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Bixby ML, Daley EC, Collins LB, Salay JM, Bryson AL, Hirsch EB. Skipped wells and scientific error during fosfomycin agar dilution and broth microdilution lead to inconsistent minimal inhibitory concentrations and may be cause for reevaluating testing methods for Klebsiella pneumoniae. Microbiol Spectr 2024:e0420523. [PMID: 38940588 DOI: 10.1128/spectrum.04205-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2023] [Accepted: 05/29/2024] [Indexed: 06/29/2024] Open
Abstract
Despite the first-line recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are pressing barriers for optimizing its use for the treatment of non-Escherichia coli Enterobacterales UTI. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for minimal inhibitory concentration (MIC) determination is largely impractical. Using 160 clinical Klebsiella pneumoniae isolates, we sought to understand rates of skipped wells and MIC imprecision in broth microdilution (BMD) and how that compares to rates of error using AD. Though the Clinical and Laboratory Standards Institute refers to the skipped well phenomena in their recommendation against the use of BMD, there is a paucity of data on its frequency. While AD and BMD produced similar MIC50/90 values (32/256 µg/mL for AD and 64/256 µg/mL for BMD), essential agreement was poor. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells at a given concentration, as the most frequent scientific error. Growth in concentrations above the measured MIC occurred in up to 3.3% of wells and was seen within three dilutions of the MIC for BMD. Observation of single colonies either at or beyond the measured MIC for AD was also common and occurred up to 8.3% and 2.5% of the time, respectively. The frequent scientific error in both testing methods should prompt re-evaluation of AD guidelines and expansion of MIC testing methods for fosfomycin susceptibility testing, as poor agreement with another method prone to scientific error should not be the main detractor from BMD use.IMPORTANCEDespite the recommendation of fosfomycin for uncomplicated urinary tract infections (UTIs), there are barriers for optimizing its use. There are no approved breakpoints for oral use against other Enterobacterales, and the recommended agar dilution (AD) reference method for MIC determination is largely impractical. The use of broth microdilution (BMD) for fosfomycin testing is not recommended by the Clinical and Laboratory Standards Institute due to unsatisfactory precision and skipped wells-occurrence of no-growth in a single well before the minimal inhibitory concentration (MIC)-and trailing endpoints. We sought to understand rates of skipped wells and growth at concentrations above measured MICs in BMD and how that compares to scientific error using AD. No-growth wells at concentrations below the MIC occurred in up to 10.9% of wells for BMD and single colonies at or beyond measured MICs for AD were also common. Frequent scientific error in both methods should prompt re-evaluation of both AD and BMD for fosfomycin susceptibility testing.
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Affiliation(s)
- Morgan L Bixby
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
| | - Ellora C Daley
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
| | - Lindsey B Collins
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
| | - Jenna M Salay
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
| | | | - Elizabeth B Hirsch
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
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Jariyapamornkoon N, Nuanualsuwan S, Suanpairintr N. In Vitro Antibacterial Activities of Fosfomycin against Escherichia coli Isolates from Canine Urinary Tract Infection. Animals (Basel) 2024; 14:1916. [PMID: 38998027 PMCID: PMC11240368 DOI: 10.3390/ani14131916] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2024] [Revised: 06/23/2024] [Accepted: 06/27/2024] [Indexed: 07/14/2024] Open
Abstract
Fosfomycin is a bactericidal drug recommended as an alternative treatment for canine bacterial cystitis, particularly in cases involving multidrug-resistant (MDR) infections when no other options are available. In this study, minimum inhibitory concentration (MIC) and mutant prevention concentration (MPC) of fosfomycin were determined against 79 clinical E. coli isolates using the agar dilution method. The susceptibility rate of E. coli to fosfomycin was 86.06%, with MIC50 and MIC90 values of 4 mg/L and 96 mg/L, respectively. MPC50 and MPC90 values were 64 mg/L and 192 mg/L. Using pharmacokinetic (PK) data from dogs given a single 80 mg/kg oral dose of fosfomycin, the area under the curve per MIC50 (AUC0-24/MIC50) was 85.79 with time above MIC50 (T > MIC50) exceeding 50%. In urine, the AUC0-24/MIC50 was 10,694.78, and the AUC0-24/MPC90 was 222.81, with T > MPC90 extending beyond 24 h. Therefore, fosfomycin exhibited significant antibacterial activity against canine uropathogenic E. coli, including MDR strains, at concentrations below the susceptible MIC breakpoint. However, the high MPC values, especially the MPC90, indicate the critical importance of performing susceptibility testing for fosfomycin and maintaining ongoing resistance monitoring.
