Phenotypic methods for the detection of metallo-beta-lactamase production by gram-negative bacterial isolates from hospitalized patients in a Tertiary care hospital in India

Drug resistant bacteria are a global health concern owing to the high morbidity and mortality they can cause, especially in countries such as India. Gram-negative bacteria, including Enterobacteriaceae, Pseudomonas, and Acinetobacter, are primarily responsible for expanding the scope of drug resistance. These antibiotic-resistant pathogens are particularly associated with serious infections in hospitals. The production of carbapenemase by gram-negative bacteria appears to be the major reason for their resistance to carbapenems. The study was a prospective study done from March 2018 to December2020. All the carbapenem-resistant isolates from various clinical samples were further tested for the production of carbapenemases/metallo-beta-lactamases production by various phenotypic tests like carbaNp, Imipenem–EDTA combined disc synergy test, Double-disc synergy test and E-test methods. Of all carbapenem-resistant gram-negative bacteria isolated from patients in a hospital in India, 237 (88.1%) carbapenemase producers were identified, among which 217 (91.5%) were metallo-betalactamase (MBL) producers. Therefore, the detection of MBL producers is important for preventing their infectious spread. The present study revealed that most MBL producers were isolated from patients of 0–9 to years of age (63.9%). The double-disc synergy test (DDST) and E-test MBL strips were more sensitive than the combined disc test in detecting MBLs. Because the DDST was the simplest and most effective method, it can be used for the routine laboratory screening of MBL producers in hospitals.