Activity of Fosfomycin and Amikacin against Fosfomycin-Heteroresistant Escherichia coli Strains in a Hollow-Fiber Infection Model

ABSTRACT We evaluated human-like the efficacy of intravenous doses of fosfomycin of 8 g every 8 h (8 g/Q8h) and of amikacin (15 mg/kg/Q24h) in monotherapy and in combination against six fosfomycin-heteroresistant Escherichia coli isolates using a hollow-fiber infection model (HFIM). Six fosfomycin-heteroresistant E. coli isolates (four with strong mutator phenotype) and the control strain E. coli ATCC 25922 were used. Mutant frequencies for rifampin (100 mg/liter), fosfomycin (50 and 200 mg/liter), and amikacin (32 mg/liter) were determined. Fosfomycin and amikacin MICs were assessed by agar dilution (AD), gradient strip assay (GSA), and broth microdilution (BMD). Fosfomycin and amikacin synergies were studied by checkerboard and time-kill assays at different concentrations. The efficacies of fosfomycin (8 g/Q8h) and amikacin (15 mg/kg/Q24h) alone and in combination were assessed using an HFIM. Five isolates were determined to be resistant to fosfomycin by AD and BMD, but all were determined to be susceptible by GSA. All isolates were determined to be susceptible to amikacin. Antibiotic combinations were synergistic in two isolates, and no antagonism was detected. In time-kill assays, all isolates survived under fosfomycin at 64 mg/liter, although at 307 mg/liter only the normomutators and two hypermutators survived. Four isolates survived under 16 mg/liter amikacin, and none survived at 45 mg/liter. No growth was detected under combination conditions. In HFIM, fosfomycin and amikacin monotherapies failed to sterilize bacterial cultures; however, the combination of fosfomycin and amikacin yielded a rapid eradication. There may be a risk of treatment failure of fosfomycin-heteroresistant E. coli isolates using either amikacin or fosfomycin in monotherapy. These results support that the amikacin-fosfomycin combination can rapidly decrease bacterial burden and prevent the emergence of resistant subpopulations against fosfomycin-heteroresistant strains.

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Evaluating Polymyxin B-Based Combinations against Carbapenem-Resistant Escherichia coli in Time-Kill Studies and in a Hollow-Fiber Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01509-16 ◽

2016 ◽

Vol 61 (1) ◽

Cited By ~ 2

Author(s):

Yiying Cai ◽

Tze-Peng Lim ◽

Jocelyn Qi-Min Teo ◽

Suranthran Sasikala ◽

Eric Chun Yong Chan ◽

...

Keyword(s):

Escherichia Coli ◽

Growth Rate ◽

Bactericidal Activity ◽

Hollow Fiber ◽

Polymyxin B ◽

Phenotypic Characterization ◽

Infection Model ◽

Content Type ◽

Carbapenem Resistant ◽

Time Kill

ABSTRACT Polymyxin B-based combinations have emerged as a mainstay treatment against carbapenem-resistant Escherichia coli (CREC). We investigated the activity of polymyxin B-based two-antibiotic combinations against CREC using time-kill studies (TKS) and validated the findings in a hollow-fiber infection model (HFIM). TKS were conducted using 5 clinical CREC strains at 5 log10 CFU/ml against 10 polymyxin B-based two-antibiotic combinations at maximum clinically achievable concentrations. HFIMs simulating dosing regimens with polymyxin B (30,000U/kg/day) and tigecycline (100 mg every 12 h) alone and in combination were conducted against two CREC strains at 5 log10 CFU/ml over 120 h. Emergence of resistance was quantified using antibiotic-containing media. Phenotypic characterization (growth rate and stability of resistant phenotypes) of the resistant isolates was performed. All five CREC strains harbored carbapenemases. Polymyxin B and tigecycline MICs ranged from 0.5 mg/liter to 2 mg/liter and from 0.25 mg/liter to 8 mg/liter, respectively. All antibiotics alone did not have bactericidal activity at 24 h in the TKS, except for polymyxin B against two strains. In combination TKS, only polymyxin B plus tigecycline demonstrated both bactericidal activity and synergy in two out of five strains. In the HFIM, polymyxin B alone was bactericidal against both CREC strains before regrowth was observed at 8 h. Phenotypically stable polymyxin B-resistant mutants were observed for both strains, with a reduced growth rate observed in one strain. Tigecycline alone resulted in a slow reduction in bacterial counts. Polymyxin B plus tigecycline resulted in rapid and sustained bactericidal killing up to 120 h. Polymyxin B plus tigecycline is a promising combination against CREC. The clinical relevance of our results warrants further investigations.

