Detection of Pathogens and Ampicillin-resistance Genes Using Multiplex Padlock Probes

Diagnostic assays for pathogen identification and characterization are limited either by the number of simultaneously detectable targets, which rely on multiplexing methods, or by time constraints due to cultivation-based techniques. We recently presented a 100-plex method for human pathogen characterization to identify 75 bacterial and fungal species as well as 33 clinically relevant β-lactamases ( Barišić et al., 2016 ). By using 16S rRNA gene sequences as barcode elements in the padlock probes, and two different fluorescence channels for species and antibiotic resistance identification, we managed to cut the number of microarray probes needed by half. Consequently, we present here the protocol of an assay with a runtime of approx. 8 h and a detection limit of 10⁵ cfu ml^-1. A total of 89% of β-lactamases and 93.7% of species were identified correctly.