Aztreonam Research Articles

Testing new waters in management of Stenotrophomonas maltophilia blood stream infection in a post cardiac surgery patient

Hospital acquired infections are the most common non-cardiac complications after cardiac surgery. Organisms commonly found in this cohort of patients include Klebsiella spp, Escherichia coli, Pseudomonas spp, Staphylococcus aureus, Coagulase negative Staphylococcus and Enterococcus spp etc. We hereby present a case of post cardiac surgery patient presenting with Stenotrophomonas maltophilia bloodstream infection. Combination of ceftazidime-avibactam (CZA) and aztreonam(AT) was used as inactivity was exhibited to primary panel of drugs. Broth disc elution testing was done to exhibit synergy between CZA and AT. This case highlights the growing need for active interaction between the treating physician and the microbiologist.

In Vitro Synergistic Activity of Ceftazidime-Avibactam and Aztreonam against New Delhi Metallo-β-Lactamase-Producing Clinical Enterobacterales Isolates

Background: Carbapenemase-producing-Enterobacterales (CPE) infections are on the rise and associated with increased morbidity and mortality, due to a limited number of therapeutic options. The goal of this study was to assess the synergistic activity of ceftazidime-avibactam (CZA) and aztreonam (ATM) combination against phenotypically and genetically characterized blaMBL-producing Enterobacterales.Methods: In this study, forty (n=40) non-repeat, CPE clinical isolates, including: n=35 Klebsiella pneumoniae, n=2 each of Escherichia coli and Klebsiella oxytoca, and n=1 Enterobacter cloacae isolates were identified and susceptibilities were assessed using the Vitek-II compact (bioMérieux, Inc., France) and Microscan Walkaway (Beckman Coulter) systems. Genotypic analysis of clinically relevant carbapenemases was performed by using Xpert-Carba-R assay on GeneXpert (Cepheid, USA). The minimum inhibitory concentrations (MICs) and synergy testing of CZA and ATM, were tested by the Etest fixed ratio method (bioMérieux, Inc., France). The fractional inhibitory concentration index (FICI) was calculated for each antibiotic.Results: Our results showed that 97.5% of blaMBL-producing Enterobacterales isolates were susceptible to an in-vitro CZA + ATM combination regimen. The fractional inhibitory concentration index (FICI) ranged from 0.001 to 1.001. Among the tested CPE isolates, Synergy was observed in 36/40 (90%), an additive effect was observed in 5% (n=2)’ while two (5%) isolates showed indifference. There was no antagonism observed in our study.Conclusion: Our study exhibited a potent activity of CZA and ATM combination synergy against clinical CPE metallo- β-lactamase producers. More extensive studies involving a variety of Gram-negative pathogens with different resistance mechanisms are required to determine the efficacy of this combination regimen.Keywords: Synergy; Aztreonam; Ceftazidime-Avibactam; Carbapenem-Resistant Enterobacterales; Etest

Continuously producible aztreonam-loaded inhalable lipid nanoparticles for cystic fibrosis-associated Pseudomonas aeruginosa infections – Development and in-vitro characterization

Cystic fibrosis (CF) is a genetic disorder affecting nearly 105,000 patients worldwide and is characterized by poor respiratory function due to accumulation of thick mucus in the lungs, which not just acts as a physical barrier, but also provides a breeding ground for bacterial infections. These infections can be controlled with the help of antibiotics which can be delivered directly into the lungs for amplifying the local anti-bacterial effect. More than 50 % of CF patients are associated with Pseudomonas aeruginosa infection in their lungs which requires antibiotics such as Aztreonam (AZT). In this study, we prepared inhalable AZT-loaded lipid nanoparticles using Hot-melt extrusion (HME) coupled with probe sonication to target Pseudomonas aeruginosa infection in the lungs. The optimized nanoparticles were tested for physicochemical properties, stability profile, in-vitro aerosolization, and antimicrobial activity against Pseudomonas aeruginosa. The optimized nanoparticles with a PEI concentration of 0.1 % demonstrated a uniform particle size of <50 nm, a spherical shape observed under a transmission electron microscope, and >70 % drug entrapment. Incorporating cationic polymer, PEI, resulted in sustained drug release from the lipid nanoparticles. The in-vitro aerosolization studies exhibited a mass median aerodynamic diameter (MMAD) of <4.3 μm, suggesting deposition of the nanoparticles in the respirable airway. The antimicrobial activity against Pseudomonas aeruginosa showed the minimum inhibitory concentration of the formulation is 2-fold lower than plain AZT. Stability profile showed the formulations are stable after exposure to accelerated conditions. In conclusion, hot-melt extrusion in combination with probe sonication can be used as a potential method for the continuous production of AZT-loaded lipid nanoparticles with enhanced anti-bacterial activity.

