BACTERIOSTASIS OF A MILK-SENSITIVE STRAIN OF ESCHERICHIA-COLI BY IMMUNOGLOBULINS AND IRON-BINDING PROTEINS IN ASSOCIATION

  • 1 January 1978
    • journal article
    • research article
    • Vol. 35  (4) , 663-671
Abstract
The growth of a milk-sensitive strain of E. coli in 1% peptone water can be inhibited for at least 3 h by Ig[immunoglobulin]A isolated from human milk or IgG1 from bovine colostrum acting with native Fe-binding proteins from milk or serum. The Ig alone are inactive; the native Fe binding proteins alone are sometimes partially active. All this activity is inconsistent and not always enhanced by the addition of bicarbonate ions. The growth of E. coli in human milk inactivated by heating at 100.degree. is consistently inhibited by IgA or IgG1 acting with native Fe-binding proteins. The Ig are inactive alone but the Fe-binding proteins have considerably more activity when added alone to inactivated milk than to peptone water, suggesting that the growth medium is contributing to or stabilizing the activity. The addition of bicarbonate ions is without effect. Attempted absorption of antibody with suspensions of E. coli and replacement of bacteriostatic activity by addition of purified milk proteins did not suggest any participants in the bacteriostasis of milk-sensitive strains other than antibody and Fe-binding protein. Bacteriostasis is abolished by saturating the transferrins with Fe. The Fe-free apo-derivatives are not more inhibitory than the native proteins except for human apo-lactotransferrin in peptone water which inhibits growth completely. This latter inhibition is not attributable to the low pH and 10-100 times more Fe is needed to abolish this activity than is needed to abolish that of bovine apo-lactotransferrin.