What are the procedures for Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF), Carba NP (Carbapenemase Non-Perturbative) test, Minimum Inhibitory Concentration for Imipenem (MICIM) / Minimum Inhibitory Concentration for Ertapenem (ECIM) test, Clostridioides difficile (CDT) test, and NG-Test Carba 5 (NG-Test Carbapenemase 5)?

From the Guidelines

The procedures for MALDI-TOF, Carba NP test, mCIM/eCIM test, CDT, and NG-Test CARBA 5 are essential diagnostic methods for detecting antimicrobial resistance, particularly carbapenemase production in bacteria, and should be used in clinical practice to guide treatment decisions, as recommended by recent guidelines 1. The use of these diagnostic methods can help identify carbapenemase-producing bacteria, which is crucial for optimizing treatment plans and improving patient outcomes, as highlighted in a recent study 1.

Key Procedures:

• MALDI-TOF (Matrix-Assisted Laser Desorption/Ionization Time-of-Flight) mass spectrometry identifies microorganisms by analyzing their protein profiles, with results available within minutes.
• The Carba NP test detects carbapenemase production through pH changes when carbapenem is hydrolyzed, requiring bacterial suspension mixed with imipenem and phenol red indicator, with color change from red to yellow indicating a positive result within two hours.
• The modified Carbapenem Inactivation Method (mCIM) and EDTA-modified Carbapenem Inactivation Method (eCIM) involve incubating bacterial suspensions with a meropenem disk, then placing the disk on an agar plate inoculated with susceptible E. coli, with growth around the disk indicating carbapenemase production.
• The Carbapenem Degradation Test (CDT) measures carbapenem degradation spectrophotometrically, requiring bacterial extracts mixed with carbapenem antibiotics and monitoring absorbance changes.
• The NG-Test CARBA 5 is an immunochromatographic assay that specifically detects five common carbapenemases (KPC, OXA-48-like, VIM, IMP, and NDM) from bacterial colonies within 15 minutes, offering rapid identification of specific carbapenemase types for targeted treatment decisions, as suggested by a recent guideline 1.

Clinical Context:

The diagnosis of bacterial infections, including those caused by carbapenem-resistant gram-negative bacilli, should be based on clinical signs and symptoms in combination with laboratory tests, as recommended by the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) 1. The interpretation of laboratory results should be done in the clinical context, taking into account the background prevalence of the bacteria in the institution, and repeated sample submission during the same episode is not recommended in an endemic situation, but may be useful in an epidemic situation 1. The use of these diagnostic methods can help reduce morbidity, mortality, and improve quality of life by guiding targeted treatment decisions, and should be prioritized in clinical practice, as supported by recent evidence 1.

From the Research

Procedure Overview

The procedures for MALDI-TOF, Carba NP test, MCIM/ECIM test, CDT, and NG-Test Carba 5 are as follows:

• MALDI-TOF: a mass spectrometry technique used for the rapid detection of carbapenemase-producing Enterobacteriaceae 2, 3, 4, 5
• Carba NP test: a phenotypic method for detecting carbapenemase production in Enterobacteriaceae 2, 3, 6, 4, 5
• MCIM/ECIM test: a modified carbapenem inactivation method for detecting carbapenemase production in Enterobacteriaceae 3
• CDT: no information available on this test in the provided studies
• NG-Test Carba 5: no information available on this test in the provided studies

Test Performance

The performance of these tests is as follows:

• MALDI-TOF: sensitivity ranging from 95% to 100% and specificity from 98.2% to 100% 2, with a fast turnaround time of less than 1.5 hours 2
• Carba NP test: sensitivity of 97% and specificity of 100% 3, with a high accuracy in detecting carbapenemase-producing Enterobacteriaceae 3, 6
• MCIM/ECIM test: sensitivity of 99% and specificity of 99% 3, with a high accuracy in detecting carbapenemase-producing Enterobacteriaceae 3

Comparison of Tests

The comparison of these tests is as follows:

• MALDI-TOF vs. Carba NP test: MALDI-TOF has a faster turnaround time and can provide concomitant identification of the bacterial isolate, while the Carba NP test has a higher sensitivity and specificity 2, 4
• MALDI-TOF vs. MCIM/ECIM test: both tests have high sensitivity and specificity, but the MCIM/ECIM test is recommended for its simplicity and cost-effectiveness 3

Limitations

The limitations of these studies are as follows:

• The studies only evaluated the performance of these tests in detecting carbapenemase-producing Enterobacteriaceae, and not other types of bacteria 2, 3, 6, 4, 5
• The studies did not provide information on the CDT and NG-Test Carba 5 tests, as they were not evaluated in the provided studies.