Chemotherapeutic and Chemical Agents Microbiology 156.
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Transcript of Chemotherapeutic and Chemical Agents Microbiology 156.
Antibiotics
Drugs that interfere with bacterial cell metabolism
They produce a bacteriocidal or bacteriostatic effect on prokaryote cells
Origin of Antibiotics
These are agents that have been synthesized by bacteria or fungi against other organisms
Example – Penicillin was isolated from the mold Penicillium notatum. It was first observed by Alexander Fleming and later purified by Howard Florey.
Mode of Action
Interfere with the synthesis of the cell wall( peptidoglycans)
Disruption of the cell membrane Inhibition of folic acid Interference with protein synthesis Interference with nucleic acid
synthesis Ribosomal interference
Penicillin – The first
Effects the synthesis of the peptidoglycans cell wall
Makes the bacteria vulnerable to the phagocytes in the immune system
Antibiotics from Actinomycetes
Actinomycetes are soil bacteria
They produce compounds that inhibit other microorganisms
Competition for food and space in the soil environmentSelman Waksman,
Rutgers University, NJ
Pharmacology
Synthetic drugs are designed based upon the structure of molecules produced in nature by bacteria
They are then tested for their antimicrobial activity – in vitro and in vivo
KirbyBauer
The determination of antibiotic sensitivity or resistance
Sensitivity – The organisms growth is inhibited by the presence of the antibiotic
Resistance – The organism has a means of interfering with the mode of action of the antibiotic
Kirby Bauer
Plate bacteria on Mueller Hinton Agar Plate
Distribute bacteria evenly over the surface of the agar
Place discs impregnated with antibiotic on the agar at indicated spots.
Incubate
Chemical agents
Incubate the plates for 24 hours Measure the diameter of the plate to
determine efficacy of the chemical agents
Determination of resistance or sensitivity Measure the diameter of the ring
around the disc Compare the measurement in mm
with the table in your lab manual, page 284. Table 44.2
Record your results in Table on page 287.
Heat- Destruction of bacterial cells
Autoclave – heat under pressure 121 0C at 15 psi for 15 minutesBoiling For more than 30 minutes
Chemical agentsAgent Mechanism of
ActionUse
Peroxygens Oxidations Use in wounds and abrasions
Alcohols Protein denaturation
Skin disinfection
Organic acids Disrupt proteins- low pH
Used to control moleds
Detergents Disrupts cell membranes
Disinfection
Halogens derivative IodineChlorine
Inhibits protein action in bacteria
Surface area disinfection
Chemical Agents- Agar Plate sensitivity assay Plate the bacteria by spreading it
evenly across the Mueller- Hinton agar.
Dip sterile filter discs into chemotherapeutic agents.
Carefully place the discs in indicated spots on the agar plate
Determination of activity
Measure the zone of inhibition around the disc to determine if the antiseptic or disinfectant had sufficient activity to inhibit the growth of the bacteria in your study