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Infection and Immunity, June 2001, p. 3755-3761, Vol. 69, No. 6
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

Ashalla D. Magee and Janet Yother*

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.

* 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.

Infection and Immunity, June 2001, p. 3755-3761, Vol. 69, No. 6
0019-9567/01/$04.00+0   DOI: 10.1128/IAI.69.6.3755-3761.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.


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