Evaluation of NitroSpeed-Carba NP test for rapid identification among different classes of carbapenemases in Enterobacterales and Pseudomonas aeruginosa

Diagnostic Test Precision of Modified Carbapenem Inactivation Method and Carbapenemase Nordmann-Poirel Test for Phenotypic Detection of Carbapenemase Production in Enterobacterales: A Systematic Review

Carbapenem-resistant Enterobacterales, particularly those that produce carbapenemases, pose a significant public health concern due to very limited treatment options. The timely identification of carbapenemase-producing Enterobacterales (CPE) is essential for putting in place efficient infection control measures and selecting appropriate antimicrobial therapies, thereby improving the clinical outcome of the patient. The purpose of this systematic review is to compare the diagnostic accuracy and practicality between two phenotypic tests, namely the modified carbapenem inactivation method (mCIM) and carbapenemase Nordmann-Poirel (Carba NP) test, in detecting carbapenemase production by Enterobacterales and thereby aiding the clinician in making a decision to choose an appropriate test for their phenotypic detection. This systematic review involved combining sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), accuracy, diagnostic odds ratio with 95% confidence interval (CIs), Forest plot for sensitivity and specificity, and plotting suitable summary receiver operating characteristic curve with the area under the curve. Of the 20 studies included in this review, the overall effect sizes of Carba NP and mCIM with 95% CIs were as follows: sensitivity, 91% (86-96%) and 97% (95-99%); specificity, 93% (88-97%) and 97% (93-100%); PPV, 97% and 98%; NPV, 79% and 90%; accuracy, 93% and 97%; diagnostic odds ratio, 1487.8879 and 8527.5541; and AUC, 0.85 and 1, respectively. In conclusion, the mCIM method showed superior sensitivity (97%), specificity (97%), and accuracy compared to the Carba NP test in detecting carbapenemase production, even though both these methods had a few technical limitations. The Carba NP test is rapid, affordable, and dependable, whereas mCIM is more accurate and cost-effective but time-consuming. We propose that both tests can be reliably used for screening of carbapenemase production in Enterobacterales, as endorsed by the Clinical and Laboratory Standards Institute even in resource-limited clinical laboratories, in the order of prioritizing the mCIM method first and then followed by the Carba NP test when situation demands expedited results.

Detection of rare carbapenemases in Enterobacterales-comparison of two colorimetric and three CIM-based carbapenemase assays

Rapid and reliable detection of carbapenemase-producing Enterobacterales (CPE) is crucial for prompt treatment and infection control. Most assays target the primary four enzymes (KPC, OXA-48-like, VIM, and NDM), often missing less common variants (e.g., GES, IMI, OXA-23, and OXA-58). Therefore, assays based on the hydrolysis of carbapenems are recommended in addition to differentiation tests such as PCR or immunochromatographic assays. The aim of this study was to compare the currently Clinical and Laboratory Standards Institute (CLSI)-recommended tests mCIM (modified carbapenem inactivation method) and Carba NP with new colorimetric tests (NitroSpeed-Carba NP) and novel variations of the carbapenem inactivation method (CIM) such as simplified CIM (sCIM) or modified zinc-supplemented CIM (mzCIM). The challenge collection included 205 clinical isolates, 139 CPE vs 66 non-CPE. Among all 205 isolates, the sensitivity/specificity of mCIM was 81.3%/98.5%, Carba NP 76.3%/100%, NitroSpeed-Carba NP 86.3%/78.8%, sCIM 100%/94%, and mzCIM 97.8%/98.5%. For rare carbapenemases (n = 48), the sensitivity of mzCIM (98.3%) and sCIM (100%) was higher than that of mCIM (60.4%), Carba NP (50%), or NitroSpeed-Carba NP (70.2%). Most indeterminate results occurred for mCIM (14.4%), Carba NP (8.2%), and sCIM (6.3%). The detection of rare carbapenemases remains challenging with the currently recommended assays. The CIM-based tests demonstrated superior sensitivity, with sCIM and mzCIM outperforming the currently recommended mCIM and Carba NP, especially among isolates with weakly hydrolyzing carbapenemases (e.g., OXA-23 and OXA-58). Although colorimetric assays provide more rapid results, laboratories have to be aware of the low sensitivity for rare carbapenemases. Both sCIM and the new mzCIM performed well, are cost-effective, and can easily be implemented in any laboratory.IMPORTANCEDetection of so-called rare carbapenemases (e.g., GES, IMI, OXA-23, and OXA-58) in Enterobacterales is challenging, and data on the performance of currently available assays are scarce. This study systematically assessed the performance of currently recommended and novel hydrolysis-based assays on a set of molecularly characterized isolates. It demonstrates that the currently recommended assays mCIM and Carba NP perform well on isolates producing common carbapenemases such as KPC, VIM, NDM, and OXA-48, but have only a moderate sensitivity in the detection of rare carbapenemases. In contrast, the newer CIM-based variants, sCIM and mzCIM, are equally capable of detecting frequent and uncommon carbapenemases. These assays could potentially help to improve our knowledge on the epidemiology of these "rare" enzymes.

Advances in the detection of β-lactamase: A review

β-lactamase, an enzyme secreted by bacteria, is the main resistant mechanism of Gram-negative bacteria to β-lactam antibiotics. The resistance of bacteria to β-lactam antibiotics can be evaluated by testing the activity of β-lactamase. Traditional phenotypic detection is a golden principle, but it is time-consuming. In recent years, many new methods have emerged, which improve the efficiency by virtue of their sensitivity, low cost, easy operation, and other advantages. In this paper, we systematically review these researches and emphasize their limits of detection, sample operation, and test duration. Noteworthily, some detection systems can identify the β-lactamase subtype conveniently. We mainly divide these tests into three categories to elaborate their characteristics and application status. Both advantages and disadvantages of these methods are discussed. Additionally, we analyze the recent 5 years published researches to predict the trend of development in this field.

The development of a colorimetric biosensing assay for the detection of Helicobacter pylori in feces

As Helicobacter pylori (H. pylori) is closely related to the occurrence of gastric diseases such as chronic gastritis, peptic ulcer, and gastric cancer, early detection of H. pylori is an urgent need. In this study, oligonucleotide probes conjugated with gold nanoparticles (AuNPs) were used in combination with H. pylori-specific aptamers for the rapid detection of H. pylori in stool samples, which converted the method of detection from proteins to nucleic acids. Therefore, qualitative detection of H. pylori can be achieved by observing color changes through the aggregation (red to purple) or deaggregation (purple to red) of AuNPs, and further quantitative detection can be achieved through UV spectrometry. The detection limit of the colorimetric biosensing method is 25 CFU/mL (S/N = 3), which is favorably comparable to other reported detection methods. Compared with the existing detection methods for H. pylori, this colorimetric biosensing method has no limitations to the test subjects. All these features render the colorimetric biosensing assay a promising method for the clinical field detection of H. pylori.