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Affiliation(s)
- Nattha Jariyapamornkoon
- Graduate Program in Veterinary Bioscience, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand;
| | - Suphachai Nuanualsuwan
- Department of Veterinary Public Health, Faculty of Veterinary Sciences, Chulalongkorn University, Bangkok 10330, Thailand;
- Center of Excellence for Food and Water Risk Analysis (FAWRA), Department of Veterinary Public Health, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
| | - Nipattra Suanpairintr
- Center of Excellence for Food and Water Risk Analysis (FAWRA), Department of Veterinary Public Health, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
- Department of Pharmacology, Faculty of Veterinary Science, Chulalongkorn University, Bangkok 10330, Thailand
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Bixby ML, Salay JM, Krueger AR, Mathers AJ, Hirsch EB. Fosfomycin Disk Diffusion Testing among Klebsiella pneumoniae Results in Frequent Inner Colonies and Categorical Disagreement Based on Conflicting Breakpoint Organization Recommendations. Microbiol Spectr 2023; 11:e0336322. [PMID: 36877020 PMCID: PMC10101107 DOI: 10.1128/spectrum.03363-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2022] [Accepted: 02/13/2023] [Indexed: 03/07/2023] Open
Abstract
Recent studies indicate that discrete inner colonies (ICs) arise during fosfomycin disk diffusion (DD) testing. CLSI and EUCAST have contradicting recommendations on the interpretation of ICs; CLSI recommends considering them while EUCAST recommends ignoring them when interpreting DD results. We sought to compare the categorical agreement of DD and agar dilution (AD) MIC and to assess the implications of ICs interpretation on zone diameter readings. A convenience sample of 80 Klebsiella pneumoniae clinical isolates with varied phenotypic profiles collected from 3 United States locations was included. Susceptibility was determined in duplicate, using both organization recommendations and interpretations for Enterobacterales. Correlations between methods were calculated using EUCASTIV AD as the reference method. MIC values ranged from 1 to >256 μg/mL with an MIC50/90 of 32/256 μg/mL. Extrapolating EUCASToral and CLSI AD Escherichia coli breakpoints, 12.5% and 83.8% of isolates were susceptible, respectively, whereas 66.3% were susceptible by EUCASTIV AD-which applies to K. pneumoniae. CLSI DD measurements were 2 to 13 mm smaller than EUCAST measurements due to 66 (82.5%) isolates producing discrete ICs. Categorical agreement with EUCASTIV AD was greatest for CLSI AD (65.0%) and poorest for EUCASToral DD (6.3%). Isolates among this collection were frequently classified into different interpretive categories based on varying breakpoint organization recommendations. The more conservative oral breakpoints of EUCAST resulted in more isolates categorized as resistant despite frequent ICs. Differing zone diameter distributions and poor categorical agreement highlight issues of extrapolating E. coli breakpoints and methods to other Enterobacterales, and the clinical relevance of this issue warrants further investigation. IMPORTANCE Fosfomycin susceptibility testing recommendations are complex. Both the Clinical and Laboratory Standards Institute and the European Committee on Antimicrobial Susceptibility Testing (EUCAST) recognize agar dilution as the reference method, but they also support disk diffusion as an approved method for Escherichia coli. However, these two organizations have conflicting recommendations for the interpretation of inner colonies that arise during disk diffusion testing which can lead to varying zone diameters and interpretations despite isolates having identical MIC values. Using a collection of 80 Klebsiella pneumoniae isolates, we found that a large (82.5%) portion produced discrete inner colonies during disk diffusion and isolates were frequently classified into different interpretive categories. The more conservative breakpoints of EUCAST resulted in more isolates categorized as resistant despite frequent inner colonies. Differing zone diameter distributions and poor categorical agreement highlight issues of extrapolating E. coli breakpoints and methods to other Enterobacterales, and the clinical relevance of this issue warrants further investigation.
