In vitro activities of ceftazidime/avibactam alone or in combination with antibiotics against multidrug-resistant Acinetobacter baumannii isolates

Significant in-Vitro and in-Vivo Antimicrobial and Antibiofilm Activity of Colloidal Silver Nanoparticles (cAgNPs) in Chronic Diabetic Foot Ulcers

Infection is a foremost challenge in the cases of wound care, especially in cases of chronic wounds. The present study was conducted to determine the antimicrobial and antibiofilm activity of the colloidal silver nanoparticles (cAgNPs) on Gram positive organisms and to evaluate the in-vivo response of cAgNPs on patients of chronic diabetic foot ulcers (DFUs). cAgNPs were tested against selected Gram-positive organisms like methicillin-sensitive and resistant Staphylococcus aureus (MSSA, MRSA), Enterococcus faecalis and vancomycin resistant enterococci (VRE) using microbroth dilution assay to estimate minimum inhibitory/bactericidal concentration (MIC/MBC). Biofilm inhibition capacity and time kill assay was performed. Further, the in-vivo response of topical application of cAgNPs was evaluated on patients of DFUs. The susceptibility testing demonstrated the MIC and MBC values of the cAgNPs ranging from 0.5μg/ml to 1.0 μg/ml and 1.0 μg/ml to 8 μg/ml against the tested organisms respectively. The cAgNPs showed inhibition of biofilm formation in the low, medium and high biofilm producers by 91%, 83% and 75% respectively at the highest concentration (52ppm). The time kill kinetics showed significant reduction in the number of viable cells (p < 0.0001). Significant reduction in microbial load (p = 0.0062) and in the number of moderate to strong biofilm producing organisms (p = 0.0069) after treatment with cAgNPs was seen. cAgNPs exhibited significant in-vitro bactericidal and bacteriostatic activity against MRSA, MSSA and VRE respectively along with anti-biofilm activity. Additionally, cAgNPs showed significant reduction in microbial load of the chronic DFUs.

Cationic antimicrobial peptide CC34 potential anticancer and apoptotic induction on cancer cells

To evaluate the potential of antimicrobial peptide CC34 for use as therapeutic agents for gastric cancer SGC-7901 and hepatocellular carcinoma HepG-2. In this study, the antibacterial activity and antibacterial mechanism were tested by the minimum inhibitory concentration (MIC) analysis, minimal bactericidal concentration (MBC) analysis, bacterial biofilm and NaCl permeability assays. Then, we assessed the hemolytic activity and cytotoxicity of CC34 for red blood cells and cancer cells, respectively. Apoptosis assay, cell cycle analysis, determination of intracellular ROS, western blot analysis caspase activity assay and ATP assay were further performed to investigate the mechanism of CC34 affected cancer cells. The novel peptide could inhibit Gram-negative and Gram-positive bacteria, with low hemolytic activity against mouse and chicken erythrocytes. Moreover, CC34 exhibited higher inhibitory activity against biofilm formation. In addition, our data showed that CC34 significantly suppressed cell proliferation, in a dose dependent manner. CC34 induced apoptosis, induced reactive oxygen species (ROS) generation, inhibited B-cell lymphoma-2 (Bcl-2) expression, increase B-cell lymphoma protein 2 associated X protein (Bax) expression, release of cytochrome c (Cyt C), promoted caspase-3 and - 9 activities and reduced cellular ATP levels in cancer cells. Our results indicate that CC34 with antimicrobial activity have a highly potent ability to induced apoptosis via mitochondrial-mediated apoptotic pathway in cancer cells.

Global trends of ceftazidime-avibactam resistance in gram-negative bacteria: systematic review and meta-analysis

BACKGROUND

The emergence of antimicrobial resistance in Gram-negative bacteria (GNB) is a major global concern. Ceftazidime-avibactam (CAZ-AVI) has been identified as a potential treatment option for complicated infections.

OBJECTIVES

This meta-analysis aimed to evaluate the global resistance proportions of GNB to CAZ-AVI comprehensively.

METHODS

Studies were searched in Scopus, PubMed, and EMBASE (until September 2024), and statistical analyses were conducted using STATA software (version 20.0).

