Experimental staphylococcal infection in the mouse

McKay, Sheila Elizabeth (1975) Experimental staphylococcal infection in the mouse. PhD thesis, University of Glasgow.

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Several strains of Staphylococcus aureus, all clinical isolates, were tested for haemolytic activity and for the production of extracellular enzymes. From these strains four were chosen for their varied toxin and enzyme patterns. Also included were two reference strains of Staph, aureus, Wood 46 and BB. Each of these six strains was tested for antibiotic sensitivity, production of leucocidin and the presence of protein A on washed cell suspensions. In-vitro growth rates were also measured. These six characteristically different strains were used in a study of virulence for the mouse. Suspensions of known viability of the strains were prepared, dispensed in small aliquots and frozen in liquid nitrogen. This allowed the same suspension of organisms to be used for animal experiments carried out over a long time. The Initial virulence studies were made in three age groups of mice, 3-day old, 10-day old and 21-day old. The response of the mice to subcutaneous challenge with the strains, i.e. death or the development of lesions was recorded. As measured by these criteria the neonatal mice were most susceptible to infection by each strain, although strains varied considerably in virulence. Age-related susceptibility to the four organisms, Esch. coli, P. aeruginosa, Klebsiella sp and Strep. pyogenes, although evident, was less marked than to the staphylococci. Further work is required to determine how widely this phenomenon applies to organisms other than Staph. aureus. The strains of Staph. aureus varied in virulence as measured by the ability to cause death and to produce lesions in the mice. These lesions were of two types; a diffuse, necrotic type and a localised abscess type. It was noted that the necrotic lesions were produced by the toxinogenic strains and the abscess lesion was produced by the non-toxinogenic strain, SM 9. Further evidence that toxins (particularly alpha- and beta-lysin) were the cause of the necrosis was obtained by injecting cell-free culture filtrates of each strain into the mice. Filtrates from the toxinogenic strains produced necrosis similar to that observed in a lesion caused by whole organisms. The filtrate from strain SM 9 produced no observable effect. Histological examination of the lesions produced by SM 9 and SM 10, a toxinogenic strain of similar virulence to SM 9, confirmed that necrosis was associated with the toxin-producing strain. Further comparative growth studies of these two strains were made in 3-day old and 21-day old mice. Numbers of staphylococci present in the injection/lesion site and the liver were counted. Both SM 9 and SM 10 multiplied to a very limited extent in the skin of 21-day old mice but very rapidly in the skin of 3-day old mice. Staphylococci were not recovered from the livers of the weanling mice but were detected in livers of neonatal animals. SM 10 multiplied faster in the skin of the neonates than SM 9 and was present in the liver from the initial stages while SM 9 did not appear in significant numbers until late In the infection. It is suggested that both these properties are associated with the ability of SM 10 to produce alpha-toxin. Although the two strains multiplied at different rates, just prior to death the number of staphylococci recovered from the tissues of the neonates was the same for both strains. Also there was good correlation between the clinical state of the mice and the number of organisms in the tissues. Administration of Cephaloridine at different times during the infection confirmed that actual numbers of organisms were an important feature of staphylococcal infection in this model. The possibility of the final number of organisms in the tissues as a direct cause of death is discussed. Possible future studies involving the neonatal mouse are suggested.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: J P Arbuthnott
Keywords: Microbiology, Pathology
Date of Award: 1975
Depositing User: Enlighten Team
Unique ID: glathesis:1975-73109
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 14 Jun 2019 08:56
Last Modified: 14 Jun 2019 08:56
URI: https://theses.gla.ac.uk/id/eprint/73109

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