Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic Synergy

<b>Background</b>: Multi-drug-resistant Gram-negative bacteria producing metallo-β-lactamase are an increasing concern. Here, we described three cases of infection due to difficult-to-treat and drug-resistant <i>P. aeruginosa</i> producing metallo-β-lactamases, which were suc...

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Main Authors: Guido Granata, Carolina Venditti, Claudia Rotondo, Valentina Dimartino, Silvia D’Arezzo, Assunta Gallo, Gabriella Parisi, Alessandro Capone, Carla Fontana, Stefania Cicalini
Format: Article
Language:English
Published: MDPI AG 2025-02-01
Series:Antibiotics
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Online Access:https://www.mdpi.com/2079-6382/14/2/210
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author Guido Granata
Carolina Venditti
Claudia Rotondo
Valentina Dimartino
Silvia D’Arezzo
Assunta Gallo
Gabriella Parisi
Alessandro Capone
Carla Fontana
Stefania Cicalini
author_facet Guido Granata
Carolina Venditti
Claudia Rotondo
Valentina Dimartino
Silvia D’Arezzo
Assunta Gallo
Gabriella Parisi
Alessandro Capone
Carla Fontana
Stefania Cicalini
author_sort Guido Granata
collection DOAJ
description <b>Background</b>: Multi-drug-resistant Gram-negative bacteria producing metallo-β-lactamase are an increasing concern. Here, we described three cases of infection due to difficult-to-treat and drug-resistant <i>P. aeruginosa</i> producing metallo-β-lactamases, which were successfully treated with antibiotic combination of cefiderocol plus imipenem–relebactam, and reported on the molecular and epidemiological features of the isolates and the in vitro synergistic effects of different antibiotic combinations guiding antibiotic treatment. <b>Patients and methods</b>: Three <i>P. aeruginosa</i> strains were isolated from respiratory or blood cultures of three different patients. Minimum inhibitory concentrations breakpoints were interpreted according to EUCAST recommendations. Next-generation sequencing data were used for in silico identification of resistance genes and sequence types and for core genome multi-locus sequence typing analysis. The fractional inhibitory concentration index was performed as a measure of synergy of cefiderocol plus imipenem and imipenem–relebactam. <b>Results</b>: The three isolates exhibited different multi-drug-resistant and molecular profiles carrying blaIMP-13 (imipenemase metallo-β-lactamase-13) (isolates named Pse-1 and Pse-3) and blaVIM-2 (Verona integron-encoded metallo-β-lactamase-2) (isolate Pse-2). Typing showed that the isolates did not cluster and belonged to different sequence types. The E-test method showed the presence of synergy of cefiderocol in combination with imipenem–relebactam in the two <i>P. aeruginosa</i> isolates producing IMP-13 (Pse-1 and Pse-3). No synergy was observed in the isolate producing VIM-2 (Pse-2). <b>Conclusions</b>: Cefiderocol in association with imipenem–relebactam exhibited a synergistic effect against IMP-producing <i>P. aeruginosa</i> isolates. Further studies with a range of drugs and an expanded number of isolates are required to ascertain potential novel synergistic associations and the clinical utility of the fractional inhibitory concentration index.
