zone of inhibition

(noun)

This is an area of media where bacteria are unable to grow, due to presence of a drug that impedes their growth.

Related Terms

Examples of zone of inhibition in the following topics:

  • Kirby-Bauer Disk Susceptibility Test

    • A larger zone of inhibition around an antibiotic-containing disk indicates that the bacteria are more sensitive to the antibiotic in the disk.
    • KB tests are performed under standardized conditions and standard-sized zones of inhibition have been established for each antibiotic.
    • KB test results are usually reported as sensitive, intermediate, or resistant, based on the size of the zone of inhibition.
    • If the observed zone of inhibition is greater than or equal to the size of the standard zone, the microorganism is considered to be sensitive to the antibiotic.
    • Conversely, if the observed zone of inhibition is smaller than the standard size, the microorganism is considered to be resistant.

  • Dendritic Cells

    • Langerhans cells of the epidermis) are located in main portals of entry of microbes (skin and gut epithelia).
    • Mature dendritic cells reside in the T cell zones of the lymph nodes, and in this location they display antigens to T cells.
    • Subsets of dendritic cells can be distinguished by the expression of cell surface markers.
    • Some may even inhibit T cell activation.
    • An example of this includes the interaction of the membrane proteins of the B7 family of the dendritic cell with a CD28 cell surface molecule present on the lymphocyte.

  • The Deep Sea and Barophilism

    • Because of the unique challenges (particularly the high barometric pressure, extremes of temperature, and absence of light), it was long believed that little life existed in this hostile environment.
    • Zones of the deep sea include the mesopelagic zone, the bathyal zone, the abyssal zone, and the hadal zone.
    • Some have been found at the bottom of the Pacific Ocean where the maximum pressure is roughly 117 MPa.
    • Obligate barophiles cannot survive outside of such environments.
    • For example, the Halomonas species Halomonas salaria requires a pressure of 1000 atm (100 MPa) and a temperature of three degrees Celsius.

  • Inhibiting Essential Metabolite Synthesis

    • An antimetabolite is a chemical that inhibits the use of a metabolite, a chemical that is part of normal metabolism.
    • An antimetabolite is a chemical that inhibits the use of a metabolite, a chemical that is part of normal metabolism.
    • For example, methotrexate is a folic acid analogue, and owing to structural similarity with folic acid, methotrexate binds and inhibits the enzyme dihydrofolate reductase, and thus prevents the formation of tetrahydrofolate.
    • Because tetrahydrofolate is essential for purine and pyrimidine synthesis, its deficiency can lead to inhibited production of DNA, RNA and proteins.
    • The second type of antimetabolite antibiotics consist of pyrimidine analogues which mimic the structure of metabolic pyrimidines .

  • Antibiotic Classifications

    • Bactericidal antibiotics kill bacteria; bacteriostatic antibiotics inhibit their growth or reproduction.
    • One way that bactericidal antibodies kill bacteria is by inhibiting cell wall synthesis.
    • The MIC (minimum inhibitory concentration) is the minimum concentration of drug which can inhibit the growth of the microorganism.
    • Penicillin and most other β-lactam antibiotics act by inhibiting penicillin-binding proteins, which normally catalyze cross-linking of bacterial cell walls.
    • Tetracycline antibiotics are protein synthesis inhibitors, inhibiting the binding of aminoacyl-tRNA to the mRNA-ribosome complex.

  • Inhibiting Cell Wall Synthesis

    • β-Lactam (beta-lactam) and glycopeptide antibiotics work by inhibiting or interfering with cell wall synthesis of the target bacteria.
    • Two types of antimicrobial drugs work by inhibiting or interfering with cell wall synthesis of the target bacteria.
    • This includes penicillin derivatives (penams), cephalosporins (cephems), monobactams, and carbapenems. β-Lactam antibiotics are bacteriocidal and act by inhibiting the synthesis of the peptidoglycan layer of bacterial cell walls .
    • This class of drugs inhibit the synthesis of cell walls in susceptible microbes by inhibiting peptidoglycan synthesis.
    • Describe the two types of antimicrobial drugs that inhibit cell wall synthesis: beta-lactam and glycopeptide antibiotics

  • Inhibiting Nucleic Acid Synthesis

    • Antimicrobial drugs inhibit nucleic acid synthesis through differences in prokaryotic and eukaryotic enzymes.
    • For example, the antimicrobial rifampin binds to DNA-dependent RNA polymerase, thereby inhibiting the initiation of RNA transcription.
    • Any of the steps in the process of DNA replication can be targeted by antimicrobial drugs.
    • For instance, quinolones inhibit DNA synthesis by interfering with the coiling of DNA strands.
    • Portions of the enzyme were made transparent so as to make the path of RNA and DNA more clear.

  • Toxins

    • The release of toxins into the surrounding environment, regardless of when released, results in the disruption of metabolic pathways in the host eukaryote .
    • These metabolic pathways include damaging cell membranes, disrupting protein synthesis, inhibiting neurotransmitter release, or activating the host immune system.
    • Upon activation of the immune system, the release of large amounts of cytokines, inflammatory related molecules, causes significant inflammation.
    • Aflatoxins are a type of mycotoxin that are produced by certain strains of Aspergillus fungi.
    • These strains are present in a wide range of agricultural commodities associated with tropic and subtropic zones.

  • Sulfate and Sulfur Reduction

    • Thus, the black color of sludge on a pond is due to metal sulfides that result from the action of sulfate-reducing bacteria .
    • An important fraction of the methane formed by methanogens below the seabed is oxidized by sulfate-reducing bacteria in the transition zone separating the methanogenesis from the sulfate reduction activity in the sediments.This process is also considered a major sink for sulfate in marine sediments.
    • In hydrofracturing fluids used to frack shale formations to recover methane (shale gas), biocide compounds are often added to water to inhibit the microbial activity of sulfate-reducing bacteria in order to avoid anaerobic methane oxidation and to minimize potential production loss.
    • The interaction of water and metal creates a layer of molecular hydrogen on the metal surface.
    • The black color of this pond is due to metal sulfides that result from the action of sulfate-reducing bacteria.

  • Ecological Associations Among Microorganisms

    • However, their growth can be increased by warmth and sweat; in humans, large populations of these organisms are the cause of body odor .
    • In soil, microorganisms that reside in the rhizospehere (a zone that includes the root surface and the soil that adheres to the root after gentle shaking) carry out nitrogen fixation, converting nitrogen gas to nitrogenous compound.
    • For example, the presence of over one thousand bacterial species in the normal human gut flora of the intestines can contribute to gut immunity.
    • The presence of this gut flora also inhibits the growth of potentially pathogenic bacteria (usually through competitive exclusion), and these beneficial bacteria are consequently sold as probioticdietary supplements.
    • Each species of pathogen has a characteristic spectrum of interactions with its human hosts.