Inhibition of Fosfomycin Resistance Protein FosA by Phosphonoformate (Foscarnet) in Multidrug-Resistant Gram-Negative Pathogens

ABSTRACT FosA proteins confer fosfomycin resistance to Gram-negative pathogens via glutathione-mediated modification of the antibiotic. In this study, we assessed whether inhibition of FosA by sodium phosphonoformate (PPF) (foscarnet), a clinically approved antiviral agent, would reverse fosfomycin resistance in representative Gram-negative pathogens. The inhibitory activity of PPF against purified recombinant FosA from Escherichia coli (FosA3), Klebsiella pneumoniae (FosAKP), Enterobacter cloacae (FosAEC), and Pseudomonas aeruginosa (FosAPA) was determined by steady-state kinetic measurements. The antibacterial activity of PPF against FosA in clinical strains of these species was evaluated by susceptibility testing and time-kill assays. PPF increased the Michaelis constant (Km ) for fosfomycin in a dose-dependent manner, without affecting the maximum rate (V max) of the reaction, for all four FosA enzymes tested, indicating a competitive mechanism of inhibition. Inhibitory constant (Ki ) values were 22.6, 35.8, 24.4, and 56.3 μM for FosAKP, FosAEC, FosAPA, and FosA3, respectively. Addition of clinically achievable concentrations of PPF (∼667 μM) reduced the fosfomycin MICs by ≥4-fold among 52% of the K. pneumoniae, E. cloacae, and P. aeruginosa clinical strains tested and led to a bacteriostatic or bactericidal effect in time-kill assays among representative strains. PPF inhibits FosA activity across Gram-negative species and can potentiate fosfomycin activity against the majority of strains with chromosomally encoded fosA. These data suggest that PPF may be repurposed as an adjuvant for fosfomycin to treat infections caused by some FosA-producing, multidrug-resistant, Gram-negative pathogens.

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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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The Novel β-Lactam Enhancer Zidebactam Augments theIn VivoPharmacodynamic Activity of Cefepime in a Neutropenic Mouse LungAcinetobacter baumanniiInfection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02146-18 ◽

2019 ◽

Vol 63 (4) ◽

Cited By ~ 10

Author(s):

S. S. Bhagwat ◽

H. Periasamy ◽

S. S. Takalkar ◽

S. R. Palwe ◽

H. N. Khande ◽

...

Keyword(s):

Bactericidal Effect ◽

Multidrug Resistant ◽

Mouse Lung ◽

Infection Model ◽

Bactericidal Action ◽

Content Type ◽

Time Kill ◽

The Impact

ABSTRACTWCK 5222 is a combination of cefepime and the high-affinity PBP2-binding β-lactam enhancer zidebactam. The cefepime-zidebactam combination is active against multidrug-resistant Gram-negative bacteria, including carbapenemase-expressingAcinetobacter baumannii. The mechanism of action of the combination involves concurrent multiple penicillin binding protein inhibition, leading to the enhanced bactericidal action of cefepime. The aim of the present study was to assess the impact of the zidebactam-mediated enhancedin vitrobactericidal action in modulating the percentage of the time that the free drug concentration remains above the MIC (percentfT>MIC) for cefepime required for thein vivokilling ofA. baumannii. Cefepime and cefepime-zidebactam MICs were comparable and ranged from 2 to 16 mg/liter for theA. baumanniistrains (n = 5) employed in the study. Time-kill studies revealed the improved killing of these strains by the cefepime-zidebactam combination compared to that by the constituents alone. Employing a neutropenic mouse lung infection model, exposure-response analyses for all theA. baumanniistrains showed that the cefepimefT>MIC required for 1-log10kill was 38.9%. In the presence of a noneffective dose of zidebactam, the cefepimefT>MIC requirement dropped significantly to 15.5%, but it still rendered a 1-log10kill effect. Thus, zidebactam mediated the improvement in cefepime’s bactericidal effect observed in time-kill studies, manifestedin vivothrough the lowering of cefepime’s pharmacodynamic requirement. This is a first-ever study demonstrating a β-lactam enhancer role of zidebactam that helps augment thein vivoactivity of cefepime by reducing the magnitude of its pharmacodynamically relevant exposures againstA. baumannii.

