Osmotically sensitive Brucella in infected normal and immune macrophages

Survival and growth of Yersinia pestis within macrophages and an effect of the loss of the 47-megadalton plasmid on growth in macrophages

The survival and growth of Yersinia pestis cells within mouse peritoneal cavities and within mouse peritoneal macrophages maintained in vitro was examined. Two strains were used which differed only in that one (KIM) contained the 47-megadalton plasmid associated with virulence and the second (KIM1) lacked this plasmid. The KIM cells, but not the KIM1 cells, acquired some resistance to phagocytosis during growth at 37 degrees C which was not evident when cells were grown at 26 degrees C. Whether previously grown at 26 or 37 degrees C, however, a substantial portion of the cells of either strain which were phagocytized were apparently killed after phagocytosis in vivo, although this was not observed in vitro. KIM cells which survived phagocytosis proliferated within macrophages in vivo, but no increase in viable cells was seen with the KIM1 cells. Growth of the KIM1 cells within macrophages in vitro required that a complex supportive medium be used in which the bacteria could have grown if extracellular. This was not the case for the KIM cells which proliferated within macrophages supported in medium not permissive to bacterial growth. After phagocytosis of cells of either strain by macrophages maintained in vitro, phagolysosome formation occurred normally, as shown by the acridine orange dye staining technique. KIM and KIM1 cells were equally sensitive to hydrogen peroxide and superoxide anion, although the sensitivity in each case varied with growth temperature. The oxidative burst, as determined by the luminol chemiluminescence assay, was low when compared with that seen after phagocytosis of Escherichia coli cells. Chemiluminescence after phagocytosis of yeast cells by macrophages which had engulfed KIM or KIM1 was also low. We conclude that survival within macrophages is substantially independent of the 47-megadalton plasmid and may be a consequence, as least in part, of blockage of the oxidative burst or rapid removal of the oxidizing compounds formed. The 47-megadalton plasmid is apparently required for subsequent proliferation within the macrophage.

Ingestion and intracellular survival of Brucella abortus in human and bovine polymorphonuclear leukocytes

Bovine polymorphonuclear leukocytes (PMNs) were found to be significantly more bactericidal than human PMNs against a smooth-intermediate strain of Brucella abortus (45/0), whereas there was no difference in bactericidal activity of the two kinds of PMNs against a rough strain of B. abortus (45/20). Electron microscopy of thin sections of PMNs revealed that both strains of B. abortus were readily ingested; however, the extent of degranulation was significantly less than in PMNs incubated with an extracellular parasite, Staphylococcus epidermidis. Amounts of myeloperoxidase and lactoferrin released through exocytosis by PMNs incubated with S. epidermidis were 4.7- and 1.2-fold greater, respectively, than those released from PMNs incubated with B. abortus 45/0. When azurophil and specific granules were isolated after incubation of PMNs with either B. abortus 45/0 or S. epidermidis, results showed that the extent of degranulation by both types of granules was greater in PMNs incubated with S. epidermidis than in those incubated with B. abortus 45/0. Amounts of degranulation by azurophil and specific granules were similar in PMNs incubated with either the smooth-intermediate strain 45/0 or the rough strain 45/20. Degranulation was not stimulated when glutaraldehyde-killed strain 45/0 was substituted for viable cells. These data suggest that B. abortus does not stimulate an effective level of degranulation after ingestion, as observed with extracellular parasites, and that the smooth intermediate strain 45/0 is more resistant to intraleukocytic killing system than the rough strain 45/20.

Properties of a cell-wall-defective variant of Brucella abortus of bovine origin

The properties of an atypical Brucella strain isolated from lymph node tissue of a cow slaughtered as a brucellosis reactor were examined. The organism was Gram negative and highly pleomorphic, existing as cocci, coccobacilli, rods, branched and irregular forms which stained with fluorescent antibody conjugates prepared against rough and smooth Brucella abortus strains. It produced lecithinase and required at least 15% v/v equine or bovine serum for growth. It did not need supplementary CO2 for growth, produced H2S and was inhibited by brucella dyes and partially by i-erythritol. Growth inhibition or lysis was produced by brucella-phages. The organism was not pathogenic for guinea-pigs or mice but evoked antibodies mainly to rough Brucella antigens.

Interaction of polymorphonuclear leukocytes with smooth and rough strains of Brucella abortus

The bactericidal activity of guinea pig and human polymorphonuclear leukocytes (PMNs) against a smooth-intermediate strain (45/0) and a rough strain (45/20) of Brucella abortus has been examined. After incubation for 120 min, guinea pig PMNs incubated with either the smooth strain 45/0 or the rough strain 45/20 exhibited no bactericidal activity against the former and caused only a 34% decrease in viability of the latter. Human PMNs were more bactericidal than guinea pig PMNs to both strains; however, the killing of strain 45/20 by human PMNs was less than that observed in control experiments with S. aureus strain 502A. Both strains of B. abortus readily associated with guinea pig and human PMNs, and the bacteria were apparently ingested without stimulation of the hexose monophosphate pathway. Lysates (10 micrograms/ml, pH 5.5), prepared from guinea pig or human granules, were not particularly toxic to either strain unless supplemented with H2O2 and a halide (I- or Cl-). An oxygen-dependent killing system appeared to be lethal against both strains of B. abortus, with I- being more active than Cl- in the presence of H2O2 and granule lysate. The data suggest that degranulation after ingestion of Brucella by phagocytes does not occur due to the lack of a proper stimulus or possibly the baccilli actively inhibit the degranulation process thereby protecting the microbe from killing systems normally effective against extracellular parasites.

The cell wall as the antigenic site for antibodies stimulating ingestion (MSF) and inhibition (BIF) of Brucella in macrophages from normal and immune animals

Following extraction with hot trichloracetic acid and digestion with trypsin, deoxyribonuclease and ribonuclease, cell wall residues of Brucella melitensis strain Rev I contained an antigenic moiety capable of removing antibodies responsible for stimulation of ingestion, inhibition of Brucella growth by macrophages, and agglutination of Brucella. The preparation was dermonecrotic for both normal and immune rabbits and, when injected in oil, stimulated antibody production. The peptidoglycan-containing structure was degraded by egg-white lysozyme and enzymes from normal and immune macrophages with an accompanying loss of dermonecrotic and serumabsorbing capacity.