RESULTS

CAZ-AVI resistance proportions were determined in 136 studies, with 25.8% (95% CI 22.2-29.7) for non-fermentative gram-negative bacilli and 6.1% (95% CI 4.9-7.4) for Enterobacterales. The CAZ-AVI resistance proportion significantly increased from 5.6% (95% CI 4.1-7.6) of 221,278 GNB isolates in 2015-2020 to 13.2% (95% CI 11.4-15.2) of 285,978 GNB isolates in 2021-2024. Regionally, CAZ-AVI resistance was highest in Asia 19.3% (95% CI 15.7-24.23.4), followed by Africa 13.6% (95% CI 5.6-29.2), Europe 11% (95% CI 7.8-15.2), South America 6.1% (95% CI 3.2-11.5) and North America 5.3% (95% CI 4.2-6.7). Among GNB resistance profiles, colistin-resistant isolates and XDR isolates exhibited the highest resistance proportions (37.1%, 95% CI 14-68 and 32.1%, 95% CI 18.5-49.6), respectively), followed by carbapenem-resistant isolates and MDR isolates [(25.8%, 95% CI 22.6-29.3) and (13%, 95% CI 9.6, 17.3)].

CONCLUSION

A high proportion of GNB isolates from urinary tract infections remained susceptible to CAZ-AVI, indicating its potential as a suitable treatment option. However, the increasing resistance trends among GNB are concerning and warrant continuous monitoring to maintain CAZ-AVI's effectiveness against GNB infections.

Ceftazidime-avibactam combination therapy versus monotherapy for treating carbapenem-resistant gram-negative infection: a systemic review and meta-analysis

BACKGROUND

This meta-analysis was conducted to compare the efficacy of ceftazidime-avibactam combination therapy with that of monotherapy in the treatment of carbapenem-resistant Gram-negative bacterial (CR-GNB).

METHODS

A literature search of PubMed, Embase, the Cochrane Library, and ClinicalTrials.gov was conducted until September 1, 2023. Only studies that compared CZA combination therapy with monotherapy for CR-GNB infections were included.

RESULTS

A total of 25 studies (23 retrospective observational studies and 2 prospective studies) involving 2676 patients were included. There was no significant difference in 30-day mortality between the study group receiving combination therapy and the control group receiving monotherapy (risk ratio [RR] 0.91; 95% confidence interval [CI] 0.71-1.18). In addition, no significant differences were observed between the study and the control group in terms of in-hospital mortality (RR 1.00; 95% CI 0.79-1.27), 14-day mortality (RR 1.54; 95% CI 0.24-9.91), 90-day mortality (RR 1.18; 95% CI 0.62-2.22), and clinical cure rate (RR 0.95; 95% CI 0.84-1.08). However, the combination group had a borderline higher microbiological eradication rate than the control group (RR 1.15; 95% CI 1.00-1.32).

CONCLUSIONS

Compared to monotherapy, CZA combination therapy did not yield additional clinical benefits. However, combination therapy may be associated with favorable microbiological outcomes.

The place of new antibiotics for Gram-negative bacterial infections in intensive care: report of a consensus conference

INTRODUCTION

New beta-lactams, associated or not with beta-lactamase inhibitors (NBs/BIs), can respond to the spread of carbapenemase-producing enterobacteriales and nonfermenting carbapenem-resistant bacteria. The risk of emergence of resistance to these NBs/BIs makes guidelines necessary. The SRLF organized a consensus conference in December 2022.

METHODS

An ad hoc committee without any conflict of interest (CoI) with the subject identified the molecules (ceftolozane-tazobactam, ceftazidime-avibactam, imipenem-cilastatin-relebactam, meropenem-vaborbactam and cefiderocol); defined 6 generic questions; drew up a list of subquestions according to the population, intervention, comparison and outcomes (PICO) model; and reviewed the literature using predefined keywords. The quality of the data was assessed using the GRADE methodology. Seven experts in the field proposed their own answers to the questions in a public session and answered questions from the jury (a panel of 10 critical-care physicians without any CoI) and the public. The jury then met alone for 48 h to write its recommendations. Due to the frequent lack of powerful studies that have used clinically important criteria of judgment, the recommendations were formulated as expert opinions as often as necessary.

