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Bhatnagar AS, Machado MJ, Patterson L, Anderson K, Abelman RL, Bateman A, Biggs A, Bumpus-White P, Craft B, Howard M, LaVoie SP, Lonsway D, Sabour S, Schneider A, Snippes-Vagnone P, Tran M, Torpey D, Valley A, Elkins CA, Karlsson M, Brown AC. Antimicrobial Resistance Laboratory Network's multisite evaluation of the ThermoFisher Sensititre GN7F broth microdilution panel for antimicrobial susceptibility testing. J Clin Microbiol 2023; 61:e0079923. [PMID: 37971271 PMCID: PMC10729754 DOI: 10.1128/jcm.00799-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 09/25/2023] [Indexed: 11/19/2023] Open
Abstract
In 2017, the Centers for Disease Control and Prevention (CDC) established the Antimicrobial Resistance Laboratory Network to improve domestic detection of multidrug-resistant organisms. CDC and four laboratories evaluated a commercial broth microdilution panel. Antimicrobial susceptibility testing using the Sensititre GN7F (ThermoFisher Scientific, Lenexa, KS) was evaluated by testing 100 CDC and Food and Drug Administration AR Isolate Bank isolates [40 Enterobacterales (ENT), 30 Pseudomonas aeruginosa (PSA), and 30 Acinetobacter baumannii (ACB)]. We assessed multiple amounts of transfer volume (TV) between the inoculum and tubed 11-mL cation-adjusted Mueller-Hinton broth: 1 µL [tribe Proteeae (P-tribe) only] and 10, 30, and 50 µL, resulting in respective CFU per milliter of 1 × 104, 1 × 105, 3 × 105, and 5 × 105. Four TV combinations were analyzed: standard (STD) [1 µL (P-tribe) and 10 µL], enhanced standard (E-STD) [1 µL (P-tribe) and 30 µL], 30 µL, and 50 µL. Essential agreement (EA), categorical agreement, major error (ME), and very major error (VME) were analyzed by organism then TVs. For ENT, the average EA across laboratories was <90% for 7 of 15 β-lactams using STD and E-STD TVs. As TVs increased, EA increased (>90%), and VMEs decreased. For PSA, EA improved as TVs increased; however, MEs also increased. For ACB, increased TVs provided slight EA improvements; all TVs yielded multiple VMEs and MEs. For ENT and ACB, Minimum inhibitory concentrations (MICs) trended downward using a 1 or 10 µL TV; there were no obvious MIC trends by TV for PSA. The public health and clinical consequences of missing resistance warrant increased TV of 30 µL for the GN7F, particularly for P-tribe, despite being considered "off-label" use.
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Affiliation(s)
- Amelia S. Bhatnagar
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - María-José Machado
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Logan Patterson
- Wisconsin State Laboratory of Hygiene, Madison, Wisconsin, USA
| | - Karen Anderson
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | | | - Allen Bateman
- Wisconsin State Laboratory of Hygiene, Madison, Wisconsin, USA
| | - Angela Biggs
- Maryland Department of Health, Baltimore, Maryland, USA
| | - Porscha Bumpus-White
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
- Goldbelt C6, LLC, Chesapeake, Virginia, USA
| | - Bradley Craft
- Minnesota Department of Health, St. Paul, Minnesota, USA
| | | | - Stephen P. LaVoie
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - David Lonsway
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Sarah Sabour
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | | | | | - Michael Tran
- Washington State Department of Health, Shoreline, Washington, USA
| | - David Torpey
- Maryland Department of Health, Baltimore, Maryland, USA
| | - Ann Valley
- Wisconsin State Laboratory of Hygiene, Madison, Wisconsin, USA
| | - Christopher A. Elkins
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
| | - Maria Karlsson
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
- Goldbelt C6, LLC, Chesapeake, Virginia, USA
| | - Allison C. Brown
- Division of Healthcare Quality Promotion, Centers for Disease Control and Prevention, Atlanta, Georgia, USA
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Cartagena AJ, Taylor KL, Smith JT, Manson AL, Pierce VM, Earl AM, Bhattacharyya RP. The carbapenem inoculum effect provides insight into the molecular mechanisms underlying carbapenem resistance in Enterobacterales. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.23.541813. [PMID: 37292717 PMCID: PMC10245868 DOI: 10.1101/2023.05.23.541813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Carbapenem-resistant Enterobacterales (CRE) are important pathogens that can develop resistance via multiple molecular mechanisms, including hydrolysis or reduced antibiotic influx. Identifying these mechanisms can improve pathogen surveillance, infection control, and patient care. We investigated how resistance mechanisms influence the carbapenem inoculum effect (IE), a phenomenon where inoculum size affects antimicrobial susceptibility testing (AST). We demonstrated that seven different carbapenemases impart a meropenem IE in Escherichia coli. Across 110 clinical CRE isolates, the carbapenem IE strictly depended on resistance mechanism: all carbapenemase-producing CRE (CP-CRE) exhibited a strong IE, whereas porin-deficient CRE displayed none. Concerningly, 50% and 24% of CP-CRE isolates changed susceptibility classification to meropenem and ertapenem, respectively, across the allowable inoculum range in clinical guidelines. The meropenem IE, and the ratio of ertapenem to meropenem minimal inhibitory concentration (MIC) at standard inoculum, reliably identified CP-CRE. Understanding how resistance mechanisms affect AST could improve diagnosis and guide therapies for CRE infections.
