Scope In response to the current public health concerns with the microbiological safety of fresh and fresh-cut produce, researchers have investigated the efficiency of numerous physical, chemical, and biological methods for reducing the microbiological load of produce. This chapter focuses on this growing area of research with a particular emphasis on human pathogenic microorganisms; however, research related to mitigation treatment effects on nonpathogenic organisms is also included. There have been several reviews that address this topic and they are pointed out throughout the chapter; therefore, the focus here is on the latest and most significant research findings. A matrix (Table V-1) summarizing the characteristics of intervention methods is also included at the end of the chapter.

Methods to Reduce/Eliminate Pathogens from Fresh and Fresh-Cut Produce

The chemical, microbiologic, and toxic characteristics of povidone-iodine solution, a commonly used antiseptic agent, are addressed in a collective review of relevant works published from 1956 to the present. Interactions of this agent with the thyroid gland and the kidneys and its toxicity at the cellular and systemic level are discussed.

Chemical and microbiologic characteristics and toxicity of povidone-iodine solutions.

Cytotoxicity of Ophthalmic Preservatives

A study was carried out to compare the antibacterial properties of four cationic antiseptics, three of which are available as commercial mouthrinse preparations. Minimum inhibitory concentrations for alexidine, cetyl pyridinium chloride, chlorhexidine gluconate and hexetidine against a range of standard test organisms, were determined by tube dilution. Similar values for Oxford staphylococcus were then obtained in Dubos medium to which protein as yeast, or food extract, or serum was added in doubling dilutions to 16%. Salivary bacterial counts after a single rinse with the antiseptics or water throughout the day were measured in 10 subjects together with the duration of any residual antiseptic activity in the saliva. All antiseptics were effective at low concentrations against the organisms tested but the minimum inhibitory concentration values for hexetidine were the highest. Food extract and serum markedly increased the minimum inhibitory concentration values of all antiseptics, although alexidine and hexetidine were the least affected in percentage terms. The activity of a 1% povidone iodine preparation, used for comparison, was almost completely vitiated. An immediate significant fall in salivary bacterial counts was produced by the cationic antiseptics. Return to pre-rinse levels was seen for hexetidine after 90 min, cetyl pyridinium chloride after 3 hours, alexidine after 5 hours and chlorhexidine gluconate after 7 hours. Residual salivary antibacterial activity remained to 90 min for cetyl pyridinium chloride, to 3 hours for hexetidine and alexidine and to 5 hours for chlorhexidine gluconate. The antibacterial properties measured, in particular the duration of effect in vivo, may be relevant to the anti-plaque activity of cationic antiseptics.

Comparison of the in vivo and in vitro antibacterial properties of antiseptic mouthrinses containing chlorhexidine, alexidine, cetyl pyridinium chloride and hexetidine. Relevance to mode of action.

The destruction of bacterial spores

Effectiveness of antibacterial agents presently employed in ophthalmic preparations as preservatives against pseudomonas aeruginosa.

Since the latter part of the nineteenth century, much has been written extolling the alleged virtues of iodine as an antiseptic. This has been largely due to the fact that it fulfills a function that many bactericides do not and cannot fulfill. Iodine has been used in various forms as an antiseptic for the skin, wounds, and mucous surfaces of the body; for the sterilization of the air and of inanimate objects such as catgut and surgical instruments; as a prophylactic and therapeutic agent in diseases caused by bacteria, viruses, and fungi; for the disinfection of drinking water and swimming pool water; and for the sanitization of eating utensils. These uses of iodine will be considered later. Properties of Iodine. Iodine, a solid crystalline element, bluish-black in color, with a bright metallic lustre, possesses the highest atomic weight of the common halogens. It is the only halogen which is solid a t ordinary room temperature. Iodine has the unique property of changing spontaneously a t room temperatures (20°C.) into the vapor state without first passing through a liquid phase. The vapor state is referred to as nascent iodine. True liquid iodine is rarely seen, except under special laboratory conditions. Iodine is only slightly soluble in water (1:3450 a t 2OOC.) but freely soluble in aqueous solutions containing soluble iodides and also in many organic solvents. Iodine exhibits different colors when dissolved in organic solvents. Chloroform, carbon disulfide, carbon tetrachloride, and benzene solutions produce a violet color, whereas, in alcohol, ether, glycerin, and propylene glycol, a brown color is produced. The solubility of iodine has been reported to increase in the presence of cane sugar.’ Action of Iodine as a Bactericide. Iodine is a highly reactive element and, precisely because it is so reactive, it is a good germicide. When iodine acts as a disinfectant, free iodine is the effective agent?. Sollmann4 states, “Elementary iodine precipitates proteins, the iodine being partly absorbed, partly loosely bound and partly converted into iodide ions.. . . Since the iodine is loosely bound, it continues to penetrate so that the action extends deeply.” McCulloch6 believed that iodine destroyed microorganisms by the “formation of salts with proteins by direct halogenation.” The Bactericidal Eficiency of Iodine. In gathering laboratory data on the efficacy of an antiseptic one must recognize that today there is not as yet available a universal single laboratory test applicable under all conditions. In all instances, laboratory data should be obtained and interpreted under conditions paralleling as closely as possible those found in actual practice. In the final analysis, efficacy under conditions of use (as recommended in labeling) is the important criterion. When an antiseptic shows constantly satisfactory effectiveness by many different in vilro and ila vioo methods, one can then state that it deserves a high rating of usefulness as a bactericidal agent.

Iodine as an antiseptic.

The effectiveness of iodine is detailed in the field of therapy and especially in the fields of prophylaxis and sanitation of many infections caused by viruses. The use of a suitable antiseptic for preparing the surface to be traumatized, either by injections or by operative procedure, is of great importance. Of the local antiseptics tested, iodine tincture was found to be most effective in quickly destroying the poliomyelitis virus. ' In the author's laboratory, concentrations of free iodine as may be used in preparing a mouth wash were found to be capable of destroying polio virus.

Iodine as a virucidal agent

Since the latter part of the 19th century, much has been written extolling the alleged virtues of iodine as an antiseptic. The sporicidal action of iodine has been reported but discrepancies appear in the results. Comparative studies have been made between water and water-alcoholic iodine solutions in which the water solutions have consistently been shown to be more efficient. This in vitro study reports on the sporicidal efficiency of a 2 per cent water-iodine solution (iodine solution N. F. IX). Both “wet” and “dry” techniques were employed, using conditions with different pH values. Iodine solution N. F. IX was found to be effective against the spores of B. anthracis, B. subtilis, B. megatherium, B. mesentericus, and Cl. tetani.

Louis Gershenfeld

Papers

Effectiveness of antibacterial agents presently employed in ophthalmic preparations as preservatives against pseudomonas aeruginosa.

Iodine as an antiseptic.

Iodine as a virucidal agent

Iodine Solution as a Sporicidal Agent

Antibacterial agents not presently employed as preservatives in ophthalmic preparations found effective against Pseudomonas aeruginosa