scholarly journals Comparison of the In Vitro Susceptibility of Ceftolozane-Tazobactam With the Cumulative Susceptibility Rates of Standard Antibiotic Combinations When Tested Against Pseudomonas aeruginosa From ICU Patients With Bloodstream Infections or Pneumonia

2019 ◽  
Vol 6 (6) ◽  
Author(s):  
Dee Shortridge ◽  
Michael A Pfaller ◽  
S J Ryan Arends ◽  
Janet Raddatz ◽  
Daryl D DePestel ◽  
...  

Abstract Background Pseudomonas aeruginosa remains an important cause of hospital-acquired infections in the United States and is frequently multidrug-resistant (MDR). The Infectious Diseases Society of America guidelines recommend empiric combination therapy that includes an antipseudomonal β-lactam with an aminoglycoside or fluoroquinolone likely to cover ≥95% of P. aeruginosa infections in seriously ill patients at risk of having an MDR pathogen. Ceftolozane is an antipseudomonal cephalosporin, combined with the β-lactamase inhibitor tazobactam. Ceftolozane-tazobactam is approved for treatment of complicated urinary tract infections and complicated intra-abdominal infections. A phase 3 clinical trial for the treatment of hospital-acquired pneumonia including ventilator-associated pneumoniae was recently completed. We compared the in vitro susceptibility rate of ceftolozane-tazobactam with the cumulative susceptibility rates of antibiotic combinations commonly used against P. aeruginosa. Methods Isolates were collected from intensive care unit patients hospitalized in 32 US hospitals from 2011 to 2017. The susceptibilities of 1543 P. aeruginosa isolates from bloodstream infections (198 isolates, 12.8%) or pneumonia (1345 isolates, 87.2%) were determined for ceftolozane-tazobactam and comparators. Results The most active antimicrobials were colistin (99.4% susceptible), amikacin (98.1% susceptible), and ceftolozane-tazobactam (96.5% susceptible). The susceptibilities to other antipseudomonal β-lactams and fluoroquinolones were <84%. A cumulative susceptibility of ≥95% was reached for cefepime, ceftazidime, meropenem, and piperacillin-tazobactam only in combination with amikacin due to the lower susceptibilities of gentamicin, ciprofloxacin, and levofloxacin. Monotherapies that exceeded 95% were ceftolozane-tazobactam, amikacin, and colistin. Conclusions Ceftolozane-tazobactam monotherapy is likely to be active against more isolates than a combination of another β-lactam and a fluoroquinolone or gentamicin for serious P. aeruginosa infections.

2020 ◽  
Vol 7 (Supplement_1) ◽  
pp. S733-S733
Author(s):  
Dee Shorttidge ◽  
Jennifer M Streit ◽  
Michael D Huband ◽  
Robert K Flamm

Abstract Background Delafloxacin (DLX) is an anionic fluoroquinolone (FQ) that has been approved in the United States and in Europe for the treatment of acute bacterial skin and skin structure infections and was recently approved in the US for treatment of community-acquired bacterial pneumonia (CABP). In the present study, in vitro susceptibility (S) results for DLX and comparator agents were determined for CABP pathogens including Streptococcus pneumoniae (SPN), Haemophilus influenzae (HI), H. parainfluenzae (HP) and Moraxella catarrhalis (MC) clinical isolates from European hospitals participating in the SENTRY Program during 2014-2019. Methods A total of 2,835 SPN, 1,484 HI, 959 MC, and 20 HP isolates were collected from community-acquired respiratory tract infections (CARTI) during 2014-2019 from European hospitals. Sites included only 1 isolate/patient/infection episode. Isolate identifications were confirmed at JMI Laboratories. Susceptibility testing was performed according to CLSI broth microdilution methodology, and EUCAST (2020) breakpoints were applied where applicable. Other antimicrobials tested included levofloxacin (LEV) and moxifloxacin (MOX; not tested in 2015). Multidrug-resistant (MDR) SPN isolates were categorized as being nonsusceptible (NS) to amoxicillin-clavulanate, erythromycin (ERY), and tetracycline; other SPN phenotypes were ERY-NS, or penicillin (PEN)-NS. β-lactamase (BL) presence was determined for HI, HP, and MC. Results The activities of the 3 FQs are shown in the table. The most active agent against SPN was DLX, with the lowest MIC50/90 values of 0.015/0.03 mg/L. DLX activities were the same when tested against the MDR or PEN-NS for SPN phenotypes. ERY-NS isolates had DLX MIC50/90 results of 0.015/0.03 mg/L. DLX was the most active FQ against HI, HP, and MC. BL presence did not affect FQ MIC values for HI or MC; only 1 HP isolate was BL-positive. Conclusion DLX demonstrated potent in vitro antibacterial activity against SPN, HI, HP, and MC. DLX was active against MDR SPN that were NS to the agents commonly used as treatments for CABP. These data support the utility of DLX in CABP including when caused by antibiotic resistant strains. Table 1 Disclosures Jennifer M. Streit, BS, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support) Robert K. Flamm, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Amplyx Pharmaceuticals (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)


