Journal of Global Antimicrobial Resistance (Dec 2024)
Phenotypic Detection of Carbapenemase Production Among Enterobacteriaceae Using a Modified Carbapenem Inactivation Method
Abstract
AIM: We aimed to evaluate the effectiveness of a modified Carbapenem Inactivation Method (CIM) in detecting carbapenemase production among different clinical Enterobacteriaceae strains. BACKGROUND: Given the increasing prevalence of carbapenem-resistant Enterobacteriaceae, there is a critical need for rapid and effective diagnostic methods for carbapenemase activity. While the original CIM provides a cost-effective approach for phenotypic detection, its modifications could potentially increase diagnostic accuracy and speed. METHODS: We analyzed 122 rectal swab samples from hospitalized patients using both the original and modified CIM (mCIM). Initial screening was conducted using MacConkey agar containing 2 mg/L meropenem. Species identification was confirmed via MALDI-TOF MS, and carbapenem resistance was assessed using a meropenem disk. The mCIM involved incubating swabs directly in nutrient broth at 35-37°C for 24 hours, followed by exposure to a 10 µg meropenem disk for two hours. The disk was then placed on Mueller-Hinton agar seeded with carbapenem-susceptible Escherichia coli (ATCC 29522), where inhibition zones of ≤16 mm indicated carbapenemase activity (Figure 1). RESULTS: Out of 53 isolated Enterobacteriaceae strains, 26 were meropenem-resistant. The mCIM identified carbapenemase activity in 53.8% of these resistant strains and 51.8% of meropenem-susceptible strains. In contrast, the CIM detected carbapenemase in only 26.9% of resistant strains and 7.4% of susceptible strains (Figure 2, Table 1). CONCLUSIONS: Our study demonstrated that mCIM significantly improves the detection of carbapenemase in both resistant and susceptible Enterobacteriaceae, suggesting its potential to enhance clinical diagnostics and treatment strategies. Polymerase chain reaction testing is needed to validate the findings.
