Estimation of Virulence of Staphylococcus Aureus for Mice: The Exceptional Virulence of the Smith Strain

Abstract

A precise method of assaving viruIence of Sfaphylo~occmis a u r a s for mice by intraperitmml injection with mucin is described; the resuIts indicated that most bacteriophage types of S. aprreus possessed similar virulence, an LDgo consisting of millions of orga~lisms. The variability in results of similar tests by previo~is authors i s thought to reside in the use of techniques allowing excessive variability.The Smith strain of S. alcreus is shown to be exceptionally virulent, requiring only one colony-form in^ unit to kill a mouse. However, the survival time of mice after inoculation with the Smith strain i s longcr than that of other strains giving equivalent mortality. An esplanation is suggested for this latter phenomenon, and the manner in which the Smith strain causes death is considered. IntroductionThe purpose of the work described in this paper was to inject strains of Staphylococcus aureus into mice in an attempt to obtain a reproducibIe test of virulence. When the work was started, certain bacteriophage types, notably 80/81, seemed to be more frequentlv associated with outbreaks of infection in hospitals OVilliams 1959) and, since no tests comparing the virulence of different bacteriophage types had been reported, we thought it of importance to investigate this. A preliminary review of the Iiterature revealed a

Antibody Response to Staphylococcus aureus in Rabbits: Sequence of Immunoglobulin Synthesis and Its Correlation with Passive Protection in Mice

“…In both groups of animals, the titers reached a peak 2 weeks after the immunizing injections, declined over the next R-31 and R-23: single immunizing injection, 10 week booster. R-28 and R-27: three daily immunizing injections, 10 week booster. Symbols: solid lines, untreated serum; broken lines, mercaptoethanol-treated serum.…”

“…The protective activity of the sera was determined as previously described (2,4). In testing the IgM and IgG fractions for mouse protection, the mucin challenge method of Parker et al (10) was used, as modified in this laboratory (13). The animals were then observed and deaths were recorded for 2 weeks, at which time the experiments were terminated.…”

Relation of Mucoid Growth of Staphylococcus aureus to Clumping Factor Reaction, Morphology in Serum-Soft Agar, and Virulence

“…One of the most discouraging aspects of research in the field of infection and resistance to Staphylococcus aureus has been the lack of a suitable laboratory experimental system. Since Hunt and Moses (7) described the greater mouse virulence of the diffuse variant of the Smith strain of S. aureus, several investigators have used this organism, or a strain with similar properties, to study various aspects of experimental staphylococcal disease (1,5,6,10,13,15). Our own studies with the Smith diffuse strain of S. aureus (2,3) suggested that, in addition to the "Smith Surface Antigen" described by Morse (11), teichoic acid from this strain also shows in vitro immunological properties and is an important protection-inducing antigen in mice.…”

Possible common biological and immunological properties for detecting encapsulated strains of Staphylococcus epidermidis

“…A number of studies have investigated the presence of capsules in Staphylococcus aureus strains as a virulence factor of the organisms (3,(9)(10)(11)(12)20). Ichiman and Yoshida (7) postulated the capsule as a virulence factor of S. epidermidis strains in coagulase-negative staphylococci.…”