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Relationship between Fosfomycin Exposure and Amplification of Escherichia coli Subpopulations with Reduced Susceptibility in a Hollow-Fiber Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00355-16 ◽

2016 ◽

Vol 60 (9) ◽

pp. 5141-5145 ◽

Cited By ~ 15

Author(s):

Brian VanScoy ◽

Jennifer McCauley ◽

Sujata M. Bhavnani ◽

Evelyn J. Ellis-Grosse ◽

Paul G. Ambrose

Keyword(s):

Escherichia Coli ◽

Hollow Fiber ◽

Drug Exposure ◽

Drug Susceptibility ◽

Infection Model ◽

Content Type ◽

E Coli ◽

Control Regimen ◽

Dosing Regimens ◽

The Relationship

ABSTRACTUnderstanding the relationship between antibiotic exposure and amplification of bacterial subpopulations with reduced drug susceptibility over time is important for evaluating the adequacy of dosing regimens. We utilized a hollow-fiber infection model to identify the fosfomycin intravenous dosing regimens that prevented the amplification ofEscherichia colibacterial subpopulations with reduced fosfomycin susceptibility. The challenge isolate wasE. coliATCC 25922 (agar MIC with glucose-6-phosphate, 1 mg/liter; agar MIC without glucose-6-phosphate, 32 mg/liter). The fosfomycin dosing regimens studied were 1 to 12 g every 8 h for 10 days to approximate that planned for clinical use. The studies included a no-treatment control regimen. Two bacterial subpopulations were identified, one with reduced susceptibility with agar MIC values ranging from 32 to 128 mg/liter and the other resistant with agar MIC values of 256 to >1,024 mg/liter on plates containing 5× and 256× the baseline MIC value, respectively. An inverted-U-shaped function best described the relationship between the amplification of the two bacterial subpopulations and drug exposure. The lowest fosfomycin dosing regimen that did not amplify a bacterial subpopulation with reduced susceptibility was 4 g administered every 8 h. Nearly immediate amplification of bacterial subpopulations with reduced susceptibility was observed with fosfomycin dosing regimens consisting of 1 to 2 g every 8 h. These data will be useful to support the selection of fosfomycin dosing regimens that minimize the potential for on-therapy amplification of bacterial subpopulations with reduced susceptibility.

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In Vivo Bioluminescent Monitoring of Therapeutic Efficacy and Pharmacodynamic Target Assessment of Antofloxacin against Escherichia coli in a Neutropenic Murine Thigh Infection Model

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01281-17 ◽

2017 ◽

Vol 62 (1) ◽

Cited By ~ 2

Author(s):

Yu-Feng Zhou ◽

Meng-Ting Tao ◽

Yu-Zhang He ◽

Jian Sun ◽

Ya-Hong Liu ◽

...

Keyword(s):

