Ceftazidime-Avibactam plus aztreonam synergistic combination tested against carbapenem-resistant Enterobacterales characterized phenotypically and genotypically: a glimmer of hope

Aztreonam Acts as a Synergist for Ceftazidime/Avibactam Against Carbapenem-Resistant Enterobacteriaceae (CRE) of Various Carbapenemase Phenotypes in Southwestern China

Background

Carbapenem-resistant Enterobacteriaceae (CRE) presents a significant challenge due to its role in severe and multidrug-resistant infections.

Purpose

This study aims to evaluate aztreonam (ATM) as a synergistic agent with ceftazidime/avibactam (CZA) for treating CRE strains with different carbapenemase phenotypes.

Methods

A total of 87 non-repeated clinical CRE strains were collected from various clinical specimens at The First Affiliated Hospital of Guangxi Medical University. Carbapenemase genotypes and phenotypes were identified using polymerase chain reaction (PCR) and NG-Test Carba 5 methods. The synergistic effect of CZA combined with ATM was assessed via the checkerboard MIC and disk stacking methods.

Results

The clinical analysis revealed that underlying pulmonary disease, pneumonia, urinary catheter, and central intravenous catheter were associated with poor prognosis in CRE infections (p<0.05). All 87 CRE strains showed high resistance to most antibiotics, especially cefazolin, ceftriaxone, piperacillin/tazobactam, ertapenem, and meropenem, with a rate of 100.00%. For strains with a single carbapenemase gene, NG-Test Carba 5 demonstrated 100.00% accuracy. Notably, The combination of CZA and ATM showed synergy in 95.40% (83/87) of the CRE strains overall, with specific rates of 100.00% (4/4) in strains lacking detectable carbapenemase genes, 94.29% (33/35) in those with blaNDM, and 100.00% (3/3) in those with blaNDM plus blaKPC-2 or blaKPC-2 plus blaIMP-4.

Conclusion

In conclusion, ATM significantly enhances CZA's activity against CRE strains in Guangxi, achieving a high synergy rate across diverse isolates, regardless of the carbapenemase genes present.

Prevalence of New Delhi Metallo-β-lactamase (blaNDM) gene in a selected population of drug-resistant clinical isolates

OBJECTIVES

Drug-resistant Enterobacterales carrying carbapenem-resistant genes cause severe infections in clinical settings worldwide. Among these, the New Dehli Metallo-β-lactamase (blaNDM) gene is significantly prevalent and associated with high morbidity. This study was designed to investigate the susceptibility profiling of Carbapenem-Resistant-Enterobacterales (CRE), prevalence of blaNDM and its variants, and associated risk factors.

METHODS

CRE isolates from a tertiary care hospital, in Islamabad, Pakistan, were identified and the susceptibility testing was performed using disc diffusion method. MICs were determined for imipenem, tigecycline, and colistin through E-strips and microbroth dilution method respectively. For molecular characterization and typing of the blaNDM gene, PCR products were sequenced, and the phylogenetic analysis was performed using MEGA ver 6.0 software.

RESULTS

Among 5,134 clinical samples, 42.13% (n = 2,163) yielded pathogens including 42.58% (n = 921) Enterobacterales. On further screening, 39.52% (n = 364) of Enterobacterales were identified as CRE. The blaNDM gene was detected in 75.27% (n = 274) in CRE isolates, comprising blaNDM-1 (44%), blaNDM-5 (53%), and blaNDM-7 (3%) variants. Tigecycline (86.7%) and colistin (100%) were most effective antimicrobial agents with MICs ranging from 0.064 to 8 and 0.125-1 µg/ml respectively. blaNDM-1-harboring bacteria exhibited high antimicrobial resistance compared to blaNDM-5 and blaNDM-7. Cefiderocol was 75.6% and ceftazidime/avibactam with aztreonam was 97.08% effective against blaNDM-harboring bacteria. The phylogenetic analysis indicated that blaNDM variants showed close genetic relationships and homology to the previously described sequences in GenBank databases having diverse connection with worldwide sequences.

CONCLUSION

The high prevalence of blaNDM in our study has of great concern for clinical practice and public health. Clinicians are left with few therapeutic options. However, ceftazidime/avibactam with aztreonam may show therapeutic success. Continuous surveillance is crucial to monitorgenetic variations of continuously evolving blaNDM gene, which is essential for effective clinical management.