RESULTS

The jury provided 17 statements answering 6 questions: (1) Is there a place in the ICU for the probabilistic use of new NBs/IBs active against Gram-negative bacteria? (2) In the context of documented infections with sensitivity to several of these molecules, are there pharmacokinetic, pharmacodynamic, ecological or medico-economic elements for prioritization? (3) What are the possible combinations with these molecules and in what context? (4) Should we integrate these new molecules into a carbapenem-sparing strategy? (5) What pharmacokinetic and pharmacodynamic data are available to optimize their mode of administration in critically ill patients? (6) What are the dosage adaptations in cases of renal insufficiency, hepatocellular insufficiency or obesity?

CONCLUSION

These recommendations should optimize the use of NBs/BIs in ICU patients.

Geographic patterns of Acinetobacter baumannii and carbapenem resistance in the Asia-Pacific Region: results from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program, 2012-2019

OBJECTIVES

This study aimed to investigate the geographic distribution of carbapenem-resistant Acinetobacter baumannii (CR-AB) isolates in the Asia-Pacific region.

METHODS

We collected A. baumannii isolates using the Antimicrobial Testing Leadership and Surveillance program from 2012 to 2019. The minimum inhibitory concentrations (MICs) of the isolates were determined using the broth microdilution method. The major carbapenemase genes were identified using multiplex polymerase chain reaction assays for the isolates collected between 2012 and 2014. CR-AB was defined as isolates with meropenem MICs ≥8 mg/l.

RESULTS

In total, 2674 A. baumannii isolates were collected from 13 countries, of which 1918 (71.7%) were CR-AB. The carbapenem resistance rates among A. baumannii isolates were as low as 2.8% and 6.5% in Japan and Australia, respectively, but as high as 88% and 87.2% in South Korea and India, respectively. Of the 232 CR-AB isolates that underwent carbapenemase gene screening, 224 (96.6%) harbored at least one carbapenemase gene. A total of 226 carbapenemase genes were detected, with bla_OXA-23 (94.7%, 214/226) being the most dominant, followed by bla_OXA-72 (2.7%, 6/226), bla_OXA-58 (2.2%, 5/226), and bla_NDM-1 (0.4%, 1/226). CR-AB isolates had >80% resistance to amikacin, ampicillin/sulbactam, cefepime, ceftazidime, ciprofloxacin, levofloxacin, and piperacillin/tazobactam. The rates of CR-AB resistance to minocycline and colistin were 7.2% (31/429) and 1.7% (23/1368). For cefoperazone/sulbactam and tigecycline, 50.2% (527/1049) and 93.3% (1789/1918) of CR-AB isolates had an MIC ≤16 mg/l and ≤2 mg/l, respectively.

CONCLUSION

The prevalence of carbapenem resistance in A. baumannii showed significant differences among countries in the Asia-Pacific region, and the treatment options were limited.

In search for a synergistic combination against pandrug-resistant A. baumannii; methodological considerations

PURPOSE

Pending approval of new antimicrobials, synergistic combinations are the only treatment option against pandrug-resistant A. baumannii (PDRAB). Considering the lack of a standardized methodology, the aim of this manuscript is to systematically review the methodology and discuss unique considerations for assessing antimicrobial combinations against PDRAB.

METHODS

Post-hoc analysis of a systematic review (conducted in PubMed and Scopus from inception to April 2021) of studies evaluating antimicrobial combination against A. baumannii, based on antimicrobials that are inactive in vitro alone.

RESULTS

Eighty-four publications were reviewed, using a variety of synergy testing methods, including; gradient-based methods (n = 11), disk-based methods (n = 6), agar dilution (n = 2), checkerboard assay (n = 44), time-kill assay (n = 50), dynamic in vitro PK/PD models (n = 6), semi-mechanistic PK/PD models (n = 5), and in vivo animal models (n = 11). Several variations in definitions of synergy and interpretation of each method were observed and are discussed. Challenges related to testing combinations of antimicrobials that are inactive alone (with regards to concentrations at which the combinations are assessed), as well as other considerations (assessment of stasis vs killing, clinical relevance of re-growth in vitro after initial killing, role of in vitro vs in vivo conditions, challenges of clinical testing of antimicrobial combinations against PDRAB infections) are discussed.