Escherichia Coli ◽

Subcutaneous Administration ◽

Free Drug ◽

Infection Model ◽

Bioluminescent Imaging ◽

Time Curve ◽

Content Type ◽

E Coli ◽

Tract Infections

ABSTRACT Antimicrobial resistance among uropathogens has increased the rates of infection-related morbidity and mortality. Antofloxacin is a novel fluoroquinolone with broad-spectrum antibacterial activity against urinary Gram-negative bacilli, such as Escherichia coli. This study monitored the in vivo efficacy of antofloxacin using bioluminescent imaging and determined pharmacokinetic (PK)/pharmacodynamic (PD) targets against E. coli isolates in a neutropenic murine thigh infection model. The PK properties were determined after subcutaneous administration of antofloxacin at 2.5, 10, 40, and 160 mg/kg of body weight. Following thigh infection, the mice were treated with 2-fold-increasing doses of antofloxacin from 2.5 to 80 mg/kg administered every 12 h. Efficacy was assessed by quantitative determination of the bacterial burdens in thigh homogenates and was compared with the bioluminescent density. Antofloxacin demonstrated both static and killing endpoints in relation to the initial burden against all study strains. The PK/PD index area under the concentration-time curve (AUC)/MIC correlated well with efficacy (R 2 = 0.92), and the dose-response relationship was relatively steep, as observed with escalating doses of antofloxacin. The mean free drug AUC/MIC targets necessary to produce net bacterial stasis and 1-log10 and 2-log10 kill for each isolate were 38.7, 66.1, and 147.0 h, respectively. In vivo bioluminescent imaging showed a rapid decrease in the bioluminescent density at free drug AUC/MIC exposures that exceeded the stasis targets. The integration of these PD targets combined with the results of PK studies with humans will be useful in setting optimal dosing regimens for the treatment of urinary tract infections due to E. coli.

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Optimization and Evaluation of Piperacillin-Tobramycin Combination Dosage Regimens againstPseudomonas aeruginosafor Patients with Altered Pharmacokinetics via the Hollow-Fiber Infection Model and Mechanism-Based Modeling

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00078-18 ◽

2018 ◽

Vol 62 (5) ◽

Cited By ~ 4

Author(s):

Rajbharan Yadav ◽

Kate E. Rogers ◽

Phillip J. Bergen ◽

Jürgen B. Bulitta ◽

Carl M. J. Kirkpatrick ◽

...

Keyword(s):

Critically Ill ◽

Hollow Fiber ◽

Critically Ill Patient ◽

Infection Model ◽

Case Scenario ◽

Bacterial Killing ◽

Worst Case ◽

Content Type ◽

Dosage Regimens ◽

Time Kill

ABSTRACTAugmented renal clearance (ARC) in critically ill patients can result in suboptimal drug exposures and treatment failure. Combination dosage regimens accounting for ARC have never been optimized and evaluated againstPseudomonas aeruginosaby use of the hollow-fiber infection model (HFIM). Using aP. aeruginosaisolate from a critically ill patient and static-concentration time-kill experiments (SCTKs), we studied clinically relevant piperacillin and tobramycin concentrations, alone and in combinations, against two inocula (105.8and 107.6CFU/ml) over 72 h. We subsequently evaluated the effects of optimized piperacillin (4 g every 4 h [q4h], given as 0.5-h infusions) plus tobramycin (5 mg/kg of body weight q24h, 7 mg/kg q24h, or 10 mg/kg q48h, given as 0.5-h infusions) regimens on killing and regrowth in the HFIM, simulating a creatinine clearance of 250 ml/min. Mechanism-based modeling was performed in S-ADAPT. In SCTKs, piperacillin plus tobramycin (except combinations with 8 mg/liter tobramycin and against the low inoculum) achieved synergistic killing (≥2 log10versus the most active monotherapy at 48 h and 72 h) and prevented regrowth. Piperacillin monotherapy (4 g q4h) in the HFIM provided 2.4-log10initial killing followed by regrowth at 24 h and resistance emergence. Tobramycin monotherapies displayed rapid initial killing (≥5 log10at 13 h) followed by extensive regrowth. As predicted by mechanism-based modeling, the piperacillin plus tobramycin dosage regimens were synergistic and provided ≥5-log10killing with resistance suppression over 8 days in the HFIM. Optimized piperacillin-tobramycin regimens provided significant bacterial killing and suppressed resistance emergence. These regimens appear to be highly promising for effective and early treatment, even in the near-worst-case scenario of ARC.

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In VitroandIn VivoActivities of OP0595, a New Diazabicyclooctane, against CTX-M-15-Positive Escherichia coli and KPC-Positive Klebsiella pneumoniae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.02704-15 ◽

2016 ◽

Vol 60 (5) ◽

pp. 3001-3006 ◽

Cited By ~ 11

Author(s):

Akihiro Morinaka ◽

Yuko Tsutsumi ◽

Keiko Yamada ◽

Yoshihiro Takayama ◽

Shiro Sakakibara ◽

...

