Synergistic Activity of Ceragenins Against Carbapenem-Resistant Acinetobacter baumannii Strains in Both Checkerboard and Dynamic Time-Kill Assays

ABSTRACT Due to limited treatment options for carbapenem-resistant Acinetobacter baumannii (CR-AB) infections, antibiotic combinations are now considered potential treatments for CR-AB. This study aimed to explore the utility of fosfomycin-sulbactam combination (FOS/SUL) therapy against CR-AB isolates. Synergism of FOS/SUL against 50 clinical CR-AB isolates was screened using the checkerboard method. Thereafter, time-kill studies against two CR-AB isolates were performed. The time-kill data were described using a semimechanistic pharmacokinetic/pharmacodynamic (PK/PD) model. Monte Carlo simulations were then performed to estimate the probability of stasis, 1-log kill, and 2-log kill after 24 h of combination therapy. The FOS/SUL combination demonstrated a synergistic effect against 74% of isolates. No antagonism was observed. The MIC50 and MIC90 of FOS/SUL were decreased 4- to 8-fold, compared to the monotherapy MIC50 and MIC90. In the time-kill studies, the combination displayed bactericidal activity against both isolates and synergistic activity against one isolate at the highest clinically achievable concentrations. Our PK/PD model was able to describe the interaction between fosfomycin and sulbactam in vitro. Bacterial kill was mainly driven by sulbactam, with fosfomycin augmentation. FOS/SUL regimens that included sulbactam at 4 g every 8 h demonstrated a probability of target attainment of 1-log10 kill at 24 h of ∼69 to 76%, compared to ∼15 to 30% with monotherapy regimens at the highest doses. The reduction in the MIC values and the achievement of a moderate PTA of a 2-log10 reduction in bacterial burden demonstrated that FOS/SUL may potentially be effective against some CR-AB infections.

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In Vitro Synergistic Antimicrobial Activity of Combinations of Meropenem, Colistin, Tigecycline, Rifampin, and Ceftolozane/Tazobactam Against Carbapenem-Resistant Acinetobacter Baumannii

10.21203/rs.3.rs-1168856/v1 ◽

2021 ◽

Author(s):

Yong Guk Ju ◽

Hak Joon Lee ◽

Hong Soon Yim ◽

Chang Kyu Lee ◽

Mingoo Lee ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Bactericidal Effect ◽

Drug Combinations ◽

Synergistic Activity ◽

Antibiotic Concentration ◽

Carbapenem Resistant ◽

Potential Alternative ◽

Time Kill ◽

Antimicrobial Combinations

Abstract The aim of this study was to investigate the in vitro activity of various antimicrobial combinations against carbapenem-resistant Acinetobacter baumannii (CRAB) isolates producing OXA-23 carbapenemases.In vitro activity of six two-drug combinations against CRAB isolates collected from patients with CRAB bacteremia was evaluated using the checkerboard method and time-kill assay [0.5 ×, 1 ×, 2 × minimum inhibitory concentrations (MIC)], to identify potential synergistic and bactericidal two-drug combinations against CRAB isolates, using meropenem, colistin, tigecycline, rifampin, and ceftolozane/tazobactam. All 10 CRAB isolates in our study carried the OXA-58-type and OXA-23-type carbapenem-hydrolyzing oxacillinase. The colistin-ceftolozane/tazobactam combination demonstrated a synergistic effect in both the time-kill assay (using an antibiotic concentration of 1 × MIC) and the checkerboard method, while simultaneously showing a bactericidal effect in the time-kill assay. For all 10 CRAB isolates, time-kill curves showed a significant synergistic bactericidal activity of the colistin-ceftolozane/tazobactam combination at 0.5 × MIC. Overall, there is substantial discordance of synergistic activity between the checkerboard microdilution and time-kill assay (with a concordance of 35%). Our study demonstrated that the two-drug combinations of colistin and ceftolozane/tazobactam can be a potential alternative for treating CRAB infections. The effect of these antibiotic combinations should be evaluated through clinical trials.