2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S577-S578
Author(s):  
Dee Shortridge ◽  
Jennifer M Streit ◽  
Michael D Huband ◽  
Robert K Flamm

Abstract Background Delafloxacin (DLX) is an anionic fluoroquinolone (FQ) antimicrobial that was approved in 2017 by the United States (US) Food and Drug Administration for the treatment of acute bacterial skin and skin structure infections. DLX recently successfully completed a clinical trial for the treatment of community-acquired bacterial pneumonia (CABP). In the present study, in vitro susceptibility (S) results for DLX and comparator agents were determined for CABP pathogens including Streptococcus pneumoniae (SPN), Haemophilus influenzae (HI), H. parainfluenzae (HP) and Moraxella catarrhalis (MC) clinical isolates from US hospitals participating in the SENTRY Program during 2014–2018. Methods A total of 1,975 SPN, 1,128 HI, 684 MC, and 43 HP isolates were collected from community-acquired respiratory tract infections (CARTI) during 2014–2018 from US hospitals. Sites included only 1 isolate/patient/infection episode. Isolate identifications were confirmed at JMI Laboratories. Susceptibility testing was performed according to CLSI broth microdilution methodology, and CLSI (2019) breakpoints were applied where applicable. Other antimicrobials tested included levofloxacin (LEV) and moxifloxacin (MOX; not tested in 2015). Multidrug-resistant (MDR) SPN isolates were categorized as being nonsusceptible (NS) to amoxicillin-clavulanate, erythromycin, and tetracycline; other SPN phenotypes were LEV-NS or penicillin (PEN)-NS. β-Lactamase (BL) presence was determined for HI, HP, and MC. Results The activities of the 3 FQs are shown in the table. The most active agent against SPN was DLX, with the lowest MIC50/90 values of 0.015/0.03 mg/L. DLX activities were similar when tested against the MDR or PEN-NS for SPN phenotypes. LEV-NS isolates had DLX MIC50/90 results of 0.12/0.25 mg/L. DLX was the most active FQ against HI, HP, and MC. BL presence did not affect FQ MIC values for HI or MC; only 2 HP isolates were BL-positive. Conclusion DLX demonstrated potent in vitro antibacterial activity against SPN, HI, HP, and MC. DLX was active against MDR SPN that were NS to the agents commonly used as treatments for CABP. DLX had excellent activity against LEV-NS SPN. These data support the continued study of DLX as a potential treatment for CABP. Disclosures All authors: No reported disclosures.


2016 ◽  
Vol 19 (4) ◽  
pp. 448 ◽  
Author(s):  
Katie E. Barber ◽  
Jessica K. Ortwine ◽  
Ronda L Akins

