Detection of Multidrug-Resistant Enterobacterales-From ESBLs to Carbapenemases

Abstract

Multidrug-resistant Enterobacterales (MDRE) are an emerging threat to global health, leading to rising health care costs, morbidity and mortality. Multidrug-resistance is commonly caused by different β-lactamases (e.g., ESBLs and carbapenemases), sometimes in combination with other resistance mechanisms (e.g., porin loss, efflux). The continuous spread of MDRE among patients in hospital settings and the healthy population require adjustments in healthcare management and routine diagnostics. Rapid and reliable detection of MDRE infections as well as gastrointestinal colonization is key to guide therapy and infection control measures. However, proper implementation of these strategies requires diagnostic methods with short time-to-result, high sensitivity and specificity. Therefore, research on new techniques and improvement of already established protocols is inevitable. In this review, current methods for detection of MDRE are summarized with focus on culture based and molecular techniques, which are useful for the clinical microbiology laboratory.

Keywords: CPE; ESBL; carbapenemase; detection methods; multidrug resistance; preanalytical parameters.

Figure 1

Ambler’s classification with examples of main β-lactamases in Enterobacterales.

Figure 2

ESBL and carbapenemase detection by disc diffusion tests. Schematic overview of disc diffusion assay variations for detection of ESBL and carbapenemase-producing strains. (A) Principle of susceptibility testing by disc diffusion assay. (B) Modified Hodge test. (C) Combined disc test. (D) Double-disc synergy test. (E) β-lactam inactivation assay (e.g., CIM).

Figure 3

Principle of colorimetric assays for detection of ESBLs and carbapenemases. The test isolate is lysed and incubated in phenol red solution with an antibiotic. (a) If the test isolate is positive for ESBL/carbapenemase production, the enzyme hydrolyzes the antibiotic, resulting in a pH shift and a color change from magenta to yellow. (b) ESBL/carbapenemase-negative isolates do not induce a change in color. (c) Addition of enzyme-specific inhibitors prevents hydrolysis of the antibiotic, and no color change is visible.

Figure 4

Basic principle of lateral flow assays. Schematic illustration of different zones of commercially available lateral flow assays for detection of, i.e., β-lactamases. Antigens within the sample migrate along the nitrocellulose membrane by capillary flow. Antigens (e.g., β-lactamase) conjugate with specific dye-labeled antibodies and are captured by immobilized antigen-specific antibodies, resulting in the visualization of the test line. Non-conjugated and unbound antibodies migrate further to the control line and are captured by immobilized anti-IgG antibodies, resulting in the visibility of a control line.

Figure 5

Algorithm for the detection of carbapenemases in routine laboratory as proposed by Baeza et al. * OXA-48-like KPC, VIM, NDM, (IMP). ** Multiplex PCR targeting rare carba-penemases (e.g., IMI, GES, etc.), whole genome sequencing, other tests [61].