Establishment of Colonial Variants of Brucellae in vivo

Abstract

illthough recent studies have demonstrated the mutational character of dissociation (1) and the selective role of metabolites on population changes in synthetic broth cultures of brucellae( 2.3) information on population changes in infected animals is fragmentary. Most investigations on the establishment of colonial variants in animal tissues have been with animals inoculated with variants isolated from stock cultures either alone or in combination with smooth (S) brucellae(4-7). These experiments demonstrated a selective advantage of the S type over variants manifested in all host species but to a lesser extent in those which have a relatively high order of natural resistance to infection with brucellae (8). The ability of mutants with decreased pathogenicity to persist in normally resistant hosts is paralleled by the ability of relatively apathogenic mutants of a variety of pathogens to establish themselves in immunized and carrier hosts( 9.10). Controlled observations of the establishment of variant organisms in tissues of animals inoculated with S brucellae alone have not been made. although Huddleson ( 1 1 ) has described the isolation of smooth-intermediate (SI) , rough ( R ) and mucoid (31) types of BruceZZa abortus from fetuses aborted by naturally infected cows. SI types were also isolated from the milk of naturally infected cows. Buddle and Boyes (12) investigated the properties of a nonsmooth organism isolated from cases of genital infection of sheep in Xew Zealand and suggest that it is a stabilized mutant or variety of Br. meZitensis. Braun et a L ( 7 ) recovered intermediate (I) types from guinea pigs inoculated with S and 31 organisms. The observations reported here were made to determine the fate of colonial variants arising during the course of experimental infections initiated with S cultures of Br. abortus ___ ~~~ * Published with -4pproval of the Director of the Wis. Agric. Exper. Station. Paper Xo. NS-170.and BI. suis in guinea pigs.S trep tompc in resist ant cultures of Br. abortus, strain 2308. and Br. suis, strain B, were used. Groups of 28 male guinea pigs each were inoculated intraperitoneally with lo3 cells of Br. suis or 3.5 ?I lo6 cells of Br. abortus. Replicate platings of heavy suspensions from which inocula were prepared were examined by the methods of Henry (4) and White and Wilson ( 13 ) : only S colonies were observed. Two animals from each group were sacrificed at intervals from 2 to 24 weeks after inoculation. The following organs were macerated and cultured on 2-1 agar(4) and 2-1 agar containing 500 pg streptomycin/ml : different lymph nodes, liver, spleen: testes, kidneys, and femoral bone marrow. Abscesses which developed were cultured separately. The colonial morphology of all isolates was determined by direct observation, the crystal violet and the acriflavine spot tests. Questionable colonies were picked and streaked on fresh plates for further examination. Observations were made of the colonial morphology of brucellae isolated from bovine material. Tissues and fluids f...

Intracellular Behavior of Brucella Variants in Chick Embryo Cells in Tissue Culture.

“…The unaltered smooth selective capacity of fibroblasts cultured in antiserum (lacking in SS factor), indicates one reason why animals lacking the SS factor, and even immune animals, clear non-smooth brucellae from their body much more rapidly than they do the smooth type ( 14).…”

“…Thus, they have been generally considered to be of little significance in brucellosis. However, several instances of mutation from smooth to mucoid in vivo have recently been demonstrated, in which the mucoid variants were recovered as often from unabscessed as from abscessed tissue ( 14) .…”

Leptospiral Colonial Morphology

“…Recovery of approximately equal numbers of all three colonial types from infected hamster blood may reflect selection of mutants or an equilibration process. The establishment of colonial variants of brucellae in vivo has been reported by Berman, Redfearn, and Simon (1955), who suggested that local accumulations of metabolites may favor the establishment of variants. The role of immunity in the selection of colonial variant brucellae was studied by Redfearn, Simon, and Berman (1956).…”