The Collaborative International Dictionary of English v.0.48:

Bacteriology \Bac*te"ri*ol`o*gy\, n. [Bacterium + -logy.]
   (Biol.)
   The branch of microbiology relating to bacteria.
   [1913 Webster]

WordNet (r) 3.0 (2006):

bacteriology
    n 1: the branch of medical science that studies bacteria in
         relation to disease

Moby Thesaurus II by Grady Ward, 1.0:

38 Moby Thesaurus words for "bacteriology":
   aerobiology, agrobiology, anatomy, astrobiology, biochemics,
   biochemistry, biochemy, bioecology, biological science, biology,
   biometrics, biometry, bionics, bionomics, biophysics, botany,
   cell physiology, cryobiology, cybernetics, cytology, ecology,
   electrobiology, embryology, enzymology, ethnobiology, exobiology,
   genetics, gnotobiotics, life science, microbiology,
   molecular biology, pharmacology, physiology, radiobiology,
   taxonomy, virology, xenobiology, zoology