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Time-kill curve analysis and pharmacodynamic modelling for in vitro evaluation of antimicrobials against Neisseria gonorrhoeae
Institute of Social and Preventive Medicine (ISPM), University of Bern, Bern, Switzerland; Institute for Infectious Diseases, University of Bern, Bern, Switzerland; WHO Collaborating Centre for Gonorrhoea and other STIs, National Reference Laboratory for Pathogenic Neisseria, Faculty of Medicine and Health, Örebro University, Örebro, Sweden; Graduate School for Cellular and Biomedical Sciences, University of Bern, Bern, Switzerland.
Örebro University, School of Health Sciences. WHO Collaborating Centre for Gonorrhoea and other STIs, National Reference Laboratory for Pathogenic Neisseria.
Institute for Infectious Diseases, University of Bern, Bern, Switzerland.
Institute of Social and Preventive Medicine (ISPM), University of Bern, Bern, Switzerland.
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2016 (English)In: BMC Microbiology, ISSN 1471-2180, E-ISSN 1471-2180, Vol. 16, 216Article in journal (Refereed) Published
Abstract [en]

Background: Gonorrhoea is a sexually transmitted infection caused by the Gram-negative bacterium Neisseria gonorrhoeae. Resistance to first-line empirical monotherapy has emerged, so robust methods are needed to evaluate the activity of existing and novel antimicrobials against the bacterium. Pharmacodynamic models describing the relationship between the concentration of antimicrobials and the minimum growth rate of the bacteria provide more detailed information than the MIC only.

Results: In this study, a novel standardised in vitro time-kill curve assay was developed. The assay was validated using five World Health Organization N. gonorrhoeae reference strains and a range of ciprofloxacin concentrations below and above the MIC. Then the activity of nine antimicrobials with different target mechanisms was examined against a highly antimicrobial susceptible clinical strain isolated in 1964. The experimental time-kill curves were analysed and quantified with a previously established pharmacodynamic model. First, the bacterial growth rates at each antimicrobial concentration were estimated with linear regression. Second, we fitted the model to the growth rates, resulting in four parameters that describe the pharmacodynamic properties of each antimicrobial. A gradual decrease of bactericidal effects from ciprofloxacin to spectinomycin and gentamicin was found. The beta-lactams ceftriaxone, cefixime and benzylpenicillin showed bactericidal and time-dependent properties. Chloramphenicol and tetracycline were purely bacteriostatic as they fully inhibited the growth but did not kill the bacteria. We also tested ciprofloxacin resistant strains and found higher pharmacodynamic MICs (zMIC) in the resistant strains and attenuated bactericidal effects at concentrations above the zMIC.

Conclusions: N. gonorrhoeae time-kill curve experiments analysed with a pharmacodynamic model have potential for in vitro evaluation of new and existing antimicrobials. The pharmacodynamic parameters based on a wide range of concentrations below and above the MIC provide information that could support improving future dosing strategies to treat gonorrhoea.

Place, publisher, year, edition, pages
London, United Kingdom: BioMed Central, 2016. Vol. 16, 216
Keyword [en]
Neisseria gonorrhoeae, Gonorrhoea, Antimicrobial resistance, Time-kill curves, Pharmacodynamics
National Category
Infectious Medicine Microbiology
Identifiers
URN: urn:nbn:se:oru:diva-52414DOI: 10.1186/s12866-016-0838-9ISI: 000383425700001PubMedID: 27639378ScopusID: 2-s2.0-84988372926OAI: oai:DiVA.org:oru-52414DiVA: diva2:972634
Note

Funding Agencies:

SystemsX.ch (Swiss Initiative for Systems Biology)

Swiss Platforms for Translational Medicine initiative, SwissTransMed 25/2013

Available from: 2016-09-21 Created: 2016-09-20 Last updated: 2016-10-11Bibliographically approved

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