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Affiliation(s)
- Morgan L. Bixby
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
| | - Jenna M. Salay
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
| | - Amanda R. Krueger
- University of Minnesota College of Pharmacy, Minneapolis, Minnesota, USA
| | - Amy J. Mathers
- Department of Medicine and Pathology, University of Virginia, Charlottesville, Virginia, USA
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Roch M, Sierra R, Andrey DO. Antibiotic heteroresistance in ESKAPE pathogens, from bench to bedside. Clin Microbiol Infect 2023; 29:320-325. [PMID: 36270588 DOI: 10.1016/j.cmi.2022.10.018] [Citation(s) in RCA: 22] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2022] [Revised: 09/23/2022] [Accepted: 10/13/2022] [Indexed: 11/27/2022]
Abstract
BACKGROUND Heteroresistance refers to subpopulation-mediated differential antimicrobial susceptibility within a clonal bacterial population. Usually, it designates a resistant subpopulation identified within an isolate considered susceptible by classical antimicrobial susceptibility testing. Heteroresistance lacks a uniform microbiological definition for diagnostic laboratories, and its clinical impact remains unclear for most bacterial species. OBJECTIVES This narrative review aims to provide a practical overview on the latest developments in the field of heteroresistance for both clinical microbiologists and physicians, with a particular focus on ESKAPE pathogens. SOURCES A literature search was performed on Pubmed and Google with the key words heteroresistance (heterogeneity OR heterogeneous) AND antibiotic resistance. Among the 836 publications selected based on their abstracts, the most relevant for the detection, epidemiology and clinical impact of heteroresistance in ESKAPE pathogens are discussed here. CONTENT Heteroresistance is only clearly defined for heterogeneous vancomycin intermediate Staphylococcus aureus. We compiled a larger microbiological definition to be applicable to other bacterial species and antibiotics in the clinical context. We highlighted the key technical points of population analysis profile, which is the reference standard for detecting heteroresistance. Heteroresistance to polymyxins, β-lactams (carbapenems, cefiderocol), fosfomycin, tigecycline and aminoglycosides is frequently reported in multidrug-resistant gram-negative pathogens. Treatment failure due to heteroresistance has been described in case reports or retrospective studies, so far confirmed by meta-analyses in the case of heterogeneous vancomycin intermediate S. aureus only. Finally, to treat pandrug-resistant bacterial infections, the option of targeting susceptible subpopulations of resistant isolates using tailored antibiotic combinations is also discussed. IMPLICATIONS Systematic heteroresistance screening by clinical laboratories is not currently recommended. Nevertheless, we should be aware of this phenomenon, and in specific cases, such as treatment failure, heteroresistance should be tested by reference laboratories. Additional studies using standardized methods are needed to improve our understanding of heteroresistance and further assess its clinical impact.
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Affiliation(s)
- Mélanie Roch
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland
| | - Roberto Sierra
- Department of Microbiology and Molecular Medicine, Faculty of Medicine, University of Geneva, Geneva, Switzerland; Division of Infectious Diseases, Department of Medicine, Geneva University Hospitals and Medical School, Geneva, Switzerland
| | - Diego O Andrey
- Division of Infectious Diseases, Department of Medicine, Geneva University Hospitals and Medical School, Geneva, Switzerland; Division of Laboratory Medicine, Department of Diagnostics, Geneva University Hospitals and University of Geneva, Geneva, Switzerland.
