Assessment of in vitro colistin susceptibility of carbapenem-resistant clinical Gram-negative bacterial isolates using four commercially available systems & Whole-genome sequencing: A diagnostic accuracy study

Abstract

AimTo analyze the diagnostic utility of commercially available platforms and Whole-genome sequencing (WGS) for accurate determination of colistin susceptibility test results. Material & methodsAn exploratory diagnostic accuracy study was conducted in which sixty carbapenem-resistant Gram-negative bacteria were subjected to identification and AST using MALDI-TOF MS & MicroScan walkaway 96 Plus. Additional AST was performed using the BD Phoenix system and Mikrolatest colistin kit. The test isolates were subjected to Vitek-2 and WGS at CRL, Bengaluru. ResultsThere was no statistically significant agreement between the colistin susceptibility results obtained by WGS, with those of commercial phenotypic platforms. The MicroScan 96 Plus had the highest sensitivity (31 %) & NPV (77 %), and the BD Phoenix system had the highest specificity (97 %) and PPV (50 %), respectively, for determining colistin resistance. ConclusionThe utility of WGS as a tool in AMR surveillance and validation of phenotypic AST methods should be explored further.