Biochemical detection of a metallo-β-lactamase in carbapenem resistant strain of Streptomyces sp. CN229 isolated from soil

Abstract

Streptomyces sp. CN229 was isolated from Tunisia soil. This strain displayed antimicrobial activity against Gram positive and Gram negative bacteria. In addition it is resistant to most β-lactam antibiotics including imipenem and meropenem (MIC imipenem > 70 pg/ml). Metallo-β;-lactamase (MβL) production was confirmed by either imipenem MIC decrease in the presence of ethylene diamine tetraactic acid (EDTA) or the inhibition zone enhancement around EDTA-impregnated imipenem or meropenem discs. Isolectric focusing analysis demonstrated the production of β;-lactamase with pi of 5.8 that is inhibited by EDTA. Streptomyces sp. CN229 was screened for the imipenem resistance genes, blaaVIM and blaIMP previously identified in Pseudomonas aeruginosa. The presence of these genes was not confirmed by specific PCR analysis. We concluded that carbapenem resistance in Streptomyces sp. CN229 strain is mainly due to production of a novel carbapenemase. Our data show for the first time that MβL is produced by Streptomyces sp. MβL-mediated imipenem and meropenem resistance in Streptomyces is a cause for concern in the study of resistance evolution and antibiotic cluster biosynthetic genes.