Since March 2015, we have been using the VITEK System (BioMérieux); this is an automated system which can be used to rapidly identify bacterial organisms. Antimicrobial susceptibility testing can also be carried out using this equipment and provides quantitative results (minimum inhibitory concentrations (MIC) of the antibiotics for the organisms tested), as opposed to the qualitative results obtained with the disc diffusion system (resistant vs. susceptible).
Infections caused by multi-drug resistant (MDR) organisms are emerging as a significant problem in veterinary medicine, with clinicians faced with treating infections caused by agents such as methicillin-resistant Staphylococcus aureus, methicillin-resistant Staphylococcus pseudintermedius and MDR Gram-negative organisms. Because the VITEK system tests up to 20 antimicrobials at the same time, this system is invaluable when the veterinarian is dealing with infections caused by MDR organisms. No unnecessary delays are incurred arising from the laboratory having to carry out further disk diffusion testing when a resistant result is determined for all 6 antimicrobial compounds used in the first test, as happens under the current testing system. A further advantage of this system arises when prescribing under the ‘cascade’ system is required; the clinician can combine the MIC data provided by the VITEK system with pharmacokinetic data (available on the package insert or from a textbook) to accurately calculate the dosage required. This optimizes both the efficacy and the cost-effectiveness of treatments for these highly problematic infections.
Advantages of the VITEK System:
- It is current international best standard
- Results available approximately 24 hours earlier than when using standard biochemical tests for identification and disc diffusion for antibiotic susceptibility testing
- The availability of MIC data allows the clinician, when appropriate, to combine this data with pharmacokinetic data (available on the package insert or from a textbook) and thus calculate antimicrobial dosage more accurately. This results in dosage regimens that are more efficacious and ultimately more cost effective than simply utilising the labelled doses
- The use of appropriate antibiotics at effective dose levels helps reduce antimicrobial resistance
- The data generated enhances the quality of research papers requiring such results
- Adoption of this automated test system has resulted in faster turnaround and more consistent results
- Please see the VITEK Information Guide for information on how to interpret the reports generated using the VITEK system. This document also gives tables detailing intrinsic resistance of common bacterial pathogens and MIC cut-offs for selected veterinary pathogens