The added value of the selective SuperPolymyxin™ medium in detecting rectal carriage of Gram-negative bacteria with acquired colistin resistance in intensive care unit patients receiving selective digestive decontamination

Abstract

The objective of this study was to determine the value of using SuperPolymyxin™ selective medium (ELITech Group, Puteaux, France) in addition to conventional non-selective inoculation methods in the detection of acquired colistin resistance in a Dutch intensive care unit (ICU) that routinely uses selective decontamination of the digestive tract (SDD). We performed a cross-sectional study with prospective data collection in a tertiary-care ICU. All consecutive surveillance rectal swabs of ICU-patients receiving SDD were included and cultured in an observer-blinded approach using (1) a conventional culture method using non-selective media and (2) SuperPolymyxin™ selective medium. MIC values for colistin of non-intrinsically colistin-resistant Gram-negative isolates were determined with broth microdilution (BMD) using Sensititre™ and colistin resistance was confirmed using BMD according to EUCAST guidelines. One thousand one hundred five rectal swabs of 428 unique ICU-patients were inoculated using both culture methods, yielding 346 and 84 Gram-negative isolates for BMD testing with the conventional method and SuperPolymyxin™ medium, of which 308 and 80 underwent BMD, respectively. The number of identified rectal carriers of isolates with acquired colistin resistance was 3 (0.7%) for the conventional method, 4 (0.9%) for SuperPolymyxin™, and 5 (1.2%) for both methods combined. The number of isolates with acquired colistin resistance was 4 (1.0%) for the conventional method, 8 (2.1%) for SuperPolymyxin™ and 9 (2.3%) for both methods combined. In a surveillance setting of low prevalence of acquired colistin resistance in patients that receive SDD in a Dutch tertiary-care ICU, SuperPolymyxin™ had a higher diagnostic yield than conventional inoculation methods, but the combination of both had the highest diagnostic yield.

A prospective matched case-control study on the genomic epidemiology of colistin-resistant Enterobacterales from Dutch patients

“…This study provides important insights into the epidemiology of colistin resistance in the Netherlands. Most previous studies examining colistin resistance in humans in the Netherlands focused on the mcr-1 gene 43 – 45 , specific patient populations 46 – 51 or travellers 52 – 54 . Similar to the current study, a higher percentage of colistin resistance caused by chromosomal mutations compared to mcr genes was also found by Bourrel et al 55 , who screened patients in six Parisian hospitals for rectal carriage of colistin-resistant E. coli .…”

The Use of CHROMID® Colistin R for the Detection of Colistin-Resistant Gram-Negative Bacteria in Positive Blood Cultures

“…A variety of methods have been developed for rapid determination of colistin susceptibility, and these were recently reviewed by Leshaba et al [ 19 ]. Several agar-based methods are available, including CHROMagar™ Col-APSE [ 20 ], SuperPolymyxin [ 21 ] and CHROMID ® Colistin R [ 17 ], but few methods have been applied to direct testing of positive blood cultures. Malli et al applied the Rapid Polymyxin™ NP test, which is a 2–3 h test based on the acidification of glucose in the presence of polymyxin, to the detection of colistin-resistant Enterobacterales directly from positive blood cultures [ 22 ].…”

Genomic Epidemiology of Colistin-resistant Enterobacterales from Dutch Patients: A Prospective Matched Case-control Study

“…Most previous studies examining colistin resistance in humans in the Netherlands focused on the mcr-1 gene, [23][24][25] specific patient populations [26][27][28][29][30][31] or travelers. [32][33][34] Similar to the current study, a higher percentage of colistin resistance caused by chromosomal mutations compared to mcr genes was also found by Bourrel et al, 35 who screened patients in six Parisian hospitals for rectal carriage of colistinresistant E. coli.…”