Detection of Colistin-resistant Isolates From Patients of Intensive Care Units and Oncohaematology Wards.

Overview

The increasing use of colistin in multidrug resistant strains, as Enterobacteriaceae producing extended-spectrum β-lactamases or carbapenemases, is associated with the emergence of colistin resistant isolates. The main objective of this project is to estimate the diagnostic accuracy (sensitivity and specificity) of a new rapid detection test of colistin resistant strains (Rapid Polymyxin NP test) isolated in clinical settings.

For 15 years, the prevalence of the extended-spectrum β-lactamases producing Enterobacteriaceae (ESBLE), resistant to the 3rd generation cephalosporins, has constantly increased worldwide. Since 2010 an additional threat appeared with the emergence of the bacteria resistant to carbapenems, the antibiotic of choice in case of infection due to ESBLE. To treat the infection due to these extremely resistant strains, there are still only few molecules, as the colistin. Very quickly, the colistin resistance appeared, especially a plasmid-born resistance described in December 2015 and which has already spread a lot, most probably from an animal reservoir. The control of the resistance dissemination requires reliable tools for detection of colistin resistant isolates, in particular in immunocompromised patients, as those of intensive care unit (ICU) or oncohaematology ward, that are often exposed to multidrug resistant strains. Currently, the colistin resistance is difficult to detect and that is probably why it was underestimated for a long time and has already diffuse worldwide. Some recent tests for the detection of colistin resistant isolates have been developed and tested in laboratory. They have now to be evaluated in clinical situation in order to be correctly used and interpreted. From rectal swabs of patients admitted in ICU and oncohaematology ward, investigators will use first a new culture medium (SuperPolymyxin) for screening the colistin resistant Gram negative bacteria and then a new rapid test (Rapid Polymyxin NP test) to confirm this resistance. These tests will be compared to the reference test of MIC (Minimal Inhibitory Concentration) determined by the broth micro-dilution (BMD) method. The isolates will be collected on the screening medium, during 12 months, from 4 centers (Mont de Marsan, Limoges, Dax, Bordeaux) and sent to Bordeaux University Hospital where the rapid test and the BMD method will be centralized.

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