The Variable Response of Bacteria to Free Haemoglobin in the Tissues

Abstract

SUMMARY. The local enhancement of infection by exogenous ferric iron, as ferric ammonium citrate, and by ferrous iron as guinea-pig haemoglobin, was assessed in studies with 55 strains of bacteria injected into the skin of guinea-pigs. The test organisms included Staphylococcus aureus, Streptococcus spp., Klebsiella spp., Escherichia coli and Pseudornonas aeruginosa. Four strains of Bacteroides spp. were tested with haemoglobin only. As previously reported with other strains, enhancement of infection by members of a given species by ferric iron was variable; in this study infection with only 1 1 of 59 strains was enhanced. Haemoglobin either of equal or lesser iron content was a more potent enhancer, affecting 27 of the 59 strains. The enhancement ranged from two-fold to 80-fold, the higher figures on the whole being characteristic of haemoglobin enhancement. Some few instances of depression by both haemoglobin and ferric ammonium citrate were noted. A few tests were made with systemic haemoglobin but the concentrations attainable were largely ineffective. Enhancement of infection did not appear to be related to the capacity of a strain to lyse or digest host red blood cells.In so far as guinea-pigs, whose antibacterial defences are lowered by ferric or ferrous iron, represent human subjects at risk of infection because of clinical circumstances characterised by excess of available iron-either exogenous or as a result of haemolysis-our results with organisms of a kind commonly associated with infection in hospitals suggest that only a small proportion of environmental bacteria can take advantage of any decreased resistance associated with iron excess.

The Antagonism of Tetracycline and Ferric Iron in Vivo

“…The iron enhancement of S. aureus strain MI was great but the response lines were so shallow and far apart that a numerical estimate of enhancement was impossible. As explained fully by Maskell and Miles (1984), this type of enhancement is indicated by + symbols; the + + results in table I1 indicate a very strong enhancement. Fig.…”

Effect of hemoglobin and of ferric ammonium citrate on the virulence of periodontopathic bacteria

“…However, bacteria differ widely in their abilities in this respeet (26,36), and in particular in their abilities to obtain iron from specific host-iron-binding or hostiron-containing proteins (7,13,20,32,36). Thus, the virulence of some bacteria has been shown to be enhanced by the addition of the iron-containing protein hemoglobin, while the virulence of other bacteria is unaffected (3,9,II,14,18,20,34).…”