Screening Of Quinolone Resistance Bacteria In Water Environment Of Jinan And Detection Of Its Plasmid-mediated Resistance Gene

The discovery of antibiotics is a major medical achievement of the20th century. Human use antibiotics as the most powerful weapon to fight against the bacteria.However, with the extensive even abuse use of antibiotics, resistance rates of bacteria continue rising in the environment. A variety of pathogen tends towards a great comeback after having achieved resistance. It seems that human once again go back to a non-antibiotic time especially after the appearing of superbacteria. To strengthen the management of the use of antibiotics in bacterial resistance problem can only slow the spread of bacterial resistance to antibiotics.Only by deep research of the mechanisms of bacteria resistance, we can know both our own and bacteria’s situations clearly to solve the problems according to the problems themselves,also understand and control the problem of bacteria resistance.The quinolone resistance mechanism of bacteria contains chromosome-mediated resistance and plasmid-mediated resistance (PMQR), the latter is important to the broad spreading of bacteria resistance. This article mainly studies plasmid-mediated resistance mechanism.Quinolone is a synthetic antibiotics with the advantage of wide antibiotic spectrum little side effect. Nowadays, it has been used widely and this also resulted in the improvement of bacterial resistance rates to it.In this study, I collect water samples from Xiaoqing River, sewage treatment plant and around the hospital. At last,215different kinds of quinolone resistance bacteria are sellected. After detecting three plasmid-mediated quinolone resistance genes in bacteria, I find that there are fifteen positive qnr genes including one qnr A, eleven qnrB and four qnrS. There are91strains that qepA gene are positive and30strains that the variant aac(6’)-Ib-cr of qepA gene are positive. In the experiment, I use conjugal transfer method to detect the transferability of qnr gene and find transfer functions are available in four strains which are all qnrB gene.The experiment also makes a detection of class Ⅰ,Ⅱ,Ⅲ integron to the215 strains. There are158strains containing class Ⅰ integron, one strain containing class Ⅱ integron, four strains containing both of class Ⅰ,Ⅱ integron and no strains containing class Ⅲ integron. In the following detection of the gene cassettes to the bacteria with integron,13different gene cassette arrays are found in number. Among the gene cassette arrays, the size of1740bp gene cassette dfrA17—aadA5and the size of1989bp gene cassette dfrA12-orfF-aadA2have a larger appearing frequency than others. The frequency of the two gene cassettes are28and24. Qnr may be coupled to the integron-cassettes system and have metastasis. In the experiment, the orf513gene related to the coupling and the integron-cassettes system of conjugants is detected..In the agar tape susceptibility test, I find that the resistance of bacteria to nalidixic acid, ampicillin etc. has reached to more than90percent. This resistance situation is very serious and should cause people’s enough attention.