Newly developed antibiotics against multidrug-resistant and carbapenem-resistant Gram-negative bacteria: action and resistance mechanisms

Antimicrobial resistance stands as one of the most urgent global health concerns in the twenty-first century, with projections suggesting that deaths related to drug-resistant infections could escalate to 10 million by 2050 if proactive measures are not implemented. In intensive care settings, managing infections caused by multidrug-resistant (MDR) Gram-negative bacteria is particularly challenging, posing a significant threat to public health and contributing substantially to both morbidity and mortality. There are numerous studies on the antibiotics responsible for resistance in Gram-negative bacteria, but comprehensive research on resistance mechanisms against new antibiotics is rare. Considering the possibility that antibiotics may no longer be effective in combating diseases, it is crucial to comprehend the problem of emerging resistance to newly developed antibiotics and to implement preventive measures to curb the spread of resistance. Mutations in porins and efflux pumps play a crucial role in antibiotic resistance by altering drug permeability and active efflux. Porin modifications reduce the influx of antibiotics, whereas overexpression of efflux pumps, particularly those in the resistance-nodulation-cell division (RND) family, actively expels antibiotics from bacterial cells, significantly lowering intracellular drug concentrations and leading to treatment failure.This review examines the mechanisms of action, resistance profiles, and pharmacokinetic/pharmacodynamic characteristics of newly developed antibiotics designed to combat infections caused by MDR and carbapenem-resistant Gram-negative pathogens. The antibiotics discussed include ceftazidime-avibactam, imipenem-relebactam, ceftolozane-tazobactam, meropenem-vaborbactam, aztreonam-avibactam, delafloxacin, temocillin, plazomicin, cefiderocol, and eravacycline.

Targeted 'knock out' therapy with a combination antimicrobial regimen restores treatment options in the management of extensively drug-resistant carbapenemase-producing organisms

Introduction. Cefiderocol (FDC) and the combination of ceftazidime-avibactam and aztreonam (CZA+ATM) are emerging therapeutic options to combat carbapenemase-producing organisms (CPOs) that exhibit resistance due to multiple β-lactamases.Hypothesis/Gap Statement. Molecular diagnostics and specialized antimicrobial susceptibility testing (AST) are infrequently available in most clinical laboratories, and outputs from reference laboratories are not always timely. Practical methods must be explored to provide meaningful advice to treat infections due to CPOs in real time.Aim. To evaluate the in vitro efficacy of FDC and CZA+ATM against CPOs and to compare colistin (CST) MICs obtained locally with those from the reference laboratory.Methodology. CPOs isolated from 2017 to 2023 inclusive were retrieved. AST for FDC was performed using disc diffusion, CZA and ATM individually by E-tests and the E-test superposition method for the combination CZA+ATM. CST AST was performed locally using the VITEK2 system, and MICs were compared with those attained from the reference laboratory where manual broth microdilution is performed.Results. Fifty-eight CPOs were analysed. OXA-48 was the most frequently detected carbapenemase (37.9%, n=22). Co-existing β-lactamases of Ambler classes A and C were present for 79.3% of CPOs (n=46). Twenty-nine isolates (50%) were found to be susceptible to FDC. Fifty-seven isolates (98.3%) were susceptible to CST according to the VITEK2, compared to 44 of 47 tested isolates (93.6%) by the reference broth microdilution. Essential agreement was found to be 78.7%, and categorical agreement was 91.5% with one major error and three very major errors (VMEs) reported. CZA+ATM was tested against 26 CPOs, all of which harboured metallo-β-lactamases. Synergy was detected for all except one isolate where additivity was noted. Of the 32 isolates where combination therapy was not assessed, 29 (90.6%) possessed serine-β-lactamases and were susceptible to CZA monotherapy, whilst three (9.4%) possessed an isolated metallo-β-lactamase and were susceptible to ATM monotherapy.Conclusions. FDC appears to perform favourably against CPOs harbouring serine-β-lactamases, but not metallo-β-lactamases. The VITEK2 may provide presumptive categorical information for CST susceptibility, but MICs must be confirmed by broth microdilution as VMEs can lead to treatment failures. Moreover, our study confirms potent in vitro activity of CZA+ATM against CPOs expressing multiple β-lactamases.