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Thiostrepton Hijacks Pyoverdine Receptors To Inhibit Growth ofPseudomonas aeruginosa

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00472-19 ◽

2019 ◽

Vol 63 (9) ◽

Cited By ~ 8

Author(s):

Michael R. M. Ranieri ◽

Derek C. K. Chan ◽

Luke N. Yaeger ◽

Madeleine Rudolph ◽

Sawyer Karabelas-Pittman ◽

...

Keyword(s):

Biofilm Formation ◽

Opportunistic Pathogen ◽

Multidrug Resistant ◽

Clinical Isolates ◽

23S Rrna ◽

Dependent Manner ◽

Peptide Antibiotics ◽

Iron Starvation ◽

Gram Negative ◽

Content Type

ABSTRACTPseudomonas aeruginosais a biofilm-forming opportunistic pathogen and is intrinsically resistant to many antibiotics. In a high-throughput screen for molecules that modulate biofilm formation, we discovered that the thiopeptide antibiotic thiostrepton (TS), which is considered to be inactive against Gram-negative bacteria, stimulatedP. aeruginosabiofilm formation in a dose-dependent manner. This phenotype is characteristic of exposure to antimicrobial compounds at subinhibitory concentrations, suggesting that TS was active againstP. aeruginosa. Supporting this observation, TS inhibited the growth of a panel of 96 multidrug-resistant (MDR)P. aeruginosaclinical isolates at low-micromolar concentrations. TS also had activity againstAcinetobacter baumanniiclinical isolates. The expression of Tsr, a 23S rRNA-modifying methyltransferase from TS producerStreptomyces azureus, intransconferred TS resistance, confirming that the drug acted via its canonical mode of action, inhibition of ribosome function. The deletion of oligopeptide permease systems used by other peptide antibiotics for uptake failed to confer TS resistance. TS susceptibility was inversely proportional to iron availability, suggesting that TS exploits uptake pathways whose expression is increased under iron starvation. Consistent with this finding, TS activity againstP. aeruginosaandA. baumanniiwas potentiated by the FDA-approved iron chelators deferiprone and deferasirox and by heat-inactivated serum. Screening ofP. aeruginosamutants for TS resistance revealed that it exploits pyoverdine receptors FpvA and FpvB to cross the outer membrane. We show that the biofilm stimulation phenotype can reveal cryptic subinhibitory antibiotic activity, and that TS has activity against select multidrug-resistant Gram-negative pathogens under iron-limited growth conditions, similar to those encountered at sites of infection.

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In Vitro Activity of Ceftolozane-Tazobactam against Multidrug-Resistant Nonfermenting Gram-Negative Bacilli Isolated from Patients with Cystic Fibrosis

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02688-16 ◽

2017 ◽

Vol 61 (4) ◽

Cited By ~ 11

Author(s):

Patrick Grohs ◽

Gary Taieb ◽

Philippe Morand ◽

Iheb Kaibi ◽

Isabelle Podglajen ◽

...

Keyword(s):

Cystic Fibrosis ◽

Pseudomonas Aeruginosa ◽

Stenotrophomonas Maltophilia ◽

Active Agent ◽

Multidrug Resistant ◽

In Vitro Activity ◽

Gram Negative ◽

Content Type ◽

Time Kill

ABSTRACT Ceftolozane-tazobactam was tested against 58 multidrug-resistant nonfermenting Gram-negative bacilli (35 Pseudomonas aeruginosa, 11 Achromobacter xylosoxydans, and 12 Stenotrophomonas maltophilia isolates) isolated from cystic fibrosis patients and was compared to ceftolozane alone, ceftazidime, meropenem, and piperacillin-tazobactam. Ceftolozane-tazobactam was the most active agent against P. aeruginosa but was inactive against A. xylosoxydans and S. maltophilia. In time-kill experiments, ceftolozane-tazobactam had complete bactericidal activity against 2/6 clinical isolates (33%).

