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

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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

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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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no drug

drug

S. marcescens E. coli

BCG

SLIC Vs. The Market

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SLIC microscan Pheonix Vitek 2 BacT/ALERT BACTEC VersaTREK

Min

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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