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Gupta A, Malik S, Kaminski M, Landman D, Quale JM. In Vitro and In Vivo Activity of Amoxicillin-Clavulanate Combined with Ceftibuten or Cefpodoxime Against Extended-Spectrum β-Lactamase-Producing Escherichia coli and Klebsiella pneumoniae. Microb Drug Resist 2022; 28:419-424. [PMID: 35451880 DOI: 10.1089/mdr.2021.0025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Infections due to extended-spectrum β-lactamase (ESBL)-producing Enterobacterales are an increasingly common problem. For many of these infections, no oral treatment options are available. The activity of amoxicillin-clavulanate combined with ceftibuten or cefpodoxime was evaluated against a group of Escherichia coli and Klebsiella pneumoniae clinical isolates possessing a variety of CTX-M- and SHV-type ESBLs; some possessed blaTEM1 as well. In time-kill studies, the combination of subinhibitory concentrations of amoxicillin-clavulanate with ceftibuten was bactericidal and synergistic for all strains with an amoxicillin-clavulanate MIC ≤32 μg/mL, regardless of the type of ESBL and the cephalosporin minimal inhibitory concentration (MIC). The combination with cefpodoxime was also bactericidal and synergistic against all but one of these strains. These combinations were further tested against two strains of K. pneumoniae and one E. coli in a sepsis model using Galleria mellonella larvae. The combination of amoxicillin-clavulanate with ceftibuten demonstrated a synergistic survival benefit against all three strains. The combination with cefpodoxime also improved survival against the two K. pneumoniae strains, but not the E. coli strain. These findings support combining amoxicillin-clavulanate with ceftibuten, and possibly cefpodoxime, for the treatment of infections due to ESBL producers and suggest that having an amoxicillin-clavulanate MIC of 32 μg/mL or less may predict activity at clinically achievable concentrations. Clinical studies are warranted to further evaluate this therapeutic approach.
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Affiliation(s)
- Aanchal Gupta
- Infectious Diseases Division, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - Saquib Malik
- Infectious Diseases Division, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - Monica Kaminski
- Infectious Diseases Division, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - David Landman
- Infectious Diseases Division, SUNY Downstate Medical Center, Brooklyn, New York, USA
| | - John M Quale
- Infectious Diseases Division, SUNY Downstate Medical Center, Brooklyn, New York, USA
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Abbott IJ, van Gorp E, Wyres KL, Wallis SC, Roberts JA, Meletiadis J, Peleg AY. OUP accepted manuscript. J Antimicrob Chemother 2022; 77:1324-1333. [PMID: 35211736 PMCID: PMC9047678 DOI: 10.1093/jac/dkac045] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 01/24/2022] [Indexed: 11/14/2022] Open
Abstract
Introduction The use of oral fosfomycin for urinary tract infections (UTIs) caused by non-Escherichia coli uropathogens is uncertain, including Klebsiella pneumoniae, the second most common uropathogen. Methods A multicompartment bladder infection in vitro model was used with standard media and synthetic human urine (SHU) to simulate urinary fosfomycin exposure after a single 3 g oral dose (fAUC0–72 16884 mg·h/L, t½ 5.5 h) against 15 K. pneumoniae isolates including ATCC 13883 (MIC 2 to >1024 mg/L) with a constant media inflow (20 mL/h) and 4-hourly voiding of each bladder. The impact of the media (CAMHB + G6P versus SHU) on fosfomycin MIC measurements, drug-free growth kinetics and regrowth after fosfomycin administration was assessed. A low and high starting inoculum (5.5 versus 7.5 log10 cfu/mL) was assessed in the bladder infection model. Results Compared with CAMHB, isolates in SHU had a slower growth rate doubling time (37.7 versus 24.1 min) and reduced growth capacity (9.0 ± 0.3 versus 9.4 ± 0.3 log10 cfu/mL), which was further restricted with increased inflow rate (40 mL/h) and more frequent voids (2-hourly). Regrowth was commonly observed in both media with emergence of fosfomycin resistance promoted by a high starting inoculum in CAMHB (MIC rise to ≥1024 mg/L in 13/14 isolates). Resistance was rarely detected in SHU, even with a high starting inoculum (MIC rise to ≥1024 mg/L in 2/14 isolates). Conclusions Simulated in an in vitro UTI model, the regrowth of K. pneumoniae urinary isolates was inadequately suppressed following oral fosfomycin therapy. Efficacy was further reduced by a high starting inoculum.