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Effects of Efflux Pump Inhibitors on Colistin Resistance in Multidrug-Resistant Gram-Negative Bacteria

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00248-16 ◽

2016 ◽

Vol 60 (5) ◽

pp. 3215-3218 ◽

Cited By ~ 42

Author(s):

Wentao Ni ◽

Yanjun Li ◽

Jie Guan ◽

Jin Zhao ◽

Junchang Cui ◽

...

Keyword(s):

Stenotrophomonas Maltophilia ◽

Efflux Pump ◽

Multidrug Resistant ◽

Gram Negative Bacteria ◽

Colistin Resistance ◽

Gram Negative ◽

Content Type ◽

Resistant Strains ◽

Efflux Pump Inhibitors ◽

Time Kill

ABSTRACTWe tested the effects of various putative efflux pump inhibitors on colistin resistance in multidrug-resistant Gram-negative bacteria. Addition of 10 mg/liter cyanide 3-chlorophenylhydrazone (CCCP) to the test medium could significantly decrease the MICs of colistin-resistant strains. Time-kill assays showed CCCP could reverse colistin resistance and inhibit the regrowth of the resistant subpopulation, especially inAcinetobacter baumanniiandStenotrophomonas maltophilia. These results suggest colistin resistance in Gram-negative bacteria can be suppressed and reversed by CCCP.

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Interplay among Different Fosfomycin Resistance Mechanisms in Klebsiella pneumoniae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01911-20 ◽

2020 ◽

Vol 65 (3) ◽

Author(s):

M. Ortiz-Padilla ◽

I. Portillo-Calderón ◽

B. de Gregorio-Iaria ◽

J. Blázquez ◽

J. Rodríguez-Baño ◽

...

Keyword(s):

Klebsiella Pneumoniae ◽

Growth Curves ◽

Resistant Mutant ◽

Bactericidal Effect ◽

Clinical Isolates ◽

Growth Monitoring ◽

Content Type ◽

Fosfomycin Resistance ◽

Time Kill

ABSTRACT The objectives of this study were to characterize the role of the uhpT, glpT, and fosA genes in fosfomycin resistance in Klebsiella pneumoniae and evaluate the use of sodium phosphonoformate (PPF) in combination with fosfomycin. Seven clinical isolates of K. pneumoniae and the reference strain (ATCC 700721) were used, and their genomes were sequenced. ΔuhpT, ΔglpT, and ΔfosA mutants were constructed from two isolates and K. pneumoniae ATCC 700721. Fosfomycin susceptibility testing was done by the gradient strip method. Synergy between fosfomycin and PPF was studied by checkerboard assay and analyzed using SynergyFinder. Spontaneous fosfomycin mutant frequencies at 64 and 512 mg/liter, in vitro activity using growth curves with fosfomycin gradient concentrations (0 to 256mg/liter), and time-kill assays at 64 and 307 mg/liter were evaluated with and without PPF (0.623 mM). The MICs of fosfomycin against the clinical isolates ranged from 16 to ≥1,024 mg/liter. The addition of 0.623 mM PPF reduced fosfomycin MIC between 2- and 8-fold. Deletion of fosA led to a 32-fold decrease. Synergistic activities were observed with the combination of fosfomycin and PPF (most synergistic area at 0.623 mM). The lowest fosfomycin-resistant mutant frequencies were found in ΔfosA mutants, with decreases in frequency from 1.69 × 10−1 to 1.60 × 10−5 for 64 mg/liter of fosfomycin. In the final growth monitoring and time-kill assays, fosfomycin showed a bactericidal effect only with the deletion of fosA and not with the addition of PPF. We conclude that fosA gene inactivation leads to a decrease in fosfomycin resistance in K. pneumoniae. The pharmacological approach using PPF did not achieve enough activity, and the effect decreased with the presence of fosfomycin-resistant mutations.

