Interplay between pathogenicity island carriage, resistance profile and plasmid acquisition in uropathogenic Escherichia coli

This study aimed to characterize the relationship between pathogenicity islands (PAIs), single virulence genes and resistance among uropathogenic Escherichia coli, evaluating the resistance plasmid carriage fitness cost related to PAIs. For 65 urinary E. coli, antimicrobial susceptibility and extended-spectrum beta-lactamase production were determined with the Vitek 2 Advanced Expert system. Phylogroup determination, detection of PAIs and virulence genes papAH, papC, sfa/foc, afa/dra, iutA, kpsMII, cnf1, eaeA, hlyA, stx1 and stx2, plasmid replicon typing and screening for plasmidic resistance determinants gnr, aac(6')-lb-cr, gepA and bla(CTX-M) were carried out by PCR. Conjugation was performed between a donor carrying IncF, IncK and bla(CTX-M-15), and receptors carrying one to six PAIs. The relative fitness of transconjugants was estimated by pairwise competition experiments. PAI IV536 (68%), gene iutA (57 %) and resistance to ampicillin were the most prevalent traits. PAI I-536, PAI II536, PAI III536 and PAI IIJ96 were exclusively associated with susceptibility to amoxicillin/clavulanic acid, cefotaxime, ceftazidime, ciprofloxacin, gentamicin and trimethoprim/sulfamethoxazole, and were more prevalent in strains susceptible to ampicillin and cefalotin. PAI IV536, PAI IICFT073 and PAI I-CFT073 were more prevalent among isolates showing resistance to amoxicillin/clavulanic acid, cefalotin, cefotaxime, ceftazidime and gentamicin. An inverse relationship was observed between the number of plasmids and the number of PAIs carried. Transconjugants were obtained for receptors carrying three or fewer PAls. The mean relative fitness rates of these transconjugants were 0.87 (two PAIs), 1.00 (one PAI) and 1.09 (three PAI). The interplay between resistance, PAI carriage and fitness cost of plasmid acquisition could be considered PAI specific, and not necessarily associated with the number of PAIs.