Chromosomal DNA, iron-transport systems, outer membrane proteins, and enterotoxin (heat labile) production in Salmonella typhi strains

Abstract

We examined a representative collection of Salmonella typhi strains from Chile, Peru, Mexico, India, and England for the presence of several properties. Ail strains had a conserved pattern of outer membrane proteins, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The electrophoresis profiles of chromosomal DNA digested with EcoRI and PstI restriction enzymes were similar for all the strains. A conserved pattern of hybridization was observed when digested chromosomal DNA was hybridized with DNA probes for the 36-kilodalton porin, enterobactin synthesis, and enterobactin receptor genes. AUl the strains produced enterobactin but not aerobactin in bioassays. None of the strains produced heat-labile toxin, as measured by an enzyme-linked immunosorbent assay. Colony and Southern hybridizations with DNA probes for aerobactin synthesis and its receptor and heat-labile toxin genes were negative. These results indicate that S. typhi strains from different origins have similar phenotypic and genetic properties and, as has been suggested, constitute a clone.

Further consideration of the clonal nature of Salmonella typhi: evaluation of molecular and clinical characteristics of strains from Indonesia and Peru

“…Comment. In previous studies we and other investigators have found that S. typhi strains from different geographic areas are virtually identical, compatible with the concept that S. typhi strains are clonal in origin (4,17,20,23,25). Faundez et al (4) found minimal differences among strains from Chile, Peru, Mexico, India, and England by using chromosomal restriction digests, Southern blot analysis (with probes to the 36-kDa porin, enterobactin synthesis, and enterobactin receptor genes), and outer membrane protein profiles.…”

“…While it is reasonable to hypothesize that variations in clinical presentation are related to strain differences, previous studies have suggested that with few exceptions S. typhi represents a single clone that has shown minimal intraspecies divergence in its spread to different parts of the world (4,17,20,23,25). The present study was designed to look more closely at this issue by using strains from Peru (an area with relatively mild disease) and Indonesia (an area in which disease manifestations may be quite severe).…”

Restricted growth of ent− and tonB mutants of Salmonella enterica serovar Typhi in human Mono Mac 6 monocytic cells

“…Iron is an essential nutrient for both eukaryotic and prokaryotic cells and plays a central role in electron transport chains involved in intermediary metabolism [1,2]. Because its reactivity under aerobic conditions can generate toxic free radicals, strict control of iron uptake and localization is a necessity.…”

“…Because its reactivity under aerobic conditions can generate toxic free radicals, strict control of iron uptake and localization is a necessity. Within mammals for example, levels of free iron are estimated to be less than 10 315 mM because intracellular iron is complexed with heme, Fe^S proteins and ferritin, and extracellular iron is complexed with transferrin in the plasma or with lactoferrin at mucosal surfaces and in exocrine secretions [1,2].…”

“…From the periplasm, Fe 3 siderophores are transported across the cell membrane into the cytoplasm by ATP binding cassette-type transport systems [1]. All S. enterica serovar Typhi appear to express enterochelin-mediated iron transport [2]. It is not known whether serovar Typhi expresses an additional but less well-characterized iron uptake system that involves the recently described Sit iron transporter system encoded in the serovar Typhimurium pathogenicity island 1 [7,8].…”