A dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the degree of Master of Pharmacy, Johannesburg, 2017 / Oral diseases in South Africa remain a huge public health problem due to the high cost, prevalence, severity and the influence on the patients well-being. Treatment for oral diseases requires the need for specialist dental health care workers and come at a high cost causing a great burden on the health system. The three most important oral diseases are dental caries, caused by Streptoccocus mutans, Streptococcus sanguis, Lactobacillus acidophilus and Lactobacillus casei, periodontal diseases caused by Porphrymonas gingivalis and Fusobacterium nucleatum and oral candidiasis caused by Candida albicans, Candida glabrata and Candida krusei. An ethnobotanical review has revealed that over a 120 South African medicinal plants are used for the treatment of oral diseases. This coupled with the lack of research on the subject, allowed for the investigation of the antimicrobial efficacy of some South African plants against oral pathogens. A total of 140 aqueous and organic extracts and six essential oils were prepared from 31 different plant species. These plant samples were screened for antimicrobial efficacy against nine oral pathogens using the micro-titre plate dilution assay. Plant extracts that were found to have noteworthy antimicrobial activity against Streptococcus mutans were further evaluated on the effect on S. mutans biofilm formation using the glass slide method. The toxicity profiles of plant samples that were found to have noteworthy antimicrobial activity were evaluated using the brine shrimp lethality assay. The plants did not exhibit antimicrobial efficacy against all nine pathogens in this study, instead, most were very specific to disease conditions. Some plants did show good antimicrobial activity against four of the nine pathogens tested (A. afra leaves, C. torulosa stems, C, brachiata leaves and H. natalensis leaves).The organic extract of Cissampelos torulosa stems displayed the lowest MIC value of 0.05 mg/ml against both Lactobacillus spp. This antimicrobial activity was also observed with the organic extract of Spirostachys africana leaves against Candida albicans. In some instances, a direct relationship was found between the traditional use of the plant and the antimicrobial activity observed. For example, noteworthy activity (MIC < 1.00 m/ml) was observed against all three Candida spp. for Clematis brachiata (leaves), a plant traditionally used to treat oral thrush. Englerophytum vi magalismonatanum (stems) displayed notable activity against both Streptococcus spp. (MIC 0.83 mg/ml against S. mutans and MIC 0.67 mg/ml against S. sanguis). Spirostachys africana leaves displayed the greatest anti-adherent properties against S. mutans biofilm formation at both 24 and 48 h, reducing the biofilm by 97.56% and 86.58% respectively. The majority of plant samples tested in the brine shrimp lethality assay (BSLA) were considered safe, however, 13 plant samples were considered toxic, at a concentration of 1 mg/ml, and their LC50 values were determined. The findings from the results favour the potential use of these plants in treating oral diseases such as dental caries, periodontal diseases and oral thrush, and scientifically validates the traditional use of some of these plants. / XL2017

THE UNIVERSITY OF MANCHESTER ABSTRACT OF THESIS submitted by Raja Moftah Moman for the Degree of Doctor of Philosophy entitled Interactions of Oral Bacteria with Host Tissues and Allochthonous Microorganism. 15th June 2017. The oral microbiome is a taxonomically diverse microbial community situated principally upon the hard and soft tissue surfaces of the mouth. It represents a readily accessible biofilm community for the investigation of bacteria-bacteria and bacteria-host interactions, which are responsible for some of the main features of oral biofilms in health and disease (colonisation resistance, antimicrobial tolerance, metabolic cross feeding, and other cooperative phenomena). In the oral cavity these relate specifically to cariogenesis and interactions with soft tissue that are responsible for periodontal disease. This doctoral thesis presents a series of investigations that consider processes for which growth in the biofilm phenotype or bacterial-bacteria or bacteria-host cell interaction are responsible. Four distinct methods were used to assess the effect of the biofilm phenotype on susceptibility of eight distinct oral hygiene actives with various modes of action. Bisphenol microbicide triclosan and the bis-biguanide chlorhexidine were most effective. All were markedly more effective against bacteria grown planktonically than the same organisms grown as biofilms illustrating antimicrobial tolerance, an important biofilm characteristic. In studies of interactions between oral isolates, bacteria previously isolated from the saliva and different oral sites of the oral cavity were tested using a modified cross streak method, in all possible pair-wise combinations. The frequency and strength of physical interactions (coaggregation) between these isolates was also assessed. The incidence of positive interactions was higher than the incidence of negative interactions (15.21% vs. 1.04%) and the incidence of coaggregation in bacteria isolated from saliva was significantly lower than for bacteria isolated from oral biofilms. Together, these data suggest that bacterial cooperation plays a greater role in oral biofilm development and maintenance than competition. With respect to putatively beneficial interactions between bacteria and host, the potential of the candidate dental probiotics L. rhamnosus GG, L. reuteri and S. salivarius to protect host tissues from damage by three Gram negative periodontal pathogens were investigated using human oral cells culture and the (invertebrate) G. mellonella model system. All probiotics inhibited the growth of the test pathogens when applied simultaneously, and significantly decreased toxicity (p P. gingivalis &gt; A. actinomycetemcomitans) in two distinct cell lines. Whilst all probiotics conferred protection against the periodontal pathogens, L. rhamnosus GG, had the greatest protective effect, regardless of probiotic or pathogen used, followed by L. reuteri. S. salivarius was the least effective. Prophylactic treatment with probiotics conferred greater protection than treatment concomitant with pathogen challenge. The data presented in this doctoral thesis demonstrate the functional significance of interactions between taxonomically distinct bacteria and between bacteria and host tissues. Such interactions may determine the outcome of exposure to antimicrobials and are, particularly significant in health and through further research, may be harnessed for prevention and treatment of oral disease.