NDM was the most common resistance enzyme detected in both groups examined in a Lebanese hospital study, and isolates carrying it were often less susceptible to the newer antibiotics tested in the laboratory. NDM was found in 64% of 100 carbapenem-resistant Escherichia coli isolates and 57.5% of 40 carbapenem-resistant Klebsiella pneumoniae isolates. OXA-48 was detected in 29% and 22.5% of the two groups, respectively.
The analysis covered 140 non-duplicate clinical isolates collected at the American University of Beirut Medical Center from January 2024 to February 2025: 100 E. coli and 40 K. pneumoniae. The study grouped the isolates by the carbapenemase detected, meaning the resistance enzyme identified as NDM or OXA-48, and compared how often different drugs were judged active against each group. In this context, susceptibility means the share of isolates that a laboratory test judged responsive to a drug.
A sharp divide by resistance type
The clearest split appeared in the routine drugs. Seven tested agents showed only 0% to 48% activity against NDM-producing K. pneumoniae. Among the E. coli isolates, tigecycline, fosfomycin and amikacin retained 79% to 100% activity in the NDM and OXA-48 groups.
Several newer drug combinations showed the same pattern. Meropenem-vaborbactam was active against 10% of NDM E. coli isolates and 6% of NDM K. pneumoniae isolates, compared with 96% and 55% of the corresponding OXA-48 groups. Ceftazidime-avibactam showed no activity against either NDM group, but was active against 86% of OXA-48 E. coli and 78% of OXA-48 K. pneumoniae.
Imipenem-relebactam also favored the OXA-48 groups, although the results were uneven. Susceptibility was 0% in both NDM groups, compared with 41% in OXA-48 E. coli and 11% in OXA-48 K. pneumoniae. The carbapenems tested performed poorly: ertapenem susceptibility was 2% in NDM E. coli and 0% in the other three groups, while imipenem susceptibility was 0%, 10%, 0% and 0% in NDM E. coli, OXA-48 E. coli, NDM K. pneumoniae and OXA-48 K. pneumoniae, respectively.
Cefiderocol also showed a clear gap between the resistance groups. It was active against 72% of NDM E. coli and 93% of OXA-48 E. coli, and against 60% of NDM K. pneumoniae and 100% of OXA-48 K. pneumoniae. These are laboratory susceptibility results, not evidence that cefiderocol or any other drug improves patient outcomes.
A focused laboratory snapshot
To build the sample, the laboratory identified isolates with MALDI-TOF and used the rapid NG-Test CARBA to determine the carbapenemase type. Carbapenem resistance was screened with ertapenem disk diffusion and confirmed with E-test minimum inhibitory concentrations for ertapenem, imipenem and meropenem, using CLSI interpretation.
For the newer agents, ceftazidime-avibactam was measured with an E-test, while imipenem-relebactam, meropenem-vaborbactam and cefiderocol were assessed using inhibition zones from disk diffusion, following CLSI guidance. The study therefore measured how the isolates responded under laboratory conditions; it did not test a treatment in patients.
Useful results, narrow reach
The results are not a national estimate for Lebanon. All 140 isolates came from one tertiary-care center, and the analysis did not include detailed patient histories or clinical outcomes. The carbapenemase test was not a molecular reference test, although the authors reported 99.2% sensitivity and 100% specificity for the Carba-5 test. Without broader molecular testing, the study may not identify every carbapenemase variant or alternative resistance mechanism.
The authors say the pattern calls for careful antimicrobial use, stewardship, surveillance, rapid detection and infection-control measures. Their conclusion is about in-vitro activity, not proven patient benefit or transmission effects. The authors reported that no financial support was received for the work or its publication.
Paper data and sources
Original title: Resistance to novel antimicrobial agents among NDM-and OXA-48-producing Carbapenem-resistant Enterobacterales in Lebanon
Authors: Araj G, Matar J, Al Ghor C et al.
Journal/Repository: Frontiers in cellular and infection microbiology
Status: Peer-reviewed
First online: 2026-10-09
DOI: Not available
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