Prof. Trinad Chakraborty, Justus Liebig University Giessen; Dr Linda Falgenhauer, Justus Liebig University Giessen; Dr Konrad Gwozdzinski, Justus Liebig University Giessen; Dr Can Imirzalioglu, Justus Liebig University Giessen
In vitro evaluation of colistin susceptibility is fraught with complications, due in part to the inherent cationic properties of colistin. Methods routinely used to determine colistin susceptibility (disk diffusion method, epsilometer test strips) are not reliable (high rate of false-susceptibility), while the dilution methods considered as the reference technique are tedious and time-consuming. The detection of colistin-resistant bacteria, in particular those encoding plasmid-borne colistin resistance genes like mcr-1, is problematic, because they often depict very low minimum inhibitory concentration (MIC) values towards colistin.
The invention provides a method for 1. improved detection and 2. simplified colistin susceptibility testing of polymyxin-resistant gram-negative bacteria in particular of the genus Enterobacteriaceae. The advantage of our devised invention is that it enables colistin-resistance testing in well-adapted agar-diffusion-based formats.
The invention may be used in two different areas: clinical and veterinary microbiology as well as in food processing diagnostics and analysis. The area of clinical microbiology recorded a turnover of about 750 million US $ in 2016 in Western Europe. At a moderate annual average growth rate of 2.8%, the market research institute Frost & Sullivan predicts growth of its market volume to US $ 863.8 million by 2021 in this sub-segment. The market segment of food diagnostics and analysis reached a level of US $ 2.6 billion in 2012 . For the period from 2012 to 2017, Frost & Sullivan calculated an annual growth of 17.5%.
Both parts of the invention (improved detection and simplified susceptibility testing) have been tested with pure cultures of clinical Enterobacteriaceae isolates (sensitive and resistant). In addition, rectal swabs from patients have been tested on the plates to detect colistin-resistant Enterobacteriaceae.
A European patent (EP) application has been made of 1st of June 2017. The EP application covers 38 countries of geographical Europe. The search report from the EPO confirms both its novelty and inventive step.
Liu, Y.-Y., Wang, Y., Walsh, T. R., Yi, L.-X., Zhang, R., Spencer, J., et al. (2016). Emergence of plasmid-mediated colistin resistance mechanism MCR-1 in animals and human beings in China: a microbiological and molecular biological study. Lancet Infect. Dis. 16, 161–168. doi:10.1016/S1473-3099(15)00424-7.
Falgenhauer, L., Waezsada, S.-E., Yao, Y., Imirzalioglu, C., Kasbohrer, A., Roesler, U., Michael, G.B.G.B., Schwarz, S., Werner, G., Kreienbrock, L., Chakraborty, T., Käsbohrer, A., Roesler, U., Michael, G.B.G.B., Schwarz, S., Werner, G., Kreienbrock, L., Chakraborty, T., 2016. Colistin resistance gene mcr-1 in extended-spectrum β-lactamase-producing and carbapenemase-producing Gram-negative bacteria in Germany. Lancet Infect. Dis. 16, 282–283. doi:10.1016/S1473-3099(16)00009-8.
Gwozdzinski, K., Azarderakhsh, S., Imirzalioglu, C., Falgenhauer, L., Chakraborty, T., 2018. An improved medium for colistin susceptibility testing. J Clin Microbiol. 56,e01950-17. doi:10.1128/JCM.01950-17.