Multicenter evaluation of activity of aztreonam in combination with avibactam, relebactam, and vaborbactam against metallo-β-lactamase-producing carbapenem-resistant gram-negative bacilli.

Treatment options for carbapenem-resistant gram-negative bacilli (CR-GNB), especially metallo-β-lactamase (MBL)-producing CR-GNB, are limited. Aztreonam (ATM) in combination with avibactam (AVI) has shown potential for treating MBL-producing carbapenem-resistant Enterobacterales (CREs) and Stenotrophomonas maltophilia. However, data on ATM in combination with other β-lactamase inhibitors (BLIs) are limited. We performed a multicenter study to evaluate the in vitro activities of ATM in combination with AVI, vaborbactam (VAB), relebactam (REL), tazobactam (TAZ) as well as with their commercially available formulations against CREs and S. maltophilia using broth microdilution. AVI restored ATM activity for MBL-producing CREs (ATM: 9.8% vs ATM-AVI: 78.0%) and S. maltophilia (ATM: 0% vs ATM-AVI: 93.3%). REL also moderately restored activity of ATM in MBL-producing CREs (ATM: 9.8% vs ATM-REL: 42.7%) and S. maltophilia (ATM: 0% vs ATM-REL: 68.9%). VAB and TAZ demonstrated very limited effect on the activity of ATM against CR-GNB evaluated. The combination of ATM with ceftazidime-AVI (CAZ-AVI) demonstrated maximum activity against CREs. Although ATM-CAZ-AVI is the most potent regimen available for CREs and S. maltophilia, ATM-IMI-REL might be a reasonable alternative.

Assessment of in vitro antimicrobial activity of ceftazidime-avibactam and phenotypic synergy testing with aztreonam against carbapenem resistant Gram-negative bacilli in a tertiary care hospital

Objectives: Ceftazidime avibactam (CZA) is a drug used against carbapenemase producing Gram-negative bacterial infections. Avibactam (AVI) is a non-beta-lactam-beta-lactamase inhibitor which has no action against metallo-β-lactamase (MBL) enzymes. This inadequacy is counteracted by combining CZA with aztreonam (ATM). The present study aims to denote the in vitro susceptibility pattern of the CZA and CZA-ATM combination in our area. Materials and Methods: In this study conducted prospectively from January to June 2023, the samples growing Enterobacterales and Pseudomonas aeruginosa were proceeded for carbapenemase detection by phenotypic testing for EDTA carbapenem inactivation method and modified carbapenem inactivation method. The minimum inhibitory concentration MIC of CZA was determined by E-strip and interpreted as per clinical and laboratory standard institute (CLSI) guidelines, while synergy testing of CZA and ATM was performed using ATM discs. Statistical Analysis: All data were entered in Microsoft Excel and analyzed for basic statistics. Results: The study included 150 carbapenem resistant organisms (131 Enterobactarales and 19 P. aeruginosa). Among these Enterobacterale strains, 72 (54.9%) were MBL producers. CZA resistance was detected in 69.3% of Klebsiella spp., 61.53% of Escherichia coli, and 50% of Serratia spp. Among Klebsiella spp. and E. coli, 88.9% and 65.2% of MBL isolates showed in vitro synergy to CZA-ATM. Conclusions: The study highlights a good in vitro sensitivity pattern of the CZA and ATM combination. However, we also highlight a growing percentage of non-synergistic interactions that need further genetic evaluation.

Determine Biofilm Genes in Pseudomonas Aeruginosa Isolated from Clinical and Environmental Samples

