Validation of a Hollow Fibre Infection model for in vitro dynamic evaluation of antimicrobial efficacy against veterinary pathogens

Supervisors: Dr Ludovic Pelligand (lpelligand@rvc.ac.uk), Prof. Andrew Rycroft (RVC), Dr. Joseph Standing (UCL), Dr. John Mitchell (Veterinary Medicines Directorate).

 Antimicrobial resistance is a global concern that interests human and animal health. Therapeutic success is likely if susceptible bacteria are exposed to doses of antimicrobial drug (AMD) that translate in vivo into sufficiently high plasma concentrations that are sustained for a sufficient time.  For dose optimisation, three key components are required: (1) the pharmacokinetics in the target host, (2) the range of susceptibility of bacteria encountered in the field (Minimal Inhibitory Concentration MIC), (3) the relationship between AMD concentrations, the MIC value and the antimicrobial effect (PK/PD index).  While points (1) and (2) are well known, the optimal PK/PD indices in veterinary species are mainly unknown.  Until now, the PK/PD indices were either extrapolated from other species (mouse infection models) or from in vitro bacterial-kill assays that only expose a known bacterial inoculum to fixed concentrations of AMD.  The latter have been superseded by Hollow Fibre Infection Models (HFIM) (Cadwell J. 2012) that have recently received regulatory approval to support therapeutic innovations in the treatment of tuberculosis in people.  This in vitro system mimics real-time changes in concentration without loss of bacteria from the culture and allows mathematical modelling of pharmacodynamics with changing concentrations (Nielsen and Friberg, 2013).   The aim of this project is to validate the HFIM for dynamic evaluation of antimicrobial efficacy against veterinary pathogens, taking the example of tetracyclines.  Tetracyclines represent the highest tonnage of veterinary AMD sold in the UK but the mechanisms of their antimicrobial activity are yet to be completely understood.

We have 4 objectives:

1) First, we will measure the MICs for tetracycline, oxytetracycline and doxycycline against bovine veterinary pathogens (Pasteurella multocida or Manheimia haemolytica) in both optimised culture media (Mueller Hinton Broth type) and serum.

2) The second step is the pharmacokinetic validation (HPLC measurement) to reproduce the average bovine plasma concentration-time course of a chosen tetracycline in the HFIM using perfusion with a matrix with low protein content (MHB) and with a biological matrix rich in protein (serum).

3) Thirdly, we will inoculate and enumerate at different time points bacteria in MHB and serum, both without antibiotic and with a concentration-time profile that reproduces the average free (MHB) or total (serum) plasma concentration in the average bovine.

4)   In the fourth step, we will attempt mathematical modelling to describe the rate of growth/kill in response to changing perfusing concentrations of AMD.  

The outcome of this study is to demonstrate that the HFIM can address crucial questions in the field of veterinary therapeutics, while reducing animal use. The student will be supported by a multidisciplinary team including clinical pharmacology, mathematical modelling and medical microbiology experts. The student will interact with researchers from the Royal Veterinary College (the largest small animal referral service in Europe) and the London Pharmacometrics Interest Group. We will build-up proficiency within the team to apply for a collaborative PhD research programme grant. The results of this research will be highly relevant to veterinary practitioners and microbiologists, pharmacologists in academia or industry, as well as policy makers.  

Funding - This is a funded MRes Scholarship that covers the full UK/EU tuition fee, plus a stipend and research expenses.

Eligibility - Candidates should have an undergraduate degree in microbiology (or a related subject) with a classification of 2.1 (or above) or be a veterinary or medical graduate with a background clinical microbiology or mathematical modelling.  The studentships are full-time for 12 months commencing on 3rd October 2016 with a 2 day compulsory induction.  

Travel – the candidate will be based in the Hawkshead campus (Hatfield) but may have travel to central London (Camden campus) occasionally

Who Can Apply - these studentships are open to Home/EU students only

How to Apply - information on how to apply can be found here

Contacts: About the project - lpelligand@rvc.ac.uk. About the application process - researchdegrees@rvc.ac.uk

Deadline - the deadline for applications is Sunday 14th August 2016.  The date for the interview is 22nd August 2016.  

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