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The numbers of S. mutans and S. sanguinis are negatively associated. If the level of S. mutans is high, the level of S. sanguinis is low; while if the level of S. sanguinis is high, the level of S. mutans is low. This possibly explains the reason why cariesactive individuals have low numbers of S. sanguinis and caries-free subjects have higher numbers of S. sanguinis. In a dual-species S. mutans and S. sanguinis biofilm, if S. mutans colonized first, the growth of the later colonized S. sanguinis would be inhibited by S. mutans. However, if S. sanguinis colonized first, the growth of the later colonized S. mutans would be inhibited by S. sanguinis. Furthermore, if S. mutans and S. sanguinis colonized together at the same time, either species can inhibit the other. Therefore, the order of colonization determines the result of the competition.19 This result confirmed earlier research done by Kemp et al. in 1983.69 Clinical studies also confirmed the competition between S. gordonii and S. mutans or between S. sanguinis and S. mutans.70 Further research19 suggested the inhibition of S. mutans on S. sanguinis was caused by an excreted diffusible substance instead of nutrient deprivation. However, the amount of nutrients present plays a significant role in the competition. When nutrients were rich, both S. mutans and S. sanguinis grew well, no matter which species colonized first.
A swan neck flask, also known as a gooseneck flask, is a round-bottom flask with a narrow s-shaped tube as its opening to reduce contact between the inner contents and external environment. The motion of air through the tube is slowed and aerosolized bacteria or other particles in the air tend to become trapped by moisture on the tube's inner surfaces. The contents of the flask thus remain free of microbes, a property showcased by French microbiologist Louis Pasteur in 19th century experiments used to support germ theory as the cause of fermentation over spontaneous generation from bad air (miasma).[1][2][3]
Chlorine compounds are good disinfectants on clean surfaces, but are quickly inactivated by organic matter and thus reducing the biocidal activity. They have a broad spectrum of antimicrobial activity and are inexpensive and fast acting. Hypochlorites, the most widely used of the chlorine disinfectants, are available in liquid (e.g., Sodium hypochlorite), household bleach and solid (e.g., calcium hypochlorite, sodium dichloroisocyanurate) forms. Household bleach has an available chlorine content of 5.25%, or 52,500 ppm. Because of its oxidizing power, it loses potency quickly and should be made fresh and used within the same day it is prepared. The free available chlorine levels of hypochlorite solutions in both opened and closed polyethylene containers are reduced to 40% to 50% of the original concentration over a period of one month at room temperature.
Iodophors are used both as antiseptics and disinfectants. An iodophor is a combination of iodine and a solubilizing agent or carrier; the resulting complex provides a sustained-release reservoir of iodine and releases small amounts of free iodine in aqueous solution. Antiseptic iodophors are not suitable for use as hard-surface disinfectants because they contain significantly less free iodine than do those formulated as disinfectants.
Of the sterilants listed above, Ethylene Oxide (ETO) has wide use as an alkyl acting agent with very broad biocide activity including spores and viruses. It is believed that the oxide ring reacts with free amino, sulfhydryl and hydroxyl groups on proteins. ETO is highly flammable and needs an inerting agent when used in a sterilizer. It is also toxic, mutagenic, and a suspected carcinogen. Additionally, beta propiolactone behaves similarly to ETO.
In regard to the Gram-positive cocci, mainly Staphylococcus (Fig. 2B) and Micrococcus (Fig. 2C) genera, they showed the same distribution as the Gram-positive rods. However, Micrococcus was prevalent in water from the irrigation channel, free from phytosanitary treatments of the plowing field. 153554b96e