3.5 Conjugative transfer and stability of plasmids harboring MDR regions
Transconjugants were obtained from mating experiments withKlebsiella pneumoniae M297-1 donors, in E. coli J53 recipients, at rates of 10−5 to 10−6transconjugants per recipient cell. All 13 putative transconjugants tested were found to be the recipient background species and to be β-lactamase positive by antimicrobial susceptibility testing. Notably, 8 of the 13 transconjugants were resistance to sulfamethoxazole, chloramphenicol and tetracycline , which was suggested to be transconjugants carrying with pM297-1.2 (Table 3). The another 4 strains were not resistant to the sulfamethoxazole, chloramphenicol andtetracycline (Table 3),which was considered to be transconjugants carried pM297-1.1. All positive transconjugants colonies tested, resistance to cefotaxime , remained detectable throughout the 6-day passage experiment, even in the absence of antibiotic selection. Therefore, it was confirmed that the two plasmids carried byKlebsiella pneumoniae M297-1 had stronger transferability and stability in new host bacteria.