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Infection and Immunity, June 2002, p. 2886-2890, Vol. 70, No. 6
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.6.2886-2890.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Upper and Lower Respiratory Tract Infection by Streptococcus pneumoniae Is Affected by Pneumolysin Deficiency and Differences in Capsule Type

Aras Kadioglu,1* Sally Taylor,1 Francesco Iannelli,2 Gianni Pozzi,2 Tim J. Mitchell,3 and Peter W. Andrew1

Department of Microbiology and Immunology, University of Leicester, Leicester, LE1 9HN,1 Division of Infection and Immunity, University of Glasgow, Glasgow, G12 8QQ, United Kingdom,3 Laboratory of Molecular Microbiology and Biotechnology, Department of Molecular Biology, University of Siena, Siena, Italy2

Received 26 November 2001/ Returned for modification 9 January 2002/ Accepted 26 February 2002

Pneumococci frequently colonize the upper respiratory tract, and these pneumococci are believed to act as a reservoir for infection of the lower respiratory tract and bacteremia. We investigated how the pneumococcal toxin pneumolysin affects the capacity of pneumococci to infect the upper and lower respiratory tract of the mouse. Wild-type Streptococcus pneumoniae serotype 2 and 3 strains, a serotype 2 pneumolysin-deficient mutant, and a serotype 2 mutant with the pneumolysin gene reinserted were used to study differences in colonization and disease. In addition, we also examined a pneumococcal chimeric mutant (capsule type switched from serotype 2 to serotype 3) to gain further insight into the role that capsule plays in nasopharyngeal infection. Absence of pneumolysin was found to be associated with significantly lower numbers of pneumococci in the nasopharynx, trachea, and lungs. Differences in pneumococcal capsule type were found to have significant effects on pneumococcal infection of the nasopharynx, trachea, and lungs. However, it was the combination of capsule type and genetic background that was important, and the influence of this combination varied with the site of infection. For example, in the nasopharynx the wild-type serotype 3 strain and the capsule-switched mutant behaved similarly, whereas in the lungs the mutant that was switched to serotype 3 survived less well than the wild-type serotype 3 strain. The combination of capsule type and genetic background also determined virulence. Thus, the wild-type serotype 3 strain was virulent, whereas the capsule-switched mutant was avirulent.


* Corresponding author. Mailing address: Department of Microbiology and Immunology, P.O. Box 138, University Rd., Leicester, LE1 9HN, United Kingdom. Phone: 44 116 2523018. Fax: 44 116 2525030. E-mail: ak13{at}le.ac.uk.

Editor: E. I. Tuomanen


Infection and Immunity, June 2002, p. 2886-2890, Vol. 70, No. 6
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.6.2886-2890.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.




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