micropara lab ex. 5

• Pasteur and others observed that infecting an animal with Pseudomonas aeruginosa protected the animal against 


  Bacillus anthracis
• Investigators coined the word antibiosis which means


  against life
• Inhibiting substance


  Antibiotic
• Alexander Fleming observed antibiosis around a mold (Penicillium) growth on a culture of staphylococci. When was this?


  1928
• Who observed antibiosis around a mold (Penicillium) growth on a culture of staphylococci


  Alexander Fleming
• He found that culture filtrate of Penicillium inhibited the growth of many gram-positive cocci and Neisseria spp.


  Alexander Fleming
• In 1940, Selman A. Waksman isolated the antibiotic 


  streptomycin
• In 1940, Selman A. Waksman isolated the antibiotic streptomycin, produced by an 


  actinomycete
• Remains an important source of antibiotics

  Actinomycetes
• Antimicrobial chemicals absorbed or used internally, whether natural (antibiotics) or synthetic, are called

  chemotherapeutic agents
• In this method, bacteria to be tested are added to melted Mueller Hinton agar and poured onto solidified agar in a petri plate


  Agar diffusion method
• Paper disks impregnated with various chemotherapeutic agents are placed on the

  surface of the agar
• The chemotherapeutic agent diffuses from the disk during

  Incubation
• In an agar diffusion method, bacteria to be tested are added to melted

  Mueller Hinton agar
• The concentration of the chemotherapeutic agent at the edge of the zone of inhibition represents its

  minimum inhibitory concentration (MIC)
• Determined by comparing the zone of inhibition with the MIC values in a standard table

  minimum inhibitory concentration (MIC)
• Affected by such factors as the diffusion rate of the antibiotic and the growth rate of organism.

  Zone size
• What cultures are used in this experiment?

  Staphylococcus aureus and Escherichia coli
• Chemical agents used on inanimate objects to lower the level of microbes on that surface

  Disinfectant
• Chemicals used on living tissue to decrease the number of microbes

  Antiseptic
• Additional variables to consider in selecting an antimicrobial agent include

  pH, solubility, toxicity, organic material present, and cost
• One method of measuring the effectiveness of a chemical agent is to determine

  Phenol coefficient
• Kill bacteria by damaging the plasma membrane, inactivating enzymes, and denaturing proteins


  Phenolics
• The phenol coefficient is a comparative test using a standard organism such as 


  Staphylococcus aureus
• Cause temporary inhibition of growth


  Bacteriostatic agents
• Results in bacterial death


  Bactericidal agents
• Important criteria in evaluating the effectiveness of the antimicrobial agents

  The concentration, length of contact, and whether it is lethal (- cidal) or inhibiting (-static)
• Swab in _ directions to ensure complete plate coverage.

  Three (3)
• With the filter paper disks, soak them in the laboratory chemical of choice for at least

  5 minutes
• Incubate the plate on an inverted position at


  35°C
• Title of Experiment

  Chemical Methods of Control