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Category: Industrial Microbiology; Clinical Microbiology
Introduction, Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816445/9781555819019_Chap01-1.gif /docserver/preview/fulltext/10.1128/9781555816445/9781555819019_Chap01-2.gifAbstract:
Microorganisms play important roles in our lives. Of primary interest are those microorganisms that cause diseases under a variety of circumstances. Other issues include the economic aspects associated with microbial contamination, such as food spoilage, plant infections, and surface damage. This introductory chapter of Antisepsis, Disinfection, and Sterilization provides a brief description of the various types of target microorganisms, as well as a discussion of some key considerations for biocidal applications, including the evaluation of efficacy, formulation effects, and the importance of cleaning. It offers brief insights of the topics discussed in each chapter in the book. A section presents definitions of the biocidal applications consistent with international consensus documents.
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A typical helminth life cycle (example: Enterobius vermicularis).
Typical fungal structures. (A) Filamentous fungus (mold). Hyphae are shown as long lines of unseparated cells, with the development of a fruiting body with attached spores. (B) Typical unicellular fungal (yeast) cells. The cells are generally polymorphic. In one case, a budding cell is shown.
Simplified fungal cell envelope. The cross-linked cell wall is linked to the cell membrane. The cell wall usually consists of innermost fibrils of chitin or cellulose, with outer layers of amorphous, cross-linked glucans.
Life cycle of Toxoplasma gondii.
Simple representation of a mycoplasma cell surface structure.
Basic structure of a bacterial cell, showing the cell surface in greater detail.
Bacterial cell wall structures. The cell membranes are similar structures in all types. grampositive bacteria have a large peptidoglycan layer (shown as crossed lines) with associated polysaccharides and proteins. gramnegative bacteria have a smaller peptidoglycan layer linked to an outer membrane. The mycobacterial cell has a series of covalently linked layers, including the peptidoglycan-, arabinogalactan-, and mycolic acid-containing sections.
Basic structure of peptidoglycan. Polysaccharides of repeating sugars are cross-linked by peptide bridges. Two different types of peptide bridges, which have been described in grampositive and gramnegative bacterial cell walls, are shown.
Cells of Mycobacterium tuberculosis. Courtesy of Clifton Barry, NIAID.
Basic viral structure.
Typical viral life cycle. The stages include (1) attachment, (2) penetration into the cell, and (3) multiplication. Depending on the virus type, viral particles can be released by cell lysis (4a) or by budding (4b); alternatively, the virus can remain dormant in the cell (4c).
E. coli bacteriophages. The T-phages are complex DNA viruses; MS2 and ϕ6 are RNA viruses, with ϕ6 enveloped.
Theory of prions as infectious proteins. PrPc is the normal form of the protein, and PrPSc the abnormal form.
Representation of the proposed structural changes in PrP.
The general structure of lipopolysaccharide. The lipid A component is integrated into the outer membrane of the gramnegative cell wall, with the polysaccharide portion extending to the outside of the cell.
Typical fungal aflatoxin structure.
General microbial resistance to biocides and biocidal processes. This classification can vary depending on the biocide or biocidal process under consideration.
Typical time kill, or D-value, determination. A known concentration of the test culture is exposed to the biocide, samples are withdrawn at various times and neutralized, and the population of survivors is determined by incubation on growth medium. The actual exposure can be conducted at various temperatures, in the presence or absence of test soils, or under other test conditions.
Determination of the D value on microbial exposure to a biocide.
Typical survivor curves on biocide exposure. Curve 1 is concave downward, curve 2 is sigmoidal, and curve 3 is concave upward.
Qualitative and semiquantitative population determinations.
D-value estimation using most probable number estimations.
Example of a self-contained biological indicator. The 3M Attest 1292 Rapid Readout Biological Indicator is used to monitor steam sterilization cycles. Reproduced with permission of 3M Health Care.
Example of a chemical-indicator color change.
Rate of microbial inactivation on exposure to sterilization processes. In this case, the test microorganism (generally bacterial spores) at a starting population of 106 is exposed to the sterilizing agent under two conditions (A and B). The number of microorganisms can be determined over contact time or dose using a combination of direct-enumeration and fraction-negative methods (solid lines). In process A, “tailing” is observed, which may not allow the extrapolation of the kill curve to a defined probability of survival (known as an SAL). In process B, the kill curve is linear, allowing extrapolation (dotted line) to an SAL of 10–6.
Basic structures of surfactants and soaps and micelles (a water-in-oil micelle is shown).
Examples of single (left)- and multiple (right)-chamber washer and washer-disinfector machines. Washer-disinfectors can come in a variety of shapes and sizes, depending on their required uses.
Various types of cleaning chemical formulations.
Examples of various types of microorganisms
Some advantages and disadvantages of microorganisms
Comparison of general prokaryotic and eukaryotic structuresa
Helminths associated with disease
Examples of common fungi
Classification of protozoa, based on their motility mechanisms and microscopic morphologies
Examples of pathogenic mycoplasmas
General differentiation of types of bacteria based on their microscopic morphologies and reactions to Gram staining
Examples of grampositive bacteria
Examples of gramnegative bacteria
Cell wall structures in mycobacteria and related organisms
Examples of extremophile archaea
Viral families, with examples of classifications, including size, presence of a lipophilic envelope, and nucleic acid type
Examples of viral diseases
Examples of bacterial, fungal, and algal toxins
Common examples of bacterial exotoxins
Examples of surrogate microorganisms used to test and verify antimicrobial activities of biocides, products, and processes
Examples of standardized suspension tests
Examples of standardized carrier tests
Examples of simulated-use and/or in-use tests and/or guidelines a
Bacterial-endospore species used to monitor and validate sterilization processes
Examples of biological-indicator standards
A typical classification of chemical indicators
Examples of chemical-indicator standards
Examples of standards and guidelines for antisepsis, disinfection and sterilization
Various constituents of formulated biocidal products
Examples of process variables in various disinfection/sterilization techniques
Various components of cleaning formulations
Examples of common water contaminants and their effects