Why might E.coli develop a partial resistance to streptomycin?

Question

i say partial as the streptomycin in my experiment did inhibit the E.coli but not as much as much as it should do. Any links would be appreciated.

Answer 1

Streptomycin is an aminoglycoside antibiotic. It works by preventing the formation of the initiation complex during translation (protein synthesis). Bacterial resistance to aminoglycosides is often a result of enzymatic inactivation of the antibiotic. Another possibility is whether or not the antibiotic was present at higher concentrations than the MIC (minimum inhibitory concentration).

If the bacteria seemed to gain resistance over multiple platings, I would suspect that you were selecting for strains that expressed the necessary gene for aminoglycoside resistance (aadA gene). If they were resistant right off, maybe it was the concentration of the antibiotic.

See the link below for some introductory information:

Answer 2

Maybe the streptomycin is overused.