Enzymic hydrolysis of erythromycin by a strain of Escherichia coli. A new mechanism of resistance.

Escherichia coli BM2195 is highly resistant to erythromycin by inactivation of the antibiotic. We have determined the structure of the modified antibiotic by physico-chemical techniques including mass spectrometry, infrared spectrophotometry, 13C nuclear magnetic resonance, and circular dichroism. The results obtained indicate that E. coli BM2195 resists erythromycin by the production of an erythromycin esterase which hydrolyzes the lactone ring of the antibiotic.