Genomic Analysis of an I1 Plasmid Hosting a sul3 -Class 1 Integron and bla SHV-12 within an Unusual Escherichia coli ST297 from Urban Wildlife.

Wild birds, particularly silver gulls ( Chroicocephalus novaehollandiae ) that nest near anthropogenic sites, often harbour bacteria resistant to multiple antibiotics, including those considered of clinical importance. Here, we describe the whole genome sequence of Escherichia coli isolate CE1867 from a silver gull chick sampled in 2012 that hosted an I1 pST25 plasmid with bla SHV-12, a β-lactamase gene that encodes the ability to hydrolyze oxyimino β-lactams, and other antibiotic resistance genes. Isolate CE1867 is an ST297 isolate, a phylogroup B1 lineage, and clustered with a large ST297 O130:H11 clade, which carry Shiga toxin genes. The I1 plasmid belongs to plasmid sequence type 25 and is notable for its carriage of an atypical sul3- class 1 integron with mefB ∆260 , a structure most frequently reported in Australia from swine. This integron is a typical example of a Tn 21 -derived element that captured sul3 in place of the standard sul1 structure. Interestingly, the mercury resistance ( mer ) module of Tn 21 is missing and has been replaced with Tn 2 - bla TEM-1 and a bla SHV-12 encoding module flanked by direct copies of IS 26 . Comparisons to similar plasmids, however, demonstrate a closely related family of ARG-carrying plasmids that all host variants of the sul3 -associated integron with conserved Tn 21 insertion points and a variable presence of both mer and mefB truncations, but predominantly mefB ∆260 .