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Synergistic Activity of Colistin-Containing Combinations against Colistin-ResistantEnterobacteriaceae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00873-18 ◽

2018 ◽

Vol 62 (10) ◽

Cited By ~ 28

Author(s):

Thea Brennan-Krohn ◽

Alejandro Pironti ◽

James E. Kirby

Keyword(s):

Treatment Options ◽

Multidrug Resistant ◽

Synergistic Activity ◽

Gram Negative ◽

Content Type ◽

Carbapenem Resistant ◽

Resistant Strains ◽

Bacterial Outer Membrane ◽

Time Kill ◽

Synergistic Combinations

ABSTRACTResistance to colistin, a polypeptide drug used as an agent of last resort for the treatment of infections caused by multidrug-resistant (MDR) and extensively drug-resistant (XDR) Gram-negative bacteria, including carbapenem-resistantEnterobacteriaceae(CRE), severely limits treatment options and may even transform an XDR organism into one that is pan-resistant. We investigated the synergistic activity of colistin in combination with 19 antibiotics against a collection of 20 colistin-resistantEnterobacteriaceaeisolates, 15 of which were also CRE. All combinations were tested against all strains using an inkjet printer-assisted digital dispensing checkerboard array, and the activities of those that demonstrated synergy by this method were evaluated against a single isolate in a time-kill synergy study. Eighteen of 19 combinations demonstrated synergy against two or more isolates, and the 4 most highly synergistic combinations (colistin combined with linezolid, rifampin, azithromycin, and fusidic acid) were synergistic against ≥90% of strains. Sixteen of 18 combinations (88.9%) that were synergistic in the checkerboard array were also synergistic in a time-kill study. Our findings demonstrate that colistin in combination with a range of antibiotics, particularly protein and RNA synthesis inhibitors, exhibits synergy against colistin-resistant strains, suggesting that colistin may exert a subinhibitory permeabilizing effect on the Gram-negative bacterial outer membrane even in isolates that are resistant to it. These findings suggest that colistin combination therapy may have promise as a treatment approach for patients infected with colistin-resistant XDR Gram-negative pathogens.

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Rescued chlorhexidine activity by resveratrol against carbapenem-resistant Acinetobacter baumannii via down-regulation of AdeB efflux pump

PLoS ONE ◽

10.1371/journal.pone.0243082 ◽

2020 ◽

Vol 15 (12) ◽

pp. e0243082

Author(s):

Uthaibhorn Singkham-in ◽

Paul G. Higgins ◽

Dhammika Leshan Wannigama ◽

Parichart Hongsing ◽

Tanittha Chatsuwan

Keyword(s):

Acinetobacter Baumannii ◽

Ethidium Bromide ◽

Antimicrobial Agents ◽

Efflux Pump ◽

Intracellular Accumulation ◽

Efflux Pump Inhibitor ◽

Carbapenem Resistant ◽

Efflux Pump Inhibition ◽

Synergistic Mechanism ◽

Time Kill

The aim of this study was to determine the activity and synergistic mechanisms of resveratrol in combination with chlorhexidine against carbapenem-resistant Acinetobacter baumannii clinical isolates. The activity of resveratrol plus antimicrobial agents was determined by checkerboard and time-kill assay against carbapenem-resistant A. baumannii isolated from patients at the King Chulalongkorn Memorial Hospital, Bangkok, Thailand. Overexpression of efflux pumps that mediates chlorhexidine susceptibility was characterized by the ethidium bromide accumulation assay. The effect of resveratrol on the expression of efflux pump genes (adeB, adeJ, adeG abeS, and aceI) and the two-component regulators, adeR and adeS was determined by RT-qPCR. The combination of resveratrol and chlorhexidine resulted in strong synergistic and bactericidal activity against carbapenem-resistant A. baumannii. Up-regulation of adeB and aceI was induced by chlorhexidine. However, the addition of resveratrol increased chlorhexidine susceptibility with increased intracellular accumulation of ethidium bromide in A. baumannii indicating that resveratrol acts as an efflux pump inhibitor. Expression of adeB was significantly reduced in the combination of resveratrol with chlorhexidine indicating that resveratrol inhibits the AdeB efflux pump and restores chlorhexidine effect on A. baumannii. In conclusion, reduced adeB expression in A. baumannii was mediated by resveratrol suggesting that AdeB efflux pump inhibition contributes to the synergistic mechanism of resveratrol with chlorhexidine. Our finding highlights the potential importance of resveratrol in clinical applications.