Keyword(s):

Escherichia Coli ◽

Klebsiella Pneumoniae ◽

Infection Model ◽

Gram Negative Bacteria ◽

Content Type ◽

Effective Combination ◽

Time Kill ◽

Lactamase Inhibitor

ABSTRACTGram-negative bacteria are evolving to produce β-lactamases of increasing diversity that challenge antimicrobial chemotherapy. OP0595 is a new diazabicyclooctane serine β-lactamase inhibitor which acts also as an antibiotic and as a β-lactamase-independent β-lactam “enhancer” againstEnterobacteriaceae. Here we determined the optimal concentration of OP0595 in combination with piperacillin, cefepime, and meropenem, in addition to the antibacterial activity of OP0595 alone and in combination with cefepime, inin vitrotime-kill studies and anin vivoinfection model against five strains of CTX-M-15-positiveEscherichia coliand five strains of KPC-positiveKlebsiella pneumoniae. An OP0595 concentration of 4 μg/ml was found to be sufficient for an effective combination with all three β-lactam agents. In bothin vitrotime-kill studies and anin vivomodel of infection, cefepime-OP0595 showed stronger efficacy than cefepime alone against all β-lactamase-positive strains tested, whereas OP0595 alone showed weaker or no efficacy. Taken together, these data indicate that combinational use of OP0595 and a β-lactam agent is important to exert the antimicrobial functions of OP0595.

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Azidothymidine Produces Synergistic Activity in Combination with Colistin against Antibiotic-Resistant Enterobacteriaceae

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01630-18 ◽

2018 ◽

Vol 63 (1) ◽

Cited By ~ 11

Author(s):

Yanmin Hu ◽

Yingjun Liu ◽

Anthony Coates

Keyword(s):

Bacterial Infections ◽

Therapeutic Potential ◽

Infection Model ◽

Synergistic Activity ◽

Antibiotic Resistant ◽

Content Type ◽

E Coli ◽

Broth Microdilution Method ◽

Peritoneal Infection ◽

Time Kill

ABSTRACT Bacterial infections remain a leading killer worldwide, which is worsened by the continuous emergence of antibiotic resistance. In particular, antibiotic-resistant Enterobacteriaceae are prevalent and extremely difficult to treat. Repurposing existing drugs and improving the therapeutic potential of existing antibiotics represent an attractive novel strategy. Azidothymidine (AZT) is an antiretroviral drug which is used in combination with other antivirals to prevent and to treat HIV/AIDS. AZT is also active against Gram-negative bacteria but has not been developed for that purpose. Here, we investigated the in vitro and in vivo efficacy of AZT in combination with colistin against antibiotic-resistant Enterobacteriaceae, including strains producing extended-spectrum beta-lactamases (ESBLs) or New Delhi metallo-beta-lactamase 1 (NDM) or carrying mobilized colistin resistance (mcr-1). The MIC was determined using the broth microdilution method. The combined effect of AZT and colistin was examined using the checkerboard method and time-kill analysis. A murine peritoneal infection model was used to test the therapeutic effect of the combination of AZT and colistin. The fractional inhibitory concentration index from the checkerboard assay demonstrated that AZT synergized with colistin against 61% and 87% of ESBL-producing Escherichia coli and Klebsiella pneumoniae strains, respectively, 100% of NDM-1-producing strains, and 92% of mcr-1-producing E. coli strains. Time-kill analysis demonstrated significant synergistic activities when AZT was combined with colistin. In a murine peritoneal infection model, AZT in combination with colistin showed augmented activities of both drugs in the treatment of NDM-1 K. pneumoniae and mcr-1 E. coli infections. The AZT and colistin combination possesses a potential to be used coherently to treat antibiotic-resistant Enterobacteriaceae infections.

