In Vitro Study On Antagonistic Activity Of Streptococcus Mutans Against Actinobacillus Actinomycetemcomitans

Aggressive periodontitis is a kind of early onset (before age 35) dental disease which alveolar rapidly absorbed and causes severe destructive periodontal loss. AgP is divided into localized AgP (LAgP) and generalized AgP (GAgP). LAgP often occurred in young people aged 11²5, the incidence is about 0.1%¹5%, however, Caries in the young age group is suffering from a peak. The relationship between the two disease has been a focus of debate . Clinical studies in the past found that, the incidence of Aggressive periodontitis and dental caries shows a certain relevance, that adolescents with aggressive periodontitis often features with a low rate of caries, and the high prevalence of dental caries in patients features with less aggressive periodontitis, particularly in the proximal surface where caries and Aggressive periodontitis were vulnerable violated, the two diseases were more obvious confrontational. Studies confirmed that, Actinobacillus actinomycetemcomitans is the main pathogenic bacteria of localized aggressive periodontitis, while Streptococcus mutans is the main pathogenic bacteria of caries. Daniel.H.Fine etc. matched 11 Aa-negative controls subjects and 11 Aa-positive subjects (seven with LAgP) ,and A total of 5 ml saliva obtained from each subject was tested for CO₂ levels, pH, and effects on survival of Aa and Sm. They concluded that Aa-positive subjects had a salivary factor that significantly reduced survival of Sm, which may help to explain the fact that aggressive periodontitis group typically has minimal proximal decay. At present, the research is more concentrated in clinical trials and epidemiological investigation, less research on the main mechanism of the interaction between caries pathogens and aggressive periodontitis pathogens , and more attentions was paid to the effection of Aa to the activity of the Sm, but no reports showed whether Sm can antagonism Aa. Thus in this experiment, we selected the two pathogens: Sm which main cause caries, and Aa which main cause aggressive periodontitis, to discuss the effection of Sm against Aa.The specific method is as follows: (1) Bacterial culture. Massively raises Sm Gs-5 (serological type c) and Aa Y4 and prepare respectively the certain concentration bacterial suspension. (2) Sabine agar plate Preparation. Uses the agar plate which Sabine states, and spread certain concentration bacterial suspension which has prepared on the agar plate with sterile glass rod, then drill a hole in the plate (5mm diameter), adding the melt Ms agar culture in the hole as the substrate. (3)the treatment to Sm. i. Prepare certain concentration bacterial suspension of Sm; ii. Collect Supernatant of Sm.; iii. Pulverize Sm with ultrasonic wave and filtrated with 0.45μm filtration membrane, then collect the pulverized liquid. (4) Bacteriostasis experiment. the holes in the agar plate were filled in with suspension of Sm, supernatant of Sm and pulverized liquid of Sm, and we set Ms liquid medium as control group。Then Place each group plates into anaerobic cans, and incubate them anaerobic at 37℃48h with 800ml/L N2,100ml/L CO₂, 100ml/L H₂ atmospheric environment, catalyzed by Palladium grain ,the purpose is to observe the size of the inhibition zone around the hole.This experimental result shows as follows :(1) a range of antibacterial circle in plate appeared, there is little Aa colony around the Sm hole in the experimental group (Sm viable cells) , statistics test shows that the diameter of the circle increasing with the reduce of Aa concentration. Aa colony of the control group grows well and uniformly, no inhibition zone formed around the hole. (2) Aa colony in pulverized liquid of Sm group grows well and uniformly, no inhibition zone can been seen around the hole. (3) Aa colony in supernatant of Sm group also grows well and uniform, no inhibition zone can been seen around the hole. We Draw conclusions that: Sm has Antagonism action against Aa, Sm viable cell secretion may inhibit the growth of Aa viable cell. The matter is not mutacin which is produced by Streptococcus mutans, there is no relationship with intracellular active compound of streptococcus mutans. The matter should be metabolic product of Streptococcus mutans living cells produced constantly.Some research has demonstrated that the nature of acid produced by Streptococcus mutans can eventually decrease the pH value below 4.5 and raise the redoc potential in dental plaque, finally make the plaque environment can not be fit for the growth of anaerobic bacteria . Therefore, we inferred that Streptococcus mutans produce acid with a pH decrease inhibits the growth of Actinobacillus actinomycetemcomitans is one of the mechanism of antagonism. Another, H₂O₂ is a non-specific antibacterial substance which can inhibit microbial growth in significant concentrations local reserves. It has been confirmed in research on Streptococcus sanguis that Streptococcus sanguis can produce H₂O₂ to antagonise Actinobacillus actinomycetemcomitans and other periodontal pathogens. The research also shows Streptococcus mutans has the ability to produce hydrogen peroxide, So based on this study we inferred Streptococcus mutans producing H₂O₂ inhibites the growth of Actinobacillus actinomycetemcomitans is one of the mechanism of antagonism.There are still some problems to be solved:we have proved that Streptococcus mutans has a certain degree of inhibition against Actinobacillus actinomycetemcomitans. Next, Molecular biology, immunological and biochemical techniques will be used to investigate the role of specific substances and mechanisms on our further study. Moreover, how the two bacteria planting in the plaque, the dynamic link between subgingival plaque and subgingival plaque in LAGP patients is the key issue of this antagonistic mechanism; In different stages of disease progression,how will the plaque microbiology condition change influent the interaction of the two kind of bacteria, and whether such antagonism is affected by gene regulation are all need to be discuss further and clear, We will follow-up studies to explore these issues in depth gradually.The topic has some clinical significance:Competition and antagonism of oral bacteria is an important link in maintaining oral microecosystem , to understanding in depth the symbiotic relationship between the bacteria is to enhance the recognition of the formation and maturity of the plaque. To research the etiopathology and interaction of these two diseases from the relationship of Actinobacillus actinomycetemcomitans and Streptococcus mutans can reveal not only the significance on antagonism between caries pathogens and aggressive periodontitis pathogens colonization but can reveal colonization number of mutual relations between caries and aggressive periodontitis pathogens, and also provide more specific theory for the prevention and treatment of aggressive periodontitis and caries.