Biostatic effect

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. 

In order to provide a biostatic effect for any particular organism, nonoxidizers are required to be present at a certain minimum inhibitory concentration (MIC), and for a biocidal effect, at a minimum kill concentration... 

Nano-technology has been used for a zinc oxide UV absorber by Elementis Pigments Decelox UV. A particle size of only 50-60 nm gives enhanced UV performance compared with conventional products plus transparency and a biostatic effect. A biostatic additive using the same technology is also being launched under the name Decelox Bio. 

Various-borate ester formation, polymer cross-linker, alkaline pH buffer, corrosion inhibition, sparingly soluble salt formation, biostatic effect, oxidizing property... 

A comprehensive analytical program for characterising wastewaters should be based on relevance to unit treatment process operations, the poUutant or pollutants to be removed ia each, and effluent quality constraints. The qualitative and quantitative characteristics of waste streams to be treated not only serve as a basis for sising system processes within the facility, but also iadicate streams having refractory constituents, potential toxicants, or biostats. Such streams are not amenable to effective biological treatment, as iadicated by the characterization results, and requite treatment usiag alternative processes. 

In general, the continuous, biostatic, slow-release bromination of smaller comfort cooling systems is also both practical and cost-effective. But it is the rationale for routinely recommending periodic applications of relatively expensive nonoxidizing biocides to cooling systems of any size, without benefit of proof of need, effectiveness, or program costs, that should be questioned. 

In general, the solid materials tend to act as biostats rather than biocides. Programs that use biostatic control in partnership with periodic applications of nonoxidizing biocides have proved to be extremely effective in many comfort cooling and general industrial cooling systems. 

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. 

Low levels of residual chlorine may be regarded as a biostat, i.e. preventing colonisation or restricting biofilm development. In a particular laboratory experiment [Kaur et al 1988] chlorine levels as low as 0.2 - 0.6 mg/l inhibited biofilm attachment and growth. The effect of flow velocity and chlorine concentration are shown on Fig. 14.14. 

Rose, S. and M.J. van der Laan. Why match investigating matched case-control study designs with causal effect estimation. Int Biostat, 5, Article 1, 2009, http / / www.bepress.com / ijb / vol5 / issl /1 /. 

Stitelman, O.M. and M.J. van der Laan. Targeted maximum likelihood estimation of effect modification parameters in survival analysis. Int J Biostat, 7(1), 2011. 

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