Cytopathogenic Effect of Brucella Spheroplasts on Monocytes in Tissue Culture.

Freeman, Bob A. (The University of Chicago, Chicago, Ill.), and Barry H. Rumack. Cytopathogenic effect of Brucella spheroplasts on monocytes in tissue culture. J. Bacteriol. 88:1310-1315. 1964.-Mononuclear phagocytes from guinea pig peritoneal exudates were shown to ingest both normal Brucella suis and spheroplasts prepared from B. suis by treatment with glycine and with penicillin. Quantitative ingestion studies with P(32)-labeled Brucella showed that rough normal Brucella are ingested at a greater rate than are smooth normal Brucella. Spheroplasts prepared from smooth cells were phagocytized at a greater rate than were the normal smooth cells, and spheroplasts prepared from rough Brucella were phagocytized well, although apparently to a lesser extent than from the normal rough Brucella. The degree of phagocytosis of all spheroplasts appeared to reach a peak and then decrease, indicating a release of ingested bacteria; this release of intracellular bacteria is believed to be due to the cytopathogenic effect exerted by the spheroplasts. Direct microscopic observations showed that infection with living spheroplasts prepared from either smooth or rough Brucella destroyed a major portion of the host cells within 4 hr, but that formalin-killed spheroplasts were no more destructive than were normal Brucella. When host cell destruction was assayed by the release of cellular constituents into the medium, it was apparent that host-cell destruction by spheroplasts reaches a significant level within 0.5 hr after ingestion begins, and is almost complete by 4 hr. The implications of these findings in studies on the nature of intracellular Brucella are discussed.