Multiple High-affinity Iron-uptake Systems of Vibrio vulnificus

Vibrio vulnificus is a Gram-negative halophilic bacterium that causes necrotizing wound infections and fatal septicemia, which mainly occur in patients with elevated serum or tissue iron levels. Accumulated experimental data clearly show that V. vulnificus is a ferrophilic bacterium that requires more available iron for growth than other pathogenic bacteria, has multiple iron-uptake systems, which play important roles in the pathogenesis of the V. vulnificus infections. This review summarized the composition, regulation and significance of V. vulnificus iron-uptake systems. These iron-uptake systems may be attractive candidates for the development of V. vulnificus vaccine. Iron-chelating therapy can also be a promising modality for the prevention and treatment of V. vulnificus infections.

Activity of Iron-uptake System of Staphy lococcus aureus According to the Isolation Sites / 감염

OBJECTIVE: We tried to investigate the activity of iron-uptake system (IUS) of Stap hylococcus aureus according to the isolation sites and thus the relatedness between IUS and virulence. METHODS: Seventy clinical isolates were classified into the isolates from patients (56), from doctors and nurses (7) and from hospital environments (7). The isolates from patients (56) were sub-classified into the isolates from hospitalized patients (40; HP) and from outpatients (16; OP). Siderophore activity was measured CAS agar diffusion assay and transferrin-binding protein (tbp) was detected by receptor-ligand binding assay. RESULTS: There was no difference of siderophore production among the isolates from patients, doctors and nurses, and hospital environments (P>0.05). However, the isolates from patients expressed more tbp than the isolates from doctors and nurses and hospital environments (P<0.05). The isolates from OP produced more siderophore and expressed more tbp than the isolates from HP (P<0.05). CONCLUSION: These results suggested that Staphylococcus aureus with more active IUS is more virulent and more easily causes infection even in patients with relatively good general condition.

Effect of Iron-Uptake System on the Growth of Staphylococcus aureus according to the Iron Concentration and Oxygen Tension / 감염

BACKGROUND: We previously reported that activity of iron-uptake systems (IUS) influenced on the growth of Staphylococcus aureus in body fluids which are relatively iron-restrictive conditions. Iron and oxygen are closely related each other in several microbial metabolism. In the present study, we tried to investigate the effect of IUS on the growth of S. aureus according to the iron concentration and oxygen tension. METHODS: SR-1 strain, whose IUS are defective, was isolated from the standard strain, ATCC 6538. These two strains were cultured under the aerobic, microaerobic and anaerobic condition in the iron-sufficient BHI and iron-depleted BHI, respectively. Bacterial growth was measured by optical density. RESULTS: Growth of both strains was inhibited in the iron-depleted BHI. Growth of parental strain was more active in the iron-sufficient BHI as well as in the ion-depleted BHI than that of SR-1 strain. Growth of both strains was more active under the aerobic condition than under the microaerobic or anaerobic condition. In the iron-depleted BHI, parental strain showed a striking difference of growth according to the oxygen tension. In the iron-depleted BHI, growth of SR-1 strain was markedly inhibited regardless of oxygen tension. CONCLUSION: IUS influenced more on the growth of S. aureus in the iron-depleted environments than in the iron-sufficient environments, and under the aerobic condition than under the microaerobic or anaerobic condition in the iron-depleted environments. These results indicated the possibility that oxygen as well as iron regulate activity and expression of IUS.

Cell Wall Proteins of Staphylococcus aureus Responsive to Oxygen Tension and Iron Concentration / 감염

BACKGROUND: We previously reported that activity of iron-uptake systems (IUS) influenced on the growth of Staphylococcus aureus in laboratory medium and body fluids according to the iron and oxygen concentrations, which they are closely related each other in several microbial metabolism. In the present study, we tried to investigate the profiles of cell wall proteins of S. aureus according to the change of iron and oxygen concentrations. METHODS: SR-1 strain, whose IUS are defective, was isolated from the standard strain ATCC 6538 by repeated exposure against streptonigrin. These two strains were cultured under the aerobic, microaerobic and anaerobic conditions in the iron-sufficient BHI and iron-depleted BHI, respectively. Cell wall proteins were visualized by Coomassie staining after SDS-PAGE. RESULTS: Cell wall proteins of the both strains were expressed more than under the aerobic condition than under the anaerobic condition in the iron-sufficient medium as well as in the iron-deficient medium. However, expression of cell wall proteins of SR-1 strain was markedly inhibited compared to that of parental ATCC 6538 strain, especially in the iron-deficient medium. Among the proteins more expressed under the aerobic culture condition in the iron-deficient medium, about 88, 55, 39, 36, 35 and 33 kDa of proteins were iron-repressible and oxygen-inducible, and corresponded to the iron-repressible proteins which other researchers reported. CONCLUSION: Expression of cell wall proteins of S. aureus was affected by simultaneous and respective change of iron and oxygen concentrations. Activity of IUS influenced more on the expression of cell wall proteins of S. aureus in the iron-deficient environment than in the iron-sufficient environment. These results suggest the possibility that the iron-repressible and oxygen-inducible proteins mimic those (antigens) found commonly in clinical infections.