Thesis

Staphlococcal alpha toxin: an investigation into the rapid, lethal effect

An increased interest has been shown in the exotoxins of the bacterium Staphylococcus aureus and their relationship to disease since 1872 when Klebs, speaking of staphylococcal infections, suggested that these organisms produce disease by means of diffusible substances which he termed "sepsins." Early investigators were able to demonstrate that in addition to dermonecrotic and lethal effects, the staphylococcal toxin had a leucocidic effect on rabbit white blood cells and lysed rabbit erythrocytes. Although this knowledge was available, it was largely neglected until the Bundaberg disaster in 1928. In Bundaberg, Australia, 12 children died after being inoculated with a diphtheria toxin-antitoxin mixture which had become contaminated with S. aureus. The lethal effect was attributed to the staphylococcal toxin. Burnet's (10,11) subsequent investigations of the disaster disclosed that the toxin could be produced in significant quantities for laboratory investigations and that the toxin was a true exotoxin capable of killing rabbits on intravenous injection. These findings prompted increased interest in the investigation of staphylococcal toxins (12, 15, 30, 50). It is now known that a crude staphylococcal toxin preparation is composed of various substances. These include coagulase, staphylokinase, and hyaluronidase, the so-called "spreading factors", Panton--Valentine leucocidin, a distinct enterotoxin, and four hemolysins (17, 63). The latter have been termed alpha, beta, gamma, and delta hemolysins (25, 57, 64, 72). Of these, the alpha hemolysin has received the most attention and has been so frequently associated with the lethal and necrotizing factors that the terms alpha hemolysin and alpha toxin have been used interchangeably. Supernatants from staphylococcal cultures are hemolytic in vitro, lethal for small laboratory animals, produce necrotizing lesions following injection into the skin of animals, cause smooth muscle to undergo contractions and loss of function, and bring about cortical necrosis of the kidneys when injected intravenously into experimental animals (1, 17, 30, 65, 67, 68). Until recently, it had been difficult to ascribe a specific function to alpha toxin because of the unavailability of purified material. However, as more gentle and effective methods of protein separation have become available, attempts at alpha toxin purification and characterization have met with various degrees of success. Several groups of investigators claim to have prepared purified alpha toxin which was homogeneous, producing a single precipitin line on gel diffusion and immunoelectrophoresis (9, 14, 26, 31, 37, 39). With these preparations and with many others known to be impure, a variety of tests have been conducted to determine the activity of alpha toxin. Based on the conclusions reached by various investigators (9, 26, 31, 36) there seems to be some agreement that the lethal, dermonecrotic and hemolytic effect of supernatants from staphylococcal cultures are due to one and the same substance, the alpha toxin fraction (5). Other effects attributed to alpha toxin are a lytic effect on rabbit and human leukocytes (8, 26, 30), necrosis of human skin (26), damage to human platelets (7, 40, 59), damage to rabbit kidney, Ehrlich ascites, human epidermoid (KB), and monkey kidney cells in tissue culture (3, 4, 33), damage to pleuropneumonia-like PPLO) organisms (6), and damage to rabbit liver lysoscmes (8). In this investigation, sane localization of a lethal dose of alpha toxin in the heart and lungs of a mouse after intravenous injection was demonstrated by means of a fluorescent antibody technique. In addition, a possible direct action of the toxin on heart tissue was suggested by the observation that serum levels of alpha hydroxybutyric dehydrogenase and glutamic oxalacetic transaminase rose immediately after inoculation of the toxin.

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