[Analyses of antibiotic susceptibility and plasmid profile of normal human intestinal Lactobacillus]

To investigate the level of antibiotic resistance in normal human intestinal lactobacillus, the existence frequency of plasmid in bacterial strains, and the relationship between the plasmid carried by the strains and the antibiotic resistance profile.

The minimum inhibitory concentration (MIC) was determined by microbroth dilution technique. The plasmid profile of all strains was examined and the stability of plasmids were investigated.

The antibiotic resistances of the intestinal lactobacillus strains were strong for ciprofldocacin, levofloxacin and vancomycin, among which it was the strongest for vancomycin. Most bacterial strains were tolerant to levofloxacin, gentamycin, tetracycline and ciprofloxacin, but susceptible to low concentration of rifampicin, penicillin and ampicillin. The multiple drug resistance (MDR) was existing in all the tested strains, and getting more severe with the increase of bacterial host age. 93% of lactobacillus strains contained plasmids. After cultured for many times, 4 bacterial strains lost some of plasmids and also, at the same time, lost the drug resistance to gentamycin and cephalosporin. This result was consistent with the that of plasmids eliminated.

The antibiotic resistance and MDR of the lactobacillus strains in are very severe and correlated with people's age. Most of bacterial strains contain plasmids. There may be a correlation between 5.8 kb plasmid and the resistance of strains to gentamycin and cephalosporin.