDR-AB strains formed biofilms, among which 0, 3, 6, and 2 strains exhibited a low level, low, intermediate, and high level of biofilm formation, respectively.
From the experiments, we found that in a planktonic state, the PDR-AB strains with low biofilm formation ability tolerated a desiccate environment for fewer than 14 d, an alcohol concentration less than 20%, and temperature no higher than 50°C, whereas the PDR-AB strains with a high biofilm formation ability tolerated a desiccate environment for 21 d, an alcohol concentration of 30%, and a temperature of 40°C. However, the PDR-AB strains with moderate biofilm formation survived 42 to 49 d in a desiccate environment and tolerated an alcohol concentration of 60% and temperature of 50°C, whereas the PDR-AB strains with high biofilm formation survived over 49 d in a desiccate environment and tolerated an alcohol concentration of 60% and temperature of 60°C. In addition, the survival rate of the strains with high biofilm formation surpassed that of those with moderate biofilm formation by several hundredfold.
Experimental results confirmed that the ability of PDR-AB to form biofilms is correlated to the ability of the biofilms to tolerate environmental conditions. The results indicated that in a planktonic state, PDR-AB could not tolerate a desiccate environment lacking nutrients; thus, cell death readily occurred. The formation of the biofilm increases treatment difficulty and enhances the ability of PDR-AB to tolerate the surrounding environment. Consequently, the survival period of PDR-AB is prolonged and the dissemination through channels, such as hospital environments and medical equipment, is facilitated.
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