[In vitro activity of ceftazidime- avibactam and ceftolozane- tazobactam against clinical isolates of enterobacteriaceae and pseudomonas æruginosa: results from a trauma center and burn unit in tunisia]

Antibiotic resistance is an escalating public health challenge, particularly among Enterobacteriaceae and Pseudomonas aeruginosa. In this study conducted at a burn center in Tunisia, we collected 307 non-redundant strains of Enterobacteriaceae from predominantly hospitalized patients, with a majority in the burn intensive care unit (59%), the primary identified species being Klebsiella pneumoniae (34.8%). We evaluated the efficacy of two antibiotics, ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (CT). The results revealed that the overall resistance to CZA was 11.7%, while to CT it was 25.7%. CZA proved to be the second most sensitive molecule among all tested antibiotics, following fosfomycin. Among strains resistant to third-generation cephalosporins, 73.3% were sensitive to CZA, and 41.5% to CT. Out of seventy-nine CT-resistant strains, eight were ESBL producers, twenty-two were high-level cephalosporinases, thirty-three carried blaNDM, twelve carried blaOXA48, and four carried both blaNDM and blaOXA-48. Indeed, blaNDM were the most prevalent carbapenemases. For Pseudomonas aeruginosa strains (n=161), resistance to CZA was 42.2%, and to CT it was 47.8%. These antibiotics ranked as the second and third most active beta-lactams after aztreonam. Among the 71 strains of CZA and carbapenem-resistant P. aeruginosa, 54.1% produced VIM2. Resistance to enterobacteriaceae against CZA and CT is relatively high in our study. However, CZA remains a salvage therapy for infections caused by carbapenem-resistant organisms, and its use should be considered only after documentation and in the absence of other alternatives among β-lactams. For P. aeruginosa, CZA currently represents the most active β-lactam against CAZ-R strains and the second most active molecule overall, including those producing carbapenemases.

A systematic review and individual bacterial species level meta-analysis of in vitro studies on the efficacy of ceftazidime/avibactam combined with other antimicrobials against carbapenem-resistant Gram-negative bacteria

BACKGROUND

Carbapenem-resistant Gram-negative bacteria (CR-GNB) develop resistance to many antimicrobials. To effectively manage infections caused by these organisms, novel agents and/or combinations of antimicrobials are required.

OBJECTIVES

Evaluated the in vitro efficacy of ceftazidime/avibactam in combination with other antimicrobials against CR-GNB.

METHODS

PubMed, Web of Science, Embase and Scopus were searched. Study outcomes were quantified by counting the number of isolates exhibiting synergy, defined as a fractional inhibitory concentration index ≤ 0.5 for checkerboard and Etest, and a >2 log cfu/mL reduction for time-kill studies. The proportion of synergy was calculated as the ratio of isolates exhibiting synergy to the total number of isolates tested. These proportions were analysed using a random-effects model, following the Freeman-Tukey double-arcsine transformation.

RESULTS

Forty-five in vitro studies were included. A total of 734 isolates were tested, and 69.3% of them were resistant to ceftazidime/avibactam. The combination of ceftazidime/avibactam with aztreonam showed a high synergy rate against carbapenem-resistant Klebsiella pneumoniae (effect size, ES = 0.91-0.98) and Escherichia coli (ES = 0.75-1.00). Ceftazidime/avibactam also demonstrated a high synergy rate (ES = 1) in time-kill studies when combined with azithromycin, fosfomycin and gentamicin against K. pneumoniae. Compared to ceftazidime/avibactam alone, a higher bactericidal rate was reported when ceftazidime/avibactam was combined with other antimicrobials against carbapenem-resistant K. pneumoniae (57% versus 31%) and E. coli (93% versus 0%).

CONCLUSIONS

Ceftazidime/avibactam frequently demonstrates synergistic bactericidal activity when combined with various antimicrobials against CR-GNB in in vitro tests. Further pre-clinical and clinical studies are warranted to validate the utility of ceftazidime/avibactam-based combination regimens for CR-GNB infections.