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Affiliation(s)
- Iain J. Abbott
- Department of Infectious Diseases, Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
- Corresponding author. E-mail:
| | - Elke van Gorp
- Department of Infectious Diseases, Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Kelly L. Wyres
- Department of Infectious Diseases, Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Steven C. Wallis
- University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia
| | - Jason A. Roberts
- University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia
- Department of Intensive Care Medicine and Pharmacy Department, Royal Brisbane and Women’s Hospital, Brisbane, Australia
- Division of Anaesthesiology Critical Care Emergency and Pain Medicine, Nîmes University Hospital, University of Montpellier, Nîmes, France
| | - Joseph Meletiadis
- Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Haidari, Athens, Greece
| | - Anton Y. Peleg
- Department of Infectious Diseases, Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
- Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, VIC, Australia
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Use of Fosfomycin Etest To Determine In Vitro Susceptibility of Clinical Isolates of Enterobacterales Other than Escherichia coli, Nonfermenting Gram-Negative Bacilli, and Gram-Positive Cocci. J Clin Microbiol 2021; 59:e0163521. [PMID: 34495708 DOI: 10.1128/jcm.01635-21] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Clinical isolates of Enterobacterales other than Escherichia coli (EOTEC), nonfermenting Gram-negative bacilli, and Gram-positive cocci were tested for susceptibility to fosfomycin using Etest and reference agar dilution. Applying EUCAST (v. 11.0, 2021) intravenous fosfomycin breakpoints, Etest MICs for EOTEC showed essential agreement (EA), categorical agreement (CA), major error (ME), and very major error (VME) rates of 70.4%, 88.4%, 4.1%, and 32.1%, respectively. No species of EOTEC tested with acceptable rates for all of EA (≥90%), CA (≥90%), ME (≤3%), and VME (≤3%). Etest MICs for Enterococcus faecalis, interpreted using CLSI oral/urine criteria (M100, 2021) showed EA, CA, minor error, ME, and VME rates of 98.5%, 81.2%, 18.8%, 0%, and 0%. Against Staphylococcus aureus, EA, CA, and ME rates were 84.1%, 98.7%, and 1.3% (EUCAST intravenous criteria). S. aureus isolates with fosfomycin MICs of >32 μg/ml (resistant) were not identified by agar dilution. We conclude that performing fosfomycin Etest on isolates of S. aureus will reliably identify fosfomycin-susceptible isolates with low, acceptable rates of MEs and VMEs. Testing of urinary isolates of E. faecalis by Etest is associated with an unacceptably high rate of minor errors (18.8%) but low, acceptable rates of MEs and VMEs when results are interpreted using CLSI criteria. Isolates of EOTEC tested by Etest with resulting MICs interpreted by EUCAST criteria were associated with an unacceptably high VME rate (32.1%). In vitro testing of clinical isolates beyond E. coli, E. faecalis, and S. aureus to determine susceptibility to fosfomycin is problematic with current methods and breakpoints.
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Abbott IJ, Mouton JW, Peleg AY, Meletiadis J. Pharmacokinetic/pharmacodynamic analysis of oral fosfomycin against Enterobacterales, Pseudomonas aeruginosa and Enterococcus spp. in an in vitro bladder infection model: impact on clinical breakpoints. J Antimicrob Chemother 2021; 76:3201-3211. [PMID: 34473271 DOI: 10.1093/jac/dkab313] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2021] [Accepted: 07/23/2021] [Indexed: 11/15/2022] Open
Abstract
OBJECTIVES Fosfomycin is an established treatment for uncomplicated urinary tract infections (UTIs), yet evidence supporting susceptibility breakpoints is limited. We examine the UTI susceptibility criteria. METHODS Fosfomycin susceptibility, heteroresistance and in vitro growth in a bladder infection model, after a single 3 g dose of oral fosfomycin, were bridged to human pharmacokinetics with pharmacokinetic/pharmacodynamic and Monte Carlo analyses. Data from common uropathogens (24 Escherichia coli, 20 Klebsiella pneumoniae, 4 Enterobacter cloacae, 14 Pseudomonas aeruginosa, 8 Enterococcus faecalis and 8 Enterococcus faecium) were compared and analysed to ascertain species-specific PTA. RESULTS Glucose-6-phosphate (G6P) increased MICs of E. coli, K. pneumoniae and E. cloacae (median 2-fold dilutions 3-5), but not of P. aeruginosa and Enterococcus. Atypical E. coli lacking G6P potentiation were killed in the bladder infection model despite high MICs (32-128 mg/L). Fosfomycin heteroresistance was uncommon in E. coli (MIC > 2 mg/L) but was detected in the majority of K. pneumoniae (MIC > 1 mg/L) and P. aeruginosa (MIC >8 mg/L). For these species, baseline heteroresistance was a strong predictor for treatment failure in the model. No heteroresistance was found in Enterococcus. The fAUC/MIC targets for stasis were 1935, 3393, 9968, 2738 and 283 for typical E. coli, K. pneumoniae, E. cloacae, P. aeruginosa and E. faecalis, respectively (synthetic human urine medium alone promoted a 1 log10 kill in E. faecium). A >95% PTA for stasis was only found at MIC ≤ epidemiological cut-off (ECOFF) for E. coli (4 mg/L). For other species, PTAs were low for WT populations. CONCLUSIONS With the exception of E. coli, fosfomycin is a poor target for other uropathogen species. A reduction in oral fosfomycin UTI breakpoints is supported.
