China
Africa
Explore chapters and articles related to this topic
Steam Sterilization
Published in Sandeep Nema, John D. Ludwig, Parenteral Medications, 2019
The steeper the slope of this line, the less resistant the organism is to sterilization process. The D-value can be influenced by a number of factors aside from the microbial identity including recovery media, age of the microbe, recovery methods, substrate on which the microbe is exposed, etc. [2]. The D-value is defined as the time in minutes to reduce the microbial population by 1 logarithm or 90%. D-values are determined through the use of a specially designed sterilizer called a Biological Indicator Evaluation Resistometer (BIER) [4]. BIER vessels provide precise control over exposure temperature and process time to allow for determination of the microbial death curve. The inverse of this slope is known as the D-value and is usually expressed in minutes. Bioburden (BB) microorganisms are destroyed far more rapidly than the moist-heat-resistant spore formers customarily utilized as biological indicators (BIs) (see Figure 31.3). The United States Pharmacopeia (USP) has new content on sterilization that emphasizes that the true target of sterilization processes is the natural BB present and that the BI is merely a tool for measurement of the process and should not be used to define the minimum process duration [5]. Nearly all sterilization processes are validated using BIs with higher resistance whose death in the validation exercise provides added assurance that the BB microorganisms with lower resistance are destroyed in routine usage of the sterilizer (when the BI is not present).
Sterilization Methods
Published in Jeanne Moldenhauer, Disinfection and Decontamination, 2018
Some types of bacteria (Gram-positive rods) can form structures that are resistant to adverse conditions called spores as a defensive survival method. These are different from fungal spores (mold spores) that are manufactured as reproductive bodies. The genus and species of bacteria resistant to a specific sterilization process may be different across sterilization processes. Additionally, the same bacterial spore may have different levels of resistance to varying sterilization processes. The level of resistance to a sterilization process is expressed as the D-value. D-values are specific for a sterilization medium and a specific temperature. The D-value is defined as the amount of time in minutes that are required at a specific reference temperature to reduce the microbial population by one log. The higher the D-value at a specific set of sterilizing conditions, the more resistant the organism is to the sterilization process (Moldenhauer, 2013 and 2014).
Validation of Terminal Sterilization
Published in James Agalloco, Phil DeSantis, Anthony Grilli, Anthony Pavell, Handbook of Validation in Pharmaceutical Processes, 2021
Kevin D. Trupp, Thomas J. Berger
Refer to Figure 14.6 for a schematic of the steam BIER vessel used to generate the D and z-value data. D-value is the time in minutes required for a one log or 90% reduction in microbial population. The z-value is the number of degrees of temperature required for a 10-fold change in the D-value (Refer to Chapter 11 for additional details on F-, D- and z-values).
Computational simulation of incineration of chemically and biologically contaminated wastes
Published in Journal of the Air & Waste Management Association, 2021
Paul Lemieux, Timothy Boe, Anna Tschursin, Martin K. Denison, Kevin Davis, Dave Swensen
where y0 is the initial number of viable spores. The form of the rate constant as a function of temperature is needed next. The concept of the Z value from microbiology (Prescott, Harley, and Klein 2002) is used as guidance in providing this form. If D is the time required at a given temperature to achieve a log reduction in organisms, then Z is defined as the number of degrees change in temperature needed to change the D value by a factor of 10. For example, if Z is 5°C, and if D is 5 minutes at 65°C, then D will be 50 minutes at 60°C. It follows that Z = T2 – T1 if
Evaluation of the effectiveness of nonthermal plasma disinfection
Published in Environmental Technology, 2020
YuJung Chen, YungChih Chen, WeiChieh Chung, BaoShun Tong, Moo Been Chang
The survival curve represents the decrease rate of bacterial colonies achieved with disinfection. Survival curves indicate not only disinfection efficiency but also decimal time which is also known as D-value. However, the survival curve does not give us the baseline information on the original colony number for comparison. Therefore, the disinfection efficiency is expressed by the germicidal effect in this study. The germicidal effect (GE) is defined as Equation (1):where N0 and N represent colony forming units (CFU/mL) of controlled and disinfected set, respectively.
Toward Efficient Low-Temperature Ozone Gas Sterilization of Medical Devices
Published in Ozone: Science & Engineering, 2020
Sandy A. Thill, Marc Spaltenstein
The decimal reduction factor, also known as D-value, represents the resistance of a specific germ (e.g. BI batch) for a sterilization process under defined conditions. This D-value can be obtained from the slopes of the survivor curves and corresponds to the time or dose necessary to obtain 1 log10 reduction. The D-values, obtained for the data in Figure 4 as well as for the additional temperatures, are plotted in Figure 6.