[R] Best way to model colonization: logistic regression vs. Poisson regression, or perhaps some other technique.

[John Sorkin]

Please forgive a stats question

I am trying to model colonization with a bacterium with the aims of quantifying overall colonization rate as well as determining risk factors for colonization in a in-hospital setting. Risk factors to me measured include type of contact with a patient (e.g. feeding vs. obtaining vital signs vs. wound care etc), length of contact, use of antibiotics, etc. I believe there are two techniques that can be used to model colonization: logistic regression or Poisson regression. Either method can give me a measure of likelihood of transmission (the OR from logistic regression or a true rate from Poisson regression. n.b. the OR from logistic regression can be converted to a probability). Can anyone suggest reasons for using one technique or the other?  
Thank you for your help and understanding about posting a stats question to the R listserver.
Thanks,

John

John David Sorkin M.D., Ph.D.
Chief, Biostatistics and Informatics
University of Maryland School of Medicine Division of Gerontology
Baltimore VA Medical Center
10 North Greene Street
GRECC (BT/18/GR)
Baltimore, MD 21201-1524
(Phone) 410-605-7119
(Fax) 410-605-7913 (Please call phone number above prior to faxing)

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