Multidrug-resistance in Enterobacteriaceae is an increasingly challenging problem from therapeutic, infection control and public health perspectives (Ben-
David et al., 2010).
One of the most important emerging resistance traits corresponds to the production of the carbapenem hydrolyzing β-lactamases, which confer resistance to almost all β-lactams. ( Nordmann et al., 2011).
The high rate of transmissibility of the carbapenemase genes, which are mostly located on self-conjugative plasmids carrying other resistance determinants, explains the need to rapidly identify the carbapenemase producers. In order to guide antibiotic therapy and prevent the development of outbreaks (Patrice and Laurent, 2013).
Carbapenemase-producing pathogens have been associated with high rates of morbidity and mortality, particularly among critically ill patients with prolonged hospitalization (Zarkotou et al., 2011).
Carbapenemase producing enterobacteriaceae (CPE) are usually multidrug- resistant pathogens, making them even more worrisome, since the treatment options are very restricted (Carmeli et al., 2010).
Carbapenemases hydrolyse most β-lactams, including the carbapenems (imipenem, ertapenem, meropenem, and doripenem) (Nordmann et al., 2011).
The clinically-significant carbapenemases in Enterobacteriaceae belong to several Ambler classes of ß-lactamases that differ by chemical structures and biochemical properties ( Ambler et al., 1991).
They are mostly of the Ambler class A (KPC) that hydrolyze all β- lactams and their activity is only inhibited partially in vitro by clavulanic acid, tazobactam and boronic acid. (Cuzon et al., 2011).
The zinc-dependent Ambler class B metallo-β-lactamases (MBLs) (NDM, VIM, and IMP) that hydrolyze all β- actams except aztreonam , their activit is not affected by any of the inhibitors that are in clinical use, but they can be inhibited in vitro with compounds such as zinc chelators (EDTA, for example) (Cuzon et al., 2011).
The level of resistance to carbapenems provided by those carbapenemase producers may vary significantly, making their detection difficult when based only on high-level carbapenem resistance (Castanheira et al., 2011).
The presence of carbapenemases in Klebsiella spp. and E. coli in the majority of hospitalized patients is considered an infection control emergency; therefore, clinical microbiology laboratories should be able to rapidly detect these enzymes among members of the Enterobacteriaceae (Nordmann et al., 2011).
Phenotypic and molecular-based techniques are able to identify these carbapenemase producers (Nordmann et al., 2012).
ChromID CARBA (by bioMérieux) is a chromogenic solid medium particularly designed for CPE detection and supplemented with specific agents that inhibit the growth of Gram positive and non carbapenemase producers (Vrioni et al., 2012).
Mast Diagnostics released commercial disks containing meropenem with different inhibitors designed for the detection of Enterobacteriaceae that produce different types of carbapenemase (Doyle et al., 2012).
Molecular-genetic techniques are now considered as the standard tests for the detection and identification of certain carbapenemase genes (Sandle et al., 2014).
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