Evaluation of inhibitor-combination mCIM for detecting MBL-producing Enterobacterales using three MBL inhibitors

Tackling Carbapenem Resistance and the Imperative for One Health Strategies-Insights from the Portuguese Perspective

Carbapenemases, a class of enzymes specialized in the hydrolysis of carbapenems, represent a significant threat to global public health. These enzymes are classified into different Ambler's classes based on their active sites, categorized into classes A, D, and B. Among the most prevalent types are IMI/NMC-A, KPC, VIM, IMP, and OXA-48, commonly associated with pathogenic species such as Acinetobacter baumannii, Klebsiella pneumoniae, and Pseudomonas aeruginosa. The emergence and dissemination of carbapenemase-producing bacteria have raised substantial concerns due to their ability to infect humans and animals (both companion and food-producing) and their presence in environmental reservoirs. Adopting a holistic One Health approach, concerted efforts have been directed toward devising comprehensive strategies to mitigate the impact of antimicrobial resistance dissemination. This entails collaborative interventions, highlighting proactive measures by global organizations like the World Health Organization, the Center for Disease Control and Prevention, and the Food and Agriculture Organization. By synthesizing the evolving landscape of carbapenemase epidemiology in Portugal and tracing the trajectory from initial isolated cases to contemporary reports, this review highlights key factors driving antibiotic resistance, such as antimicrobial use and healthcare practices, and underscores the imperative for sustained vigilance, interdisciplinary collaboration, and innovative interventions to curb the escalating threat posed by antibiotic-resistant pathogens. Finally, it discusses potential alternatives and innovations aimed at tackling carbapenemase-mediated antibiotic resistance, including new therapies, enhanced surveillance, and public awareness campaigns.

Practical agar-based disk-diffusion tests using sulfamoyl heteroarylcarboxylic acids for identification of subclass B1 metallo-β-lactamase-producing Enterobacterales

The worldwide distribution of carbapenemase-producing Enterobacterales (CPE) is a serious public health concern as they exhibit carbapenem resistance, thus limiting the choice of antimicrobials for treating CPE infections. The combination treatment with a β-lactam and one of the newly approved β-lactamase inhibitors, such as avibactam, relebactam, or vaborbactam, provides a valuable tool to cope with CPE; however, these inhibitors are active only against serine-type carbapenemases, and not against metallo-β-lactamases (MβLs). Therefore, it is important to readily differentiate carbapenemases produced by CPE by using simple and reliable methods in order to choose an appropriate treatment. Here, we developed three practical agar-based disk-diffusion tests (double-disk synergy test [DDST], disk potentiation test, and modified carbapenem inactivation method [mCIM]) to discriminate the production of subclass B1 MβLs, such as IMP-, NDM-, and VIM-type MβLs, from the other carbapenemases, especially serine-type carbapenemases. This was accomplished using B1 MβL-specific sulfamoyl heteroarylcarboxylic acid inhibitors, 2,5-dimethyl-4-sulfamoylfuran-3-carboxylic acid (SFC) and 2,5-diethyl-1-methyl-4-sulfamoylpyrrole-3-carboxylic acid (SPC), originally developed by us. The DDST and mCIM using SFC and SPC revealed high sensitivity (95.3%) and specificity (100%) in detecting B1 MβL-producing Enterobacterales. In disk potentiation test, the sensitivities using SFC and SPC were 89.1% and 93.8%, respectively, whereas the specificities for both were 100%. These methods are simple and inexpensive, and have a high accuracy rate. These methods would, therefore, be of immense assistance in the specific detection and discrimination of B1 MβL-producing Enterobacterales in clinical microbiology laboratories, and would lead to better prevention against infection with such multidrug-resistant bacteria in clinical settings.

Modified CIM test as a useful tool to detect carbapenemase activity among extensively drug-resistant Klebsiella pneumoniae, Escherichia coli and Acinetobacter baumannii

Purpose

Timely detection of carbapenemases is essential for developing strategies to control the spread of infections by carbapenem-resistant isolates. The purpose of this study was to determine the epidemiology of carbapenemase genes among carbapenem-resistant isolates of Acinetobacter baumannii, Klebsiella pneumoniae, and Escherichia coli. In addition, the efficacy of the modified Hodge test (MHT), Carba NP test, and modified carbapenem inactivation method (mCIM) were compared.

Methods

A total of 122 carbapenem-resistant clinical isolates including 77 K. pneumoniae, 39 A. baumannii, and six E. coli were collected from hospitalized patients. Three phenotypic methods, including the MHT, Carba NP test, and mCIM were used for investigation of carbapenemase production. In addition, polymerase chain reaction (PCR) was performed to detect carbapenemase-encoding genes.

