Sporicidal activity

A number of aldehydes possess antimicrobial properties, including sporicidal activity however, only two, formaldehyde and glutaraldehyde, are used for disinfection. Both these aldehydes are highly effective biocides and their use as chemosterilants reflect this. 

Sporicidal activity can be determined against spores in liquid suspension or against spores dried on carriers. In principle, techniques are similar to those described for bactericidal tests. However, it should be realized that spores must germinate and outgrow before colony formation is observed. For this reason, incubation of recovery media should be continued for several days. 

Formaldehyde is available as a 40% w/v solution in water (100% formalin). An 8% formaldehyde solution in water has a broad spectrum of activity against bacteria, fungi, and viruses. Sporicidal activity may take as long as 18 hours. Its rapidity of action is increased by solution in 70% isopropanol. Formaldehyde solutions are used for high-level disinfection of hemodialyzers, preparation of vaccines, and preservation and embalming of tissues. The 4% formaldehyde (10%... 

The experimental disinfectant solutions tested exhibited significant sporicidal activity against B. subtilis spores. The B. subtilis strain used in these evaluations is the same one specified in the AO AC sporicidal test. Spores from... 

The degree of ionization of acidic and basic antimicrobial agents depends on pH. Some compounds are active only in the unionized state (e.g., phenolics) whereas others are preferentially active as either the anion or cation. It therefore follows that the activity of a particular concentration of an agent will be enhanced at a pH that favors the formation of the active species. Thus, cationic antibacterials such as acridines and quaternary ammonium compounds are more active under alkaline conditions. Conversely, phenols and benzoic acid are more active in an acid medium. Chlorbutol is less active above pH 5 and unstable above pH 6. Phenylmercuric nitrate is only active at above pH 6 whereas thiomersal is more active under acid conditions. The sporicidal activity of glutaraldehyde is considerably enhanced under alkaline conditions whereas hypochlorites are virtually ineffective at above pH 8. 

Abdelaziz AA, El-Nakeeb MA. Sporicidal activity of local anaesthetics and their binary combinations with preservatives. J Clin Pharm Ther 1988 13 249-256. 

The acridine dyes, acriflavine and aminacrine, have also been employed for skin disinfection and treatment of infected wounds or burns. They are slow acting and mainly bacteriostatic in effect, with no useful fungicidal or sporicidal activity. Acriflavine is a mixture of two components, proflavine and euflavine. Only euflavine has effective antimicrobial properties. 

CHG at antiseptic concentrations (0.5-4%) demonstrates a high degree of antimicrobial activity, both -static and -cidal, on vegetative phases of gram-positive and gram-negative bacteria, but it has little sporicidal activity. While there... 

Iodine, in neutral aqueous solution, exists mainly as such and the sporicidal action is due to elementary iodine. At pH 8.5, the hypoiodous acid iodine ratio rises to 1 1, with a consequent drop in sporicidal activity. Hypoiodous acid (p/T 10) is a weak acid. Iodine does not form a depot substance with ammonia, but its complex (KI3) with potassium iodide has depot properties. A great excess of potassium iodide is required to hold iodine as this tri-iodide in aqueous solution (Wyss and Strandskov, 1945). 

In the liquid phase, time-survival curves of bacterial spores treated with formaldehyde have been reported to show initial shoulders, irrespective of whether aqueous or alcoholic solutions are used [62, 74], although this phenomenon has not been observed by other workers [75]. Various alcohols have also been shown to reduce the sporicidal activity of glutaraldehyde [62, 63]. 

Aldehyde Chemical Name Chemical Formulae Sporicidal Activity... 

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