JCM Accepts, published online ahead of print on 4 November 2009

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J. Clin. Microbiol. doi:10.1128/JCM.01011-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

An unusual pneumococcal sequence type is the predominant cause of serotype 3 invasive disease in South Africa

Kedibone M. Mothibeli^*, Mignon du Plessis, Anne von Gottberg, Linda de Gouveia, Peter Adrian, Shabir A. Madhi, Keith P. Klugman, and for GERMS-SA (Group for Enteric Respiratory, and Meningeal Disease Surveillance in South Africa)

Respiratory and Meningeal Pathogens Research Unit, National Institute for Communicable Diseases/Medical Research Council/University of the Witwatersrand, Johannesburg, South Africa; Department of Science and Technology/National Research Foundation: Vaccine-Preventable Diseases, Bertsham, South Africa; Hubert Department of Global Health, Rollins School of Public Health and Division of Infectious Diseases, School of Medicine, Emory University, Atlanta GA, USA

^* To whom correspondence should be addressed. Email: kedibonem{at}nicd.ac.za.

We reviewed pneumococcal serotype 3 cases reported from 2000 through 2005 to a laboratory-based surveillance system for invasive pneumococcal disease in South Africa (SA). The prevalence of serotype 3 invasive isolates was compared to their prevalence in carriage isolates to determine the odds of invasiveness due to serotype 3 among SA children. Three groups of serotype 3 strains were characterised by pulsed-field gel electrophoresis (PFGE) or BOX-PCR: randomly selected invasive isolates from one province, isolates from a carriage study involving children in the same province, and antimicrobial-resistant invasive isolates collected nationally. Examples of the identified PFGE types were further characterised by multilocus sequence typing. In total 15,980 viable isolates causing invasive disease were submitted, of which 661 (4%) were serotype 3, mostly from adults (85%, 489/575). Fewer serotype 3 isolates were non-susceptible to antimicrobial agents tested (40/661, 6%) than non-serotype 3 isolates (8480/15319, 55%) (P<0.001). Compared to non-serotype 3 cases, there was no association with HIV coinfection (2212/2569, 86% vs.72/78, 92%, P=0.1) or increased case-fatality ratio (1190/4211, 28%, vs. 54/154, 35% P=0.7). Serotype 3 in children had a low but statistically insignificant invasive disease potential (OR=0.15, CI=0.01-1.06). Strains were grouped into 3 PFGE clusters, with the largest, Cluster-A, representing 54% (84/155), including 14 isolates confirmed as ST458. The serotype 3 global strain, ST180, was confirmed for 3 isolates from Cluster-B, which represented only 12% (18/155) of the isolates. We have therefore identified ST458 as predominating in SA, but with a similar invasive potential to the predominant global clone ST180.