%0 Journal Article %A Karlsbad, Gioanna %A Kessel, R. W. I. %A De Petris, S. %A Monaco, L. %T Electron Microscope Observations of Brucella abortus Grown within Monocytes in vitro %D 1964 %J Microbiology, %V 35 %N 3 %P 383-390 %@ 1465-2080 %R https://doi.org/10.1099/00221287-35-3-383 %I Microbiology Society, %X SUMMARY: Cells of Brucella abortus, strain sa-s, grown within normal guinea-pig monocytes maintained in vitro, were examined by electron microscopy. Intracellular multiplication of brucellae was followed for 48 hr. During the entire period of observation the bacteria were present in the cytoplasm of the monocytes, localized within vacuoles limited by a “unit membrane”. No obvious ultrastructural differences (particularly in surface structures) were detected between monocyte-grown bacteria and sister cells cultivated on a lifeless medium, which might account for the known differences between the two (e.g. differences in resistance to serum bactericidal factors and in intracellular growth patterns). In spite of the large numbers of intracellular parasites present the host cells did not show evident structural modifications. Some observations made on intracellular B. abortus, strain sa-r, showed that after up to 24 hr within guinea-pig monocytes most of the bacteria had retained their morphological integrity and were indistinguishable from R organisms grown on agar. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-35-3-383