Multi-resistant Bacteria Resistant Mechanism Research

Research purposesWe researched the drug resistant mechanism of one multidrug resistant Morganella morgani strain isolated from an ill dead abalone. Identifying the specific mechanism of this bacterial drug resistant system clearly could provide theoretical and techonical surport when we used this strain as a whole-cell model for screening new broad-spectral anti multidrug resistant bacterial drugs.Research contents and methodsThis experiment was designed in two ways:The first way was to find the drug resistant mechanisms which were already reported before using the method published. The main contents of this part are as follows: the MICs of 29 antibiotics to this strain were determined by micro-well method with 2-fold serial dilution; Theβ-lactamases related experiments, the integron gene detection experiments, the comparison of the differential expression of outer membrane protein between the drug resistant strain and the standard (wild-type) strain and the efflux pumps related experiments were done to identify their existences.The second way was applying transposon insertion mutagenesis experiment to discover the unknown resistance mechanisms of this multidrug resistant Morganella morgani strain.ResultsThe results of the the first part were as follows:This Morganella morgani strain showed wider drug resistant ranges and stonger drug resistant abilities compared with the standard strains.Both the AmpC three dimensional tests and the PCR amplifying tests of the ampC structural gene proved the existentse of ampC gene in this strain. Class I integron was also amplified by PCR, it was identified that it carried the aminoglycoside resistance gene (aad) and chloramphenicol Class (catB3) resistant gene. Efflux pump related experiment results showed that there was not AcrAB efflux pump.There are some differences in the expression of outer membrane protein between the drug resistant strain and standard strain, but it still needed further validation whether they had any relationship with the bacterial drug resistant mechanisms.The results of the the second part were as follows:We got a mutant strain whose drug resistant of quinolone antibiotics was disrupted by transposon insertion mutagenesis. The sequence adjacent the transposon integration sites were amplified by reverse-pcr, but whether this sequence was the drug resistant gene or not still need more experiments to identify.