Heavy Metal Susceptibility on Escherichia coli from Urine Samples from Sweden, Germany and Spain [PublishAheadOfPrint]

Antimicrobial resistance is a major health care problem, with the intensive use of heavy metals and biocides recently being identified as potential contributing factors to the aggravation of this situation. This study investigated heavy metal susceptibility and genetic resistance determinants in Escherichia coli isolated from clinical urine samples from Sweden, Germany and Spain. A total of 186 isolates were tested for minimal inhibition concentration to sodium arsenite, silver nitrate and copper (II) sulphate. In addition, 88 of these isolates were whole genome sequenced for the characterization of their genetic resistance determinants and epidemiology. For sodium arsenite, the isolates could be categorized into a resistant and a non-resistant group, based on MIC values: isolates of the resistant group exhibited the chromosomal ars operon and belonged to non-B2 phylogenetic groups; in contrast, within the B2 phylogroup, no ars operon was found and the isolates were susceptible to sodium arsenite. Two isolates also harbored the silver/copper resistance determinant pco/sil and belonged to sequence types ST10 (phylogroup A) and ST295 (phylogroup C). The ST295 isolate had a silver nitrate MIC ≥ 512 mg/L and additionally produced extended spectrum beta-lactamases. To our knowledge, this is the first study that describes the distribution of the arsenic resistance operon ars within phylogroups of E. coli isolated from patients with urinary tract infections. The arsenic operon ars was only present in all non-B2 clades, which have previously been associated with the environment and commensalism in both humans and animals, while B2-clades lacked the ars operon.

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