A Study of the Relationship of the Normal Bactericidal Activity of Human Serum to Bacterial Infection*

Abstract

The potent heat-labile bactericidal property of fresh mammalian defibrinated blood or serum in vitro has been known since the studies of Nuttall (1) and Buchner (2) over 70 years ago. By 1928, it had been shown that serum components very like those of complement were necessary for this action (3). Although a number of investigators in the fields of bacteriology and immunology have interested themselves in this bactericidal power of fresh serum, little notice has been taken of it in clinical medicine, probably, as noted elsewhere (4), because it has been believed to be of doubtful effect in vivo.Interest has been revived in the bactericidal activity of serum by the work of Pillemer, Wardlaw and associates (5, 6). They described a normally occurring serum protein of large molecular weight which they named properdin. They attributed the bactericidal property of serum, in part at least, to the presence of properdin, which acted with the four components of complement in the presence of magnesium to kill the bacteria.The findings of Wardlaw and Pillemer (6) confirmed those of Mackie and Finkelstein (7) that the bacterial strains sensitive to the effect of serum are principally from species of gram-negative bacilli and that the degree of sensitivity is a characteristic of the strain rather than of the genus. However, whereas Wardlaw and Pillemer have described the action of the properdin system as being nonspecific and unrelated to antibody, Mackie and Finkelstein presented data showing that the absorption of a serum in the cold by a sensitive strain resulted in the removal of the killing effect only for that strain, leaving the effect

Genetical Studies of Serum Resistance in Escherichia coli

“…Serum-resistant strains are encountered, however, and may be frequently isolated from a wide range of infections in man (Roantree & Rantz, 1960;Fierer, Finley & Braude, 1972). Although the mechanism of resistance to the serum bactericidal system has yet to be fully defined, it has been suggested that certain surface structures are able to protect the bacterial cell.…”

Tetracyclines and Host-Defense Mechanisms

“…The heat-labile opsonins and the bactericidal activity present in normal human sera have both been suggested to be mediated through the recently described alternative pathway of C3 complement activation (17), bypassing the antibody-Cl classical way of activation (8,12). The bactericidal action of normal serum is an important part in host defense (1,2,19,20). Strains of Escherichia coli associated with pathological conditions have been shown to be invariably resistant to the bactericidal effect of serum (16).…”

The Bactericidal Action of Human Serum on Bacteroides Species

“…Five of these 23 sera failed to inhibit the clinical isolate of B. thetaiotaomicron, but all 60 sera inhibited B. vulgatus and B. ovatus at relatively low serum concentrations. Other investigations have also demonstrated bactericidal activity in normal serum against facultative gram-negative pathogens isolated from local infections but not from bacteraemic or septicaemic patients (Roantree and Rantz, 1960;Vosti and Randall, 1970;Young and Armstrong, 1972). The strains of B. thetaiotaomicron, B. vulgatus and B. ovatus that we studied were isolated from localised infections, post-surgical sepsis and an infected malignant ulcer and the B. fragilis was from a blood culture.…”