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Infection and Immunity, June 2001, p. 3755-3761, Vol. 69, No. 6
Department of Microbiology, University of
Alabama at Birmingham, Birmingham, Alabama 35294
Received 2 February 2001/Returned for modification 2 March
2001/Accepted 20 March 2001
Nasopharyngeal colonization is a necessary first step in the
pathogenesis of Streptococcus pneumoniae. Using isolates
containing defined mutations in the S. pneumoniae
capsule locus, we found that expression of the capsular polysaccharide
is essential for colonization by the type 2 strain D39 and the type 3 strains A66 and WU2. Nonencapsulated derivatives of each of these
strains were unable to colonize BALB/cByJ mice. Similarly, type 3 mutants that produced <6% of the parental amounts of capsule could
not colonize. Capsule production equivalent to that of the parent strain was not required for efficient colonization, however, as type 3 mutants producing approximately 20% of the parental amounts of capsule
colonized as effectively as the parent. This 80% reduction in capsule
level had only a minimal effect on intraperitoneal virulence but caused
a significant reduction in virulence via the intravenous route. In the
X-linked immunodeficient CBA/N mouse, the type 3 mutant producing
~20% of the parental amount of capsule (AM188) was diminished in its
ability to cause invasive disease and death following intranasal
inoculation. Following intravenous or intraperitoneal challenge,
however, only extended survival times were observed. Our results
demonstrate an additional role for capsule in the pathogenesis of
S. pneumoniae and show that isolates producing reduced
levels of capsule can remain highly virulent.
0019-9567/01/$04.00+0 DOI: 10.1128/IAI.69.6.3755-3761.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Requirement for Capsule in Colonization by
Streptococcus pneumoniae
*
Corresponding author. Mailing address: Department of
Microbiology, BBRB 661/12, 845 19th St. South, Birmingham, AL 35294. Phone: (205) 934-9531. Fax: (205) 975-6715. E-mail:
jyother{at}uab.edu.
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