A Possible Tool for Guiding Therapeutic Approaches to Urinary Infections with Klebsiella pneumoniae: Analyzing a Dataset from a Romanian Tertiary Hospital

Introduction: The emergence of carbapenem-resistant pathogenic bacteria is a growing global public health concern. Carbapenem-resistant uropathogenic strains of Klebsiella pneumoniae can cause uncomplicated or complicated urinary tract infections, leading to a high risk of treatment failure and the spread of resistance determinants. The objectives of this 24-month study were to identify the prognostic characteristics of patients who were infected with carbapenem-resistant Klebsiella pneumoniae (CRKpn) and to create a tool to estimate the probability of a CRKpn infection before having the complete results of a patient's antibiogram. Results: We found that 41.6% of all urinary infections with Kpn were caused by CRKpn. Factors such as male gender, the presence of upper urinary tract infections, invasive urinary maneuvers, recent infection with or carriage of the germ, and the nosocomial occurrence of UTIs with Kpn were predictive for CRKpn infection. Based on these factors, we proposed a model to estimate the presence of CRKpn. Methods: A retrospective case-control study including all hospitalized patients with urinary tract infections (UTIs) caused by Klebsiella pneumoniae was carried out. We reported data as percentages, identified independent predictors of the presence of CRKpn, and proposed a tool to evaluate the probability through multivariate analysis. Conclusions: Through this study, we aim to provide clinicians with a tool to support decision making regarding first-line antibiotic treatment.

Assessment of broth disk elution method for aztreonam in combination with ceftazidime/avibactam against Enterobacterales isolates

The combination of aztreonam with ceftazidime/avibactam is considered a potential therapeutic approach for the treatment of infections caused by metallo-β-lactamase (MBL)-producing isolates. In this study, in vitro antibacterial activity of aztreonam with avibactam against 204 carbapenemase-producing Enterobacterales was determined by broth disk elution (BDE) method of two detection volumes (5- and 2-mL broth), with broth microdilution (BMD) method as a reference. For the BDE-5mL test, the categorical agreement (CA) of ATM+CZA-lo tube (aztreonam/ceftazidime/avibactam: 6/6/4 mg/L) was 99.5%, with 0.5% major error (ME) and 0% very major error (VME); the CA of 2ATM+CZA-lo tube (12/6/4 mg/L) was 100%, with no ME and VME. For the BDE-2mL test, the CA of ATM+2CZA-hi tube (15/10/4 mg/L) was 98.5%, with 0% ME and 37.5% VME; the CA of 2ATM+2CZA-hi tube (30/10/4 mg/L) was 97.1%, with 0% ME and 75% VME. The BDE-5 mL test is an economical and practical method for clinical microbiology laboratories to determine the antibacterial susceptibility of aztreonam with avibactam against Enterobacterales, especially the 2ATM+CZA-lo tube with a final concentration of 12/6/4 mg/L of aztreonam/ceftazidime/avibactam.

IMPORTANCE

Infections caused by metallo-β-lactamase (MBL)-producing Enterobacterales are increasingly reported worldwide, and it is a significant challenge for clinical infection treatment. MBLs are adept at hydrolyzing almost all traditional β-lactam antibiotics except aztreonam, and the enzyme activity cannot be inhibited by traditional or novel β-lactamase inhibitors. The good thing is that the combination of aztreonam with ceftazidime/avibactam has been proven to be one of the potential therapeutic approaches for treating infections related with MBL-producing isolates. Broth microdilution (BMD) method is recommended as a reference method for its accuracy, but it is too complex to perform in most routine laboratories. Finding a more convenient, practical, and accurate susceptibility testing method for aztreonam/avibactam in clinical microbiology laboratories is very necessary. Here, we evaluated the performance of broth disk elution (BDE) method for aztreonam in combination with ceftazidime/avibactam against Enterobacterales isolates, with BMD as a reference.

In vitro Synergistic and Bactericidal Effects of Aztreonam in Combination with Ceftazidime/ Avibactam, Meropenem/Vaborbactam and Imipenem/Relebactam Against Dual-Carbapenemase-Producing Enterobacterales

Objective

Our aim was to elucidate the resistance mechanisms and assess the combined synergistic and bactericidal activities of aztreonam in combination with ceftazidime/avibactam (CZA), meropenem/vaborbactam (MEV), and imipenem/relebactam (IMR) against Enterobacterales strains producing dual carbapenemases.

Methods

Species identification, antimicrobial susceptibility testing and determination of carbapenemase type were performed for these strains. Plasmid sizes, plasmid conjugation abilities and the localization of carbapenemase genes were investigated. Whole-genome sequencing was performed for all strains and their molecular characteristics were analyzed. In vitro synergistic and bactericidal activities of the combination of aztreonam with CZA, MEV and IMR against these strains were determined using checkerboard assay and time-kill curve assay.