Objective: Isolates of Pseudomonas aeruginosa are an extremely adaptable bacterium that causes opportunistic diseases because of its varied metabolic pathways, genes, virulence factors, and considerable antibiotic resistance. Methods: A total of 293 samples were collected from different places: 193 samples (% 65.87) of human samples and 100 samples (% 34.13) of wastewater samples in the period between 3rd September to 15th November 2023). Bacterial isolates were identified according to microscopic, cultural, and genetic characteristics. Antibiotic susceptibility of bacterial isolates was determined against twelve of the selected antibiotics. The biofilm production was done by using phenotypic ways (Congo red agar and Microtiter plate methods) as well as genotypic ways by detection of biofilm genes (algD, pelf, and pslD genes). Results: Hundred-forty eight bacterial isolates were obtained, and sixty of these isolates were identified as Pseudomonas spp. (40.9%), twenty-six isolates of E. coli (17.9%), seventeen isolates of K. pneumoniae (11.3%), and forty-five isolates were beyond to other types of bacteria (30.1%), and out of sixty isolates of Pseudomonas spp., forty-two were identified as P. aeruginosa isolates. P. aeruginosa isolates revealed various resistance levels to antimicrobial agents gradually, ranging from 83.87% to Trimethoprim-sulfamethoxazole (SXT) to 3.22% to Aztreonam (AZT). Biofilm production by using the Congo red method showed that 27 isolates (64.28%) were positive results, while in the microtiter method, all forty-two isolates were positive (100%), the genetic detection showed that the AlgD gene was recognized in thirty-one isolates (73.8%), followed by Pelf and PslD genes in four isolates each (9.5%). Conclusion: The isolation percentage showed a high occurrence of multi-drug resistance biofilm forming Pseudomonas spp. isolates which could be a critical indicator. Methods of biofilm detection showed that the microtiter plate method has accuracy more than the Congo red method; as well AlgD gene was prevalent compared with both other genes Pelf, and PslD.

Impact of an intervention that decreased aztreonam DOT on Enterobacterales’ susceptibility to aztreonam

Background: Aztreonam (AZT) is frequently used for the treatment of Enterobacterales-related infections, particularly for patients with penicillin allergy. We aimed to analyze the impact over time of changes in AZT Days of therapy (DOTs) on AZT susceptibility from some Enterobacterales after a multifaceted intervention to improve antibiotic management at a University Hospital in Florida. Methods: The study took place at a 560-lbed academic hospital in Miami, FL. A multifaceted intervention was implemented in this hospital to improve antibiotic management of patients with reported allergies to penicillin. The intervention included use of algorithm-based guidance, education, and feedback to providers. The analysis period spans from 2018 (pre-intervention) through 2022 (post intervention); 2019 was considered the wash-out period (Figure 1). Quarterly data for AZT-DOT and percentage of resistance to AZT for Enterobacterales were collected as part of the normal operations of the antimicrobial stewardship program (ASP) using the infection control module integrated in the electronic medical record (Epic Bugsy). DOT and Enterobacterales antibiotic resistance to AZT was analyzed using linear regression in SPSS. Results: We identified a decrease in DOT AZT and percentage of AZT resistance from E. coli during the study period (Table 1). This intervention led to AZT DOT’s decrease from a quarterly average of 24 DOTs in 2018 levels to a sustained quarterly average of 4.3 DOTs for 2020 to Q2 2023 (decrease 80%) Antibiotic resistance to E. coli AZT changed from a 26.6% to 21.5% (19% decrease) (Table1). Simple linear regression identified a decrease in percentage of E. coli resistance to AZT associated with a decrease on AZT DOT (P-value 0.003), there was no association for other Enterobacterales. For each unit of decrease in AZT DOT there was 0.3% decrease in percentage of E. coli resistance to AZT (Table 2.) Conclusions: A decrease in AZT DOT during the observation period was associated with a decrease in E. coli resistance to AZT. Interventions aimed to decrease inappropriate antibiotic use are pivotal part of the fight against antimicrobial resistance; in our study we report a decrease in E. coli resistance to aztreonam related to decrease in the use of this antibiotic using education, guidance, and feedback to providers.

Synergistic Combination of Aztreonam and Ceftazidime–Avibactam—A Promising Defense Strategy against OXA-48 + NDM Klebsiella pneumoniae in Romania

With the increasing burden of carbapenem-resistant Klebsiella pneumoniae (CR-Kp), including high rates of healthcare-associated infections, treatment failure, and mortality, a good therapeutic strategy for attacking this multi-resistant pathogen is one of the main goals in current medical practice and necessitates the use of novel antibiotics or new drug combinations. Objectives: We reviewed the clinical and microbiological outcomes of seven patients treated at the “Agrippa Ionescu” Clinical Emergency Hospital between October 2023 and January 2024, aiming to demonstrate the synergistic activity of the ceftazidime–avibactam (C/A) plus aztreonam (ATM) combination against the co-producers of blaNDM + blaOXA-48-like CR-Kp. Material and Methods: Seven CR-Kp with blaNDM and blaOXA-48 as resistance mechanisms were tested. Seven patients treated with C/A + ATM were included. The synergistic activity of C/A + ATM was proven through double-disk diffusion in all seven isolates. Resistance mechanisms like KPC, VIM, OXA-48, NDM, IMP, and CTX-M were assessed through immunochromatography. Results: With a mean of nine days of treatment with the synergistic combination C/A + ATM, all patients achieved clinical recovery, and five achieved microbiological recovery. Conclusions: With the emerging co-occurrence of blaOXA-48 and blaNDM among Kp in Romania, the combination of C/A and ATM could be a promising therapeutic option.

