Free Available Chlorine Residuals for Small Nonpublic Water Supplies

Baumann, E. Robert; Ludwig, Daniel D.

doi:10.1002/j.1551-8833.1962.tb00978.x

Cited by 21 publications

(10 citation statements)

References 8 publications

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“…Few vegetative cells were recoverable after incubation in 1000 mg l -1 (1.25%) and 5000 mg l -1 (6.25%) household bleach, and viable C. difficile cells were reduced to below the limit of detection (<10 CFU ml -1 ) in 8000 mg l -1 (10%) household bleach ( Figure 5A ). As pH alters the ratio of hypochlorite (HOCl) to the hypochlorite ion (OCl - ), and thus, the effectiveness of bleach (Baumann and Ludwig, 1962), these data suggested that the pH of the aqueous solution may alter the effectiveness of sodium hypochlorite. To test this hypothesis, vegetative cells grown to an OD 600 of 1.0 in BHIS medium were pelleted and suspended in pre-reduced 1X PBS (pH 7.4).…”

Section: Resultsmentioning

confidence: 99%

Chemical and Stress Resistances of Clostridium difficile Spores and Vegetative Cells

et al. 2016

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Clostridium difficile is a Gram-positive, sporogenic and anaerobic bacterium that causes a potentially fatal colitis. C. difficile enters the body as dormant spores that germinate in the colon to form vegetative cells that secrete toxins and cause the symptoms of infection. During transit through the intestine, some vegetative cells transform into spores, which are more resistant to killing by environmental insults than the vegetative cells. Understanding the inherent resistance properties of the vegetative and spore forms of C. difficile is imperative for the development of methods to target and destroy the bacterium. The objective of this study was to define the chemical and environmental resistance properties of C. difficile vegetative cells and spores. We examined vegetative cell and spore tolerances of three C. difficile strains, including 630Δerm, a 012 ribotype and a derivative of a past epidemic strain; R20291, a 027 ribotype and current epidemic strain; and 5325, a clinical isolate that is a 078 ribotype. All isolates were tested for tolerance to ethanol, oxygen, hydrogen peroxide, butanol, chloroform, heat and sodium hypochlorite (household bleach). Our results indicate that 630Δerm vegetative cells (630 spo0A) are more resistant to oxidative stress than those of R20291 (R20291 spo0A) and 5325 (5325 spo0A). In addition, 5325 spo0A vegetative cells exhibited greater resistance to organic solvents. In contrast, 630Δerm spores were more sensitive than R20291 or 5325 spores to butanol. Spores from all three strains exhibited high levels of resistance to ethanol, hydrogen peroxide, chloroform and heat, although R20291 spores were more resistant to temperatures in the range of 60–75°C. Finally, household bleach served as the only chemical reagent tested that consistently reduced C. difficile vegetative cells and spores of all tested strains. These findings establish conditions that result in vegetative cell and spore elimination and illustrate the resistance of C. difficile to common decontamination methods. These results further demonstrate that the vegetative cells and spores of various C. difficile strains have different resistance properties that may impact decontamination of surfaces and hands.

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Section: Resultsmentioning

confidence: 99%

Chemical and Stress Resistances of Clostridium difficile Spores and Vegetative Cells

et al. 2016

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“…The idea behind the Ct concept is that for a given disinfectant, the product Ct is approximately constant for a given level of inactivation (Baumann and Ludwig 1962). The original use of this incorporated the idea of the dilution coefficient and a time exponent; this has its basis in the Chick–Watson law of disinfection.…”

Section: Discussionmentioning

confidence: 99%

“…Microbiology has so often been seen as a purely descriptive science, and this belies the voluminous work done in mathematical biology applied to the food, home and personal care, and pharmaceutical industries. The`Ct' concept, obtained from disinfection rates, is used to set disinfection times against, for example, Giardia cysts (Baumann and Ludwig 1962;Wickramanayake et al 1985;Finch et al 1993). The rationale behind the canning process is based on thermal disinfection modelling, albeit it on a less than precise model (Anderson et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Advances in disinfection testing and modelling

Lambert

2001

J Appl Microbiol

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“…Treating the water sample with 40 ppm chlorine for 3 to 5 min resulted in only .2-to .3-log reduction of bacterial population. In contrast, a 2-log kill of most common bacteria, such as Escherichia coli, in drinking water at 2 to 5 C and pH 8.5, requires less than .5 ppm for 5 min (Baumann and Ludwig, 1962). The low disinfecting action of chlorine in chiller water apparently resulted from competing reactions of chlorine with dissolved organic and inorganic matters, which reduced the availability of chlorine to act against microorganisms.…”

Section: Disinfectionmentioning

confidence: 89%

Chlorination of Poultry Chiller Water: Chlorine Demand and Disinfection Efficiency

1992

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A study was conducted to determine the general composition of equilibrated poultry chiller water (near maximum solids content) from a commercial operation, the chlorine consumption by its components, and the chlorine dosage necessary to achieve its disinfection. The equilibrated chiller water contained .35% (CV, 40%) solids, which consisted of lipids (56%), ash (33%), and total nitrogen (4.2%). Residual chlorine and survival of aerobic bacteria were determined in chiller water dosed with chlorine levels ranging from 0 to 400 ppm. Initially, the added chlorine was rapidly consumed by the components of chiller water. However, the consumption rate quickly decreased to 1/1,000 of the initial rate after about 50 min. The change of residual chlorine with time was found to fit mathematically to a two-term exponential equation. The equilibrated chiller water had a chlorine demand greater than the highest chlorine dosage tested (400 ppm). No free chlorine was detected in the water after 30 min of exposure to 300 ppm chlorine. Because of the high chlorine demand, dosages of 100 to 150 ppm chlorine were required to reduce the number of bacteria by at least 99% within 3 to 5 min in laboratory tests. Increasing the time of exposure to chlorine resulted in further reduction, although at a slow rate, of surviving bacteria from treatments that gave incomplete destruction with short exposure. (

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Free Available Chlorine Residuals for Small Nonpublic Water Supplies

Cited by 21 publications

References 8 publications

Chemical and Stress Resistances of Clostridium difficile Spores and Vegetative Cells

Chemical and Stress Resistances of Clostridium difficile Spores and Vegetative Cells

Advances in disinfection testing and modelling

Chlorination of Poultry Chiller Water: Chlorine Demand and Disinfection Efficiency

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