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In Vitro and In Vivo Activity of AS101 against Carbapenem-Resistant Acinetobacter baumannii

Pharmaceuticals ◽

10.3390/ph14080823 ◽

2021 ◽

Vol 14 (8) ◽

pp. 823

Author(s):

Tsung-Ying Yang ◽

Sung-Pin Tseng ◽

Heather Nokulunga Dlamini ◽

Po-Liang Lu ◽

Lin Lin ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Antibacterial Activities ◽

Treated Group ◽

Infection Model ◽

High Dose ◽

Mouse Infection Model ◽

Carbapenem Resistant ◽

Time Kill

The increasing trend of carbapenem-resistant Acinetobacter baumannii (CRAB) worldwide has become a concern, limiting therapeutic alternatives and increasing morbidity and mortality rates. The immunomodulation agent ammonium trichloro (dioxoethylene-O,O′-) tellurate (AS101) was repurposed as an antimicrobial agent against CRAB. Between 2016 and 2018, 27 CRAB clinical isolates were collected in Taiwan. The in vitro antibacterial activities of AS101 were evaluated using broth microdilution, time-kill assay, reactive oxygen species (ROS) detection and electron microscopy. In vivo effectiveness was assessed using a sepsis mouse infection model. The MIC range of AS101 for 27 CRAB isolates was from 0.5 to 32 µg/mL, which is below its 50% cytotoxicity (approximately 150 µg/mL). Bactericidal activity was confirmed using a time-kill assay. The antibacterial mechanism of AS101 was the accumulation of the ROS and the disruption of the cell membrane, which, in turn, results in cell death. The carbapenemase-producing A. baumannii mouse sepsis model showed that AS101 was a better therapeutic effect than colistin. The mice survival rate after 120 h was 33% (4/12) in the colistin-treated group and 58% (7/12) in the high-dose AS101 (3.33 mg/kg/day) group. Furthermore, high-dose AS101 significantly decreased bacterial population in the liver, kidney and spleen (all p < 0.001). These findings support the concept that AS101 is an ideal candidate for further testing in future studies.

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In vitro and in vivo synergistic effects of tigecycline combined with aminoglycosides on carbapenem-resistant Klebsiella pneumoniae

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkab122 ◽

2021 ◽

Author(s):

Wentao Ni ◽

Deqing Yang ◽

Jie Guan ◽

Wen Xi ◽

Dexun Zhou ◽

...

Keyword(s):