In vitro and in vivo activity of ceftazidime/avibactam and aztreonam alone or in combination against mcr-9, serine- and metallo-β-lactamases-co-producing carbapenem-resistant Enterobacter cloacae complex.

Enterobacteriaceae carrying mcr-9, in particularly those also co-containing metallo-β-lactamase (MBL) and TEM type β-lactamase, present potential transmission risks and lack adequate clinical response methods, thereby posing a major threat to global public health. The aim of this study was to assess the antimicrobial efficacy of a combined ceftazidime/avibactam (CZA) and aztreonam (ATM) regimen against carbapenem-resistant Enterobacter cloacae complex (CRECC) co-producing mcr-9, MBL and TEM. The in vitro antibacterial activity of CZA plus ATM was evaluated using a time-kill curve assay. Furthermore, the in vivo interaction between CZA plus ATM was confirmed using a Galleria mellonella (G. mellonella) infection model. All eight clinical strains of CRECC, co-carrying mcr-9, MBL and TEM, exhibited high resistance to CZA and ATM. In vitro time-kill curve analysis demonstrated that the combination therapy of CZA + ATM exerted significant bactericidal activity against mcr-9, MBL and TEM-co-producing Enterobacter cloacae complex (ECC) isolates with a 100% synergy rate observed in our study. Furthermore, in vivo survival assay using Galleria mellonella larvae infected with CRECC strains co-harboring mcr-9, MBL and TEM revealed that the CZA + ATM combination significantly improved the survival rate compared to the drug-treatment alone and untreated control groups. To our knowledge, this study represents the first report on the in vitro and in vivo antibacterial activity of CZA plus ATM against CRECC isolates co-harboring mcr-9, MBL and TEM. Our findings suggest that the combination regimen of CZA + ATM provides a valuable reference for clinicians to address the increasingly complex antibiotic resistance situation observed in clinical microorganisms.

Use of Aztreonam Plus Ceftazidime/Avibactam Combination for In vitro Susceptibility Testing of CRO Isolates in a Tertiary Care Hospital – Our experience

Abstract Background: Infections caused by metallo-beta-lactamases (MBLs) producing Gram-negative bacteria (mainly Enterobacterales) pose a great challenge for clinicians in treating these multidrug-resistant infections. In recent times, combination antibiotic therapy with ceftazidime–avibactam (CAZ-AVI) with aztreonam (ATM) has been researched by a number of laboratories worldwide and has gained much clinical attention. This study evaluated a practical laboratory method of testing for clinically significant in vitro synergy between CAZ/AVI + ATM in New Delhi MBLs (NDM) producing Gram-negative organisms. Materials and Methods: A total of 100 isolates of carbapenem-resistant Enterobacteriaceae (Klebsiella pneumoniae, Escherichia coli, Pseudomonas aeruginosa, and Enterobacter cloacae) were tested for synergy between CAZ/AVI + ATM using E-strip of CAZ/AVI and disc of ATM. The minimum inhibitory concentration value of CAZ/AVI was measured and the zone of inhibition was observed when ATM was placed parallel to the E-strip on a lawn culture of an isolate. Simultaneously, all isolates were tested for NDM and OXA-48 by Xpert Carba-R. Results: Of 100 isolates, 63/100 (63%) were harboring OXA-48 beta-lactamase, 54/100 (54%) were harboring NDM beta-lactamase and 18/100 (18%) were harboring both (OXA-48 and NDM). In vitro synergy between CAZ/AVI + ATM was noted in 99 isolates (99%). Conclusion: A significant synergy was demonstrated in vitro with CAZ/AVI + ATM combination therapy and seems to be a promising treatment strategy for infections caused by Enterobacterales harboring NDM and OXA-48 beta-lactamases.

