Long-Term Starvation-Induced Loss of Apparent Antibiotic Resistance in Cells Containing the Plasmid pSa(1+)

摘要

Escherichia coli, Pseudomonas fluorescens, and a Pseudomonas sp. strain 133B containing the pSa plasmid were starved in well water for up to 523 days. There were two patterns of apparent antibiotic resistance loss observed. In Pseudomonas sp. strain 133B, there was no apparent loss of antibiotic resistance even after starvation for 340 days. In E. coli, by day 49 there was a ten-fold difference between the number of cells that would grow on antibiotic and non-antibiotic containing plates. By day 523, only 12% of the cells were able to express their antibiotic resistance after they had been first resuscitated on non-antibiotic medium. Cells that could not grow on antibiotic medium even after resuscitation showed a permanent loss of chloramphenicol (Cm) resistance but retained resistance to kanamycin and streptomycin. Restriction enzyme digests show that a region from 13 to 15.5 Kb was deleted. This was essentially the same 2.5 Kb region previously reported as being deleted by spontaneous mutation.