Principles of Antibiotics

Question 1

• 3 parts of empirical theory?
• To cover worst cocci? Rods? Then?
• MIC? 3 tests? How do they work?
• MBC?
• Bacteriocidal?
• Static?
• To achieve adequate level at site of infection Cp>?
• Breakpoints tell you? Change over time?
• Pitfalls of breakpoints? (3)
• What should be done after labs have been run?

Answer 1

• what/where is the syndrome; pathogens involved; likley resistance profile
• MRSA; CNR pseudonomas; anaerobes
• Lowest conc. of antimicrobial that inhibits growth
• Tube (broth) dilution = see conc. with no visible growth
• Disc diffusion = mm inhibition = MIC
• E Test = Plate has conc. gradient to help dtermine MIC
• MBC/MIC 4
• Cp>MIC/MBC
• S,I,R pattern of suseptibility; yes
• Not set for site of infection, not adjusted for # of organisms at site; not adjusted for host defense
• Antibiotic therapy should be re set

Question 2

Gene Transfer:

• Parts of bacterial genome? (3)
• Bacterial evolution:
  1. ) Spontaneous advantage?
  2. ) recombination types? (2)
  3. ) Acquisition of new DNA:
  a. ) Transposable elements: Can be moved? Can also be?
  b. ) Plasmids: Essential for viability?
  c. ) Pathogenicity Islands: Influence? Usually acquired from?

Answer 2

• chromosome, plasmids, bacterial viruses
  1. ) Base pair changes that sometimes give a selective advantage
  2. ) Antigenic: Alter surface proteins to evade host; genetic exchange with unrelated species
  3. a.) One DNA location to another; an insertion sequence
  b. ) No
  c. ) Pathogenicity; unrelated organism

Question 3

Mechanisms for genetic exchange:

1. ) Transformation: DNA taken up and? (2) Can plasmid be taken up?
2. ) Transduction mediated by? 2 possible phases? Prophage?
3. ) Conjugation:
   a. ) Conjugative plasmids?
   b. ) Non- conjugative?
   c. ) Third kind?
   - Conjugative transposons mediate? Often encode? Occurs cross species?

Answer 3

• added to chrom or destroyed; yes
• bacterial virus; lysogenic/lytic; lysogenic bacterium
• self tranmissable; mediate their own uptake
• Can be passively transferred (mobilized)
• Non mobilizable
• Conjugation; resistance; sometimes