Isolation And Identification Of Staphylococcus Aureus And Candida SPP From Throat Infections

This research aimed to isolate and identify Staphylococcus aureus and Candida species from throat infections, as well as assess their antibiotic resistance. Samples were collected from both infected patients and healthy individuals, encompassing various ages and genders, in hospitals of Najaf province between December 2022 and March 2023. The findings revealed that S. aureus constituted 36.10% of isolates, followed by S. warneri at 22.81%, and S. lugdunensis at 15.29%. Notably, S. aureus isolates displayed 100% resistance to Penicillin (P), Aztreonam (ATM), and Oxacillin (OX), Amoxicillin (AMC) and Tetracycline (TE) exhibiting resistance rates of 81.95% and 78.19%, respectively. The study concluded that S. aureus was the predominant strain, followed by S. warneri. Antibiotic susceptibility testing on all S. aureus isolates (n=21) was conducted using seven selected antibiotics. Candida species identified included Candida albicans, Candida parapsilosis, and Candida glabrata, with maximum resistance observed against fluconazole (FLU) and polymyxin B (PB), followed by miconazole (MCL).

Potentiation of Antibiotic Activity of Aztreonam against Metallo-β-Lactamase-Producing Multidrug-Resistant Pseudomonas aeruginosa by 3-O-Substituted Difluoroquercetin Derivatives.

The combination of aztreonam (ATM) and ceftazidime-avibactam (CAZ-AVI; CZA) has shown therapeutic potential against serine-β-lactamase (SBL)- and metallo-β-lactamase (MBL)-producing Enterobacterales. However, the ability of CZA to restore the antibiotic activity of ATM is severely limited in MBL-producing multidrug-resistant (MDR) Pseudomonas aeruginosa strains because of the myriad of intrinsic and acquired resistance mechanisms associated with this pathogen. We reasoned that the simultaneous inhibition of multiple targets associated with multidrug resistance mechanisms may potentiate the antibiotic activity of ATM against MBL-producing P. aeruginosa. During a search for the multitarget inhibitors through a molecular docking study, we discovered that di-F-Q, the previously reported efflux pump inhibitor of MDR P. aeruginosa, binds to the active sites of the efflux pump (MexB), as well as various β-lactamases, and these sites are open to the 3-O-position of di-F-Q. The 3-O-substituted di-F-Q derivatives were thus synthesized and showed hereto unknown multitarget MDR inhibitory activity against various ATM-hydrolyzing β-lactamases (AmpC, KPC, and New Delhi metallo-β-lactamase (NDM)) and the efflux pump of P. aeruginosa, presumably by forming additional hydrophobic contacts with the targets. The multitarget MDR inhibitor 27 effectively potentiated the antimicrobial activity of ATM and reduced the MIC of ATM more than four-fold in 19 out of 21 MBL-producing P. aeruginosa clinical strains, including the NDM-producing strains which were highly resistant to various combinations of ATM with β-lactamase inhibitors and/or efflux pump inhibitors. Our findings suggest that the simultaneous inhibition of multiple MDR targets might provide new avenues for the discovery of safe and efficient MDR reversal agents which can be used in combination with ATM against MBL-producing MDR P. aeruginosa.

Evaluation of the MTS™ aztreonam-avibactam strip (Liofilchem) on New Delhi metallo-β-lactamase-producing Enterobacterales.

The combination of ceftazidime-avibactam (CAZ-AVI) and aztreonam (ATM) is used to treat MBL-producing Enterobacterales-related infections. The new combination aztreonam-avibactam (AZA) is currently in development. We compared results obtained with the new MIC test strip (MTS) AZA (Liofilchem) with broth microdilution method (BMD) on 41 MBL-producing Enterobacterales from 41 clinical samples. The MTS AZA was also compared to combination testing method using CAZ-AVI and ATM strips. Compared to BMD, categorical agreement (CA) was 100%. Compared with combination testing method, CA was 97.6%. The MTS AZA can be used to determine MICs levels of AZA or CAZ-AVI/ATM combinations.

Clone dissemination of IncX3 plasmid carrying blaNDM-1 in ST76 carbapenem resistance Klebsiella pneumoniae and bactericidal efficiency of aztreonam combined with avibactam in vitro and in vivo