Purpose: Gram-negative resistance continues to rise with treatment options becoming more limited. Ceftazidime/avibactam was recently approved in the United States and Europe, which combines an established third-generation cephalosporin with a new, unique, non-β-lactam β-lactamase inhibitor. This review conducts a thorough examination of structure, pharmacology, spectrum of activity, pharmacokinetics/pharmacodynamics, in vitro and clinical efficacy and safety/tolerability of ceftazidime/avibactam, as well as detailed future directions for the agent. Methods: Pubmed and clinicaltrials.gov searches, as well as abstracts from the 2015 Interscience Conference on Antimicrobial Agents and Chemotherapy/International Society of Chemotherapy (ICAAC/ICC) and ID Week meetings and the 2016 American Society of Microbiology Microbe meeting, were conducted from January 2004 – September 2016. Relevant search terms included ceftazidime, ceftazidime/avibactam, avibactam, NXL104 and AVE1330A. The US package insert for ceftazidime/avibactam (02/2015) and European public assessment report (06/2016) were also reviewed. Results: In vitro susceptibility for ceftazidime/avibactam displayed potent activity against many Enterobacteriaceae including extended-spectrum-β-lactamase (ESBL) and carbapenemase-producing strains, as well as Pseudomonas aeruginosa. Phase II clinical trials utilized for approval demonstrated comparable safety and efficacy to imipenem/cilistatin for treatment of complicated urinary tract infections (70.4% vs. 71.4%) and combined with metronidazole compared to meropenem in complicated intra-abdominal infections (91.2% vs 93.4%). Phase III data displayed non-inferior efficacy of ceftazidime/avibactam compared to doripenem for complicated urinary tract infections (70.2% vs 66.2%) and combined with metronidazole compared to meropenem in complicated intra-abdominal infections (82.5% vs 84.9%), as well as comparable safety. Ceftazidime/avibactam was well-tolerated but does require renal adjustments. Additionally, 3 case series and a single case report have demonstrated the potential for ceftazidime/avibactam against multidrug resistant organisms for compassionate use or failure after previous therapy. Conclusion: By adding avibactam to ceftazidime, clinicians’ antimicrobial armamentarium is expanded, potentially increasing the ability to combat multi-drug resistant gram-negative pathogens, particularly ESBL and carbapenemase-producing organisms, as well as Pseudomonas aeruginosa. This article is open to POST-PUBLICATION REVIEW. Registered readers (see “For Readers”) may comment by clicking on ABSTRACT on the issue’s contents page.


Antibiotics ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 1126
Author(s):  
George L. Daikos ◽  
Clóvis Arns da da Cunha ◽  
Gian Maria Rossolini ◽  
Gregory G. Stone ◽  
Nathalie Baillon-Plot ◽  
...  

Pseudomonas aeruginosa is an opportunistic Gram-negative pathogen that causes a range of serious infections that are often challenging to treat, as this pathogen can express multiple resistance mechanisms, including multidrug-resistant (MDR) and extensively drug-resistant (XDR) phenotypes. Ceftazidime–avibactam is a combination antimicrobial agent comprising ceftazidime, a third-generation semisynthetic cephalosporin, and avibactam, a novel non-β-lactam β-lactamase inhibitor. This review explores the potential role of ceftazidime–avibactam for the treatment of P. aeruginosa infections. Ceftazidime–avibactam has good in vitro activity against P. aeruginosa relative to comparator β-lactam agents and fluoroquinolones, comparable to amikacin and ceftolozane–tazobactam. In Phase 3 clinical trials, ceftazidime–avibactam has generally demonstrated similar clinical and microbiological outcomes to comparators in patients with complicated intra-abdominal infections, complicated urinary tract infections or hospital-acquired/ventilator-associated pneumonia caused by P. aeruginosa. Although real-world data are limited, favourable outcomes with ceftazidime–avibactam treatment have been reported in some patients with MDR and XDR P. aeruginosa infections. Thus, ceftazidime–avibactam may have a potentially important role in the management of serious and complicated P. aeruginosa infections, including those caused by MDR and XDR strains.


2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S580-S580
Author(s):  
Dee Shortridge ◽  
S J Ryan Arends ◽  
Leonard R Duncan ◽  
Jennifer M Streit ◽  
Robert K Flamm

