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Objective: To confirm AcrAB-TolC system mediated the multiple antimicrobial resistance in Salmonella typhimurium., Methods: One-step knock-out of chromosomal method was used, to disrupt chromosomal genes, in Salmonella typhimurium wild strain X2. The acrAB gene and tolC gene were knocked out and two mutants of the delta acrABX2 and delta tolCX2 were produced., Results: Results of E-test to two mutation strains and their parent strain showed that delta acrABX2 and delta tolCX2 were resistant to vancomycin and susceptible to amikacin and cephalothin, which was similar to their parents isolate X2, but (acrABX2 and (tolCX2 were susceptible to other eleven antimicrobial agents, while the parents isolate X2 was resistant to those., Conclusion: multiple antimicrobial resistance in Salmonella typhimurium. It suggested that the AcrAB-TolC system mediated the multiple antimicrobial resistance in Salmonella typhimurium.

Objective: To determine and analyse the composition of cellular fatty acids of Burkholderia gladioli., Methods: The cellular fatty acids composition of different pathovar strains of Burkholderia gladioli were determined by GC method and analyzed by MIDI-FAME., Results: The results showed that the composition of cellular fatty acids of these strains, including original food poison strains of, were similar and were identified as, and this confirmed the conclusion that Pseudomonas cocovenenans subsp farinofermentans and Burkholderia cocovenenan were the junior synonym of Burkholdria gladioli. It was interesting to find that fatty acids of C16: 0.20H, C18: 1.20H and C16: 1.20H were related to the Bongkrekic acid (BA) producing of Pseudomonas cocovenenans subsp farinofermentans., Conclusion: It provide more data for the study of the mechanism of BA production and pathogenesis.