ObjectivesThe rapid spread of the New Delhi Metal-β-lactamase-1 (NDM-1) gene in Klebsiella pneumoniae poses a substantial challenge to pediatric therapeutic care. Here, we aimed to characterise the IncX3-type plasmid carrying the blaNDM-1 gene in ST76 carbapenem resistance K. pneumoniae (CRKP) strains and assess the in vitro and in vivo bactericidal efficacy of Aztreonam (ATM) combined with Avibactam (AVI) (ATM+AVI) against CRKP. MethodsThe broth microdilution method and PCR were used to detect antimicrobial susceptibility and antibiotic resistance genes. Genetic relatedness was determined using Pulsed-Field Gel Electrophoresis (PFGE) and Multilocus Sequence Typing (MLST). The plasmid conjugation assay was used to verify the transmissibility of drug-resistant plasmids. Whole-Genome Sequencing (WGS) was employed to elucidate the genomic attributes of the genes. The Fractional Inhibitory Concentration (FIC) was calculated based on the checkerboard titration assay to determine the antimicrobial effect of ATM+AVI. The time-kill curve assay and a mouse anti-infection model were used to investigate the in vitro and in vivo bactericidal efficiency of ATM+AVI. ResultsSeven blaNDM-1-producing strains were found to be highly resistant to carbapenems, and they all belonged to the same sequence type (ST76) and were classified into the same PFGE clusters with an 89.1% similarity. The conjugation assay showed that the blaNDM-1-carrying plasmid was successfully transferred to Escherichia coli 600, resulting in transconjugants with carbapenem antibiotic resistance. A 54-kb IncX3 plasmid (pNDM-XZA88) carried the blaNDM-1 gene located on a Tn125 transposon-like element structure, demonstrating the transferability of resistance genes. Genome comparative analysis revealed that pNDM-XZA88 was highly similar to pCQ17 × 3 and pRor-30818cz and had relatively conserved backbones and variable accessory regions compared to the other four plasmids (pC39-334 kb, pNDM-1-DY1928, pNDM-K725, and pNDM-Z244). The checkerboard titration and time-kill curve assays revealed that the ATM+AVI combination therapy exerted significant bactericidal efficacy against the blaNDM-1-producing strains in vitro. The ATM+AVI combination also significantly reduced the bacterial burden in a mouse infection model constructed using the blaNDM-1-producing K. pneumoniae. ConclusionThis study demonstrated the clone dissemination of blaNDM-1-harboring IncX3 plasmids among the ST76 K. pneumoniae isolated from pediatric patients. Therefore, more attention should be paid to preventing this high-risk clone from harming pediatric patients. Moreover, we deduced that the ATM+AVI combination therapy is an effective strategy for treating blaNDM-1-producing K. pneumoniae.

Ceftazidime-avibactam in the treatment of bacteremia due to carbapenem-resistant gram-negative bacteria in hematological patients: Experience in a single center

IntroductionLimited experience exists with ceftazidime-avibactam (CAZ-AVI) in treating bacteremia caused by carbapenem-resistant Enterobacterales (CRE) and Pseudomonas aeruginosa (CRPA) in hematological patients. MethodsWe performed a single-center, retrospective, observational study including patients who received CAZ-AVI for bacteremia due to CRE or CRPA between 2018 and 2022. The primary outcome was 30-day survival. We conducted a multivariable analysis to identify predictors of survival. Results56 patients were included and 57 (41 CRE and 16 CRPA) strains were isolated. 35 strains produced carbapenemase, including 25 metallo-beta-lactamase (MBL) and 10 serine-beta-lactamase. 48 patients (85.7 %) received combination therapy. All patients with MBL-CRE bacteremia (n = 24) received combination therapy with aztreonam (AZT). The susceptibility rates to CAZ-AVI were only 26.8 % (11/41) in CRE and 80.0 % (8/10) in CRPA. The 30-day survival rates were 85.0 % (34/40) in the CRE group and 81.3 % (13/16) in the CRPA group. In patients with MBL-CRE bacteremia, the 30-day survival was as high as 91.7 % (22/24) due to combination with AZT. Ceftazidime did not influence the activity of aztreonam-avibactam against MBL-CRE in-vitro. Multivariable cox analysis revealed neutropenia >14 days (P = 0.002, HR: 34.483, 95%CI: 3.846–333.333) and a higher Pitt bacteremia score (P = 0.005, HR: 2.074, 95%CI: 1.253–3.436) were risk factors for 30-day survival. ConclusionsCAZ-AVI is highly effective in treating bacteremia due to CRPA and serine-beta-lactamase CRE. The combination of avibactam with AZT is highly effective in treating bacteremia due to AZT-resistant MBL producers.

Inhaled aztreonam lysine in the management of Pseudomonas aeruginosa in patients with cystic fibrosis: real-life effectiveness

BackgroundInhaled antibiotics have achieved or stabilised the clinical condition of patients with cystic fibrosis (CF) and chronic Pseudomonas aeruginosa infection. We aimed to determine the effectiveness of aztreonam lysine inhaled...