CONCLUSION

This review demonstrates the need for consensus on a standardized methodology and clinically relevant definitions for synergy. Modifications in the methodology and definitions of synergy as well as a roadmap for further development of antimicrobial combinations against PDRAB are proposed.

Systematic Review of Antimicrobial Combination Options for Pandrug-Resistant Acinetobacter baumannii

Antimicrobial combinations are at the moment the only potential treatment option for pandrug-resistant A. baumannii. A systematic review was conducted in PubMed and Scopus for studies reporting the activity of antimicrobial combinations against A. baumannii resistant to all components of the combination. The clinical relevance of synergistic combinations was assessed based on concentrations achieving synergy and PK/PD models. Eighty-four studies were retrieved including 818 eligible isolates. A variety of combinations (n = 141 double, n = 9 triple) were tested, with a variety of methods. Polymyxin-based combinations were the most studied, either as double or triple combinations with cell-wall acting agents (including sulbactam, carbapenems, glycopeptides), rifamycins and fosfomycin. Non-polymyxin combinations were predominantly based on rifampicin, fosfomycin, sulbactam and avibactam. Several combinations were synergistic at clinically relevant concentrations, while triple combinations appeared more active than the double ones. However, no combination was consistently synergistic against all strains tested. Notably, several studies reported synergy but at concentrations unlikely to be clinically relevant, or the concentration that synergy was observed was unclear. Selecting the most appropriate combinations is likely strain-specific and should be guided by in vitro synergy evaluation. Furthermore, there is an urgent need for clinical studies on the efficacy and safety of such combinations.

Evaluation of ceftazidime/avibactam alone and in combination with amikacin, colistin and tigecycline against Klebsiella pneumoniae carbapenemase-producing K. pneumoniae by in vitro time-kill experiment

Klebsiella pneumoniae carbapenemase-producing K. pneumoniae (KPC-Kp) poses a major threat to human health worldwide. Combination therapies of antibiotics with different mechanisms have been recommended in literatures. This study assessed in vitro antibacterial activities and synergistic activities of ceftazidime/avibactam alone and in combinations against KPC-Kp. In total, 70 isolates from 2 hospitals in Beijing were examined in our study. By using the agar dilution method and broth dilution method, we determined the minimum inhibitory concentration (MIC) of candidate antibiotics. Ceftazidime/avibactam demonstrated promising susceptibility against KPC-Kp (97.14%). Synergistic activities testing was achieved by checkerboard method and found ceftazidime/avibactam-amikacin displayed synergism in 90% isolates. Ceftazidime/avibactam-colistin displayed partial synergistic in 43% isolates, and ceftazidime/avibactam-tigecycline displayed indifference in 67% isolates. In time-kill assays, antibiotics at 1-fold MIC were mixed with bacteria at 1 × 105 CFU/ml and Mueller-Hinton broth (MHB). Combinations of ceftazidime/avibactam with amikacin and tigecycline displayed better antibacterial effects than single drug. Ceftazidime/avibactam-colistin combination did not exhibit better effect than single drug. In KPC-Kp infections, susceptibility testing suggested that ceftazidime/avibactam may be considered as first-line choice. However, monotherapy is often inadequate in infection management. Thus, our study revealed that combination therapy including ceftazidime/avibactam colistin and ceftazidime/avibactam tigecycline may benefit than monotherapy in KPC-Kp treatment. Further pharmacokinetic/pharmacodynamic and mutant prevention concentration studies should be performed to optimize multidrug-regimens.

Treatment of patients with serious infections due to carbapenem-resistant Acinetobacter baumannii: How viable are the current options?

This review critically appraises the published microbiologic and clinical data on the treatment of patients with carbapenem-resistant Acinetobacter baumannii infections. Despite being recognized as an urgent threat pathogen by the CDC and WHO, optimal treatment of patients with serious CRAB infections remains ill-defined. Few commercially available agents exhibit reliable in vitro activity against CRAB. Historically, polymyxins have been the most active agents in vitro, though interpretations of susceptibility data are difficult given issues surrounding MIC testing methodologies and lack of correlation between MICs and clinical outcomes. Most available preclinical and clinical data involve use of polymyxins, tetracyclines, and sulbactam, alone and in combination. As the number of viable treatment options is limited, combination therapy with a polymyxin is often used for patients with CRAB infections, despite the significant risk of nephrotoxicity. However, no treatment regimen has been found to reduce mortality, which exceeds 40% across most studies, or substantially improve clinical response. While some newer agents, such as eravacycline and cefiderocol, have demonstrated in vitro activity, clinical efficacy has not been fully established. New agents with clinically relevant activity against CRAB isolates and favorable toxicity profiles are sorely needed.

