Attachment of bacteria is a critical step in the pathogenesis of many infections, particularly in cases where the pathogen is confined to mucosal surfaces. Cytotoxins, siderophores, heme oxygenase (HmuO), and cell surface lipoproteins are regulated by both iron and DtxR protein ( 18, 20- 22).Įpidemic or invasive clones, as well as the atypical sucrose-fermenting biotype, of diphtheria bacilli seem to possess some selective advantage, such as increased virulence or an enhanced ability to colonize and spread ( 14). Corynebacterium diphtheriae is able to overcome host conditions, in part by producing siderophores or other iron uptake mechanisms that allow it to express virulence factors such as toxins and enzymes. During infection, the restriction of iron is stronger because the host response to the invading bacteria includes hypoferremia ( 4). Iron is essential for bacterial growth, but its availability in the human body is very limited because it is almost entirely complexed with metalloproteins or glycoproteins ( 3, 24). The examination of environmental signals controlling virulence is an essential step in comprehension of the underlying strategies that microbes have adopted to become successful pathogenic organisms ( 15). diphtheriae, the present results imply regulation of adherence and slime production as part of a global response to iron-limited environmental conditions that includes derepression of genes for the synthesis of cytotoxin and siderophores and for transport of the Fe(III)-siderophore complexes. The expression of dissimilar microbial virulence determinants may be coordinately controlled by common regulatory systems. The significant changes in the degree of lectin binding specific for d-mannose, d-galactose and sialic acid residues may have an effect on binding of host cells. diphtheriae surface carbohydrate moieties. Thus, iron exerts a regulatory role on adhesive properties of diphtheria bacilli, and low iron availability modulates the expression of C. ![]() Lectin binding assays demonstrated a reduction in the number of sialic acid residues and an increase in d-mannose and d-galactose residues on the surfaces of both strains. Conversely, iron limitation inhibited adherence to glass and expression of electron-dense material on the bacterial surface. Inhibition assays suggested the involvement of nonfimbrial protein combination 67-72p on hemagglutination of diphtheria bacilli grown under iron-limited conditions. Iron-limited conditions enhanced interaction of strain 241 with erythrocytes and HEp-2 cells. The effects of iron concentration on adhesive properties were different for strains 241 and CDC-E8392, of the sucrose-fermenting and non-sucrose-fermenting biotypes, respectively. A comparison was made between bacteria grown in (i) Trypticase soy broth (TSB), (ii) TSB treated with dipyridyl to deplete free iron, and (iii) TSB enriched with FeCl 3. ![]() ![]() mitis and evaluated their adherence to human group B erythrocytes and HEp-2 cells. The present study investigated the influence of low iron availability on the expression of proteins and surface sugar residues of two toxigenic strains of Corynebacterium diphtheriae subsp. Iron limitation may cause bacterial pathogens to grow more slowly however, it may also stimulate these microorganisms to produce greater tissue damage, given that many virulence factors are controlled by the iron supply in the environment.
0 Comments
Leave a Reply. |