In silico prediction and a systematic toxicology-based in vivo investigation uncovering the mechanism of aquatic toxicity caused by beta-lactam antibiotics

Recently, beta-lactam antibiotics have gained attention as significant contributors to public health and environmental issues due to their potential toxicity. Our study employed machine learning to develop a model for assessing the aquatic toxicity of beta-lactam antibiotics on zebrafish. Notably, aztreonam (AZT), a synthetic monobactam and a subclass of beta-lactam antibiotics, demonstrated developmental effects in zebrafish embryos comparable to cephalosporins, indicating a potential for toxicity. Using a systems toxicology-based approach, we identified apoptosis and metabolic disorders as the primary pathways affected by AZT and its impurity F exposure. During the administration of monobactams, we noted that ctsbb, nos2a, and dgat2, genes associated with apoptosis and the metabolic pathway, exhibited significant differential expression. Molecular docking studies were conducted to ascertain the binding affinity between monobactam compounds and their potential targets—Ctsbb, Nos2a, and Dgat2. Furthermore, our research revealed that monobactams influence pre-mRNA alternative splicing, resulting in disruptions in the expression of genes involved in hair cells, brain, spinal cord, and fin regeneration (e.g., krt4, krt5, krt17, cyt1). Notably, we observed a correlation between the levels of rpl3 and rps7 genes, both important ribosomal proteins, and the detected alternative splicing events. Overall, this study enhances our understanding of the toxicity of beta-lactam antibiotics in zebrafish by demonstrating the developmental effects of monobactams and uncovering the underlying mechanisms at the molecular level. It also identifies potential targets for further investigation into the mechanisms of toxicity and provides valuable insights for early assessment of biological toxicity associated with antibiotic pollutants.

Aztreonam-avibactam synergy, a validation and comparison of diagnostic tools

IntroductionAntimicrobial resistance is a growing problem that necessitates the development of new therapeutic options. Cefiderocol and aztreonam (AT) are often the last active β-lactams for treating metallo-β-lactamases (MBL)-producing Gram-negative bacilli. In these difficult-to-treat bacterial strains, AT resistance is frequently attributed to the co-occurrence of other resistance mechanisms. In the case of β-lactamases they can often be inhibited by avibactam. In the present study, we evaluated the use of the double-disc synergy test (DDST) as a screening tool for the detection of synergy between AT-avibactam (ATA). We validated both the Gradient Diffusion Strips (GDSs) superposition method and the commercially available Liofilchem’s ATA GDS.Materials and methodsWe tested AT susceptibility in combination with ceftazidime-avibactam for 65 strains, including 18 Serine-β-Lactamase (SBL)- and 24 MBL-producing Enterobacterales, 12 MBL-producing P. aeruginosa, and 11 S. maltophilia isolates. Interpretation was done with EUCAST breakpoints (version 13.0), AT breakpoints being used for ATA. The accuracy and validity of the GDSs superposition method and ATA GDS were evaluated using an AT GDS applied on Mueller Hinton Agar plates supplemented with avibactam (MH-AV). A DDST was performed to screen for synergy between antibiotic combinations.ResultsUsing MH-AV, all SBL- and MBL-positive Enterobacterales were susceptible or susceptible at increased exposure to the combination AT-avibactam. In contrast, only 2 out of the 12 (17%) P. aeruginosa strains and 9/11 (82%) of the S. maltophilia strains were susceptible- or susceptible at increased exposure for the combination of AT-avibactam. The DDST detected all synergies, demonstrating a 100% sensitivity and 100% negative predictive value for all bacterial strains.ConclusionThe DDST is a sensitive tool for screening for antibiotic synergy. Unlike S. maltophilia and SBL- and MBL-positive Enterobacterales, most MBL-positive P. aeruginosa strains remain resistant to AT-avibactam. ATA GDS should be preferred for MIC determination of the AT-avibactam combination, while the GDSs superposition method can be used as an alternative to the commercial test.

2170. It takes two to tango: ß-lactam/ß-lactamase inhibitor combinations targeting metallo-ß-lactamase (MBL)- producing Klebsiella pneumoniae.