Result

The sensitivity and specificity of the MHT were 75.0% and 100%, respectively. In addition, Carba NP displayed 80.8% sensitivity and 100% specificity, whereas the sensitivity and specificity were 90.4% and 100% for the mCIM test, respectively. Among carbapenem-resistant isolates, 70, 84, and 87 isolates exhibited positive results according to the MHT, Carba NP test, and mCIM, respectively. PCR indicated the presence of one or more carbapenemase genes in 119 of carbapenem-resistant isolates, with blaKPC and blaVIM being the most commonly encountered. Co-production of ‘KPC and OXA-48’, ‘KPC and VIM’, and ‘KPC and IMP’ was detected in three, nine, and seven isolates, respectively.

Conclusion

Our results confirm that the mCIM test is a useful tool for the reliable detection of carbapenemase activity in enterobacterial isolates, especially in clinical microbiological laboratories with limited resources.

Comparison of four low-cost carbapenemase detection tests and a proposal of an algorithm for early detection of carbapenemase-producing Enterobacteriaceae in resource-limited settings

Rapidly progressing antibiotic resistance is a great challenge in therapy. In particular, the infections caused by carbapenem-resistant Enterobacteriaceae (CRE) are exceedingly difficult to treat. Carbapenemase production is the predominant mechanism of resistance in CRE. Early and accurate identification of carbapenemase-producing carbapenem-resistant Enterobacteriaceae (CP-CRE) is extremely important for the treatment and prevention of such infections. In the present study, four phenotypic carbapenemase detection tests were compared and an algorithm was developed for rapid and cost-effective identification of CP-CRE. A total of 117 Enterobacteriaceae (54 CP-CRE, 3 non-CP-CRE, and 60 non-CRE) isolates were tested for carbapenemase production using modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), Carba NP test (CNPt), and CNPt-direct test. The overall sensitivity/specificity values were 90.7%/92.1% for MHT, 100%/100% for mCIM, 75.9%/100% for CNPt, and 83.3%/100% for CNPt-direct. OXA-48-like enzymes were detected with 93.2% sensitivity by MHT and >77.3% sensitivity by two Carba NP tests. MHT could only detect half of the NDM carbapenemase producers. CNPt-direct exhibited enhanced sensitivity compared to CNPt (100% vs 25%) for detection of NDM producers. Considering these findings we propose CNPt-direct as the first test followed by mCIM for rapid detection of CP-CRE. With this algorithm >80% of the CP-CRE could be detected within 24 hours from the time the sample is received and 100% CP-CRE could be detected in day two. In conclusion, mCIM was the most sensitive assay for the identification of CP-CRE. CNPt-direct performed better than CNPt. An algorithm consisting CNPt-direct and mCIM allows rapid and reliable detection of carbapenemase production in resource-limited settings.

EDTA-modified carbapenem inactivation method (eCIM) for detecting IMP Metallo-β-lactamase-producing Pseudomonas aeruginosa: an assessment of increasing EDTA concentrations

Background

Prompt identification of carbapenemase-harboring organisms is valuable in informing therapeutic and infection-control measures. The modified carbapenem inactivation method (mCIM) and EDTA-modified carbapenem inactivation method (eCIM) are inexpensive and easy to interpret phenotypic tests endorsed by the Clinical and Laboratory Standards Institute (CLSI) for the detection of carbapenemase-harboring Enterobacterales. Only mCIM is endorsed by CLSI for detecting carbapenemase-harboring Pseudomonas aeruginosa. eCIM’s ability to delineate serine and metallo-β-lactamases (MBL) could be advantageous in areas prevalent with carbapenemase-harboring P. aeruginosa. A recent assessment of mCIM/eCIM on MBL-harboring P. aeruginosa demonstrated high eCIM sensitivity for NDMs and VIMs but not for IMP-producers. Therefore, this study aimed to determine whether increasing EDTA concentrations would enhance eCIM sensitivity for a collection of IMP-harboring P. aeruginosa isolates.

Twenty-six IMP-harboring P. aeruginosa isolates were utilized. For test validation, additional P. aeruginosa isolates harboring NDM (n = 3), VIM (n = 3), KPC (n = 8), wild-type (n = 1), and Enterobacterales isolates harboring IMP (n = 6) and NDM (n = 1) were assessed. The mCIM test was conducted as outlined by CLSI. Simultaneously, the eCIM test was performed with the standard 5 mM EDTA concentration and doubling EDTA concentrations: 10 mM, 20 mM, and 40 mM.

Results

Concentration-dependent improvement was observed among the IMP-harboring P. aeruginosa with eCIM sensitivities at 0, 31, 85, and 100% respectively. Remaining Enterobacterales and P. aeruginosa responded concordantly with their genotype at the standard 5 mM eCIM concentration, with doubling EDTA concentrations providing no greater sensitivity.

Conclusion

Combination of mCIM and an eCIM with a 40 mM EDTA concentration appropriately capture IMP-harboring P. aeruginosa without sacrificing test utility for other carbapenemase-harboring isolates.