Results

A total of 12 Enterobacterales strains producing dual-carbapenemases were collected, including nine K. pneumoniae, two P. rettgeri, and one E. hormaechei. The most common dual-carbapenemase gene pattern observed was bla (KPC-2+NDM-5) (n=4), followed by bla KPC-2+IMP-26 (n=3), bla (KPC-2+NDM-1) (n=2), bla (KPC-2+IMP-4) (n=1), bla (NDM-1+IMP-4) (n=1) and bla (KPC-2+KPC-2) (n=1). In each strain, the carbapenemase genes were found to be located on two distinct plasmids which were capable of conjugating from the original strain to the receipt strain E. coli J53. The results of the checkerboard synergy analysis consistently revealed good synergistic effects of the combination of ATM with CZA, MEV and IMR. Except for one strain, all strains exhibited significant synergistic activity and bactericidal activity between 2 and 8 hours.

Conclusion

Dual-carbapenemase-producing Enterobacterales posed a significant threat to clinical anti-infection treatment. However, the combination of ATM with innovative β-lactam/β-lactamase inhibitor compounds had proven to be an effective treatment option.

Synergistic Effect of Ceftazidime-Avibactam with Aztreonam on Carbapenemase-Positive Klebsiella pneumoniae MBL+, NDM

Background

The difficulties in attaining effective antibiotic therapy arising from the multidrug resistance of Gram-negative bacilli compel the exploration of new possibilities for synergistic interactions among existing antibiotics.

Research Design and Methods

An analysis was conducted to assess the efficacy of two antibiotic therapy regimens in the treatment of infections caused by Klebsiella pneumoniae strains producing carbapenemases (MBL). Two patient groups were considered: Group A - individuals in whom the treatment of infection involved the application of ceftazidime-avibactam in combination with aztreonam. Group B comprised patients subjected to an alternative antibiotic therapy regimen.

Results

In the group subjected to the treatment regimen involving ceftazidime-avibactam and aztreonam, as compared to alternative antibiotic combinations, a statistically lower mortality rate during the course of treatment and a faster clinical response to the administered therapy were evident.

Conclusion

The results obtained may be applicable to routine in vitro assays performed and serve as valuable guidance for the potential utilization of the positive effect of antibiotic therapy through the synergy between ceftazidime-avibactam and aztreonam. The selection of antibiotics employed in the therapy of invasive infections caused by K. pneumoniae influences the ultimate treatment outcome.

A review of the mechanisms that confer antibiotic resistance in pathotypes of E. coli

The dissemination of antibiotic resistance in Escherichia coli poses a significant threat to public health worldwide. This review provides a comprehensive update on the diverse mechanisms employed by E. coli in developing resistance to antibiotics. We primarily focus on pathotypes of E. coli (e.g., uropathogenic E. coli) and investigate the genetic determinants and molecular pathways that confer resistance, shedding light on both well-characterized and recently discovered mechanisms. The most prevalent mechanism continues to be the acquisition of resistance genes through horizontal gene transfer, facilitated by mobile genetic elements such as plasmids and transposons. We discuss the role of extended-spectrum β-lactamases (ESBLs) and carbapenemases in conferring resistance to β-lactam antibiotics, which remain vital in clinical practice. The review covers the key resistant mechanisms, including: 1) Efflux pumps and porin mutations that mediate resistance to a broad spectrum of antibiotics, including fluoroquinolones and aminoglycosides; 2) adaptive strategies employed by E. coli, including biofilm formation, persister cell formation, and the activation of stress response systems, to withstand antibiotic pressure; and 3) the role of regulatory systems in coordinating resistance mechanisms, providing insights into potential targets for therapeutic interventions. Understanding the intricate network of antibiotic resistance mechanisms in E. coli is crucial for the development of effective strategies to combat this growing public health crisis. By clarifying these mechanisms, we aim to pave the way for the design of innovative therapeutic approaches and the implementation of prudent antibiotic stewardship practices to preserve the efficacy of current antibiotics and ensure a sustainable future for healthcare.

Reviewing novel treatment options for carbapenem-resistant Enterobacterales

INTRODUCTION

Carbapenem resistant Enterobacterales (CRE) are a major threat to global health and hospital-onset CRE infections have risen during the COVID-19 pandemic. Novel antimicrobials are now available for the treatment of CRE infections. There remains an urgent need for new antimicrobials for CRE, especially for those producing metallo-β-lactamases.

