Epidemiological Analysis of Non-M-Typeable Group A Streptococcus Isolates from a Thai Population in Northern Thailand

Abstract

Infection with group A streptococci (GAS) can lead to the development of severe postinfectious sequelae such as rheumatic fever (RF). In Thailand, RF and rheumatic heart disease (RHD) remain important health problems. More than 80% of GAS circulating in this population are non-M antigen typeable by conventional M serotyping methods. In this study, we determine the M protein sequence types of GAS isolates found in northern Thailand. The emm genes from 53 GAS isolates, collected between 1985 and 1995 from individuals with pharyngitis, impetigo, acute RF (ARF), RHD, or meningitis as well as from individuals without infections, were amplified by PCR and sequenced. Thirteen new sequence types that did not show homology to previously published sequences were characterized. Six of these sequence types could be isolated from both skin and throat sites of impetigo and pharyngitis/ARF patients, respectively. In many cases we could not specifically differentiate skin strains or throat strains that could be associated with ARF or acute glomerulonephritis. Antigenic variations in the emm gene of the isolates investigated, compared to published M protein sequences, were predominantly due to point mutations, small deletions, and insertions in the hypervariable region. One group of isolates with homology to M44 exhibited corrected frameshift mutations. A new M type isolated from an RHD patient exhibited nucleotide sequence corresponding to the N terminus of M58 and the C terminus of M25, suggesting that recombination between the two types may have occurred. This study provided epidemiological data relating to GAS endemic to northern Thailand which could be useful for identification of vaccine candidates in a specific region of endemicity.

Position statement of the World Heart Federation on the prevention and control of rheumatic heart disease

“…3,29 In some tropical regions with a high incidence of RF, GAS pyoderma is endemic yet rates of GAS pharyngeal carriage and symptomatic pharyngitis are low. 2,3,5,62 Should GAS skin infection be implicated in RF pathogenesis, a new approach to primary prevention would potentially be opened.…”

Characterization ofemmtypes and superantigens ofStreptococcus pyogenesisolates from children during two sampling periods

“…Currently, more than 170 emm types and 750 emm subtypes of GAS have been described [3]. Studies of GAS emm-typing distribution performed worldwide, have shown a differing distribution of emm types in different countries and regions [4][5][6][7]. SAgs are thought to contribute to the pathogenesis of severe GAS infections by virtue of their potent immunostimulatory activity and the distribution of profiles of genes encoding SAgs has been used as an additional epidemiological tool to explore the genomic heterogeneity and possible correlation between toxin gene content and disease type [8].…”

In silico characterisation of the two-component system regulators of Streptococcus pyogenes

“…More broadly, as epidemiological studies of streptococcal disease in developing nations routinely fail to report the presence of traditional ‘rheumatogenic’ emm -types, the concept of ‘rheumatogenic’ emm -types is currently in flux [ 79 ]. In this context, historical rheumatogenic emm -types may have reflected the epidemiology of disease in North America and Europe at the time the studies were conducted [ 80 – 82 ], but may not be representative of ARF/RHD at a global scale.…”