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Affiliation(s)
- Iain J Abbott
- Department of Infectious Diseases, Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia
| | - Johan W Mouton
- Department of Medical Microbiology and Infectious Diseases, Research and Development Unit, Erasmus Medical Centre, Rotterdam, The Netherlands
| | - Anton Y Peleg
- Department of Infectious Diseases, Alfred Hospital and Central Clinical School, Monash University, Melbourne, Victoria, Australia.,Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Joseph Meletiadis
- Department of Medical Microbiology and Infectious Diseases, Research and Development Unit, Erasmus Medical Centre, Rotterdam, The Netherlands.,Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Haidari, Athens, Greece
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Abbott IJ, Roberts JA, Meletiadis J, Peleg AY. Antimicrobial pharmacokinetics and preclinical in vitro models to support optimized treatment approaches for uncomplicated lower urinary tract infections. Expert Rev Anti Infect Ther 2020; 19:271-295. [PMID: 32820686 DOI: 10.1080/14787210.2020.1813567] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
INTRODUCTION Urinary tract infections (UTIs) are extremely common. Millions of people, particularly healthy women, are affected worldwide every year. One-in-two women will have a recurrence within 12-months of an initial UTI. Inadequate treatment risks worsening infection leading to acute pyelonephritis, bacteremia and sepsis. In an era of increasing antimicrobial resistance, it is critical to provide optimized antimicrobial treatment. AREAS COVERED Literature was searched using PubMed and Google Scholar (up to 06/2020), examining the etiology, diagnosis and oral antimicrobial therapy for uncomplicated UTIs, with emphasis on urinary antimicrobial pharmacokinetics (PK) and the application of dynamic in vitro models for the pharmacodynamic (PD) profiling of pathogen response. EXPERT OPINION The majority of antimicrobial agents included in international guidelines were developed decades ago without well-described dose-response relationships. Microbiology laboratories still apply standard diagnostic methodology that has essentially remained unchanged for decades. Furthermore, it is uncertain how relevant standard in vitro susceptibility is for predicting antimicrobial efficacy in urine. In order to optimize UTI treatments, clinicians must exploit the urine-specific PK of antimicrobial agents. Dynamic in vitro models are valuable tools to examine the PK/PD and urodynamic variables associated with UTIs, while informing uropathogen susceptibility reporting, optimized dosing schedules, clinical trials and treatment guidelines.
