Abstract: To observe the effects of efflux pump inhibitor-No.1 small peptide on antibacterial activity of antiseptic drug, the minimal inhibitory concentrations of eight kinds of antiseptic drug treated with No. 1 small peptide alone and in combination to twelve strains E. coli isolated from chickens were measured with standard microdilution method. The results showed that nine of twelve chickens E. coli were multi-drug resistant isolates, which can produce extended-spectrum β-lactometers. With the effect of No. 1 small peptide (one to two), the antibacterial activity of eight kinds of antiseptic drug, such as enrofloxacin, could be improved by twice and the antibacterial activity of Florfenicol against A8 and A15 was improved by fourth. With the effect of No. 1 small peptide (one to two or one to four), the antibacterial activity of Enrofloxacin, Gatifloxacin and Ciprofloxacin could be improved by twice and the antibacterial activity of Levofloxacin against A13 was improved by fourth. These results showed that bacterial efflux pump inhibitors-No. 1 small peptide one could improve the antibacterial activity of most antiseptic drugs and chickens E. coli which were produced enzyme and multi-drug resistanted has at least two resistance mechanisms of ESBLs and efflux pumps at the same time.

Key words: efflux pump inhibitor; No. 1 small peptide; antibacterial activity; multi-drug resistance