Genetic and Kinetic Profiles of Bacterial Resistance Enzymes to IMP and NDM Type Antibiotics in Gram-negative Pathogenic Bacilli

Abstract

Introduction: Enterobacteria are among the most frequent isolated strains in hospitalized patients. Currently, carbapenems have a broad spectrum of activity and are considered to be the last resort for the treatment of nosocomial infections. However, overuse of these valuable compounds has led to a rapid increase in antimicrobial resistance. The aim was to study the genetic and kinetic profiles of IMP and NDM bacterial resistance enzymes in Gram-negative pathogenic bacilli.
 Methodology: The carbapenems used for strain susceptibility testing consisted of Ertapenem, Meropenem, Imipenem and Doripenem. Detection of the IMP and NDM resistance genes encoding carbapenemases was carried out by conventional PCR at LABIOGENE, and hydrolysis of the enzymatic crude extracts was performed.
 Results: Strains showed high levels of resistance to Ertapenem (64%), Meropenem (41%), Imipenem (53%) and Doripenem (73%). PCR amplification of carbapenem resistance genes showed that 32% of strains carried blaIMP, 16% of strains carried blaNDM. Both blaIMP & blaNDM were identified with a prevalence of 6.76%. Escherichia coli was the majority species harboring these genes. The kinetic constants of NDM carried by E. coli are Km=333µM and Vmax=0.5 A/min. Those of IMP carried by Klebsiella sp are Km=500µM and Vmax=0.6 A/min.
 Conclusion: This study enabled us to determine the rate of carbapenem resistance in Gram-negative bacteria. We noticed that Meropenem was the most active molecule. The study also enabled us to determine the affinity of two different bacterial enzymes to nitrocefin.