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Affiliation(s)
| | - Kyra L. Taylor
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Joshua T. Smith
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Abigail L. Manson
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Virginia M. Pierce
- Microbiology Laboratory, Department of Pathology, Massachusetts General Hospital, Boston, MA 02114, USA
- Department of Pathology and Clinical Laboratories, University of Michigan, Ann Arbor, MI 48109, USA
| | - Ashlee M. Earl
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
| | - Roby P. Bhattacharyya
- Infectious Disease and Microbiome Program, Broad Institute of MIT and Harvard, Cambridge, MA 02142, USA
- Infectious Diseases Division, Department of Medicine, Massachusetts General Hospital, Boston, MA 02114, USA
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3
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Neuenschwander FR, Groß B, Schubert S. Rapid Antibiotic Susceptibility Testing of Gram-Negative Bacteria Directly from Urine Samples of UTI Patients Using MALDI-TOF MS. Antibiotics (Basel) 2023; 12:1042. [PMID: 37370361 DOI: 10.3390/antibiotics12061042] [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: 04/26/2023] [Revised: 06/06/2023] [Accepted: 06/07/2023] [Indexed: 06/29/2023] Open
Abstract
Urinary tract infections (UTIs) are one of the most common human infections and are most often caused by Gram-negative bacteria such as Escherichia coli. In view of the increasing number of antibiotic-resistant isolates, rapidly initiating effective antibiotic therapy is essential. Therefore, a faster antibiotic susceptibility test (AST) is desirable. The MALDI-TOF MS-based phenotypic antibiotic susceptibility test (MALDI AST) has been used in blood culture diagnostics to rapidly detect antibiotic susceptibility. This study demonstrates for the first time that MALDI AST can be used to rapidly determine antibiotic susceptibility in UTIs directly from patients' urine samples. MALDI-TOF MS enables the rapid identification and AST of Gram-negative UTIs within 4.5 h of receiving urine samples. Six urinary tract infection antibiotics, including ciprofloxacin, cotrimoxazole, fosfomycin, meropenem, cefuroxime, and nitrofurantoin, were analyzed and compared with conventional culture-based AST methods. A total of 105 urine samples from UTI patients contained bacterial isolates for MALDI AST. The combination of ID and AST by MALDI-TOF allowed us to interpret the result according to EUCAST guidelines. An overall agreement of 94.7% was found between MALDI AST and conventional AST for the urinary tract pathogens tested.
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Affiliation(s)
- Felix R Neuenschwander
- Max von Pettenkofer Institute of Hygiene and Medical Microbiology, Faculty of Medicine, LMU Munich, Elisabeth-Winterhalter-Weg 6, 81377 Munich, Germany
| | - Birgit Groß
- Max von Pettenkofer Institute of Hygiene and Medical Microbiology, Faculty of Medicine, LMU Munich, Elisabeth-Winterhalter-Weg 6, 81377 Munich, Germany
| | - Sören Schubert
- Max von Pettenkofer Institute of Hygiene and Medical Microbiology, Faculty of Medicine, LMU Munich, Elisabeth-Winterhalter-Weg 6, 81377 Munich, Germany
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4
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Kim K, Wang T, Ma HR, Şimşek E, Li B, Andreani V, You L. Mapping single‐cell responses to population‐level dynamics during antibiotic treatment. Mol Syst Biol 2023; 19:e11475. [PMCID: PMC10333910 DOI: 10.15252/msb.202211475] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2022] [Revised: 04/24/2023] [Accepted: 04/25/2023] [Indexed: 12/08/2023] Open
Abstract
Treatment of sensitive bacteria with beta‐lactam antibiotics often leads to two salient population‐level features: a transient increase in total population biomass before a subsequent decline, and a linear correlation between growth and killing rates. However, it remains unclear how these population‐level responses emerge from collective single‐cell responses. During beta‐lactam treatment, it is well‐recognized that individual cells often exhibit varying degrees of filamentation before lysis. We show that the cumulative probability of cell lysis increases sigmoidally with the extent of filamentation and that this dependence is characterized by unique parameters that are specific to bacterial strain, antibiotic dose, and growth condition. Modeling demonstrates how the single‐cell lysis probabilities can give rise to population‐level biomass dynamics, which were experimentally validated. This mapping provides insights into how the population biomass time‐kill curve emerges from single cells and allows the representation of both single‐ and population‐level responses with universal parameters.
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Affiliation(s)
- Kyeri Kim
- Department of Biomedical EngineeringDuke UniversityDurhamNCUSA
- Center for Quantitative BiodesignDuke UniversityDurhamNCUSA
| | - Teng Wang
- Department of Biomedical EngineeringDuke UniversityDurhamNCUSA
- Center for Quantitative BiodesignDuke UniversityDurhamNCUSA
| | - Helena R Ma
- Department of Biomedical EngineeringDuke UniversityDurhamNCUSA
- Center for Quantitative BiodesignDuke UniversityDurhamNCUSA
| | - Emrah Şimşek
- Department of Biomedical EngineeringDuke UniversityDurhamNCUSA
- Center for Quantitative BiodesignDuke UniversityDurhamNCUSA
| | - Boyan Li
- Integrated Science Program, Yuanpei CollegePeking UniversityBeijingChina
| | - Virgile Andreani
- Biomedical Engineering DepartmentBoston UniversityBostonMAUSA
- Biological Design CenterBoston UniversityBostonMAUSA
| | - Lingchong You
- Department of Biomedical EngineeringDuke UniversityDurhamNCUSA
- Center for Quantitative BiodesignDuke UniversityDurhamNCUSA
- Center for Genomic and Computational BiologyDuke UniversityDurhamNCUSA
- Department of Molecular Genetics and MicrobiologyDuke University School of MedicineDurhamNCUSA
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Antibacterial Profile of a Microbicidal Agent Targeting Tyrosine Phosphatases and Redox Thiols, Novel Drug Targets. Antibiotics (Basel) 2021; 10:antibiotics10111310. [PMID: 34827248 PMCID: PMC8615086 DOI: 10.3390/antibiotics10111310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2021] [Revised: 10/23/2021] [Accepted: 10/24/2021] [Indexed: 11/16/2022] Open
Abstract
The activity profile of a protein tyrosine phosphatase (PTP) inhibitor and redox thiol oxidant, nitropropenyl benzodioxole (NPBD), was investigated across a broad range of bacterial species. In vitro assays assessed inhibitory and lethal activity patterns, the induction of drug variants on long term exposure, the inhibitory interactions of NPBD with antibiotics, and the effect of plasma proteins and redox thiols on activity. A literature review indicates the complexity of PTP and redox signaling and suggests likely metabolic targets. NPBD was broadly bactericidal to pathogens of the skin, respiratory, urogenital and intestinal tracts. It was effective against antibiotic resistant strains and slowly replicating and dormant cells. NPBD did not induce resistant or drug-tolerant phenotypes and showed low cross reactivity with antibiotics in synergy assays. Binding to plasma proteins indicated lowered in-vitro bioavailability and reduction of bactericidal activity in the presence of thiols confirmed the contribution of thiol oxidation and oxidative stress to lethality. This report presents a broad evaluation of the antibacterial effect of PTP inhibition and redox thiol oxidation, illustrates the functional diversity of bacterial PTPs and redox thiols, and supports their consideration as novel targets for antimicrobial drug development. NPBD is a dual mechanism agent with an activity profile which supports consideration of tyrosine phosphatases and bacterial antioxidant systems as promising targets for drug development.
