Plasmid and chromosomal related toxin polymorphism of Escherichia coli serogroup O 138; plasmid transfer and co-integration with pRP4.
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 were STpb VT2, three were STpb VT2LT 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 10(6) and rare transconjugants harboured a co-integrate 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.
Woodward
M J
MJ
Department of Bacteriology, MAFF Central Veterinary Laboratory, New Haw, Weybridge, Surrey.
Wray
C
C
Ridha
G A
GA
Walton
J R
JR
D000818:Animals; D001427:Bacterial Toxins / Q000235:genetics*; D004269:DNA, Bacterial / Q000235:genetics; D004926:Escherichia coli / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D005798:Genes, Bacterial; D009693:Nucleic Acid Hybridization; D010957:Plasmids / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics*; D013552:Swine; D014162:Transfection
D001427:Bacterial Toxins; D004269:DNA, Bacterial