Identification of carbapenems resistant genes on biofilm forming K. pneumoniae from urinary tract infection

The multi-drug resistant effect of the Gram negative bacteria K. pneumoniae was identified by disc diffusion method using specific UTI panel discs of Kleb 1 HX077 and Kleb 2 HX090 HEXA. Among the multi-drug resistant bacteria, the carbapenem resistant (CR) effect of the K. pneumoniae was screened by specific carbapenem detection antibiotics of HEXA HX066 and HX0103 HEXA by disc diffusion method. In addition, the effective antibiotics were further performed against K. pneumoniae by minimum inhibition concentration method. Further, the carbapenemase genes of VIM 1 and IMP 1 were detected from the isolated strains by multiplex PCR method. Furthermore, the biofilm forming ability of selected carbapenem resistant K. pneumoniae was initially identified by tissue culture plate method and confirmed by exopolysaccharide arrest ability of congo red agar assay. Finally, our result was proved that the identified K. pneumoniae is carbapenemase producing strain, and its virulence was extended with strong biofilm formation.

Clinical characteristics and outcomes of patients with multidrug-resistant Gram-negative bacterial infections treated with ceftazidime/avibactam

OBJECTIVES

The aim of this study was to investigate the clinical characteristics and outcomes of patients with infections caused by multidrug-resistant Gram-negative bacteria (MDR-GNB) treated with ceftazidime/avibactam (CAZ/AVI) during the period September 2019 to June 2020 since CAZ/AVI had been marketed in China.

METHODS

A total of 20 MDR-GNB-infected patients were retrospectively identified using the electronic medical record system in West China Hospital.

RESULTS

The mean age of the 20 patients was 54.5 ± 17.37 years and 14 (70%) were male. Pneumonia (n = 12; 60%), complicated intra-abdominal infection (n = 10; 50%), and bloodstream infection (n = 7; 35%) were the most common infection sources. Klebsiella pneumoniae (55% 18/33) was the predominant pathogen. The 14-day clinical cure rate was 45%. The 14-day and 30-day mortality rates were 25% and 55%, respectively. No significant difference was found in 30-day mortality between treatment with CAZ/AVI monotherapy and combination regimens (P > 0.05). Three patients suffered from adverse drug reactions such as diarrhoea.

CONCLUSION

No significant difference was found between the effectiveness of CAZ/AVI in the clinical failure and cure groups as salvage treatment of MDR-GNB infection.

In vitro synergistic activity of the sulbactam/avibactam combination against extensively drug-resistant Acinetobacter baumannii

Introduction. The therapeutic options to treat Acinetobacter baumannii infections are very limited.Aim. Our aim was to evaluate the activity of sulbactam combined directly with avibactam or the ampicillin-sulbactam/ceftazidime-avibactam combination against extensively drug-resistant A. baumannii isolates.Methodology. Extensively drug-resistant A. baumannii isolates (n=127) collected at several South American hospitals were studied. Synergy with the sulbactam/avibactam combination was assessed in all isolates using the agar dilution method. Avibactam was used at a fixed concentration of 4 mg l^-1. A disc diffusion synergy test was also performed. Synergy by a time-kill experiment was performed in a selected isolate.Results. Synergy with sulbactam/avibactam was demonstrated in 124 isolates and it showed MIC values ≤4 mg l^-1. This synergy was not detected in the three New Delhi metallo-β-lactamase-harbouring isolates. Similar results were observed with the disc diffusion synergy test of ampicillin-sulbactam/ceftazidime-avibactam. In the time-kill experiments, sulbactam/avibactam showed a rapid synergistic and bactericidal activity in ampicillin-sulbactam-resistant isolates.Conclusions. This study demonstrated that the sulbactam/avibactam combination displayed synergistic activity against A. baumannii isolates. This synergy was observed when both inhibitors were also used as part of the commercially available combinations: ampicillin-sulbactam and ceftazidime-avibactam.