Poster Presentation BacPath 13: Molecular Analysis of Bacterial Pathogens Conference 2015

pCERC3: A virulence-resistance plasmid from a commensal Escherichia coli (#163)

Robert A. Moran 1 , Sashindran Anantham 1 , Ruth M. Hall 1
  1. The University of Sydney, Darlington, NSW, Australia

Escherichia coli 22.1-R1 is an ST95 commensal strain isolated from a healthy Australian adult and is the first Australian isolate in which the sulphonamide resistance gene sul3 was detected. It was known to contain several virulence determinants: K1 capsule, papC, and four siderophore receptors – aerobactin, salmochelin, yersiniabactin and ireA. 22.1-R1 also contains blaTEM (ampicillin resistance) in Tn2, cmlA1 (chloramphenicol), aadA1 and 2 (streptomycin and spectinomycin), tetA(B) (tetracycline), dfrA12 (trimethoprim) and a class 1 integron (intI1).

The genome of 22.1-R1 was sequenced using Illumina HiSeq. All resistance determinants were found in a 28.5kb resistance region on a 144,344bp RepFII RepFIB plasmid, pCERC3. The plasmid carries genes for colicin V production and the backbone is closely related to other ColV plasmids. pCERC3 also carries several virulence-associated determinants. These include genes for three siderophore systems (aerobactin, salmochelin and sit), increased serum survival (iss), a haemolysin (hlyF), an outer membrane protease (ompT) and a putative type 1 secretion system (ets).  A complete transfer region is present on pCERC3 but the plasmid is not conjugative as a copy of IS1 interrupts the gene for TraJ, which positively regulates a transfer operon.

The genome sequences of 48 other antibiotic resistant commensal E. coli strains were searched to determine whether they contained colicin V genes or the virulence determinants present on pCERC3. All or part of the ColV operon was detected in 8 strains known to harbour FII and FIB plasmid replicons and most pCERC3 virulence determinants were detected in these strains. The iss, hlyF, ompT and ets genes were detected only in colicin V-containing strains. Salmochelin was also strongly associated with the ColV operon. Aerobactin (29/48 isolates) and sit (35/48) were common. Strains that contain the ColV operon are being investigated for plasmids related to ColV plasmids including pCERC3.