@article{mbs:/content/journal/jmm/10.1099/00222615-31-4-241, author = "Woodward, M. J. and Wray, C. and Ridha, G. A. and Walton, J. R.", title = "Plasmid and chromosomal related toxin polymorphism of Escherichia coli serogroup O138; plasmid transfer and co-integration with pRP4", journal= "Journal of Medical Microbiology", year = "1990", volume = "31", number = "4", pages = "241-249", doi = "https://doi.org/10.1099/00222615-31-4-241", url = "https://www.microbiologyresearch.org/content/journal/jmm/10.1099/00222615-31-4-241", publisher = "Microbiology Society", issn = "1473-5644", type = "Journal Article", abstract = " Summary. DNA-DNA hybridisation was used to examine 89 isolates of Escherichia coli serogroup O138 for toxin gene content and location. Sixty-six isolates encoded toxin genes; 29 were STpa STpb VT2, 24 were VT2, four were STpa STpb, three wereSTpb VT2, three were STpb VT2 LT and one was STpa. None were K88-, K99- or F41-positive. The VT toxin gene was chromosomally located in all VT+ isolates tested whereas STpa, STpb and LT were plasmid borne. In co-transfer experiments with pRP4 as the mobilising plasmid, VT2 genes were not transferred to recipient E. coli K12 whereas STpa, STpb and LT genes were. Two VT2-positive isolates inhibited pRP4 transfer to K12 by a factor of 106 and rare transconjugants harboured a cointegrate plasmid comprising pRP4 (54kb) and a cryptic host plasmid (145 kb). In a K12 background, the co-integrate had transfer and incompatibility properties of pRP4 whereas in both progenitor E. coli O138 backgrounds the co-integrate was transfer inhibited and in one case resolved to give original plasmids.", }