Defence Mechanisms of the Mouth, With Particular Reference to Patients With Sjogren's Syndrome

MacFarlane, Thomas Wallace (1975) Defence Mechanisms of the Mouth, With Particular Reference to Patients With Sjogren's Syndrome. Master of Dental Surgery thesis, University of Glasgow.

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The three ecological components of the mouth are, the host tissues, saliva and the commensal micro-flora. Normally these components interact to protect the oral tissues from invasion and colonization by potentially pathogenic micro-organisms. Patients suffering from Sjogren's Syndrome develop severe xerostomia due to a progressive destruction of salivary gland tissue, and although the, changes in the host tissues, and saliva have received much study, little attention has been focused on the effect of these changes on the oral microbial flora. Microbiological assessment of the oral flora of patients with Sjogren's Syndrome showed that there was an increase in the numbers of Candida albicans and Staphylococcus aureus and a reduction in the numbers of Streptococcus salivarius, Veillonella, Neisseria pharyngis and Staphylococcus salivarius, when compared with normal control subjects. The aetiological factors related to these changes in the oral flora were considered to be complex, with many factors involved, including atrophy of the oral mucosa and a reduction in the volume and pH of saliva. The details of a new medium which was used for the isolation and enumeration of Veillonella species in these studies, was reported. Since intrinsic salivary antimicrobial substances, and microbial antagonistic mechanisms of the oral flora are thought to be the main factors which protect the mouth against infection by potentially pathogenic micro-organisms, it was decided to assess the antimicrobial activity of these two factors. The antimicrobial activity of mixed and centrifuged saliva collected from normal subjects was assessed using a new technique which possessed a number of advantages over the techniques used previously. The results of this study, suggested that the appearance of Staphylococcus aureus and Candida species in the mouth of patients with severe Sjogren's Syndrome was due to changes in the commensal microflora and the environment of the mouth, rather than to the loss of inhibitory factors derived from saliva. The antagonistic activity of Type cultures of eleven oral commensal bacteria was assessed against Candida albicans, Staphylococcus aureus and Escherichia coli. All the Type cultures possessed some antimicrobial activity, but since alpha-haemolytic streptococci possessed most activity, it was concluded that these streptococci, were of prime importance in protecting the oral tissues against invasion by non-commensal micro-organisms. The chance finding of a difference in the inhibitory activity of two strains of Streptococcus sanguis suggested that the inhibitory activity of all strains of a bacterial species could not be assumed to be the same. The next logical step was to compare the antimicrobial activity of alpha-haemolytic streptococci isolated from patients with Sjogren's Syndrome with streptococci isolated from healthy controls. The results of this study showed that the activity of streptococci isolated from control subjects was significantly greater than the activity of streptococci isolated from patients with Sjogren's Syndrome. It was concluded that the presence of Candida albicans, Staphylococcus aureus and Coliform bacilli in the oral flora of patients with Sjogren's Syndrome was related to the absence of certain alpha-haemolytic streptococci which possessed a wide spectrum of antimicrobial activity. A retrospective study of the routine microbiology results from oral samples of Sjogren's patients, showed that, Candida albicans, Staphylococcus aureus and Colifrom bacilli, were present in the mouth before any therapy was started. Since moderate to large numbers of Staphylococcus aureus and Candida albicans were isolated from the mouth of a number of Sjogren's patients at relatively regular intervals over a period of years, it appeared that these microorganisms could be regarded as a major component of the commensal flora of patients with Sjogren's Syndrome. A prospective study on the clinical response to antifungal therapy is necessary, and it was suggested that the use of artificial saliva, with added antifungal agents may be a satisfactory method of treating the oral symptoms of Sjogren's Syndrome. In addition the possibility was raised, of restoring the antimicrobial activity of the oral microflora by re-colonizing the mouth of Sjogren's patients with a strain of alpha-haemolytic streptococcus with antifungal and antibacterial activity.

Item Type: Thesis (Master of Dental Surgery)
Qualification Level: Doctoral
Keywords: Dentistry
Date of Award: 1975
Depositing User: Enlighten Team
Unique ID: glathesis:1975-78732
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:57
Last Modified: 30 Jan 2020 14:57

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