Klebsiella Pneumoniae ◽

Synergistic Effects ◽

Molecular Characteristics ◽

Synergistic Activity ◽

Significant Activity ◽

Clinical Pharmacokinetics ◽

Carbapenem Resistant ◽

Time Kill

Abstract Objectives Carbapenem-resistant Klebsiella pneumoniae (CR-KP) infections represent severe threats to public health worldwide. The aim of this study was to assess potential synergistic interaction between tigecycline and aminoglycosides via in vitro and in vivo studies. Methods Antibiotic resistance profiles and molecular characteristics of 168 CR-KP clinical isolates were investigated by susceptibility testing, PCR and MLST. Chequerboard tests and time–kill assays were performed for 20 CR-KP isolates to evaluate in vitro synergistic effects of tigecycline combined with aminoglycosides. A tissue-cage infection model of rats was established to evaluate in vivo synergistic effects. Different doses of tigecycline and aminoglycosides alone or in combination were administered for 7 days via tail vein injection. Antibiotic efficacy was evaluated in tissue-cage fluid and emergence of resistance was screened. Results The chequerboard tests showed that this combination displayed synergistic or partial synergistic activity against CR-KP. The time–kill assays further demonstrated that strong synergistic effects of such a combination existed against isolates that were susceptible to both drugs but for resistant isolates no synergy was observed if clinical pharmacokinetics were taken into consideration. The in vivo study showed that the therapeutic effectiveness of combination therapies was better than that of monotherapy for susceptible isolates, suggesting in vivo synergistic effects. Furthermore, combinations of tigecycline with an aminoglycoside showed significant activity in reducing the occurrence of tigecycline-resistant mutants. Conclusions Compared with single drugs, tigecycline combined with aminoglycosides could exert synergistic effects and reduce the emergence of tigecycline resistance. Such a combination might be an effective alternative when treating CR-KP infections in clinical practice.

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Synergistic activity of fosfomycin–meropenem and fosfomycin–colistin against carbapenem resistant Klebsiella pneumoniae: an in vitro evidence

Future Science OA ◽

10.2144/fsoa-2019-0074 ◽

2020 ◽

pp. FSO461 ◽

Cited By ~ 3

Author(s):

Yamuna Devi Bakthavatchalam ◽

Abirami Shankar ◽

Dhiviya Prabaa Muthuirulandi Sethuvel ◽

Kalaiarasi Asokan ◽

Kalaiarasi Kanthan ◽

...

Keyword(s):

Antibacterial Activity ◽

Klebsiella Pneumoniae ◽

Blood Cultures ◽

Synergistic Activity ◽

Carbapenem Resistant ◽

Resistant Genes ◽

Time Kill ◽

Synergistic Antibacterial Activity

Aim: To evaluate the antibacterial activity of fosfomycin–meropenem and fosfomycin–colistin combinations against carbapenem-resistant Klebsiella pneumoniae (CR-Kp). Methods: A total of 50 CR-Kp isolates recovered from blood cultures were included in this study. All the CR-Kp isolates were screened for the presence of carbapenem resistant genes blaIMP. blaVIM. blaNDM. blaOXA-48 like, blaKPC. blaGES.#x00A0;and blaSPM. Combination testing of fosfomycin–meropenem and fosfomycin–colistin were performed using time-kill assay. Results: Fosfomycin–meropenem combination showed synergy in 20% of the tested CR-Kp isolates. While, fosfomycin–colistin exhibited synergy against 16% of the isolates. A total of 68% (n = 34) of CR-Kp isolates were characterised as OXA-48-like producers and 22% (n = 11) as NDM producers. Synergistic activity of these combinations was observed against OXA-48, NDM and NDM + OXA-48 co-producers. Conclusion: Considerable synergistic antibacterial activity of fosfomycin–meropenem and fosfomycin–colistin was not observed against CR-Kp isolates. Therefore, these combinations may not be promising for infections associated with CR-Kp.

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Investigation of the Synergic Effect of the Colistin/ Sulbactam Combination in Carbapenem-Resistant Acinetobacter baumannii complex Strains with Time-Kill and Checkerboard Methods

Flora the Journal of Infectious Diseases and Clinical Microbiology ◽

10.5578/flora.20219916 ◽

2021 ◽

Vol 26 (1) ◽

pp. 151-162

Author(s):

İmdat Kılbaş ◽

Hüseyin Hatipoğlu ◽

Ümit Kılıç ◽

Elmas Pınar Kahraman Kılbaş ◽

Mehmet Köroğlu ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Synergic Effect ◽

Carbapenem Resistant ◽

Acinetobacter Baumannii Complex ◽

Time Kill

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In Vitro Antibacterial Activity of Cefiderocol against Multidrug-Resistant Acinetobacter baumannii

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02646-20 ◽

2021 ◽

Author(s):

Jacinda C. Abdul-Mutakabbir ◽

Logan Nguyen ◽

Philip T. Maassen ◽

Kyle C. Stamper ◽

Razieh Kebriaei ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Susceptibility Testing ◽