Abstract Background Infections caused by Pseudomonas aeruginosa (PSA) resistant to first-line agents are difficult to treat and require using more toxic antimicrobials, such as amikacin (AMK) and colistin (COL). Kadri et al. recently described the category of difficult-to-treat resistance (DTR) as intermediate or resistant to all tested first-line agents (fluoroquinolones, carbapenems, and extended-spectrum cephalosporins). Ceftolozane–tazobactam (C-T) is an antibacterial combination of an antipseudomonal cephalosporin and a β-lactamase inhibitor. C-T has been approved in >60 countries to treat complicated urinary tract infections, acute pyelonephritis, and complicated intra-abdominal infections. The filing is in progress for treatment of hospital-acquired pneumonia, including ventilator-associated pneumonia. The Program to Assess Ceftolozane–Tazobactam Susceptibility (PACTS) monitors gram-negative (GN) isolates resistant to C-T worldwide. In this study, the activity of C-T and comparators against PSA bloodstream isolates that are DTR, multidrug-resistant (MDR), or extensively drug-resistant (XDR) were analyzed. Methods A total of 922 PSA isolates from BSI were collected between 2011 and 2018 from 35 PACTS hospitals in the United States. Isolates were tested for C-T susceptibility (S) by the CLSI broth microdilution method. Other antibiotics tested included cefepime (FEP), ceftazidime (CAZ), ciprofloxacin, levofloxacin (LEV), doripenem, imipenem, meropenem (MEM), piperacillin–tazobactam (PIP-TAZ), AMK and COL. Antibiotic-resistant phenotypes analyzed using CLSI (2019) breakpoints included MDR (nonsusceptible to ≥ 1 agent in ≥ 3 drug classes), XDR (susceptible to ≤ 1 agent in ≤ 2 drug classes), or DTR. Results The percent of DTR isolates was 4.8% when compared with 15.2% MDR and 9.3% XDR. The %S for C-T and other first- and second-line agents are shown in the table for each phenotype. Conclusion C-T demonstrated 97.1%S overall for BSI isolates, similar to AMK (97.8%) and COL (99.5%). C-T had better coverage than first-line drugs against MDR (81.4%) and XDR (72.1%), and 50% for the DTR isolates, which represented only 4.8% of isolates. Only AMK and COL had > 75%S for DTR isolates. Disclosures All authors: No reported disclosures.


2020 ◽  
Vol 64 (3) ◽  
Author(s):  
Temilolu Idowu ◽  
George G. Zhanel ◽  
Frank Schweizer

ABSTRACT Ceftolozane-tazobactam is a potent β-lactam/β-lactamase inhibitor combination approved for the treatment of complicated intraabdominal and complicated urinary tract infections and, more recently, the treatment of hospital-acquired and ventilator-associated bacterial pneumonia. Although the activities of ceftolozane are not enhanced by tazobactam against Pseudomonas aeruginosa, it remains the most potent antipseudomonal agent approved to date. Emerging data worldwide has included reports of microbiological failure in patients with serious bacterial infections caused by multidrug-resistant (MDR) P. aeruginosa as a result of ceftolozane resistance developed within therapy. The objective of this study is to compare the efficacy of a tobramycin homodimer plus ceftolozane versus ceftolozane-tazobactam alone against MDR and extensively drug-resistant (XDR) P. aeruginosa. Tobramycin homodimer, a synthetic dimer of two monomeric units of tobramycin, was developed to abrogate the ribosomal properties of tobramycin with a view to mitigating aminoglycoside-related toxicity and resistance. Herein, we report that tobramycin homodimer, a nonribosomal aminoglycoside derivative, potentiates the activities of ceftolozane versus MDR/XDR P. aeruginosa in vitro and delays the emergence of resistance to ceftolozane-tazobactam in the wild-type PAO1 strain. This combination is also more potent than a standard ceftazidime-avibactam combination against these isolates. Conversely, a tobramycin monomer with intrinsic ribosomal properties does not potentiate ceftolozane under similar conditions. Susceptibility and checkerboard studies were assessed using serial 2-fold dilution assays, following the Clinical and Laboratory Standards Institute (CLSI) guidelines. This strategy provides an avenue to further preserve the clinical utility of ceftolozane and enhances its spectrum of activity against one of the most difficult-to-treat pathogens in hospitals.


