Appearance in Japan of highly macrolide-resistant Escherichia coli producing macrolide 2 '-phosphotransferase II

Escherichia coli CU1, a clinical isolate recovered in Japan in 1997, was fo und to be highly-resistant to both 14-membered and 16-membered ring macroli de antibiotics. A crude extract prepared from strain CU1 inactivated 14-, 1 5- and 16-membered ring macrolides in the presence of ATP and the Rf value of inactivated oleandomycin was identical to that of oleandomycin 2'-phosph ate. This suggested that strain CU1 produced the enzyme macrolide 2'-phosph otransferase [MPH(2')]. Substrate specificity of the crude enzyme from stra in CU1 against 14-, 15- and 18-membered ring macrolides was basically simil ar to that of MPH(2')II from strain BM2506, differing in that the former mo re effectively inactivated roxithromycin and tylosin. Subsequent attempts w ere made to clone the novel mph gene encoding for MPH(2') in strain CU1. Th e mph gene carried by strain CU1 was located on nontransmissible plasmid DN A, designated pCU001. Its molecular weight, estimated by agarose electropho resis, was similar to 57 kD. The DNA sequence of the cloned mph gene from t he Japanese isolate CU1 was identical to that of mphB, which until now had only been recovered in France. The variance in the substrate specificity of MPH(2')II from each strain led us to speculate that other factors in the r eaction affect the enzymatic inactivation activity.