1. … genetics will someday make BRD as we know it a distant memory

2. Antibiotic Selection & Use
Dee Griffin, DVM, MS or C:

3. What You Need to Know &Think About When Selecting Antibiotics
The objective will be to help folks better understand:
1) how antibiotics work … clinically
2) antibiotic classes … & what makes them different
3) how to think through developing treatment protocols
4) understand dose management & resistance development
5) how to select a proper antibiotic for different diseases
6) how the other things given sick cattle can influence an antibiotic's effectiveness
7) how to know when to switch
8) which antibiotic would make a better choice when a switch is need if an animal doesn't respond
9) when to quit
10) potential residue considerations & management

4. Parts of the Puzzle

5. IBR at work

6. Shipping fever / BRD … set up by
the role of antibiotics in treating diseases caused by different bugs … focus on respiratory disease
Shipping fever / BRD … set up by
lack of immune protection
stress, commingling, & timing
Virus destroys cells that protect the lung …
Bacteria move from their hang out to lung
Lungs cells provide lots of food with very little defense

9. Disease sequence of events:
Susceptible animal exposed.
Incubation is the period (time) from the first replication of the disease causing biological agent until sufficient compromise of the target organ(s) occurs causing loss of function of the target organ(s).
Primary viral BRD this averages 3 days.
Secondary bacterial BRD averages 3 to 5 days behind the initial viral infection.

10. Disease sequence of events:
Inflammation occurs in stages.
Early, the body diverts white blood cells and blood in to the affected area typically causing swelling of tissue, both cells and spaces between cells.
As the inflammation continues, loss of function of the affected tissue occurs.
Late stage of inflammation is involved in the body trying to clean up, remove, or repair / reconstruct the damaged tissue.
The late stage of inflammation is the first stage of recovery. … begins 7 to 10 days … last for weeks

11. KEY … the battle is lost after 7 to 10 days … why
KEY … the battle is lost after 7 to 10 days … why? … Thrombosis of blood supply to deliver drug

13. how the antibiotics work
Antibiotic – mold, 1928
Protect molds from bacteria
No effect on viruses or normal body cells
Two types -static (slows) & cidal (kills)
Four mechanisms
Cripples cell wall
Interferes with protein synthesis
Confuses metabolic processes
Blocks DNA / RNA synthesis
Different bacteria … require different mechanisms to stop them …

14. antibiotic resistance mechanisms
Decrease Cell Wall Uptake / Perm
Aminoglycosides
Efflux
Macrolides, fluoroquinolones, tetracyclines
Enzymes Induced
Aminoglycosides, florfenicol, beta-lactams
Altered Target Binding Sites
Ribosome …macrolides, lincosamides
Wall Protein … beta-lactams, glycopeptides
DNA … fluoroquinolones
Gene Resistance
Plasmids … b-lact, tetra, macro, linco, fluro, sulfa
Transposons … beta-lactams, glycopeptides
Chromosome … beta-lactams, fluoroquinolones

15. FDA antibiotic resistance potential grid (GFI 152)

16. KEY: IF YOU DON’T MANAGEMENT ANTIBIOTIC THERAPY … THE “RELAPSE”
MAY NOT BE TREATABLE !!!

17. KEY !!!

18. Key Concept

19. PK / PD Relationships
Key Concept

20. Antibiotic Movement
Key Concept

21. Key Concept

22. Critical Concept Question …
Can you increase the efficacy of:
Time Dependent Antibiotics?
YES … change dosing frequency …
Concentration Dependent Antibiotics?
YES … change dosing concentration …
Can you increase antibiotic efficacy:

23. Ab Testing … Think About It

25. select a proper antibiotic … additional points
Pneumonia …
Ab penetration not as much of a problem early as late
Bugs that live in cells … need Ab that crosses cell walls
Animal’s that are over whelmed & can’t help the drug by fighting back … cidal Ab may be better than static Ab
Can’t defend the use of Pen G (especially LA Pen) & Sulfa in BRD Rx programs
CAUTION – Generics …& AVOID Bathtub mixes
Neomycin & Gentamicin … violate BQA & reason

26. BIGGEST FACTOR … TIMING!!!
why an antibiotic may seem to work on some sets of cattle and not others
Source … Immune prep history
Source … Nutritional history
Source … Stress & Commingling
BIGGEST FACTOR … TIMING!!!
How much of a head start ???
Animal’s ability to help fight back
Differences in bugs … Diagnosis???

28. Prevention … is key Treatment salvages only part of the loss
Immune preparation
Treatment timing