2018 ◽  
Vol 5 (suppl_1) ◽  
pp. S313-S313
Author(s):  
S J Ryan Arends ◽  
Dee Shortridge ◽  
Mariana Castanheira ◽  
Jennifer M Streit ◽  
Robert K Flamm

Abstract Background Ceftolozane–tazobactam (C-T) is an antibacterial combination of a novel antipseudomonal cephalosporin and a β-lactamase inhibitor. C-T was approved by the US Food and Drug Administration in 2014 and by the European Medicines Agency in 2015 to treat complicated urinary tract infections, acute pyelonephritis, and complicated intra-abdominal infections. The Program to Assess Ceftolozane-Tazobactam Susceptibility (PACTS) monitors Gram-negative (GN) isolates resistant to C-T worldwide. In the current study, isolates were collected from patients hospitalized with bloodstream infections (BSIs) from 2015 to 2017 within the United States. Methods A total of 3,377 prevalence-based BSI GN isolates, including Escherichia coli (EC; 1,422), Klebsiella pneumoniae (KPN, 630), and Pseudomonas aeruginosa (PSA; 344), were collected during 2015 to 2017 from 32 PACTS hospitals in the United States. Isolates were tested for C-T susceptibility by CLSI broth microdilution method in a central monitoring laboratory (JMI Laboratories). Other antibiotics tested were amikacin (AMK), cefepime (FEP), ceftazidime (CAZ), colistin (COL), levofloxacin (LVX), meropenem (MEM), and piperacillin–tazobactam (TZP). Antibiotic-resistant phenotypes analyzed (CLSI, 2018) for EC and KPN included carbapenem-R (CR) and non-CR extended-spectrum β-lactamase (ESBL); as well as CAZ-nonsusceptible (CAZ-NS), MEM-NS, and COL-NS PSA. Results Of the 3,377 BSI GN isolates, 3,219 (95.3%) had a C-T MIC ≤ 4 mg/L. The three most prevalent GN species isolated from BSIs were EC (42.1%), KPN (18.7%), and PSA (10.2%). The %S of C-T and comparators for the top three pathogens are shown in the table. C-T showed activity against these isolates with %S of ≥96.0% against all three species. Of the comparators tested, AMK and COL also had high %S against these isolates. Conclusion C-T demonstrated activity against the most prevalent contemporary GN isolates from BSIs in the US. C-T was the only beta-lactam that had ≥96%S against all three species: EC, KPN, and PSA. For PSA, C-T maintained activity (>90%S) against isolates resistant to CAZ, TZP, and MEM. These data suggest that C-T may be a useful treatment for GN BSI. Disclosures S. J. R. Arends, Merck: Research Contractor, Research support. D. Shortridge, Merck: Research Contractor, Research support. M. Castanheira, Merck: Research Contractor, Research support. J. M. Streit, Merck: Research Contractor, Research support. R. K. Flamm, Merck: Research Contractor, Research support.


2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S93-S94
Author(s):  
Cecilia G Carvalhaes ◽  
Mariana Castanheira ◽  
Rodrigo E Mendes ◽  
Helio S Sader

Abstract Background We evaluated the antimicrobial susceptibility of Enterobacterales (ENT) and P. aeruginosa (PSA) causing bloodstream infections (BSIs) in the United States (US) hospitals. Methods A total of 3,317 ENT and 331 PSA isolates were consecutively collected (1/patient) from patients with BSI in 68 US medical centers in 2017–2018 and tested for susceptibility (S) by reference broth microdilution methods in a central laboratory as part of the International Network for Optimal Resistance Monitoring (INFORM) Program. β-Lactamase screening was performed by whole-genome sequencing on ENT with decreased S to broad-spectrum cephalosporins (ESBL phenotype). Results The most common ENT species isolated from BSI were E. coli (EC; 41.9% of ENT), K. pneumoniae (KPN; 24.4%), and E. cloacae (ECL; 8.7%), and the most active agents against ENT were ceftazidime–avibactam (CAZ-AVI; 99.9%S), amikacin (AMK; 99.6%S) and meropenem (MEM; 99.3%S). CAZ-AVI was active against all EC and KPN isolates (100.0%S). Only 2 ENT isolates (0.06%) were CAZ-AVI resistant, 2 NDM-1-producing ECL isolated in the New York City area. Ceftolozane–tazobactam (C-T) and piperacillin–tazobactam (PIP-TAZ) showed good activity against EC and KPN (92.2–98.9%S; Table), with limited activity against ECL (81.9–83.7%S). The most common ESBLs were CTX-M-type, which was observed in 93% of ESBL producers (mainly CTX-M-15 [64% of ESBL producers] and CTX-M-27 [13%]), and OXA-1/OXA-30 (42%); 42% of ESBL producers (n = 333, excluding carbapenemase producers) displayed ≥2 ESBL genes, mainly CTX-M-15 and OXA-1/OXA-30 (40% of ESBL producers). The most active agents against ESBL producers were CAZ-AVI (100.0%S), imipenem (99.4%S), and colistin (COL; 99.1%S). Only CAZ-AVI (99.4%S), AMK (96.2%S) and MEM (92.8%S) were active against >90% of multidrug-resistant (MDR) ENT. Among 19 carbapenem-resistant ENT (CRE; 0.6% of ENT), 9 produced a KPC-like, 2 an NDM-1, and 2 an NMC-A; carbapenemase genes were not found in 6 CRE isolates. COL (100.0%S), CAZ-AVI (98.5%S), AMK (98.5%S), C-T (98.1%S), and tobramycin (97.0%S) were very active against PSA. Conclusion CAZ-AVI exhibited potent in vitro activity and great spectrum against ENT (99.9%S) and PSA (98.5%) isolated from patients with BSI from US hospitals. Disclosures All authors: No reported disclosures.


