Studies on survival means of Proteus mirabilis treated by antibiotic in vitro and in vivo

Objective To study the survival means of P. mirabilis (PM) treated by antibiotic and its mechanism. Methods The survival means was studied by observation of its polymorph exposed to different antibiotic concentration in vitro and in vivo, and its mechanism was studied through determination of minimum inhibitory concentration (MIC), analysis of β-lactamase activity, test of outer membrane permeability. Results Swarmer cell was the main form of P. mirabilis to survive in high antibiotic environment; MIC of antimicrobial agents against swarmer cell were higher than that of swimmer cell (P > 0.05); no significant difference of β-lactamase activity was found between swarmer cell and swimmer cell; out membrane permeability was significantly decreased in swarmer cell; there were only swarmer cells in urine samples and kidney pathological sections of rat urinary tract infected by PM after teatment of antimicrobial agent. Conclusion The decreasment of out-member permeability played an important role in the increasement of drug resistance of swarmer cell, and the formation of swarmer cell may be an important survival means of P. mirabilis to overcome harsh conditions. This study could provide further information about diagnosis, prevention and therapy of P. mirabilis infection.