The Journal of Medical Microbiology, Vol 17, Issue 3 237-246, Copyright © 1984 by Society for General Microbiology
The growth and survival of capsulate and non-capsulate Bacteroides fragilis in vivo and in vitro
S. Patrick, J. H. Reid and M. J. Larkin
The growth of capsulate and non- capsulate Bacteroides fragilis in chambers
implanted in the mouse peritoneal cavity was compared. Capsulate and
essentially non- capsulate (less than 1% capsulate ) populations of B.
fragilis strains NCTC9343 and NCTC10584 consistently grew exponentially to
greater than 10(9) cfu/ml within 24 h in vivo, and low numbers of capsulate
bacteria were maintained in the essentially non- capsulate population;
however, the degree of capsulation of the capsulate population decreased by
more than 60%. B. fragilis ATCC23745 differed from strains NCTC9343 and
NCTC10584 in that growth was unpredictable and only occurred in some of the
implanted chambers. Capsule production by cells of strain ATCC23745 varied
from chamber to chamber: sometimes the proportion of capsulate cells
increased after prolonged implantation. This could occur with either an
increase or decrease in viable numbers in vivo and also after in-vitro
incubation of this strain in chambers. The survival of capsulate and non-
capsulate B. fragilis strains NCTC9343 and ATCC23745 was compared in
aerobic and anaerobic conditions in vitro. In anaerobic conditions,
capsulate and non- capsulate strain NCTC9343 survived equally well, whereas
capsulate ATCC23745 survived better than its non- capsulate variants.
Capsulate populations of both strains survived better than non- capsulate
in aerobic conditions.
