Large discrepancies in the available data on skin microbiology stimulated investigations of the number, interactions, and location of commensals and the true efficiency of disinfection by using skin biopsy, culture of frozen sections, and other methods.Most current procedures were less than 0.5% as sensitive as the biopsy method described. This gave mean bacterial counts ranging from 4,400/cm(2) on the breast to 400,000/cm(2) in the axillae. An iodine preparation removed 95% of accessible organisms, but about 20% of bacteria were protected by follicles, crevices, and lipids. Commensals in over 20% of people produced antibiotics against a wide range of pathogens. Conversely, "satellitism" was demonstrable in 12% of people.

https://www.bmj.com/content/bmj/1/5793/136.full.pdf

Skin Bacteria and Skin Disinfection Reconsidered

Further observations on an inhibitory substance (nisin) from lactic streptococci.

Evidence presented in support of the hypothesis that interrelationships among organisms in the pharynx provide one of the mechanisms that maintain the bacterial status quo Many organisms 

Evidence Suggesting Importance of Role of Interbacterial Inhibition in Maintaining Balance of Normal Flora

Oral streptococci are able to produce growth-inhibiting amounts of hydrogen peroxide (H2O2) as byproduct of aerobic metabolism. Several recent studies showed that the produced H2O2 is not a simple byproduct of metabolism but functions in several aspects of oral bacterial biofilm ecology. First, the release of DNA from cells is closely associated to the production of H2O2 in Streptococcus sanguinis and Streptococcus gordonii. Extracellular DNA is crucial for biofilm development and stabilization and can also serve as source for horizontal gene transfer between oral streptococci. Second, due to the growth inhibiting nature of H2O2, H2O2 compatible species associate with the producers. H2O2 production therefore might help in structuring the initial biofilm development. On the other hand, the oral environment harbors salivary peroxidases that are potent in H2O2 scavenging. Therefore, the effects of biofilm intrinsic H2O2 production might be locally confined. However, taking into account that 80% of initial oral biofilm constituents are streptococci, the influence of H2O2 on biofilm development and environmental adaptation might be under appreciated in current research.

/pdf/the-role-of-hydrogen-peroxide-in-environmental-adaptation-of-3zdzqhpg1b.pdf

The Role of Hydrogen Peroxide in Environmental Adaptation of Oral Microbial Communities

Bacteria in human mouths involved in the production and utilization of hydrogen peroxide

/pdf/the-inhibitory-action-of-saliva-on-the-diphtheria-bacillus-3fz2t5k17t.pdf

Madoka Shibuya

Papers

The Inhibitory Action of Saliva on the Diphtheria Bacillus: The Antibiotic Effect of Salivary Streptococci.