Ureaplasma: A bacterium that commonly infects the urogenital tract and can cause premature birth or spontaneous abortion. During delivery, ureaplasma can infect the newborn and cause meningitis, pneumonia, or septicemia.
Ureaplasma is similar to mycoplasma. They are among the smallest free-living organisms known. Ureaplasma lacks several proteins standard in comparable organisms. Its low biosynthetic capacity means that it must import more nutrients needed for growth that most other bacteria.