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Core Antibiotic-Induced Transcriptional Signatures Reflect Susceptibility to All Members of an Antibiotic Class. Antimicrob Agents Chemother 2021; 65:AAC.02296-20. [PMID: 33846128 DOI: 10.1128/aac.02296-20] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 03/29/2021] [Indexed: 01/25/2023] Open
Abstract
Current growth-based antibiotic susceptibility testing (AST) is too slow to guide early therapy. We previously developed a diagnostic approach that quantifies antibiotic-induced transcriptional signatures to distinguish susceptible from resistant isolates, providing phenotypic AST 24 to 36 h faster than current methods. Here, we show that 10 transcripts optimized for AST of one fluoroquinolone, aminoglycoside, or beta-lactam reflect susceptibility when the organism is exposed to other members of that class. This finding will streamline development and implementation of this strategy, facilitating efficient antibiotic deployment.
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Abstract
The phenomenon of attenuated antibacterial activity at inocula above those utilized for susceptibility testing is referred to as the inoculum effect. Although the inoculum effect has been reported for several decades, it is currently debatable whether the inoculum effect is clinically significant. The aim of the present review was to consolidate currently available evidence to summarize which β-lactam drug classes demonstrate an inoculum effect against specific bacterial pathogens. Review of the literature showed that the majority of studies that evaluated the inoculum effect of β-lactams were in vitro investigations of Escherichia coli, Pseudomonas aeruginosa, Klebsiella pneumoniae, Haemophilus influenzae and Staphylococcus aureus. Across all five pathogens, cephalosporins consistently displayed observable inoculum effects in vitro, whereas carbapenems were less susceptible to an inoculum effect. A handful of animal studies were available that validated that the in vitro inoculum effect translates into attenuated pharmacodynamics of β-lactams in vivo. Only a few clinical investigations were available and suggested that an in vitro inoculum effect of cefazolin against MSSA may correspond to an increased likeliness of adverse clinical outcomes in patients receiving cefazolin for bacteraemia. The presence of β-lactamase enzymes was the primary mechanism responsible for an inoculum effect, but the observation of an inoculum effect in multiple pathogens lacking β-lactamase enzymes indicates that there are likely multiple mechanisms that may result in an inoculum effect. Further clinical studies are needed to better define whether interventions made in the clinic in response to organisms displaying an in vitro inoculum effect will optimize clinical outcomes.
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Affiliation(s)
- Justin R Lenhard
- California Northstate University College of Pharmacy, Elk Grove, CA, USA
| | - Zackery P Bulman
- College of Pharmacy, University of Illinois at Chicago, Chicago, IL, USA
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8
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Leonard H, Halachmi S, Ben-Dov N, Nativ O, Segal E. Unraveling Antimicrobial Susceptibility of Bacterial Networks on Micropillar Architectures Using Intrinsic Phase-Shift Spectroscopy. ACS NANO 2017; 11:6167-6177. [PMID: 28485961 DOI: 10.1021/acsnano.7b02217] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
With global antimicrobial resistance becoming increasingly detrimental to society, improving current clinical antimicrobial susceptibility testing (AST) is crucial to allow physicians to initiate appropriate antibiotic treatment as early as possible, reducing not only mortality rates but also the emergence of resistant pathogens. In this work, we tackle the main bottlenecks in clinical AST by designing biofunctionalized silicon micropillar arrays to provide both a preferable solid-liquid interface for bacteria networking and a simultaneous transducing element that monitors the response of bacteria when exposed to chosen antibiotics in real time. We harness the intrinsic ability of the micropillar architectures to relay optical phase-shift reflectometric interference spectroscopic measurements (referred to as PRISM) and employ it as a platform for culture-free, label-free phenotypic AST. The responses of E. coli to various concentrations of five clinically relevant antibiotics are optically tracked by PRISM, allowing for the minimum inhibitory concentration (MIC) values to be determined and compared to both standard broth microdilution testing and clinic-based automated AST system readouts. Capture of bacteria within these microtopologies, followed by incubation of the cells with the appropriate antibiotic solution, yields rapid determinations of antibiotic susceptibility. This platform not only provides accurate MIC determinations in a rapid manner (total assay time of 2-3 h versus 8 h with automated AST systems) but can also be employed as an advantageous method to differentiate bacteriostatic and bactericidal antibiotics.
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Affiliation(s)
- Heidi Leonard
- Department of Biotechnology and Food Engineering, ‡Department of Urology, Bnai Zion Medical Center, Faculty of Medicine, and §The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 3200003, Israel
| | - Sarel Halachmi
- Department of Biotechnology and Food Engineering, ‡Department of Urology, Bnai Zion Medical Center, Faculty of Medicine, and §The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 3200003, Israel
| | - Nadav Ben-Dov
- Department of Biotechnology and Food Engineering, ‡Department of Urology, Bnai Zion Medical Center, Faculty of Medicine, and §The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 3200003, Israel
| | - Ofer Nativ
- Department of Biotechnology and Food Engineering, ‡Department of Urology, Bnai Zion Medical Center, Faculty of Medicine, and §The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 3200003, Israel
| | - Ester Segal
- Department of Biotechnology and Food Engineering, ‡Department of Urology, Bnai Zion Medical Center, Faculty of Medicine, and §The Russell Berrie Nanotechnology Institute, Technion-Israel Institute of Technology , Haifa 3200003, Israel
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9
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Jahn LJ, Munck C, Ellabaan MMH, Sommer MOA. Adaptive Laboratory Evolution of Antibiotic Resistance Using Different Selection Regimes Lead to Similar Phenotypes and Genotypes. Front Microbiol 2017; 8:816. [PMID: 28553265 PMCID: PMC5425606 DOI: 10.3389/fmicb.2017.00816] [Citation(s) in RCA: 45] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2016] [Accepted: 04/21/2017] [Indexed: 12/01/2022] Open
Abstract
Antibiotic resistance is a global threat to human health, wherefore it is crucial to study the mechanisms of antibiotic resistance as well as its emergence and dissemination. One way to analyze the acquisition of de novo mutations conferring antibiotic resistance is adaptive laboratory evolution. However, various evolution methods exist that utilize different population sizes, selection strengths, and bottlenecks. While evolution in increasing drug gradients guarantees high-level antibiotic resistance promising to identify the most potent resistance conferring mutations, other selection regimes are simpler to implement and therefore allow higher throughput. The specific regimen of adaptive evolution may have a profound impact on the adapted cell state. Indeed, substantial effects of the selection regime on the resulting geno- and phenotypes have been reported in the literature. In this study we compare the geno- and phenotypes of Escherichia coli after evolution to Amikacin, Piperacillin, and Tetracycline under four different selection regimes. Interestingly, key mutations that confer antibiotic resistance as well as phenotypic changes like collateral sensitivity and cross-resistance emerge independently of the selection regime. Yet, lineages that underwent evolution under mild selection displayed a growth advantage independently of the acquired level of antibiotic resistance compared to lineages adapted under maximal selection in a drug gradient. Our data suggests that even though different selection regimens result in subtle genotypic and phenotypic differences key adaptations appear independently of the selection regime.
