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Applied and Environmental Microbiology, March 2009, p. 1642-1649, Vol. 75, No. 6
0099-2240/09/$08.00+0 doi:10.1128/AEM.02155-08
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Ernesto García,2 and
Tim J. Mitchell1*
Division of Infection and Immunity, Glasgow Biomedical Research Center, University of Glasgow, 120 University Place, Glasgow G12 8TA, United Kingdom,1 Centro de Investigaciones Biológicas (CSIC) and Ciber de Enfermedades Respiratorias (CIBERES), Ramiro de Maeztu, 9, 28040 Madrid, Spain2
Received 10 September 2008/ Accepted 13 January 2009
The frequency of prophage carriage was tested in a collection of 108 clinical isolates of Streptococcus pneumoniae. A PCR-based assay was developed to allow classification of the prophage into the three groups recently identified according to genome comparisons (P. Romero, N. Croucher, N. L. Hiller, F. Z. Hu, G. D. Ehrlich, S. D. Bentley, E. García, and T. J. Mitchell, submitted for publication). Use of the assay showed that more than half of the isolates studied were lysogenic with prophage belonging to group 1 being the most abundant (56%), followed by those belonging to group 2 (26%) and those belonging to group 3 (11%). Four polylysogenic strains harboring a group 1 and a group 2 prophage were identified. Interestingly, lysogenic strains were found in 8 out of the 12 internationally distributed, relevant clones of S. pneumoniae contained in our strain collection. The high percentage of clinical pneumococcal isolates harboring prophage strongly suggests an important contribution to the diversification of the genome architecture in this species as well as a role for bacteriophage in the virulence/and or fitness of S. pneumoniae, although further studies using a significant number of isolates belonging to the most relevant pneumococcal clones are needed.
Published ahead of print on 23 January 2009.
Present address: Institute of Food Science and Nutrition, ETH Zurich, LFV B18, Schmelzbergstr. 7, 8092 Zurich, Switzerland.
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