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Activity of Tigecycline or Colistin in Combination with Zidovudine against Escherichia coli Harboring tet(X) and mcr-1

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01172-20 ◽

2020 ◽

Vol 65 (1) ◽

pp. e01172-20 ◽

Cited By ~ 1

Author(s):

Yu-Feng Zhou ◽

Ping Liu ◽

Shu-He Dai ◽

Jian Sun ◽

Ya-Hong Liu ◽

...

Keyword(s):

Escherichia Coli ◽

Multidrug Resistant ◽

Therapeutic Options ◽

Infection Model ◽

Synergistic Activity ◽

Colistin Resistance ◽

Content Type ◽

E Coli ◽

Antiretroviral Drug

ABSTRACTAlternative therapeutic options are urgently needed against multidrug-resistant Escherichia coli infections, especially in situations of preexisting tigecycline and colistin resistance. Here, we investigated synergistic activity of the antiretroviral drug zidovudine in combination with tigecycline or colistin against E. coli harboring tet(X) and mcr-1 in vitro and in a murine thigh infection model. Zidovudine and tigecycline/colistin combinations achieved synergistic killing and significantly decreased bacterial burdens by >2.5-log10 CFU/g in thigh tissues compared to each monotherapy.

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Effect of Ceftriaxone on the Outcome of Murine Pyelonephritis Caused by Extended-Spectrum-β-Lactamase-Producing Escherichia coli

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.03974-14 ◽

2014 ◽

Vol 58 (12) ◽

pp. 7102-7111 ◽

Cited By ~ 5

Author(s):

A. Tratselas ◽

M. Simitsopoulou ◽

A. Giannakopoulou ◽

I. Dori ◽

S. Saoulidis ◽

...

Keyword(s):

Escherichia Coli ◽

Histological Analysis ◽

Generation Cephalosporin ◽

Bacterial Burden ◽

Content Type ◽

Therapeutic Implications ◽

E Coli ◽

Time Points ◽

Extended Spectrum ◽

Tract Infections

ABSTRACTUrinary tract infections (UTIs) due to extended-spectrum-β-lactamase (ESBL)-producingEnterobacteriaceaein children are becoming more frequent, and they are commonly treated initially with a second- or third-generation cephalosporin. We developed a murine model of ascending UTI caused by ESBL-producingEscherichia coli. Using this model, we investigated the renal bacterial burden, interleukin-6 (IL-6) expression, and histopathological alterations caused by ESBL- and non-ESBL-producing bacteria after 1, 2, or 6 days with or without ceftriaxone therapy. The renal bacterial burden, IL-6 concentration, and histological inflammatory lesions were not significantly different between mice infected with ESBL- and non-ESBL-producing bacteria without treatment at any of the time points examined. Following ceftriaxone administration, the bacterial burden was eliminated in the kidneys of mice infected with ESBL- and non-ESBL-producing bacteria on the 6th postinfection day. The histological analysis demonstrated that among mice treated with ceftriaxone, those infected with ESBL-producing bacteria had more profound renal alterations than those infected with non-ESBL-producing bacteria on the 6th day (P< 0.001). In comparison, microbiological outcomes did not differ significantly between mice infected with ESBL- and non-ESBL-producing bacteria at any of the time points examined. The effectiveness of ceftriaxone in mice with UTIs due to ESBL-producingE. colimay have therapeutic implications; it is, however, hampered by limited activity on the histopathological lesions, a finding that needs further investigation.

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The Intimin-Like Protein FdeC Is Regulated by H-NS and Temperature in Enterohemorrhagic Escherichia coli

Applied and Environmental Microbiology ◽

10.1128/aem.02114-14 ◽

2014 ◽

Vol 80 (23) ◽

pp. 7337-7347 ◽

Cited By ~ 10

Author(s):

Donna M. Easton ◽

Luke P. Allsopp ◽

Minh-Duy Phan ◽

Danilo Gomes Moriel ◽

Guan Kai Goh ◽

...

