Open Access Research article

Factors associated with Group A Streptococcus emm type diversification in a large urban setting in Brazil: a cross-sectional study

Sara Y Tartof1, Joice N Reis2, Aurelio N Andrade3, Regina T Ramos4, Mitermayer G Reis5 and Lee W Riley6*

Author Affiliations

1 University of California, Berkeley, School of Public Health, USA

2 Faculdade de Farmácia, Universidade Federal da Bahia, Salvador, BA, Brazil; Gonçalo Moniz Research Centre, Oswaldo Cruz Foundation, Brazilian Ministry of Health, Salvador, BA, Brazil

3 Hospital São Rafael-Monte Tabor, Salvador, BA, Brazil

4 Department of Pediatrics, Federal University of Bahia School of Medicine, Salvador, BA, Brazil

5 Gonçalo Moniz Research Centre, Oswaldo Cruz Foundation, Brazilian Ministry of Health, Salvador, BA, Brazil

6 University of California, Berkeley, School of Public Health, USA

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BMC Infectious Diseases 2010, 10:327  doi:10.1186/1471-2334-10-327

Published: 11 November 2010

Abstract

Background

Group A Streptococcus (GAS) strain diversity varies across different regions of the world, according to low versus high-income countries. These differences may be related to geographic, environmental, socioeconomic, or host-related factors. However, local factors may also affect strain diversity. We compared the emm types of GAS isolates from children with and without sore throat in one large urban setting in Brazil.

Methods

Children 3-15 years of age were consecutively recruited from slum and non-slum pediatric outpatient clinics between April-October, 2008. Throat cultures were performed and data intake forms were completed. GAS isolates were typed by emm sequencing.

Results

From 2194 children, 254 (12%) GAS isolates were obtained. Of 238 GAS isolates that were emm-typed, 61 unique emm types were identified. Simpson's diversity index of the emm types was higher among isolates from slum children [97% (96%-98%)] than those of non-slum children [92% (89%-96%)]. Two emm types (66.0, 12.0) were more frequently isolated from children with sore throat (p < 0.05), and one emm type (27G.0) demonstrated a protective effect.

Conclusions

The emm type diversity from children attending slum clinics resembled the emm diversity of low income countries rather than that of children attending a non-slum clinic in the same city. Local factors, such as crowding, may enhance the frequency of GAS transmission and horizontal gene transfers that contribute to increased strain diversity in the slums. GAS vaccine coverage and control of GAS infections will need to take these local factors and strain differences into consideration.