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Affiliation(s)
- Leonie J Jahn
- Novo Nordisk Foundation Center for Biosustainability, Technical University of DenmarkHørsholm, Denmark
| | - Christian Munck
- Novo Nordisk Foundation Center for Biosustainability, Technical University of DenmarkHørsholm, Denmark
| | - Mostafa M H Ellabaan
- Novo Nordisk Foundation Center for Biosustainability, Technical University of DenmarkHørsholm, Denmark
| | - Morten O A Sommer
- Novo Nordisk Foundation Center for Biosustainability, Technical University of DenmarkHørsholm, Denmark
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10
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Evaluation of Pharmacodynamic Interactions Between Telavancin and Aztreonam or Piperacillin/Tazobactam Against Pseudomonas aeruginosa, Escherichia coli and Methicillin-Resistant Staphylococcus aureus. Infect Dis Ther 2016; 5:367-77. [PMID: 27432414 PMCID: PMC5019977 DOI: 10.1007/s40121-016-0121-2] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Indexed: 11/16/2022] Open
Abstract
Introduction In clinical trials comparing telavancin (TLV) with vancomycin for treatment of hospital-acquired pneumonia, TLV demonstrated lower clinical cure rates than vancomycin in patients who had mixed gram-positive and -negative infections and were concomitantly treated with either aztreonam (ATM) or piperacillin/tazobactam (PTZ). Here, we investigated therapeutic interactions between TLV and ATM or PTZ in an in vitro pharmacokinetic/pharmacodynamic (PK/PD) model under simulated reduced renal function conditions. Methods In vitro one-compartment PK/PD models were run over 96 h simulating TLV 10 mg/kg every 48 h, ATM 500 mg every 8 h and PTZ continuous infusion 13.5 g over 24 h alone and in combination against P. aeruginosa, E. coli and methicillin-resistant S. aureus (MRSA). The efficacy of antimicrobials was evaluated by plotting time-kill curves and calculating the reduction in log10 cfu/ml over 96 h. Results Against both MRSA strains, TLV was rapidly bactericidal at 4 h and maintained its activity over 96 h with no observed antagonism by either ATM or PTZ. PTZ maintained bacteriostatic and bactericidal activities against E. coli ATCC 25922 and clinical strain R1022 at 96 h, whereas both strains regrew as soon as 24 h in ATM models. Against P. aeruginosa ATCC 27853, regrowth was noted at 24 h in models simulating ATM and PTZ. The addition of TLV to ATM or PTZ had no appreciable impact on activity against the two E. coli strains and P. aeruginosa strain. Conclusions The combinations of TLV and either ATM or PTZ did not demonstrate any antagonistic activity. Clinical variables and patient characteristics should be further explored to determine possible reasons for discrepancies in outcomes. Funding Theravance Biopharma Antibiotics, Inc.
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11
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The controlled in vitro susceptibility of gastrointestinal pathogens to the antibacterial effect of manuka honey. Eur J Clin Microbiol Infect Dis 2010; 30:569-74. [DOI: 10.1007/s10096-010-1121-x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2010] [Accepted: 11/13/2010] [Indexed: 01/22/2023]
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12
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Peitz I, van Leeuwen R. Single-cell bacteria growth monitoring by automated DEP-facilitated image analysis. LAB ON A CHIP 2010; 10:2944-51. [PMID: 20842296 DOI: 10.1039/c004691d] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Growth monitoring is the method of choice in many assays measuring the presence or properties of pathogens, e.g. in diagnostics and food quality. Established methods, relying on culturing large numbers of bacteria, are rather time-consuming, while in healthcare time often is crucial. Several new approaches have been published, mostly aiming at assaying growth or other properties of a small number of bacteria. However, no method so far readily achieves single-cell resolution with a convenient and easy to handle setup that offers the possibility for automation and high throughput. We demonstrate these benefits in this study by employing dielectrophoretic capturing of bacteria in microfluidic electrode structures, optical detection and automated bacteria identification and counting with image analysis algorithms. For a proof-of-principle experiment we chose an antibiotic susceptibility test with Escherichia coli and polymyxin B. Growth monitoring is demonstrated on single cells and the impact of the antibiotic on the growth rate is shown. The minimum inhibitory concentration as a standard diagnostic parameter is derived from a dose-response plot. This report is the basis for further integration of image analysis code into device control. Ultimately, an automated and parallelized setup may be created, using an optical microscanner and many of the electrode structures simultaneously. Sufficient data for a sound statistical evaluation and a confirmation of the initial findings can then be generated in a single experiment.
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Affiliation(s)
- Ingmar Peitz
- Philips Research Europe, High Tech Campus, Prof. Holstlaan 4, 5656AE, Eindhoven, The Netherlands.