Inhibitory Concentration ◽

Multidrug Resistant ◽

Synergistic Activity ◽

Strong Activity ◽

Gram Negative ◽

In Vitro Antibacterial Activity ◽

Time Kill

Cefiderocol (CFDC), a novel siderophore cephalosporin, demonstrates strong activity against multidrug-resistant (MDR) Acinetobacter baumannii. Limited studies have evaluated CFDC alone and in combination with other Gram-negative antibiotics against MDR A. baumannii isolates. Susceptibility testing revealed lower CFDC minimum inhibitory concentration (MIC) values than the comparator Gram-negative agents (87% of MICs ≤ 4mg/L). Six isolates, with elevated CFDC MICs (16-32 mg/L), were selected for further experiments. Time-kill analyses presented with synergistic activity and beta-lactamase inhibitors increased CFDC susceptibility in each of the isolates.

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1542. The Evaluation of the In Vitro Synergy of Colistin in Combination with Meropenem and Tigecycline against 50 Multi-Drug-resistant Acinetobacter baumannii strains

Open Forum Infectious Diseases ◽

10.1093/ofid/ofz360.1406 ◽

2019 ◽

Vol 6 (Supplement_2) ◽

pp. S562-S563

Author(s):

Jacinda Abdul-Mutakabbir ◽

Juwom Yim ◽

Logan Nguyen ◽

Razieh Kebriaei ◽

Kyle Stamper ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Bactericidal Activity ◽

Single Agent ◽

Resistance Mechanisms ◽

Drug Resistant ◽

Initial Inoculum ◽

Log Reduction ◽

Carbapenem Resistant ◽

Time Kill

Abstract Background Acinetobacter baumannii possess inherent and acquired antibiotic resistance mechanisms that have rendered most antibiotics, including carbapenems, inactive. Colistin (COL) has risen as salvage therapy against these organisms due to its retained activity against A. baumannii. However, COL monotherapy is often met with suboptimal outcomes. Recently, combination therapy with COL and meropenem (MEM) or tigecycline (TGC) has been shown to be effective in eradicating multi-drug-resistant A. baumannii infections. The objective of this study was to further evaluate the efficacy of COL in combination with MEM or TGC against 50 multi-drug-resistant A. baumannii strains. Methods Fifty carbapenem-resistant A. baumannii strains were evaluated using combination minimum inhibitory concentration (MIC) testing and time-kill analysis (TKA). Single-drug MIC testing was performed for each strain by broth microdilution. Combination MIC testing was performed for COL+MEM and COL+TGC. Each strain was evaluated via 24-hour TKA to assess the synergistic capabilities of COL+MEM, and COL+TGC. Synergy was defined as a ≥ 2-log reduction CFU/mL in either combination from the most active single agent, while bactericidal activity was defined as a ≥ 3-log reduction CFU/mL of either combination from the initial inoculum. Results All 50 strains were resistant to MEM and TGC with MICs ≥ 64 µg/mL and ≥ 4 µg/mL respectively; while 3 strains were resistant to COL, MICs ≥ 2 µg/mL. MEM and TGC MIC values were reduced as much as 128-fold (median 2-fold) and 32-fold (median 2-fold),, respectively, in the presence of subinhibitory COL. COL MIC values were reduced as much as 512-fold (median 4-fold) from baseline in the presence of subinhibitory MEM, and as high as 16-fold (median 2-fold) in the presence of TGC. In TKAs, COL+MEM was synergistic in 45/50 (90%) strains and bactericidal against 43/50 (86%) strains. COL+TGC TKAs revealed synergy in 32/50 (64%) strains, and bactericidal activity against 28/50 (56%) strains. Conclusion The combinations of COL+MEM and COL+TGC demonstrate promise in combating highly resistant A. baumannii. Further research is mandated to explore other combinations that are capable of eradicating multi-drug-resistant A. baumannii. Disclosures All authors: No reported disclosures.

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