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Affiliation(s)
- Iain J Abbott
- Department of Infectious Diseases, the Alfred Hospital and Central Clinical School, Monash University, Melbourne, Australia
| | - Jason A Roberts
- University of Queensland Centre for Clinical Research, Faculty of Medicine, The University of Queensland, Brisbane, Australia.,School of Pharmacy, Centre for Translational Anti-infective Pharmacodynamics, The University of Queensland, Brisbane, Australia.,Department of Intensive Care Medicine, Royal Brisbane and Women's Hospital, Brisbane, Australia.,Division of Anaesthesiology Critical Care Emergency and Pain Medicine, Nîmes University Hospital, University of Montpellier, Nîmes, France
| | - Joseph Meletiadis
- Clinical Microbiology Laboratory, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Haidari, Greece
| | - Anton Y Peleg
- Department of Infectious Diseases, the Alfred Hospital and Central Clinical School, Monash University, Melbourne, Australia.,Infection and Immunity Program, Monash Biomedicine Discovery Institute, Department of Microbiology, Monash University, Clayton, Australia
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Chavan R, Naphade B, Waykar B, Bhagwat S. In Vitro Activity of Fosfomycin and Nitrofurantoin Against Contemporary Enterobacterales Pathogens Isolated from Indian Tertiary Care Hospitals. Microb Drug Resist 2020; 27:678-684. [PMID: 33983854 DOI: 10.1089/mdr.2020.0200] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Background: In India, multidrug resistance in community and hospital associated Gram-negative pathogens has increased sharply over the past few years. In the absence of novel oral multidrug resistant-pathogen active therapies, the therapeutic situation with regard to community infections is even more challenging. Hence, the focus is now shifting toward potentially expanding the utility of older antibiotics such as fosfomycin and nitrofurantoin beyond their approved pathogen coverage. The current study was undertaken to assess the activity of fosfomycin and nitrofurantoin against Enterobacterales pathogens through minimum inhibitory concentration (MIC) determination to facilitate monitoring future shifts in susceptibility to these agents. Materials and Methods: The present study used 1,350 Enterobacterales, recently collected from various Indian tertiary care hospitals and preserved at Wockhardt Strain Repository. The MIC50/90 for fosfomycin and nitrofurantoin and the comparator antibiotics was determined for Escherichia coli (N = 470), Klebsiella pneumoniae (N = 429), Enterobacter spp., (N = 144), Proteus spp. (N = 262), and Citrobacter spp. (N = 45), using Clinical and Laboratory Standards Institute recommended agar dilution method. Results: Applying E. coli breakpoints, the susceptibility rates of fosfomycin for E. coli, K. pneumoniae, Enterobacter spp., Proteus spp., and Citrobacter spp., were 95.5%, 53.2%, 71.5%, 76.7%, and 91.1%, respectively. Applying respective breakpoints, the susceptibility rates of comparator drugs, including meropenem, were lower than fosfomycin. Susceptibility of nitrofurantoin for E. coli and Citrobacter isolate was 83%, while limited coverage (<13.2% susceptibility) was observed for other genera. Conclusion: Amidst widespread resistance, a > 70% fosfomycin susceptibility observed for clinical isolates, including strains expressing carbapenemases, is encouraging and supports conducting additional susceptibility and pharmacokinetic/pharmacodynamic studies to explore its potential for expanded therapeutic use. Nitrofurantoin activity spectrum was restricted to E. coli and Citrobacter spp. and, therefore, offers a relatively limited therapeutic scope.
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Affiliation(s)
| | | | - Bhalchandra Waykar
- Department of Zoology, Dr. Babasaheb Ambedkar Marathwada University, Aurangabad, India
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Farfour E, Degand N, Riverain E, Fihman V, Le Brun C, Péan de Ponfilly G, Muggeo A, Jousset A, Piau C, Lesprit P, Chatelain N, Dortet L, Poisson A, Guillard T, Limelette A, Mizrahi A, Le Monnier A, Fournier D, Potron A, Morand P, Janvier F, Otto MP, Woerther PL, Decousser JW, Corvec S, Plouzeau-Jayle C, Broutin L, Yin N, Héry-Arnaud G, Beauruelle C, Grillon A, Lecuru M, Bille E, Godreuil S, Jean Pierre H, Amara M, Henry A, Zahar JR, Carbonelle E, Jaureguy F, Lomont A, Isnard C, Cattoir V, Canis F, Diedrich T, Flevin E, Merens A, Jacquier H, Gyde E. Fosfomycin, from susceptibility to resistance: Impact of the new guidelines on breakpoints. Med Mal Infect 2020; 50:611-616. [DOI: 10.1016/j.medmal.2020.07.003] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2020] [Accepted: 07/08/2020] [Indexed: 12/17/2022]
