Iowa State University has provided extended dilution susceptibility information for bovine pathogens. This link provides access to this information in a way that allows you to select drugs and pathogens.

Open Susceptibility Viewer in a new window.

When you use the suceptibility viewer, assume that the concentrations listed for each drugs (the MICs) include the entire susceptibility range plus one concentration (the highest one) that would normally be interpreted as "resistant". When you choose multiple organisms, the data is aggregated so that the information represents a combined susceptibility profile for all three.

Open an Example in a New Window

In this example, MICs of < or = 0.25 through 16 μg/ml would be interpreted as S for susceptible. An MIC of 32 μg/ml would be interpreted as R. This applies to all drugs in this system. Isolates with MICs at the highest concentration (all drugs) are interpreted as R on by the laboratory.

Exercise: Use the suceptibility viewer to answer the questions. Copy the questions to a separate document and answer the questions. Upload your answers. Please put your names on your papers somewhere!!!!

Bovine respiratory disease complex is predominately associated with Mannheimia haemolytica, Pasteurella multocida and Histophilus somni (previously know as Haemophilus somnus). Ampicillin, ceftiofur, enrofloxacin, erythromycin, florfenicol, oxytetracycline, penicillin G, and tilmicosin are contained in products approved for the use in cattle for this treatment of this condition (some approved for BRDC, some for bovine pneumonia).

Question 1:
Which of the drugs listed above achieve an MIC90 within the susceptible concentration range for Mannheimia haemolytica isolated from cattle?:

Question 2:
Which of the drugs listed above achieve an MIC90 within the susceptible concentration range for Pastuerella multocida isolated from cattle?:

Question 3:
Which of the drugs listed above achieve an MIC90 within the susceptible concentration range for all three pathogens typically isolated from cattle with bovine respiratory disease complex (Mannheimia haemolytica, Pasteurella multocida, Histophilus somni?

Question 4:
Compare ampicillin, oxytetracycline and ceftiofur for the combination of K99 positive and K99 negative E. coli.

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