Macrolide esterase-producing Escherichia coli clinically isolated in Japan

Current Japanese clinical practice involves the usage of large amounts of n ew macrolides such as clarithromycin and roxithromycin for the treatment of diffuse panbronchiolitis, Helicobacter pylori and Mycobacterium avium comp lex infections. In this study,the phenotypes, genotypes, and macrolide resi stance mechanisms of macrolide-inactivating Escherichia coli recovered in J apan from 1996 to 1997, were investigated. The isolation rate of erythromycin A highly-resistant E. coli (MIC greater than or equal to 1600 mu g/ml) in Japan slightly increased from 0.5% in 198 6 to 1.2% in 1997. In six macrolide-resistant strains, recovered from the s trains collected for this study during 1996 to 1997, the inactivation of ma crolide could be detected with or without added ATP in the assay system. Th e appearance of erythromycin A-inactivating enzyme independent of ATP was n ovel from Japanese isolates, and the H-1 NMR spectra of oleandomycin hydrol yzed by the three ATP-independent isolates were examined. it was clearly sh own that the lactone ring at the position of C-13 was cleaved as 13-H signa l in aglycon of oleandomycin upper shifted. These results suggested the fir st detection of macrolide-lactone ring-hydrolase from clinical isolates in Japan. These results suggested the first detection of an ATP-independent ma crolide-hydrolyzing enzyme from Japanese clinical isolates. Substrate speci ficity of the macrolide-hydrolyzing enzyme was determined with twelve macro lides including the newer members of this group and it was found that not o nly erythromycin A but also the new macrolides, such as clarithromycin, rox ithromycin, and azithromycin were inactivated. The NMR data, broad spectrum of activity, and independence of co-enzyme supported our naming of the enz yme as a macrolide esterase. PCR methodology was employed to detect an ereB -like gene from the 3 isolates producing macrolide esterase, and one of the se was subsequently shown to contain both ereB-like and eremB-like genes. I t was also clearly shown that the other three isolates, which inactivated m acrolide in the presence of ATP, had an mphA-like gene.