bmsc210 m2 p7

– The killing or removal of all viable organisms within a growth medium

– Effectively limiting microbial growth

– The treatment of an object to make it safe to handle

– Directly targets the removal of all pathogens, not necessarily all microorganisms

• is the most widely used method of controlling microbial growth (Figure 26.1)
• – High temperatures denature macromolecules
• – Amount of time required to reduce viability tenfold is called the decimal reduction time (Figure 26.2)

• Spore-forming bacteria

• is a sealed device that usessteam under pressure (Figure 26.3)
• – Allows temperature of water to exceed
• – Not the pressure that kills, but the high temperature

• is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids
• – Does not kill all organisms, it is not sterilization

• • Microwaves, UV, X-rays, gamma rays can reducemicrobial growth
• • UV has sufficient energy to cause modifications and breaks in DNA
• – UV is useful for decontamination of surfaces (Figure 26.4)
• – Cannot penetrate solid, opaque, or light-absorbingsurfaces

• – Electromagnetic radiation that produce ions andother reactive molecules
• – Generates electrons, hydroxyl radicals, and hydride radicals
• – Some microorganisms are more resistant to radiation than others
• • Amount of energy required to reduce viability tenfold is analogous to D value (Figure 26.5)

• X-rays
• nuclides

sterilization

• decontamination of foods
• • Hamburger, chicken, spices may all be irradiated

• – HEPA(High-efficiency particulate air) filters
• -filters that filter though out the medium as opposed to just at the surface. Reduces ability to be clogged

– Function more like a sieve

• -thin polycarbonate films that are perforated by a combined treatment with radiation and chemicals.
• -work like sieves, preventing the flow of any particle with a size greater than the pore.

• stops cell growth
• viable cell count=total cell count

• bacteria is killed but not destroyed
• viable cell count is decreased
• total cell count stays constant (bacterial cells linger after death)

• bacterial cells are destroyed
• viable and total cell count drops

• the smallest amount of an agent needed to inhibit growth of a microorganism
• – Varies with the organism used, inoculum size,temp, pH, etc.

– Antimicrobial agent added to filter paper disc– MIC is reached(bacteria is killed and lawn cleared) at some distance away from disc

– Area of no growth around filter paper disc

• – Products used to control microorganisms in commercial and industrial applications
• • Examples: chemicals in foods, air-conditioning cooling towers, textile and paper products, fuel tanks
• – Products designed to prevent growth of human pathogens in inanimate environments and on external body surfaces
• • Sterilants, disinfectants, sanitizers, and antiseptics

a process in which sterilization is carry out at low temperature with the help of chemicals, radiations, membranes and all other means excluding high temperature.

antimicrobial agents created by organisms naturally

• – Molecular structure
• – Mechanism of action
• – Spectrum of antimicrobial activity(range of microorganisms effected)

• -Selective toxicity is ability to inhibit or kill a pathogen without affecting the host
• -studied by Paul Ehrlich in the early 1900s

–one of the first antimicrobial drugs

• molecules structurally similar to growth factors but do not function in the cell
• – Analogs similar to vitamins, amino acids, andother compounds

• – Inhibit growth of bacteria by use of a paraminobenzoic acid analog (sulfanilamide is thesimplest;
• -discovered by Gerhard Domagkin the 1930s

• a growth analog effective only against Mycobacterium
• – Interferes with synthesis of mycolic acid (cell wall)
• effective against: Mycobacterium tuberculosis ect...

formed by the addition of bromine or fluorine to nucleic acid

• synthesized antibacterial compounds that interfere with DNA gyrase
• e.g., ciprofloxacin

supercoiling of DNA in bacteria

• -antibiotics that are modified to enhance efficacy
• – Less than 1% of known antibiotics are clinically useful

• -one of the most important groups of antibiotics of all time
• -Named for B-lactam ring
• – Include penicillins, cephalosporins, and cephamycins
• – Over half of all antibiotics used worldwide

• – Discovered by Alexander Fleming
• – Primarily effective against gram-positive bacteria
• – Some synthetic forms are effective against some gram-negative bacteria

inhibitors of cell wall synthesis, specifically transpeptidation (cross-linking of two glycan-linked peptide chains)

• – Produced by fungus Cephalosporium
• – Same mode of action as the penicillins (B-lactam ring) but broader range
• – Commonly used to treat gonorrhea

• -antibiotics created by Bacteria that contain amino sugars bonded by glycosidic linkage
• -target 30s sub unit of ribosome
• -Examples: kanamycin, neomycin, streptomycin

• -Antibiotics created by bacteria not commonly used today
• - Considered reserve antibiotics for when other antibiotics fail

• -Bacteria synthesized antibiotics that contains lactone rings bonded to sugars
• Example: erythromycin
• – Broad-spectrum antibiotic that targets the 50S subunit of ribosome

• -Bacteria synthesized antibiotics that contain four rings
• – Widespread medical use in humans and animals
• – Broad-spectrum inhibition of protein synthesis
• – Inhibits functioning of 30S ribsomal subunit

– The acquired ability of a microorganism to resist the effects of a chemotherapeutic agent to which it is normally sensitive

• 1 Organism lacks structure the antibiotic inhibits
• 2 Organism is impermeable to the antibiotic
• 3 Organism can inactivate the antibiotic
• 4 Organism may modify the target of the antibiotic
• 5 Organism may develop a resistant biochemical pathway
• 6 Organism may be able to pump out the antibiotic(efflux)

one of the few pathogens that have developed resistance to all known antimicrobial agents