Fig. 4
blaCTX-M genes present on large chromosomal insertions in E. coli. a Zam_UTH_18. This E. coli ST3580 strain possessed blaCTX-M-15 on an 11,383 bp chromosomal insertion, which was very similar to plasmid pF609 (GenBank accession no. MK965545.1). blaCTX-M-15 was closely associated with ISEcp1, which was located 255 bp upstream. The insertion also harbored the quinolone resistance gene qnrS1, located 4639 bp downstream of blaCTX-M-15. The phenotypic AMR profile of this strain showed resistance to ampicillin and susceptibility to quinolones. b Zam_UTH_42. This E. coli ST648 strain harbored blaCTX-M-15 on a 14,328 bp chromosomal insertion that was very similar to plasmid p13ARS_MMH0112-2 (GenBank accession no. LR697123.1). This insertion carried genes associated with resistance to aminoglycosides (aac(3)-IIa), aminoglycosides/quinolones (aac(6′)-Ib-cr5), β-lactams (blaOXA-1, blaTEM-1), and chloramphenicol (catB3). ISEcp1 was located 255 bp upstream of blaCTX-M-15, however, unlike in other strains, ISEcp1 in this strain was truncated by IS1 and transposase. The phenotypic AMR profile of this strain was consistent with the AMR genotype for the insertion. Zam_UTH_47 (not shown) also had a similar genetic context for its insertion. F4, F5, F6, F7, R4, R5, R6, R7; primers used for confirmation of insertions. White; susceptible. Black; resistance phenotype in the absence of corresponding AMR gene. Red; β-lactam resistance. Brown; chloramphenicol resistance. Green; aminoglycoside and/or quinolone resistance