Additive effects, antimicrobial agent

Benzoic acid occurs naturally in many types of berries, plums, prunes, and some spices. As an additive, it is used as benzoic acid or as benzoate. The latter is used more often because benzoic acid is sparsely soluble in water (0.27 percent at 18°C) and sodium benzoate is more soluble (66.0 g/100 mL at 20°C). The undissociated form of benzoic acid is the most effective antimicrobial agent. With a pKa of 4.2, the optimum pH range is from 2.5 to 4.0. This makes it an effective antimicrobial agent in high-acid foods, fruit drinks, cider, carbonated beverages, and pickles. It is also used in margarines, salad dressings, soy sauce, and jams. 

The introduction of trimethoprim in combination with sulfamethoxazole constitutes an important advance in the development of clinically effective antimicrobial agents. In addition to its combination with sulfamethoxazole (bactrim, septra, others), trimethoprim also is available as a singleentity preparation (proloprim, others). It is a diaminopyramidine. 

In recent years, silver has been successfiiUy used as an effective antimicrobial agent and silver containing wonnd dressings are now widely nsed throughout the world. In addition to silver, other metal ions have also proven effective in preventing bacterial... 

An antimicrobial agent that reduces dental plaque and can be deUvered effectively from toothpaste is a combination of Triclosan [3380-34-5] (0.2% in the toothpaste) and zinc citrate (0.5%) (7). This agent influenced plaque accumulation and reduced the incidence of gingival bleeding in clinical tests. Additional dentifrices for improved gingival health are in the offing. 

Very occasionally a combination of antimicrobial agents exhibits synergy. Synergy is measured against a single microorganism and is exhibited when a combination of two compounds exerts a greater inhibitory effect than could be expected from a simple additive effect of the two compounds in the mixture. 

Although the mechanical periodontal treatment alone is adequate to ameliorate or resolve the clinical condition in most cases, adjunctive antimicrobial agents, delivered either systemically or locally, can enhance the effect of therapy. In this connection, two recent meta-analyses [60, 61] have shown that systemic antimicrobials in conjunction with SRP can offer an additional benefit over SPR alone in the treatment of periodontitis both in terms of change in the clinical attachment level and probing pocket depth. When examining the effect of individual antibiotics, it was found that there were statistically significant improvements in clinical attachment level with tetracy-... 

In addition, the solubility of many preservatives in a mostly aqueous system may not be high enough for effective antimicrobial activity. For example, the para-bens often require heating in order to be solubilized. Additionally, it is essential to understand that bacteriostatic agents can partition between organic and aqueous phases in such a way that their activity is significantly reduced. Methyl paraben... 

The parabens are effective over a wide pH range and have a broad spectrum of antimicrobial activity, although they are most effective against yeasts and molds. Antimicrobial activity increases as the chain length of the alkyl moiety is increased, but aqueous solubility decreases therefore a mixture of parabens is frequently used to provide effective preservation. Preservative efficacy is also improved by the addition of propylene glycol (2-5%), or by using parabens in combination with other antimicrobial agents such as imidurea see Section 10. 

---