Rapid Automated Bacterial Impedance Technique - RABIT

RABIT has been developed by Don Whitley Scientific over several years with the aid of leading product and computer design consultants. As part of company philosophy RABIT will be subject to continual development ensuring utilisation of latest technology and compatibility with emerging applications. Impedance microbiology is now a well established rapid method for both quantitative and qualitative studies with bacteria, yeasts and moulds. Unlike the standard plate methods which only measure microbial activity at a single point in time, RABIT monitors real time activity and thereby produces two significant benefits. Results are determined in a significantly shorter time frame compared to conventional microbiology. Information not normally produced using standard methodology is made available thereby improving our understanding of microbial activity in the test system.

The basic RABIT system consists of a PC, additional data logging board, standard QWERTY keyboard, mouse, high resolution colour monitor, laser printer and an incubator module. Up to 32 re-usable cells can be incubated in a single module and the system can be expanded up to a total of 16 modules to give a capacity of 512 individual tests. This enables laboratory staff to start with a relatively low cost system and expand it as their workload increases.

 

RABIT is a registered trademark of Don Whitley Scientific Limited

The RABIT system has been used in some interesting studies, the links to which are given below.

An indirect conductimetric screening method for the detection of antibiotic residues in bovine kidneys

Anna-Liisa Myllyniemi,*a Hannu Sipilä,a Lasse Nuotio,a Anneli Niemib and Tuula Honkanen-Buzalskia

a Department of Bacteriology, National Veterinary and Food Research Institute, P. O. Box 45 (Hämeentie 57), FIN-00581 Helsinki, Finland. E-mail: anna-liisa.myllyniemi@eela.fi

b Department of Chemistry, National Veterinary and Food Research Institute, P. O. Box 45 (Hämeentie 57), FIN-00581 Helsinki, FinlandReceived 1st May 2002, Accepted 27th June 2002

First published as an Advance Article on the web 2nd August 2002

An indirect conductimetric screening method using three test bacterium–medium combinations was developed for rapid detection of antibiotic residues in bovine carcasses. The detection time (DT), i.e. the point when the growth of the test bacterium was detected, was determined by observing the rate of change in the conductance plotted against time. This detection time averaged half of the reference time recorded by the instrument software. Total change in conductance (TC) was used as a further measure of growth. Threshold values for DT and TC were determined with inhibitor-free kidney samples. The presence of a residue was indicated if the DT exceeded the respective threshold value and was confirmed if the TC remained below the TC threshold value. The limits of detection (LODs) determined with fortified samples were at about or below the MRLs for cephalexin, chlortetracycline, ciprofloxacin, dihydrostreptomycin, enrofloxacin, oxytetracycline and penicillin G. The LODs for penicillin G, oxytetracycline and the sum of enrofloxacin and ciprofloxacin were also estimated with incurred samples; these samples were also analysed using liquid chromatography. The LODs determined with fortified and incurred samples were in close agreement. Given its rapid detection, good sensitivity to a wide range of antibiotics and ease of performance, the indirect conductimetric method developed here would seem to offer an appealing alternative to agar diffusion tests.

To read the full article please follow this link http://dx.doi.org/10.1039/b204175h