Biostatic activity

Comparable and striking biostatic activity was also exerted on other microorganisms and the results are reported in Table 4.4. 

Biostatic activity is defined as the concentration at which the growth of the microorganism is inhibited. Depending on the actual microorganism involved, formulations are called either bacteriostatic, fungistatic or algaestatic. In Tables 14.4 and 14.5, the fatty amine... 

Choice of particular solvents is a major issue arising from health, safety and environmental legislation. Selection needs to be made carefully as there can be unexpected consequences. For example, whereas most organic solvent-based paints have an inherent biostatic activity preventing microbial spoilage, water-based paints often require the addition of biocides to prevent this. There is concern that the operation of waste water treatment plants may be adversely affected by effluents from such systems [10]. 

Because of their surfactant and filming properties fatty amines such as coco-alkylamine acetate (and more especially diamines, such as tallow propylenediamine) are also occasionally employed in other types of water treatment programs. For example, they may be used as corrosion inhibitors for steel cooling systems, especially those smaller units where minimal operational control is provided. The amines must be continuously dosed to ensure good film formation (and thus corrosion protection), typically at 5 to 10 ppm active amine. They also tend to have good biostatic control properties, which provide a benefit of algal and bacterial control at no extra cost. 

NOTE Products exerting a biostatic effect are usually continuously present in cooling water at a low level (say below 0.5 to 0.6 ppm actives) and have an inhibiting effect on the proliferation of microbiological flora but do not reduce current populations. 

The diamidines also are fungicidal. Activity in vitro against Blastomyces dermatitidis led to the successful therapeutic trial of these drugs in systemic blastomycoses. The use of amphotericin B, however, has reduced the value of the diamidines in the treatment of this disease. At near-therapeutic levels, pentamidine kills nonreplicating forms of P. jiroveci in culture, but other evidence suggests that pentamidine exerts a biostatic rather than biocidal effect. 

Additives that control bacterial growth may therefore exert both biostatic and biocidal effects. The mechanism of action responsible for each effect is not generally the same. Biostatic action is considered to represent metabolic inhibition which is released when the additive is removed. Biocidal activity causes irreversible damage to a vital structure or function of the cell. Dispersants may also be used to prevent attachment to a surface. 

Biocidal or biostatic products shall not be applied to products so as to be active during the use phase. 

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