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Susceptibility of Clinical Isolates of Escherichia coli to Fosfomycin as Measured by Four In Vitro Testing Methods. J Clin Microbiol 2020; 58:JCM.01306-20. [PMID: 32817224 DOI: 10.1128/jcm.01306-20] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 07/31/2020] [Indexed: 01/01/2023] Open
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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Treatment options for K. pneumoniae, P. aeruginosa and A. baumannii co-resistant to carbapenems, aminoglycosides, polymyxins and tigecycline: an approach based on the mechanisms of resistance to carbapenems. Infection 2020; 48:835-851. [PMID: 32875545 PMCID: PMC7461763 DOI: 10.1007/s15010-020-01520-6] [Citation(s) in RCA: 82] [Impact Index Per Article: 20.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2020] [Accepted: 08/26/2020] [Indexed: 02/07/2023]
Abstract
The management of carbapenem-resistant infections is often based on polymyxins, tigecycline, aminoglycosides and their combinations. However, in a recent systematic review, we found that Gram-negative bacteria (GNB) co-resistant to carbapanems, aminoglycosides, polymyxins and tigecycline (CAPT-resistant) are increasingly being reported worldwide. Clinical data to guide the treatment of CAPT-resistant GNB are scarce and based exclusively on few case reports and small case series, but seem to indicate that appropriate (in vitro active) antimicrobial regimens, including newer antibiotics and synergistic combinations, may be associated with lower mortality. In this review, we consolidate the available literature to inform clinicians dealing with CAPT-resistant GNB about treatment options by considering the mechanisms of resistance to carbapenems. In combination with rapid diagnostic methods that allow fast detection of carbapenemase production, the approach proposed in this review may guide a timely and targeted treatment of patients with infections by CAPT-resistant GNB. Specifically, we focus on the three most problematic species, namely Klebsiella pneumoniae, Pseudomonas aeruginosa and Acinetobacter baumannii. Several treatment options are currently available for CAPT-resistant K. pneumonia. Newer β-lactam-β-lactamase combinations, including the combination of ceftazidime/avibactam with aztreonam against metallo-β-lactamase-producing isolates, appear to be more effective compared to combinations of older agents. Options for P. aeruginosa (especially metallo-β-lactamase-producing strains) and A. baumannii remain limited. Synergistic combination of older agents (e.g., polymyxin- or fosfomycin-based synergistic combinations) may represent a last resort option, but their use against CAPT-resistant GNB requires further study.
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Oral Fosfomycin Treatment for Enterococcal Urinary Tract Infections in a Dynamic In Vitro Model. Antimicrob Agents Chemother 2020; 64:AAC.00342-20. [PMID: 32253214 DOI: 10.1128/aac.00342-20] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Accepted: 03/26/2020] [Indexed: 02/06/2023] Open
Abstract
There are limited treatment options for enterococcal urinary tract infections, especially vancomycin-resistant Enterococcus (VRE). Oral fosfomycin is a potential option, although limited data are available guiding dosing and susceptibility. We undertook pharmacodynamic profiling of fosfomycin against E. faecalis and E. faecium isolates using a dynamic in vitro bladder infection model. Eighty-four isolates underwent fosfomycin agar dilution susceptibility testing (E. faecalis MIC50/90 32/64 μg/ml; E. faecium MIC50/90 64/128 μg/ml). Sixteen isolates (including E. faecalis ATCC 29212 and E. faecium ATCC 35667) were chosen to reflect the MIC range and tested in the bladder infection model with synthetic human urine (SHU). Under drug-free conditions, E. faecium demonstrated greater growth restriction in SHU compared to E. faecalis (E. faecium maximal growth 5.8 ± 0.6 log10 CFU/ml; E. faecalis 8.0 ± 1.0 log10 CFU/ml). Isolates were exposed to high and low fosfomycin urinary concentrations after a single dose, and after two doses given over two days with low urinary concentration exposure. Simulated concentrations closely matched the target (bias 2.3%). E. faecalis isolates required greater fosfomycin exposure for 3 log10 kill from the starting inoculum compared with E. faecium The ƒAUC0-72/MIC and ƒ%T > MIC0-72 for E. faecalis were 672 and 70%, compared to 216 and 51% for E. faecium, respectively. There was no rise in fosfomycin MIC postexposure. Two doses of fosfomycin with low urinary concentrations resulted in equivalent growth inhibition to a single dose with high urinary concentrations. With this urinary exposure, fosfomycin was effective in promoting suppression of regrowth (>3 log10 kill) in the majority of isolates.
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