Phenotypic detection of extended-spectrum β-lactamase production in Enterobacteriaceae: review and bench guide

Abstract

Strains of Enterobacteriaceae producing an extended spectrum beta-lactamase have become a concern in medical bacteriology as regards both antimicrobial treatment and infection control in hospitals. Extended-spectrum beta-lactamase (ESBL) detection tests should accurately discriminate between bacteria producing these enzymes and those with other mechanisms of resistance to beta-lactams, e.g., broad-spectrum beta-lactamases, inhibitor-resistant beta-lactamases and cephalosporinase overproduction. Several phenotypic detection tests, based on the synergy between a third-generation cephalosporin and clavulanate, have been designed: the double-disk synergy test (DDST), ESBL Etests, and the combination disk method. These tests often need to be refined in order for them to detect an ESBL in some bacterial strains, such as those that also overproduce a cephalosporinase. The sensitivity of the DDST can be improved by reducing the distance between the disks of cephalosporins and clavulanate. The use of cefepime, a fourth-generation cephalosporin that is less rapidly inactivated by cephalosporinase than by ESBL, improves the detection of synergy with clavulanate when there is simultaneous stable hyperproduction of a cephalosporinase; alternatively, the cephalosporinase can be inactivated by performing phenotypic tests on a cloxacillin-containing agar. Some beta-lactamases can hydrolyse both third-generation cephalosporins and carbapenems, such as the metallo-beta-lactamases, which are not inhibited by clavulanate, but rather by EDTA. The production of an ESBL masked by a metallo-beta-lactamase can be detected by means of double inhibition by EDTA and clavulanate. Since extended-spectrum Ambler class D oxacillinases are weakly inhibited by clavulanate and not inhibited by EDTA, their detection is difficult in the routine laboratory.

Surveillance of multidrug resistant uropathogenic bacteria in hospitalized patients in Indian

“…Moreover, it had been elucidated earlier that a drug resistant mutant in a population of 10 6 -10 8 cells is most likely, without any involvement of the widely-talked-about R-plasmids, conferring resistance [28] . It is also consensus that mechanisms of drug resistance are multidimensional and there may be the expression of certain genes, beta-lactamase that degrades the applied beta-lactam or cephalosporin antibiotics [29] , or carbapenemases, degrading meropenem or imipenem or altered channels in the cell membrane that would disallow antibiotics for the entry into cells of the pathogen. The later mechanism had been demonstrated in E. coli [30] .…”

Rapid molecular detection of extended-spectrum β-lactamase gene variants with a novel ligation-mediated real-time PCR

“…Several phenotypic detection methods have problems discriminating between ESBLs and other mechanisms of resistance to b-lactams, leading to false-positive results (Drieux et al, 2008). DNA-based ESBL assays, on the other hand, are complex, as over 300 different ESBL genes have been described, making it almost impossible to detect all ESBLs (Bradford, 2001;Gniadkowski, 2008).…”

Ventriculitis Associated with Extended Spectrum Beta-Lactamase Producing Klebsiella pneumoniae after Acupuncture

“…Cefpodoxime is commonly used as it is hydrolysed by TEM, SHV, and CTX-M types, but other cephalosporins such as cefotaxime, ceftriaxone, and ceftazidime are also used [49].…”