AREAS COVERED

This article discusses previously published research supporting currently available novel antimicrobials for the treatment of CRE infections. Newer compounds currently being evaluated in clinical trials are covered. A literature search was conducted in PubMed over all available dates for relevant published papers and conference abstracts with the search terms, 'CRE,' 'carbapenem-resistant Enterobacterales,' 'β-lactam-β-lactamase inhibitor,' 'KPC,' 'NDM,' 'metallo-β-lactamase,' 'ceftazidime-avibactam,' 'meropenem-vaborbactam,' 'imipenem-cilastatin-relebactam,' 'cefiderocol,' 'eravacycline,' 'plazomicin,' 'taniborbactam,' 'zidebactam,' and 'nacubactam.'

EXPERT OPINION

Novel antimicrobials for CRE infections have been developed, most notably the β-lactam-β-lactamase inhibitor combinations, though treatment options for infections with metallo-β-lactamase producing Enterobacterales remain few and have limitations. Development of antibiotics with activity against metallo-β-lactamase producing Enterobacterales is eagerly awaited, and there are promising new compounds in clinical trials. Finally, more clinical research is needed to optimize and individualize treatment approaches, which will help guide antimicrobial stewardship initiatives aimed at reducing the spread of CRE and development of further resistance.

Virulence factors in carbapenem-resistant hypervirulent Klebsiella pneumoniae

Hypervirulence and carbapenem-resistant have emerged as two distinct evolutionary pathotypes of Klebsiella pneumoniae, with both reaching their epidemic success and posing a great threat to public health. However, as the boundaries separating these two pathotypes fade, we assist a worrisome convergence in certain high-risk clones, causing hospital outbreaks and challenging every therapeutic option available. To better understand the basic biology of these pathogens, this review aimed to describe the virulence factors and their distribution worldwide among carbapenem-resistant highly virulent or hypervirulent K. pneumoniae strains, as well as to understand the interplay of these virulence strains with the carbapenemase produced and the sequence type of such strains. As we witness a shift in healthcare settings where carbapenem-resistant highly virulent or hypervirulent K. pneumoniae are beginning to emerge and replace classical K. pneumoniae strains, a better understanding of these strains is urgently needed for immediate and appropriate response.

Evaluation of Aztreonam and Ceftazidime/Avibactam Synergism against Klebsiella pneumoniae by MALDI-TOF MS

INTRODUCTION

Resistance to carbapenems due to the co-production of NDM and ESBL or NDM and KPC is increasing. Therefore, combined therapy with aztreonam (ATM) plus ceftazidime/avibactam (CZA) has been recommended. Then, it is necessary to develop and evaluate fast and simple methods to determine synergism in vitro in microbiology laboratories.

OBJECTIVE

To develop a method to determine the synergism of ATM and CZA by MALDI-TOF MS (SynMALDI).

METHOD

Klebsiella pneumoniae (n = 22) isolates with bla_NDM and/or bla_KPC genes were tested. The time-kill curve assay was performed for four isolates (three positives for bla_NDM and bla_KPC and one positive for bla_NDM only). For SynMALDI, each isolate was incubated for 3 h in 4 tubes containing brain-heart infusion broth with the following: (1) no antibiotic; (2) ATM at 64 mg/L; (3) CZA at 10/4 mg/L; and (4) ATM at 64 mg/L plus CZA at 10/4 mg/L. After incubation, the bacterial protein extract was analyzed by MALDI-TOF MS, and the relative growth (RG) was determined for each isolate, considering intensities of the peaks of the bacterium incubated with antibiotic (tubes 2, 3, and 4) to the same bacterium incubated without antibiotic (tube 1), as follows: RG = Intensity_{With antibiotic}/Intensity_{Without antibiotic}. The combination was determined as synergistic when there was an RG decrease of 0.3 in the antibiotic combination in relation to the RG of the most active antibiotic alone.

RESULTS

The combination of ATM plus CZA proved to be synergic by time-kill curve assay. All isolates tested with the SynMALDI method also presented synergism.

CONCLUSIONS

Detection of synergism for ATM plus CZA combination can be determined by MALDI-TOF MS, providing fast results in order to improve patient treatment.