Abstract
BackgroundGroup 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.MethodsChildren 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.ResultsFrom 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.ConclusionsThe 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.
Highlights
Group A Streptococcus (GAS) strain diversity varies across different regions of the world, according to low versus high-income countries
In Salvador, Brazil we found significant differences in emm type diversity among GAS isolates obtained from different populations in the same city
The diversity index was significantly higher among GAS isolates from children residing in slum communities (97%) compared to those living in wealthier neighborhoods (92%)
Summary
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. Epidemiologic studies have revealed that developing countries have high emm type diversity [13,14], while high-income countries are more likely to have a limited number of emm types [15,16,17,18] This pattern was clearly demonstrated in a recent systematic review of 120 articles and reports on GAS emm types [19]. It found a higher diversity of emm types in Africa and the Pacific compared to high-income countries, which may be related to differences in geographic, environmental, socioeconomic or host factors. We collected isolates from children with and without sore throat to identify associations of certain emm types with clinical outcome
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