Rapid Phenotypic susceptibility testing of bacteria:
SLIC by name and Slick by nature
Robert J. H. Hammond, John A. Kennedy, Stephen H. Gillespie
■ What problem are we trying to solve ■ Evolution of SLIC ■ Functioning of SLIC ■ Comparison with the market ■ The future
Overview
■ Antibiotic resistance is a pressing problem ■ It is caused by excessive or inappropriate
antibiotic use
The Problem
■ Iden%fy the infec%ng organism – Diagnosis
■ Suscep%bility tes%ng treatment and response monitoring –Op%mise treatment
■ Iden%fy clustered organisms over-‐represented in the community-‐ Infec%on Control
What does microbiology do?
■ The speed of progression of infection is much faster than the time taken to generate results (we are too slow)
■ They do not understand the implications of the data (microbiology is complex – orthopaedic consultants will not know the significance of S. oralis vs S. intermedius)
Why do clinicians not use microbiology results?
Taken from a laboratory manual
The Problem
■ The capacity to detect small quantities of bacteria in relatively massive volumes of liquid
■ Specifically the minimum possible detection time for both slow and rapidly growing organisms
– Spectrophotometry – Flow cytometry – Nephelometry
Courtesy of National Academies Press – http://www.nap.edu/openbook.php? record_id=12658&page=212
Our solution
■ Modify existing technologies – improve them – Coulter counter – Flow cytometery
– Spectrophotometry + nephelometry!
SLIC Prototype development 1. Modelling foam
2. 3D print
3.1. 3D print, internals modified 3.2
4.0
■ What is it?
■ The rapid and inexpensive ability to generate information about particles in a liquid non-invasively
Scattered Light Integrating Collector
Laser scattering technology
Laser scattering technology
Schematic representation of how the integrating sphere collects the total scattering output.
Classic Scattering SLIC Scattering
SLIC sensitivity
1
10
100
1.00E+01 1.00E+02 1.00E+03 1.00E+04 1.00E+05 1.00E+06 1.00E+07 1.00E+08 1.00E+09 1.00E+10
mV
Dilution factor
CFU = 2.6 x 108
26 cells
2.6 (~3) cells
SLIC can detect concentrations of cells down to ~10 cells/ml, the abrupt drop in signal is indication that the limit of detection has been reached.
SLIC Vs. Spectrophotometer
Limit of detection for two common laboratory techniques versus SLIC. SLIC measurements compare favourably with CFU and far outmatch spectrophotometry
1.00E+00
1.00E+01
1.00E+02
1.00E+03
1.00E+04
1.00E+05
1.00E+06
Lim
it of
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SLIC
CFU
Spectrophotometry
Susceptibility studies
TTP data for two rapidly dividing bacterial species and one slowly dividing species. Error bars represent one standard deviation from the mean. n=9.
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Time [mins]
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Time [h]
no drug
drug
S. marcescens E. coli
BCG
SLIC Vs. The Market
30 30 30
1200
720 540 570
978
2400
600
1218
1890
942 900
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Bac
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SLIC microscan Pheonix Vitek 2 BacT/ALERT BACTEC VersaTREK
Min
utes
Comparison of SLIC to other commercial products currently on the market for establishing bacterial number.
SLIC Vs. The Market: Costs
Manufacturer Equipment Picture Eqpt. Cost ($US)
Sample cost ($US)
Becton Dickinson
BACTEC MGIT
20-40k 50-200
Dade Behring Microscan 20k 5-15 bioMérieux Vitek Two 100-120k Not known bioMérieux BacT/ALERT
3D >20k >100
Becton Dickinson
Phoenix >20k Not known
TREK diagnostic
VersaTREK 20k 100
Orbital Diagnostics
SLIC 500 upwards <5
Future plans- SLIC
■ Ready for prototype development – Internal coating to be silver leaf and diffuse paint – Miniaturised and automated – Banks of SLICs – Multiple studies – High throughput
■ Field testing of working prototype in planning
■ Fluorescence-based technology ■ Designed to detect tiny red/green signals
■ Nascent design, needs work
Alternate versions
Acknowledgements
• Richard Baggaley (SAIL) • Ewan Chirnside (St
Andrews KT office) • Katarina Oravcova • Han Xiao • Vincent Baron
• Innovative Medicines Initiative Joint Undertaking under grant agreement No. 115337
• European Union’s Seventh Framework Programme (FP7/2007-2013)
• EFPIA • IMI: www.imi.europa.eu