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13
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Development and qualification of a pharmacodynamic model for the pronounced inoculum effect of ceftazidime against Pseudomonas aeruginosa. Antimicrob Agents Chemother 2008; 53:46-56. [PMID: 18852268 DOI: 10.1128/aac.00489-08] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Evidence is mounting in support of the inoculum effect (i.e., slow killing at large initial inocula [CFUo]) for numerous antimicrobials against a variety of pathogens. Our objectives were to (i) determine the impact of the CFUo of Pseudomonas aeruginosa on ceftazidime activity and (ii) to develop and validate a pharmacokinetic/pharmacodynamic (PKPD) mathematical model accommodating a range of CFUo. Time-kill experiments using ceftazidime at seven concentrations up to 128 mg/liter (MIC, 2 mg/liter) were performed in duplicate against P. aeruginosa PAO1 at five CFUo from 10(5) to 10(9) CFU/ml. Samples were collected over 24 h and fit by candidate models in NONMEM VI and S-ADAPT 1.55 (all data were comodeled). External model qualification integrated data from eight previously published studies. Ceftazidime displayed approximately 3 to 4 log(10) CFU/ml net killing at 10(6.2) CFUo and concentrations of 4 mg/liter (or higher), less than 1.6 log(10) CFU/ml killing at 10(7.3) CFUo, and no killing at 10(8.0) CFUo for concentrations up to 128 mg/liter. The proposed mechanism-based model successfully described the inoculum effect and the concentration-independent lag time of killing. The mean generation time was 28.3 min. The effect of an autolysin was assumed to inhibit successful replication. Ceftazidime concentrations of 0.294 mg/liter stimulated the autolysin effect by 50%. The model was predictive in the internal cross-validation and had excellent in silico predictive performance for published studies of P. aeruginosa ATCC 27853 for various CFUo. The proposed PKPD model successfully described and predicted the pronounced inoculum effect of ceftazidime in vitro and integrated data from eight literature studies to support translation from time-kill experiments to in vitro infection models.
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15
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Majchrzak M, Bowater RP, Staczek P, Parniewski P. SOS repair and DNA supercoiling influence the genetic stability of DNA triplet repeats in Escherichia coli. J Mol Biol 2006; 364:612-24. [PMID: 17028021 DOI: 10.1016/j.jmb.2006.08.093] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2006] [Revised: 08/25/2006] [Accepted: 08/31/2006] [Indexed: 01/27/2023]
Abstract
Molecular mechanisms responsible for the genetic instability of DNA trinucleotide sequences (TRS) account for at least 20 human hereditary disorders. Many aspects of DNA metabolism influence the frequency of length changes in such repeats. Herein, we demonstrate that expression of Escherichia coli SOS repair proteins dramatically decreases the genetic stability of long (CTG/CAG)n tracts contained in plasmids. Furthermore, the growth characteristics of the bacteria are affected by the (CTG/CAG)n tract, with the effect dependent on the length of the TRS. In an E. coli host strain with constitutive expression of the SOS regulon, the frequency of deletions to the repeat is substantially higher than that in a strain with no SOS response. Analyses of the topology of reporter plasmids isolated from the SOS+ and SOS- strains revealed higher levels of negative supercoiling in strains with the constitutively expressed SOS network. Hence, we used strains with mutations in topoisomerases to examine the effect of DNA topology upon the TRS instability. Higher levels of negative DNA supercoiling correlated with increased deletions in long (CTG/CAG)n, (CGG/CCG)n and (GAA/TTC)n. These observations suggest a link between the induction of bacterial SOS repair, changes in DNA topology and the mechanisms leading to genetic instability of repetitive DNA sequences.
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Affiliation(s)
- Marta Majchrzak
- Centre for Medical Biology, Polish Academy of Sciences, 106 Lodowa Street, 93-232 Lodz, Poland
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LaPlante KL, Rybak MJ. Impact of high-inoculum Staphylococcus aureus on the activities of nafcillin, vancomycin, linezolid, and daptomycin, alone and in combination with gentamicin, in an in vitro pharmacodynamic model. Antimicrob Agents Chemother 2005; 48:4665-72. [PMID: 15561842 PMCID: PMC529225 DOI: 10.1128/aac.48.12.4665-4672.2004] [Citation(s) in RCA: 232] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We evaluated the impact of high (9.5 log10 CFU/g) and moderate (5.5 log10 CFU/g) inocula of methicillin-susceptible and -resistant Staphylococcus aureus (MSSA and MRSA, respectively) on the activities of nafcillin, linezolid, vancomycin, and daptomycin, alone and in combination with gentamicin in an in vitro pharmacodynamic model with simulated endocardial vegetations over 72 h. Human therapeutic dosing regimens for nafcillin, daptomycin, vancomycin, linezolid, and gentamicin were simulated. At a moderate inoculum, nafcillin (MSSA only), vancomycin, and daptomycin demonstrated equivalent and significant (P < 0.01) bactericidal (99.9% kill) activities (decreases of 3.34 +/- 1.1, 3.28 +/- 0.4, and 3.34 +/- 0.8 log10 CFU/g, respectively). Bactericidal activity was demonstrated at 4 h for nafcillin and daptomycin and at 32 h for vancomycin. Linezolid demonstrated bacteriostatic activity over the course of the study period. At a high inoculum, daptomycin exhibited bactericidal activity against both MSSA and MRSA by 24 h (decrease of 5.51 to 6.31 +/- 0.10 log10 CFU/g). Nafcillin (versus MSSA), vancomycin, and linezolid (MSSA and MRSA) did not achieve bactericidal activity throughout the 72-h experiment. The addition of gentamicin increased the rate of 99.9% kill to 8 h for daptomycin (P < 0.01) and 48 h for nafcillin (MSSA only) (P = 0.01). The addition of gentamicin did not improve the activity of vancomycin or linezolid for either isolate for the 72-h period. Overall, high-inoculum Staphylococcus aureus had a significant impact on the activities of nafcillin and vancomycin. In contrast, daptomycin was affected minimally and linezolid was not affected by inoculum.
