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Infection and Immunity, January 2003, p. 132-139, Vol. 71, No. 1
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.1.132-139.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

The Hyaluronic Acid Capsule of Streptococcus uberis Is Not Required for the Development of Infection and Clinical Mastitis

Terence R. Field,1 Philip N. Ward,1 Lars H. Pedersen,2 and James A. Leigh1*

Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berks RG20 7NN, United Kingdom,1 Institute for Veterinary Microbiology, The Royal Veterinary and Agricultural University, DK-1870 Frederiksberg C, Denmark2

Received 4 April 2002/ Returned for modification 3 August 2002/ Accepted 25 September 2002

The frequency at which the genes responsible for capsule biosynthesis occurred in field isolates of Streptococcus uberis was determined. Of the two genotypes detected (hasABC and hasC), the capsular genotype (hasABC) was more common. This genotype was present at a higher frequency in a population isolated from mastitis cases than in a population isolated from cattle bedding. The virulence of a mutant strain of S. uberis (TRF0-6) that lacked the ability to produce a hyaluronic acid capsule due to an insertion within its single copy of hasA (P. N. Ward, T. R. Field, W. G. F. Ditcham, E. Maguin, and J. A. Leigh, Infect. Immun. 69:392-399, 2001) was compared to that of the capsular parental strain (0140J). Strains TRF0-6 and 0140J infected all mammary gland quarters following experimental challenge. The wild type and the mutant induced overt signs of disease in four out of four and in six out of eight mammary gland quarters, respectively. Both the wild type and the hasA mutant were resistant to killing by bovine neutrophils following cultivation in bovine milk. The ability to withstand the bactericidal action of neutrophils following growth in milk was therefore independent of the capsule and coincided with the ability of supernatants from such cultures to prevent the bactericidal action of neutrophils. This investigation revealed that, in the absence of the capsule, S. uberis is able to withstand the bactericidal effect of bovine neutrophils and induce mastitis in dairy cows.


* Corresponding author. Mailing address: Institute for Animal Health, Compton Laboratory, Compton, Newbury, Berks RG20 7NN, United Kingdom. Phone: 44 1635 577249. Fax: 44 1635 577243. E-mail: james.leigh{at}bbsrc.ac.uk.

Editor: V. J. DiRita


Infection and Immunity, January 2003, p. 132-139, Vol. 71, No. 1
0019-9567/03/$08.00+0     DOI: 10.1128/IAI.71.1.132-139.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.




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