2020 ◽  
Vol 2020 ◽  
pp. 1-11
Author(s):  
Mustafa Elhag ◽  
Ruaa Mohamed Alaagib ◽  
Nagla Mohamed Ahmed ◽  
Mustafa Abubaker ◽  
Esraa Musa Haroun ◽  
...  

Pseudomonas aeruginosa is a common pathogen that is responsible for serious hospital-acquired infections, ventilator-associated pneumonia, and various sepsis syndromes. Also, it is a multidrug-resistant pathogen recognized for its ubiquity and its intrinsically advanced antibiotic-resistant mechanisms. It usually affects immunocompromised individuals but can also infect immunocompetent individuals. There is no vaccine against it available till now. This study predicts an effective epitope-based vaccine against fructose bisphosphate aldolase (FBA) of Pseudomonas aeruginosa using immunoinformatics tools. The protein sequences were obtained from NCBI, and prediction tests were undertaken to analyze possible epitopes for B and T cells. Three B cell epitopes passed the antigenicity, accessibility, and hydrophilicity tests. Six MHC I epitopes were found to be promising, while four MHC II epitopes were found promising from the result set. Nineteen epitopes were shared between MHC I and II results. For the population coverage, the epitopes covered 95.62% worldwide excluding certain MHC II alleles. We recommend in vivo and in vitro studies to prove its effectiveness.


Antibiotics ◽  
2020 ◽  
Vol 9 (12) ◽  
pp. 885
Author(s):  
Soraya Herrera-Espejo ◽  
Tania Cebrero-Cangueiro ◽  
Gema Labrador-Herrera ◽  
Jerónimo Pachón ◽  
María Eugenia Pachón-Ibáñez ◽  
...  

Multidrug-resistant (MDR) Pseudomonas aeruginosa is a public health problem causing both community and hospital-acquired infections, and thus the development of new therapies for these infections is critical. The objective of this study was to analyze in vitro the activity of pentamidine as adjuvant in combinations to antibiotics against seven clinical P. aeruginosa strains. The Minimum Inhibitory Concentration (MIC) was determined following standard protocols, and the results were interpreted according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints; however, the gentamicin activity was interpreted according to the Clinical and Laboratory Standards Institute (CLSI) recommendations. The bactericidal in vitro activity was studied at 1×MIC concentrations by time–kill curves, and also performed in three selected strains at 1/2×MIC of pentamidine. All studies were performed in triplicate. The pentamidine MIC range was 400–1600 μg/mL. Four of the strains were MDR, and the other three were resistant to two antibiotic families. The combinations of pentamidine at 1×MIC showed synergistic activity against all the tested strains, except for pentamidine plus colistin. Pentamidine plus imipenem and meropenem were the combinations that showed synergistic activity against the most strains. At 1/2×MIC, pentamidine plus antibiotics were synergistic with all three analyzed strains. In summary, pentamidine in combination with antibiotics showed in vitro synergy against multidrug-resistant P. aeruginosa clinical strains, which suggests its possible use as adjuvant to antibiotics for the therapy of infections from MDR P. aeruginosa.


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