Keyword(s):

Escherichia Coli ◽

Culture Conditions ◽

Enterohemorrhagic Escherichia Coli ◽

Infection Model ◽

Content Type ◽

E Coli ◽

Uremic Syndrome ◽

Animal Hosts ◽

And Function

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) is a Shiga-toxigenic pathogen capable of inducing severe forms of enteritis (e.g., hemorrhagic colitis) and extraintestinal sequelae (e.g., hemolytic-uremic syndrome). The molecular basis of colonization of human and animal hosts by EHEC is not yet completely understood, and an improved understanding of EHEC mucosal adherence may lead to the development of interventions that could disrupt host colonization. FdeC, also referred to by its IHE3034 locus tag ECOK1_0290, is an intimin-like protein that was recently shown to contribute to kidney colonization in a mouse urinary tract infection model. The expression of FdeC is tightly regulatedin vitro, and FdeC shows promise as a vaccine candidate against extraintestinalE. colistrains. In this study, we characterized the prevalence, regulation, and function offdeCin EHEC. We showed that thefdeCgene is conserved in both O157 and non-O157 EHEC and encodes a protein that is expressed at the cell surface and promotes biofilm formation under continuous-flow conditions in a recombinantE. colistrain background. We also identified culture conditions under which FdeC is expressed and showed that minor alterations of these conditions, such as changes in temperature, can significantly alter the level of FdeC expression. Additionally, we demonstrated that the transcription of thefdeCgene is repressed by the global regulator H-NS. Taken together, our data suggest a role for FdeC in EHEC when it grows at temperatures above 37°C, a condition relevant to its specialized niche at the rectoanal junctions of cattle.

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Susceptibility of Clinical Isolates of Escherichia coli to Fosfomycin as Measured by Four In Vitro Testing Methods

Journal of Clinical Microbiology ◽

10.1128/jcm.01306-20 ◽

2020 ◽

Vol 58 (10) ◽

Author(s):

James A. Karlowsky ◽

Philippe R. S. Lagacé-Wiens ◽

Nancy M. Laing ◽

Melanie R. Baxter ◽

Heather J. Adam ◽

...

Keyword(s):

Escherichia Coli ◽

Reference Method ◽

Clinical Isolates ◽

Disk Diffusion ◽

Content Type ◽

E Coli ◽

Agar Dilution ◽

Vitek 2 ◽

Urinary Isolates

ABSTRACT Clinical isolates of Escherichia coli (n = 554) were tested against fosfomycin using agar dilution, disk diffusion, and Etest. Agar dilution (reference method) identified few isolates with fosfomycin MICs of 64 (n = 3), 128 (n = 4), and ≥256 μg/ml (n = 2). Applying CLSI (M100, 2020) and EUCAST (v. 10.0, 2020) breakpoints, 98.9% and 98.4% (agar dilution), 99.3% and 99.1% (disk diffusion), and 99.1% and 98.9% (Etest) of isolates were fosfomycin susceptible, respectively. Essential agreement (agar dilution versus Etest) was low (40.8%); 59.3% (131/221) of isolates with agar dilution MICs of 2 to 128 μg/ml tested 2 to 4 doubling dilutions lower by Etest. Applying CLSI breakpoints, categorical agreement was >99% for both disk diffusion and Etest; no major errors (MEs) or very major errors (VMEs) were identified, and rates of minor errors (mEs) were <1%. EUCAST breakpoints yielded categorical agreements of >99% and no MEs for both disk diffusion and Etest; however, VMEs occurred at unacceptable rates of 44.4% (disk diffusion) and 33.3% (Etest). All isolates with agar dilution MICs of ≥32 μg/ml (n = 12) and a subset of isolates with MICs of ≤16 μg/ml (n = 49) were also tested using the Vitek 2 AST-N391 card and generated fosfomycin MICs 1 to ≥3 doubling dilutions lower than agar dilution for 11/12 isolates with agar dilution MICs of ≥32 μg/ml. We conclude that performing fosfomycin disk diffusion or Etest on urinary isolates of E. coli and interpreting results using CLSI breakpoints reliably identified fosfomycin-susceptible isolates regardless of differences in endpoint reading criteria. EUCAST breakpoints generated excessive rates of VMEs for our isolate collection of high fosfomycin susceptibility.

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