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In VitroActivity of Telavancin in Combination with Colistin versus Gram-Negative Bacterial Pathogens

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.05870-11 ◽

2012 ◽

Vol 56 (6) ◽

pp. 3080-3085 ◽

Cited By ~ 44

Author(s):

Michael Hornsey ◽

Christopher Longshaw ◽

Lynette Phee ◽

David W. Wareham

Keyword(s):

Therapeutic Option ◽

Multidrug Resistant ◽

Clinical Isolates ◽

Dilution Method ◽

Agar Dilution Method ◽

Gram Negative ◽

Content Type ◽

Log Reduction ◽

Time Kill

ABSTRACTThe treatment of Gram-negative infections is increasingly compromised by the spread of resistance. With few agents currently in development, clinicians are now considering the use of unorthodox combination therapies for multidrug-resistant strains. Here we assessed thein vitroactivity of the novel lipoglycopeptide telavancin (TLV) when combined with colistin (COL) versus 13 Gram-negative type strains and 66 clinical isolates. Marked synergy was observed in either checkerboard (fractional inhibitory concentration index [FICI], <0.5; susceptibility breakpoint index [SBPI], >2) or time-kill assays (>2-log reduction in viable counts compared with starting inocula at 24 h) versus the majority of COL-susceptible enterobacteria,Stenotrophomonas maltophilia, andAcinetobacter baumanniiisolates, but only limited effects were seen againstPseudomonas aeruginosaor strains with COL resistance. Using an Etest/agar dilution method, the activity of TLV was potentiated by relatively low concentrations of COL (0.25 to 0.75 μg/ml), reducing the MIC of TLV from >32 μg/ml to ≤1 μg/ml for 35% of the clinical isolates. This provides further evidence that glycopeptide-polymyxin combinations may be a useful therapeutic option in the treatment of Gram-negative infections.

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A Fish Galectin-8 Possesses Direct Bactericidal Activity

International Journal of Molecular Sciences ◽

10.3390/ijms22010376 ◽

2020 ◽

Vol 22 (1) ◽

pp. 376

Author(s):

Tengfei Zhang ◽

Shuai Jiang ◽

Li Sun

Keyword(s):

Bactericidal Activity ◽

Bacterial Pathogens ◽

Bactericidal Effect ◽

Immune Defense ◽

Carbohydrate Binding ◽

Dependent Manner ◽

Animal Cells ◽

Gram Negative ◽

Tongue Sole ◽

Wide Range

Galectins are a family of animal lectins with high affinity for β-galactosides. Galectins are able to bind to bacteria, and a few mammalian galectins are known to kill the bound bacteria. In fish, no galectins with direct bactericidal effect have been reported. In the present study, we identified and characterized a tandem repeat galectin-8 from tongue sole Cynoglossus semilaevis (designated CsGal-8). CsGal-8 possesses conserved carbohydrate recognition domains (CRDs), as well as the conserved HXNPR and WGXEE motifs that are critical for carbohydrate binding. CsGal-8 was constitutively expressed in nine tissues of tongue sole and up-regulated in kidney, spleen, and blood by bacterial challenge. When expressed in HeLa cells, CsGal-8 protein was detected both in the cytoplasm and in the micro-vesicles secreted from the cells. Recombinant CsGal-8 (rCsGal-8) bound to lactose and other carbohydrates in a dose dependent manner. rCsGal-8 bound to a wide range of gram-positive and gram-negative bacteria and was co-localized with the bound bacteria in animal cells. Lactose, fructose, galactose, and trehalose effectively blocked the interactions between rCsGal-8 and different bacteria. Furthermore, rCsGal-8 exerted potent bactericidal activity against some gram-negative bacterial pathogens by directly damaging the membrane and structure of the pathogens. Taken together, these results indicate that CsGal-8 likely plays an important role in the immune defense against some bacterial pathogens by direct bacterial interaction and killing.

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ZN148 Is a Modular Synthetic Metallo-β-Lactamase Inhibitor That Reverses Carbapenem Resistance in Gram-Negative Pathogens In Vivo

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02415-19 ◽

2020 ◽

Vol 64 (6) ◽

Cited By ~ 3

Author(s):

Ørjan Samuelsen ◽

Ove Alexander Høgmoen Åstrand ◽

Christopher Fröhlich ◽

Adam Heikal ◽

Susann Skagseth ◽

...