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Affiliation(s)
- Kerry L LaPlante
- Anti-Infective Research Laboratory, Eugene Applebaum College of Pharmacy & Health Sciences, Wayne State University, Detroit, Michigan 48201, USA
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17
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Bryskier A. Perfecting the ring and extending the antibacterial spectrum: 'the multiple generations'. Clin Microbiol Infect 2001; 6 Suppl 3:13-21. [PMID: 11449642 DOI: 10.1111/j.1469-0691.2000.tb02035.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- A Bryskier
- Clinical Pharmacology of Anti-infectives, Hoechst Marion Roussel, 102, route de Noisy, 93235 Romainville, France
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18
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Kohler J, Dorso KL, Young K, Hammond GG, Rosen H, Kropp H, Silver LL. In vitro activities of the potent, broad-spectrum carbapenem MK-0826 (L-749,345) against broad-spectrum beta-lactamase-and extended-spectrum beta-lactamase-producing Klebsiella pneumoniae and Escherichia coli clinical isolates. Antimicrob Agents Chemother 1999; 43:1170-6. [PMID: 10223931 PMCID: PMC89128 DOI: 10.1128/aac.43.5.1170] [Citation(s) in RCA: 60] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
An important mechanism of bacterial resistance to beta-lactam antibiotics is inactivation by beta-lactam-hydrolyzing enzymes (beta-lactamases). The evolution of the extended-spectrum beta-lactamases (ESBLs) is associated with extensive use of beta-lactam antibiotics, particularly cephalosporins, and is a serious threat to therapeutic efficacy. ESBLs and broad-spectrum beta-lactamases (BDSBLs) are plasmid-mediated class A enzymes produced by gram-negative pathogens, principally Escherichia coli and Klebsiella pneumoniae. MK-0826 was highly potent against all ESBL- and BDSBL-producing K. pneumoniae and E. coli clinical isolates tested (MIC range, 0.008 to 0.12 microgram/ml). In E. coli, this activity was associated with high-affinity binding to penicillin-binding proteins 2 and 3. When the inoculum level was increased 10-fold, increasing the amount of beta-lactamase present, the MK-0826 MIC range increased to 0.008 to 1 microgram/ml. By comparison, similar observations were made with meropenem while imipenem MICs were usually less affected. Not surprisingly, MIC increases with noncarbapenem beta-lactams were generally substantially greater, resulting in resistance in many cases. E. coli strains that produce chromosomal (Bush group 1) beta-lactamase served as controls. All three carbapenems were subject to an inoculum effect with the majority of the BDSBL- and ESBL-producers but not the Bush group 1 strains, implying some effect of the plasmid-borne enzymes on potency. Importantly, MK-0826 MICs remained at or below 1 microgram/ml under all test conditions.
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Affiliation(s)
- J Kohler
- Departments of Infectious Diseases, Merck Research Laboratories, Rahway, New Jersey 07065-0900, USA.
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19
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Kadima TA, Weiner JH. Mechanism of suppression of piperacillin resistance in enterobacteria by tazobactam. Antimicrob Agents Chemother 1997; 41:2177-83. [PMID: 9333044 PMCID: PMC164089 DOI: 10.1128/aac.41.10.2177] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Resistance to piperacillin in several isolates of Citrobacter freundii and Enterobacter cloacae was investigated and confirmed to occur at a frequency of 10(-7) to 10(-6). Development of resistance to piperacillin was significantly suppressed by tazobactam but not by clavulanic acid. To elucidate the mechanism by which resistance suppression occurs, the effect of piperacillin plus tazobactam on the induction of AmpC beta-lactamase was analyzed by monitoring the beta-galactosidase activity of an inducible ampC-lacZ gene fusion in Escherichia coli. The combination exerted no inhibitory effect on AmpC beta-lactamase induction. Tazobactam also had no effect on the accumulation of a key intermediate in the AmpC beta-lactamase induction pathway, 1,6-anhydromurotripeptide, in an ampD mutant strain of E. coli. However, the addition of tazobactam to liquid cultures of E. cloacae 40001 in the presence of piperacillin at four times the MIC caused a delay in the recovery of the culture to piperacillin-induced stress. At 16 times the MIC, a complete suppression of regrowth occurred. Analysis of culture viability on piperacillin plates showed that the culture recovery was due to growth by moderately resistant mutants preexisting in the cell population, which at 16 times the MIC became susceptible to the combination. Evidence from the kinetics of inhibition of the E. cloacae 40001 AmpC beta-lactamase by clavulanic acid, sulbactam, and tazobactam and from the effects of these drugs on the frequency of resistance to piperacillin suggests that the suppressive effect of tazobactam on the appearance of resistance is primarily mediated by the beta-lactamase inhibitory activity.
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Affiliation(s)
- T A Kadima
- Department of Biochemistry, University of Alberta, Edmonton, Canada
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20
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Annotated References. Expert Opin Investig Drugs 1994. [DOI: 10.1517/13543784.3.2.197] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
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21
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König C, Simmen HP, Blaser J. Effect of pathological changes of pH, pO2 and pCO2 on the activity of antimicrobial agents in vitro. Eur J Clin Microbiol Infect Dis 1993; 12:519-26. [PMID: 8404912 DOI: 10.1007/bf01970957] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Since standard susceptibility tests reflect the physiological rather than the pathological conditions prevailing within an infected abdomen, as recently documented, the effect of reduced pH and pO2 and increased pCO2 on the activity of antibiotics in vitro was studied. MICs were determined in vitro under standard culture conditions (MICstandard) and modified conditions (MICmodification) simulating the previously determined pathological values. Various classes of antibiotics were affected differently by the modified conditions. However, within an antibiotic class similar results were obtained for gram-negative and gram-positive pathogens. Median MICmodification/MICstandard ratios were 4 for aminoglycosides, 2 for quinolones and clindamycin, 1 for cephalosporins, and 0.5 for penicillins and vancomycin. Anaerobic conditions and a pH of 6.4 further increased the ratio of aminoglycosides to 8. Ratios were similar within an antibiotic class at inocula of 10(5) or 10(7) cfu/ml. All MICs determined in tests with imipenem against gram-negative and gram-positive bacteria and with vancomycin against gram-positive organisms were below the susceptibility breakpoint, whatever conditions and inocula were employed. In contrast, the percentage of MICs in susceptibility range using high inocula and modified conditions decreased to 78% for penicillins, 73% for cephalosporins, 22% for aminoglycosides, 11% for quinolones and 0% for clindamycin. In conclusion, routine susceptibility testing may overestimate the activity of aminoglycosides and underestimate the activity of beta-lactams under the conditions prevailing during abdominal infection.
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Affiliation(s)
- C König
- Department of Medicine, University Hospital, Zürich, Switzerland
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22
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Eng RH, Smith SM, Fan-Havard P, Ogbara T. Effect of antibiotics on endotoxin release from gram-negative bacteria. Diagn Microbiol Infect Dis 1993; 16:185-9. [PMID: 8477572 DOI: 10.1016/0732-8893(93)90109-k] [Citation(s) in RCA: 59] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
Antibiotics may inhibit bacterial growth or may kill bacteria by inhibiting cell wall synthesis or protein synthesis. The amount of endotoxin released during antibiotic action has been found to be clinically important. Nine antibiotics, representing seven classes, were studied for the amounts of endotoxin released during their action on susceptible strains of Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, and Pseudomonas aeruginosa. Staphylococcus aureus, which produces no endotoxin, was used as a control organism. Aztreonam induced the highest release of endotoxin, whereas other antibiotics such as imipenem and the quinolones induced the lowest release of endotoxin. Although the quantities of endotoxin released are not easily explained from the established mechanisms of antibiotic action, our findings may have implications for therapy of the acutely ill, septic patient in whom release of large quantities of endotoxin may be catastrophic.