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spelling doaj-art-b1d031c528b348cf8926ee3404baa3cc2025-08-20T03:11:06ZengMDPI AGAntibiotics2079-63822025-02-0114221010.3390/antibiotics14020210Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic SynergyGuido Granata0Carolina Venditti1Claudia Rotondo2Valentina Dimartino3Silvia D’Arezzo4Assunta Gallo5Gabriella Parisi6Alessandro Capone7Carla Fontana8Stefania Cicalini9Systemic and Immune Depression-Associated Infection Unit, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, Via Portuense 292, 00149 Rome, ItalyLaboratory of Microbiology, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, 00149 Rome, ItalyLaboratory of Microbiology, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, 00149 Rome, ItalyLaboratory of Microbiology, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, 00149 Rome, ItalyLaboratory of Microbiology, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, 00149 Rome, ItalyLaboratory of Microbiology, S. Camillo Hospital, 00149 Rome, ItalyLaboratory of Microbiology, S. Camillo Hospital, 00149 Rome, ItalySystemic and Immune Depression-Associated Infection Unit, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, Via Portuense 292, 00149 Rome, ItalyLaboratory of Microbiology, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, 00149 Rome, ItalySystemic and Immune Depression-Associated Infection Unit, National Institute for Infectious Diseases “L. Spallanzani”, IRCCS, Via Portuense 292, 00149 Rome, Italy<b>Background</b>: Multi-drug-resistant Gram-negative bacteria producing metallo-β-lactamase are an increasing concern. Here, we described three cases of infection due to difficult-to-treat and drug-resistant <i>P. aeruginosa</i> producing metallo-β-lactamases, which were successfully treated with antibiotic combination of cefiderocol plus imipenem–relebactam, and reported on the molecular and epidemiological features of the isolates and the in vitro synergistic effects of different antibiotic combinations guiding antibiotic treatment. <b>Patients and methods</b>: Three <i>P. aeruginosa</i> strains were isolated from respiratory or blood cultures of three different patients. Minimum inhibitory concentrations breakpoints were interpreted according to EUCAST recommendations. Next-generation sequencing data were used for in silico identification of resistance genes and sequence types and for core genome multi-locus sequence typing analysis. The fractional inhibitory concentration index was performed as a measure of synergy of cefiderocol plus imipenem and imipenem–relebactam. <b>Results</b>: The three isolates exhibited different multi-drug-resistant and molecular profiles carrying blaIMP-13 (imipenemase metallo-β-lactamase-13) (isolates named Pse-1 and Pse-3) and blaVIM-2 (Verona integron-encoded metallo-β-lactamase-2) (isolate Pse-2). Typing showed that the isolates did not cluster and belonged to different sequence types. The E-test method showed the presence of synergy of cefiderocol in combination with imipenem–relebactam in the two <i>P. aeruginosa</i> isolates producing IMP-13 (Pse-1 and Pse-3). No synergy was observed in the isolate producing VIM-2 (Pse-2). <b>Conclusions</b>: Cefiderocol in association with imipenem–relebactam exhibited a synergistic effect against IMP-producing <i>P. aeruginosa</i> isolates. Further studies with a range of drugs and an expanded number of isolates are required to ascertain potential novel synergistic associations and the clinical utility of the fractional inhibitory concentration index.https://www.mdpi.com/2079-6382/14/2/210carbapenem-resistant <i>Pseudomonas aeruginosa</i>metallo-β-LactamaseIMP-13 carbapenemasesantimicrobial synergycefiderocolimipenem–relebactam
spellingShingle Guido Granata
Carolina Venditti
Claudia Rotondo
Valentina Dimartino
Silvia D’Arezzo
Assunta Gallo
Gabriella Parisi
Alessandro Capone
Carla Fontana
Stefania Cicalini
Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic Synergy
Antibiotics
carbapenem-resistant <i>Pseudomonas aeruginosa</i>
metallo-β-Lactamase
IMP-13 carbapenemases
antimicrobial synergy
cefiderocol
imipenem–relebactam
title Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic Synergy
title_full Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic Synergy
title_fullStr Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic Synergy
title_full_unstemmed Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic Synergy
title_short Combating Metallo-β-Lactamase-Producing <i>Pseudomonas aeruginosa</i>: The Fractional Inhibitory Concentration Index as a Tool to Evaluate Antibiotic Synergy
title_sort combating metallo β lactamase producing i pseudomonas aeruginosa i the fractional inhibitory concentration index as a tool to evaluate antibiotic synergy
topic carbapenem-resistant <i>Pseudomonas aeruginosa</i>
metallo-β-Lactamase
IMP-13 carbapenemases
antimicrobial synergy
cefiderocol
imipenem–relebactam
url https://www.mdpi.com/2079-6382/14/2/210
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