Open AccessDifferent plasmids coding for heat stable enterotoxins in porcine Escherichia coli strains of O‐group 149
Author(s) -
Franklin A.,
Möllby R.
Publication year - 1981
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1981.tb06984.x
Subject(s) - escherichia coli , plasmid , heat stable enterotoxin , enterotoxin , microbiology and biotechnology , escherichia coli proteins , biology , chemistry , genetics , gene
Several reports have been published demonstrating linkage between the genes encoding production of heat-stable enterotoxin (ST) and coliein B (ColB) (Franklin et al., in prep.) or between ST and different colonisation factors [10,11]. The method generally used to assay ST was the infant mouse test [2,4]. In porcine Escherichia coli strains producing both heat stable and heat labile (LT) enterotoxins, these toxins on the basis of tests in ligated pig intestines, were considered to be encoded for by a single plasmid [5]. However, recently it has been shown, that the LT and ST enterotoxins were encoded by different plasmids in both human [11] and porcine LT+ST + strains (Franklin et al., in prep.). These conclusions were also based on the reliability of the infant mouse test for detection of ST. Lately, Burgess and co-workers [1], Olsson and Stderlind [9] reported that porcine LT + strains, which are negative regarding ST production in the infant mouse assay frequently are positive when investigated in pig intestinal loops. They concluded that the infant mouse assay could not be totally relied upon with regard to demonstration of ST production. Burgess and coworkers suggested that there are two kinds of ST, STa and STb. STa was active in the intestine of neonatal piglets and in infant mice, while STb was active only in the intestine of weaned pigs. Another view was put forward by Gyles [6], who suggested that one form of ST (ST 1) reacted both in infant mice and in the intestine of weaned pigs, while another form of ST (ST 2) was active in the intestine of weaned pigs only. The aim of the present study was to investigate whether the different ST patterns, exhibited by enterotoxigenic porcine E. coli strains, might be explained by the presence of different genetic determinants coding for ST production. Therefore, the plasmids presumed to be coding for ~ST production were transferred into E. coli K-12 strains, and the phenotypical expression of the ST genes contained in E. coli K-12 was studied by means of the infant mouse test and the pig intestinal loop assay.