Identification of Antibiotic Resistance Genes

The presence of sulfonamide resistance genes sul1, sul2 and sul3 and the most commonly found trimethoprim resistance genes dfrA1, dfrA5, dfrA7, dfrA12 and dfrA17 was investigated in the SMX/TRI-resistant bacteria by PCR as described [34 (link),38 (link)] using either QIAGEN HotStarTaq Mastermix (QIAGEN GmbH, Hilden, Germany) (sul1 and sul2), KAPA HiFi HotStart PCR Kit (KAPA Biosystems, Boston, USA) (sul3), Dream Taq Green PCR Mastermix (2x) (ThermoFisher Scientific, Waltham, USA) (dfrA1), or Kappa 2G Robust PCR kit (KAPA Biosystems, Boston Massachusetts, USA) (dfrA5, dfrA7, dfrA12 and dfrA17). The presence of integrase genes intI1, intI2 and intI3 was queried for by PCR and the variable region of class 1 integron characterised by PCR and Sanger sequencing as described elsewhere [39 (link)]. The diversity of promoters associated with detected class 1 integrons were characterised by Sanger sequencing as already described [40 (link),41 (link)]. The sequenced sections of the class I integrons were deposited at GenBank under accession numbers MK093863 –MK093896.