Abstract Background The emergence of pan drug resistant (PDR) gram-negatives co-producing NDM-1 and CTX-M-15 calls for devising more efficient biocidal regimens. Also, understanding the salient transcriptomic and phenotypic changes that contribute to persistence which aid in pathogen survival is critical to therapeutic preparation in the clinical setting. Methods A 10-day hollow fiber infection model (HFIM) was utilized to simulate humanized β-lactam regimens involving imipenem (IMI) 1g q8h, aztreonam (ATM) 2g q8h, and ceftazidime/avibactam (CAZ/AVI) 2g/500mg alone and in 3-drug combination regimens against a PDR Klebsiella pneumonia isolate co-harboring blaNDM-1 and blaCMY-6, blaCTX-M-15 and blaSHV-2. Static time kills were performed to investigate the interplay between IMI and ATM. At 2h post drug exposure, total RNA was analyzed by qRT-PCR for the expression of pertinent genes. Glutaraldehyde-fixed samples were imaged using fluorescence and scanning electron microscopy. Results In HFIM, IMI contributed synergistically to the antimicrobial action as the average bacterial concentration between 30-120h was 2.1 log10 CFU/mL lower in ATM + CAZ/AVI + IMI than in ATM + CAZ/AVI (2.44 log10 CFU/mL vs. 4.54 log10 CFU/mL, respectively). Adding IMI to ATM+ CAZ/AVI also resulted in an enhanced post-antibiotic effect. Although ATM + IMI reduced bacterial counts by ≥4 log10 CFU/mL in 6h time kill assays, regrowth to the system carrying capacity of ∼8.5 log10 CFU/mL by 24h in all arms rendered these drugs ineffective. By 2h of treatment, ATM alone resulted in long filamentous cells whereas IMI resulted in significant populations of spheroplasts. ATM+IMI caused blebbing in the center of elongating filaments followed by a burst in spheroplast formation. qRT-PCR showed upregulation of spheroplast protein Y (spy) and penicillin binding proteins (pbp1, pbp2, pbp3) for all combinations involving IMI. However, pbp1, pbp3 and spy remained unchanged and pbp2 levels were downregulated by &amp;gt;25% in ATM monotherapy. Conclusion Overall, this PDR clinical isolate persisted in the presence of ATM + CAZ/AVI. The addition of IMI to target PBP2 in β-lactam combinations maximally suppressed the emergence of filamentous persisters and may be a promising strategy to prepare for increasing rates of gram-negative resistance. Disclosures All Authors: No reported disclosures

2810. A synergy test to assess the activity of the Ceftazidime-Avibactam and Aztreonam combination: An experience from a single centre in Malaysia

Abstract Background Southeast Asia has a high prevalence of metallo-β-lactamase-producing carbapenem-resistant Enterobacterales (CRE). Ceftazidime-avibactam (CZA) and Aztreonam (ATM) combination is one of the preferred therapeutic options against them. Methods A prospective study was performed at a university hospital in Kuala Lumpur, Malaysia, involving CRE isolates resistant to CZA and ATM. Susceptibility testing results were interpreted using the Clinical and Laboratory Standards Institute (CLSI) breakpoints. A synergy test for both agents [as in Falcone et al. study (CID 2021:72)] was carried out using the double disk synergy (DDS) and the gradient test superposition (GTS) methods. Synergy was considered present when the inhibition zone between the two disks became evident and if CZA reduced the ATM minimum inhibitory concentration (MIC) below its CLSI susceptibility cut-off (≤4 mg/L). Results Eleven isolates (8 K. pneumoniae, 2 E. coli, and 1 K. aerogenes) from 10 patients were tested. Concordant results were seen for both methods for all the isolates. Synergy was demonstrated with 8 isolates; for 2 of the 3 isolates with no synergy, the MIC of ATM reduced to an intermediate result after GTS. The most common sites of infection were bloodstream infection (4) and intra-abdominal infection (3). Five patients received the CZA-ATM combination (one received two courses of CZA-ATM). Five isolates from four patients demonstrated synergy, and one showed intermediate synergy. The latter received additional IV tigecycline. The median time to CZA-ATM initiation from the index culture was 8 (3-13) days. The median duration of therapy was 21 (6-28) days. Four patients responded favorably to the agents (survived the infection), while the remaining patient died. For those that did not receive CZA-ATM, one received polymyxin-based therapy, one received high-dose, extended-infusion meropenem, and one received no treatment. Only the patient that received meropenem survived the infection. Please refer to Table 1.0 for more detail. Conclusion Based on this small sample size, only a 73% synergy rate between CZA and ATM was seen for our CRE isolates resistant to CZA and ATM. Favorable treatment response was seen in those receiving the CZA-ATM combination therapy when synergy was demonstrated Disclosures All Authors: No reported disclosures