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Affiliation(s)
- R H Eng
- Infectious Disease Section, Department of Veterans Affairs Medical Center, East Orange, NJ 07018-1095
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23
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Goldstein EJ, Citron DM, Cherubin CE. Comparison of the inoculum effect of cefoxitin and other cephalosporins and of beta-lactamase inhibitors and their penicillin-derived components on the Bacteroides fragilis group. Antimicrob Agents Chemother 1991; 35:1868-74. [PMID: 1952860 PMCID: PMC245283 DOI: 10.1128/aac.35.9.1868] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We compared the inoculum effects for 109 recent clinical isolates of the Bacteroides fragilis group of cefoxitin, cefotetan, ceftizoxime, ceftriaxone, and three beta-lactamase inhibitors (clavulanic acid, sulbactam, and tazobactam) and their penicillin-derived components. Bactericidal activity was assayed and morphologic changes were monitored for selected strains exhibiting a large inoculum effect. Ceftizoxime demonstrated the largest inoculum effect, followed by cefotetan and ceftriaxone. The large inoculum effect of ceftizoxime and ceftriaxone was correlated with filamentous transformation at the high inoculum (10(8) CFU/ml) and lack of bactericidal activity suggesting drug destruction or inactivation. Cefotetan was bactericidal for B. fragilis isolates but not for other members of the B. fragilis group. Cefoxitin showed the least inoculum effect and was consistently bactericidal at high (10(8) CFU/ml), standard (10(6) CFU/ml), and low (10(4) CFU/ml) inocula, followed by ampicillin-sulbactam. Piperacillin-tazobactam and ticarcillin-clavulanic acid showed an intermediate inoculum effect. The degree of inoculum effect observed generally correlated with bactericidal activity at all inocula.
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Affiliation(s)
- E J Goldstein
- R. M. Alden Research Laboratory, Santa Monica Hospital Medical Center, California 90404
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24
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Goldstein EJ, Citron DM, Cherubin CE. Comparison of the inoculum effects of members of the family Enterobacteriaceae on cefoxitin and other cephalosporins, beta-lactamase inhibitor combinations, and the penicillin-derived components of these combinations. Antimicrob Agents Chemother 1991; 35:560-6. [PMID: 2039208 PMCID: PMC245050 DOI: 10.1128/aac.35.3.560] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
We compared the inoculum effects of 105 recent clinical isolates of the family Enterobacteriaceae on cefoxitin, other cephalosporins, aztreonam, and three beta-lactamase inhibitors (clavulanic acid, sulbactam, and tazobactam) and their penicillin-derived components. Piperacillin and aztreonam showed the largest inoculum effect, and cefoxitin showed the smallest. The other cephalosporins tested (cefotetan, ceftizoxime, and ceftriaxone) showed an intermediate inoculum effect. In general, the inoculum effect was of greater magnitude for the penicillin and beta-lactamase inhibitor combinations than for the cephalosporins tested. Bactericidal activity was assayed and morphologic changes were monitored for selected strains exhibiting a large inoculum effect. MICs correlated with bactericidal activity at an inoculum level of 10(5) CFU/ml, while activity at 10(8) CFU/ml was variable. Cefoxitin demonstrated the least filamentous transformation and the most rapid bactericidal activity. Aztreonam showed the most marked filamentous transformation and was no longer bactericidal at 10(8) CFU/ml. The beta-lactamase inhibitor combinations showed variable bactericidal activity, and regrowth occurred with a number of strains with all three agents tested.
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Affiliation(s)
- E J Goldstein
- R. M. Alden Research Laboratory, Santa Monica Hospital Medical Center, California 90404
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25
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Smith SM. D-lactic acid production as a monitor of the effectiveness of antimicrobial agents. Antimicrob Agents Chemother 1991; 35:237-41. [PMID: 2024955 PMCID: PMC244984 DOI: 10.1128/aac.35.2.237] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Most bacteria at an infection site obtain energy by the breakdown of glucose via microaerophilic or anaerobic pathways and in the process yield various end products. In this study, production of D-lactic acid by Staphylococcus aureus and Escherichia coli was correlated with glucose utilization by bacteria during exposure to antibiotics at subinhibitory, inhibitory, and suprainhibitory concentrations. D-Lactic acid production was further correlated with production of a tissue-destroying enzyme, hyaluronidase, by S. aureus. For E. coli, all agents tested showed dose-related bacterial killing, with the most noticeable being with ampicillin, piperacillin, and ciprofloxacin. Imipenem, ciprofloxacin, and chloramphenicol had the most dose-related effects on D-lactic acid production. With few exceptions, hyaluronidase production correlated well with D-lactic acid production in S. aureus. Subinhibitory concentrations of erythromycin and clindamycin effectively decreased accumulation of D-lactic acid and hyaluronidase. Determination of D-lactic acid production may perhaps serve as a means of independently monitoring the effects of antimicrobial agents on bacterial metabolic activity, which is an important aspect of antimicrobial action that remains relatively unexplored.
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Affiliation(s)
- S M Smith
- Microbiology Section, Veterans Administration Medical Center, East Orange, New Jersey 07019
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26
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Soriano F, Santamaría M, Ponte C, Castilla C, Fernández-Roblas R. In vivo significance of the inoculum effect of antibiotics on Escherichia coli. Eur J Clin Microbiol Infect Dis 1988; 7:410-2. [PMID: 3137046 DOI: 10.1007/bf01962350] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The minimum dosage of antibiotics which reduced mortality in rats intraperitoneally inoculated with an Escherichia coli isolate was determined. Low mortality rates (0-10%) were obtained when antibiotics with minimal or no inoculum effect (cefoxitin, cefmetazole and gentamicin) were administered to yield serum levels 3 to 20 times the MIC, while antibiotics with a pronounced inoculum effect (cefotaxime and aztreonam) had to be administered to yield serum levels 200 to 1,000 times the MIC determined with a standard (low) inoculum. Thus, it seems that the inoculum effect observed in vitro with some antibiotics for Escherichia coli may have clinical significance.