Keyword(s):

Active Site ◽

Therapeutic Potential ◽

Treatment Options ◽

Carbapenem Resistance ◽

Functional Space ◽

Bactericidal Effect ◽

Gram Negative ◽

Content Type

ABSTRACT Carbapenem-resistant Gram-negative pathogens are a critical public health threat and there is an urgent need for new treatments. Carbapenemases (β-lactamases able to inactivate carbapenems) have been identified in both serine β-lactamase (SBL) and metallo-β-lactamase (MBL) families. The recent introduction of SBL carbapenemase inhibitors has provided alternative therapeutic options. Unfortunately, there are no approved inhibitors of MBL-mediated carbapenem-resistance and treatment options for infections caused by MBL-producing Gram-negatives are limited. Here, we present ZN148, a zinc-chelating MBL-inhibitor capable of restoring the bactericidal effect of meropenem and in vitro clinical susceptibility to carbapenems in >98% of a large international collection of MBL-producing clinical Enterobacterales strains (n = 234). Moreover, ZN148 was able to potentiate the effect of meropenem against NDM-1-producing Klebsiella pneumoniae in a murine neutropenic peritonitis model. ZN148 showed no inhibition of the human zinc-containing enzyme glyoxylase II at 500 μM, and no acute toxicity was observed in an in vivo mouse model with cumulative dosages up to 128 mg/kg. Biochemical analysis showed a time-dependent inhibition of MBLs by ZN148 and removal of zinc ions from the active site. Addition of exogenous zinc after ZN148 exposure only restored MBL activity by ∼30%, suggesting an irreversible mechanism of inhibition. Mass-spectrometry and molecular modeling indicated potential oxidation of the active site Cys221 residue. Overall, these results demonstrate the therapeutic potential of a ZN148-carbapenem combination against MBL-producing Gram-negative pathogens and that ZN148 is a highly promising MBL inhibitor that is capable of operating in a functional space not presently filled by any clinically approved compound.

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Antimicrobial Properties of 8-Hydroxyserrulat-14-en-19-oic Acid for Treatment of Implant-Associated Infections

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01735-12 ◽

2012 ◽

Vol 57 (1) ◽

pp. 333-342 ◽

Cited By ~ 13

Author(s):

Justyna Nowakowska ◽

Hans J. Griesser ◽

Marcus Textor ◽

Regine Landmann ◽

Nina Khanna

Keyword(s):

Structural Changes ◽

Treatment Options ◽

Antimicrobial Properties ◽

Bactericidal Effect ◽

Mouse Tissue ◽

Logarithmic Phase ◽

Content Type ◽

Gram Positive Bacteria ◽

Time Kill

ABSTRACTTreatment options are limited for implant-associated infections (IAI) that are mainly caused by biofilm-forming staphylococci. We report here on the activity of the serrulatane compound 8-hydroxyserrulat-14-en-19-oic acid (EN4), a diterpene isolated from the Australian plantEremophila neglecta. EN4 elicited antimicrobial activity toward various Gram-positive bacteria but not to Gram-negative bacteria. It showed a similar bactericidal effect against logarithmic-phase, stationary-phase, and adherentStaphylococcus epidermidis, as well as against methicillin-susceptible and methicillin-resistantS. aureuswith MICs of 25 to 50 μg/ml and MBCs of 50 to 100 μg/ml. The bactericidal activity of EN4 was similar againstS. epidermidisand its Δicamutant, which is unable to produce polysaccharide intercellular adhesin-mediated biofilm. In time-kill studies, EN4 exhibited a rapid and concentration-dependent killing of staphylococci, reducing bacterial counts by >3 log10CFU/ml within 5 min at concentrations of >50 μg/ml. Investigation of the mode of action of EN4 revealed membranolytic properties and a general inhibition of macromolecular biosynthesis, suggesting a multitarget activity.In vitro-tested cytotoxicity on eukaryotic cells was time and concentration dependent in the range of the MBCs. EN4 was then tested in a mouse tissue cage model, where it showed neither bactericidal nor cytotoxic effects, indicating an inhibition of its activity. Inhibition assays revealed that this was caused by interactions with albumin. Overall, these findings suggest that, upon structural changes, EN4 might be a promising pharmacophore for the development of new antimicrobials to treat IAI.

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