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Affiliation(s)
- F Soriano
- Department of Clinical Microbiology, Fundación Jiménez Diaz, Madrid, Spain
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27
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Satta G, Cornaglia G, Foddis G, Pompei R. Evaluation of ceftriaxone and other antibiotics against Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pneumoniae under in vitro conditions simulating those of serious infections. Antimicrob Agents Chemother 1988; 32:552-60. [PMID: 3132095 PMCID: PMC172219 DOI: 10.1128/aac.32.4.552] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
In pursuit of an in vitro system capable of reliably predicting the activities of antibiotics in serious infections and in infections occurring in immunocompromised hosts, we evaluated the abilities of four drugs to achieve virtually complete killing of bacterial cells growing in human body fluids in amounts which are very high and close to those likely to be present in serious infections; drug concentrations varied with time as they vary in human bronchial secretions or blood or urine (dynamic concentrations). The rationale for such a test was (i) to set up in vitro conditions as close as possible to those the antibiotics encounter in serious infections and (ii) to hold the drugs capable of almost completely killing the bacteria used in the assay to be highly active in vitro and likely to be the most efficacious in the treatment of serious infections. Among the antibiotics used, ceftriaxone proved to be highly active under conditions simulating pulmonary infections and septicemias caused by Streptococcus pneumoniae (bacteria grown in bronchoalveolar fluid or blood; antibiotic concentrations varying with time as in human bronchial secretions or blood) and under conditions simulating blood and urinary infections caused by Escherichia coli (bacteria grown in human blood or urine; antibiotic concentrations varying as in the various fluids). Gentamicin (not tested against pneumococci) appeared to be highly active only under conditions simulating urinary infections caused by E. coli; aztreonam (not tested against pneumococci) and ampicillin (tested only against pneumococci) did not appear to be highly active under any of the test conditions. Only the combination of gentamicin plus either ceftriaxone or aztreonam appeared to be highly active under conditions simulating serious septicemias and urinary infections caused by Psudomonas aeruginosa.
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Affiliation(s)
- G Satta
- Istituto di Microbiologia, Università degli Studi di Siena, Italy
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28
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Amsterdam D. Instrumentation for antimicrobic susceptibility testing: yesterday, today, and tomorrow. Diagn Microbiol Infect Dis 1988; 9:167-78. [PMID: 3293893 DOI: 10.1016/0732-8893(88)90026-0] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Affiliation(s)
- D Amsterdam
- Department of Microbiology, School of Medicine, State University of New York, Buffalo
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29
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Prosser BL, Taylor D, Dix BA, Cleeland R. Method of evaluating effects of antibiotics on bacterial biofilm. Antimicrob Agents Chemother 1987; 31:1502-6. [PMID: 3435100 PMCID: PMC174979 DOI: 10.1128/aac.31.10.1502] [Citation(s) in RCA: 136] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Antibiotics are generally not effective against organisms in exopolysaccharide biofilms. A simple method of studying the effect of antibiotics on bacteria in established biofilms is reported. Escherichia coli ATCC 25922 cells grown overnight at 37 degrees C on Mueller-Hinton agar were suspended in buffer and dispensed on 0.5-cm2 catheter disks. The disks were incubated for 1 h at 37 degrees C, washed, transferred to petri dishes containing 20 ml of broth, and incubated at 37 degrees C for 20 to 22 h, at which time thick biofilms were established. Disks were washed, placed in broth or broth containing antibiotic, and incubated at 37 degrees C for 4 h. The disks were removed, and viable counts were determined. This process was repeated at other selected time intervals (e.g., 8 and 24 h). Viable bacterial counts decreased from 10(3) to 10(4) CFU/cm2 in 24 h with 400 micrograms of amdinocillin or cefamandole per ml. A combination containing 400 micrograms of each antibiotic per ml decreased the viable counts to an undetectable level (less than 100 CFU/cm2) in 24 h. Other antibiotics and organisms were also examined in this system.
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Affiliation(s)
- B L Prosser
- Department of Chemotherapy, Hoffmann-La Roche Inc., Nutley, New Jersey 07110
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30
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Moody JA, Fasching CE, Peterson LR, Gerding DN. Ceftazidime and amikacin alone and in combination against Pseudomonas aeruginosa and Enterobacteriaceae. Diagn Microbiol Infect Dis 1987; 6:59-67. [PMID: 3100127 DOI: 10.1016/0732-8893(87)90115-5] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
The efficacy of ceftazidime alone and combined with amikacin was studied in a rabbit model simulating closed-space infections at locally neutropenic sites. Six strains of Pseudomonas aeruginosa, and six Enterobacteriaceae (two strains each of Klebsiella pneumoniae and Serratia marcescens and one strain each of Escherichia coli and Citrobacter freundii) in pooled rabbit serum were each inoculated into separate subcutaneous semipermeable chambers. Intramuscular antibiotic therapy was begun 4 hr later with ceftazidime (50 mg/kg) alone and combined with amikacin (15 mg/kg) for Enterobacteriaceae or ceftazidime (100 mg/kg) alone and combined with amikacin (15 mg/kg) for pseudomonads every 6 hr for 16 doses. Amikacin alone was ineffective for all 12 strains. Ceftazidime alone was successful (greater than or equal to 5.5 log10 colony forming units (CFU)/ml decrease from drug-free control) in eliminating five of six Enterobacteriaceae but was not successful against any of the pseudomonads. Ceftazidime plus amikacin was successful against the same five of six Enterobacteriaceae and five of six pseudomonads. The best in vitro tests for the prediction of in vivo outcome were high inoculum (greater than or equal to 7 log10 CFU/ml) susceptibility, checkerboard synergism testing, and conventional inoculum time-kill rates at concentrations of antimicrobials simulating extravascular levels obtained in vivo.
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31
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Pohlod DJ, Saravolatz LD, Somerville MM. In vitro susceptibility of gram-positive cocci to paldimycin. Antimicrob Agents Chemother 1987; 31:104-7. [PMID: 3105438 PMCID: PMC174662 DOI: 10.1128/aac.31.1.104] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Paldimycin (U-70138F) is a new antimicrobial agent with activity against gram-positive cocci. Clinical isolates of staphylococci and streptococci were tested. MICs were higher in Mueller-Hinton broth than in nutrient broth. Change in pH had minimal effect on the MICs in either broth. When inoculum size was varied, an inoculum effect was observed. The gram-positive cocci tested were generally more susceptible to paldimycin than to vancomycin.
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