Khosa X V, Kgasha O, Mabuza H, Moshe M, Engel K, Nchabeleng M
Department of Microbiology, School of Medicine, Sefako Makgatho Health Sciences University, Pretoria, South Africa.
S Afr Med J. 2021 Apr 30;111(5):487-490. doi: 10.7196/SAMJ.2021.v111i5.14613.
Group A streptococcus (GAS) is a human pathogen responsible for a wide range of invasive and non-invasive infections. Pharyngitis caused by GAS may have complications such as acute rheumatic fever subsequently leading to rheumatic heart disease (RHD). RHD continues to have high morbidity and mortality and affects millions of children and young adults, mostly in developing countries. An effective preventive vaccine against GAS may reduce the morbidity and mortality. A 30-valent M-protein-based vaccine is currently at the clinical trials stage of development. Potential vaccine coverage will depend on the geographical distribution of GAS emm (M protein) types.
To determine the emm types of GAS isolates circulating in the north-west of Pretoria, South Africa.
Throat swabs were collected from patients aged 3 - 20 years presenting with pharyngitis at one local clinic. In addition, GAS clinical isolates were collected from the National Health Laboratory Service diagnostic laboratory. Emm genotyping was done on the GAS isolates by amplification of the emm gene followed by sequencing of the 5' portion of the gene. The emm types were correlated with the types in the vaccine.
A total of 54 GAS isolates were collected, comprising 19 pharyngitis and 35 clinical isolates. We found 15 different emm types among the 43 GAS isolates that were successfully sequenced. Eleven isolates (20%) could not be typed. The most prevalent emm type was 92 (26%), which is part of the 30-valent vaccine. This was followed by emm 25 and 75, each accounting for 12% of the isolates. Up to 67% of the emm types are not covered in the 30-valent vaccine.
Fifteen emm types were identified, of which 92 was the most prevalent. It is concerning that 67% of the emm types are not covered in the vaccine currently under development. It is recommended that surveillance studies be extended to include other parts of the country in order to expand knowledge of the circulating emm types.
A 组链球菌（GAS）是一种可引发多种侵袭性和非侵袭性感染的人类病原体。GAS 引起的咽炎可能会引发诸如急性风湿热等并发症，进而导致风湿性心脏病（RHD）。RHD 的发病率和死亡率仍然很高，影响着数百万儿童和年轻人，其中大多数在发展中国家。一种有效的 GAS 预防性疫苗可能会降低发病率和死亡率。一种基于 30 价 M 蛋白的疫苗目前正处于临床试验开发阶段。潜在的疫苗覆盖范围将取决于 GAS emm（M 蛋白）类型的地理分布。
确定在南非比勒陀利亚西北部流行的 GAS 分离株的 emm 类型。
从当地一家诊所中 3 - 20 岁患咽炎的患者处采集咽拭子。此外，从国家卫生实验室服务诊断实验室收集 GAS 临床分离株。通过扩增 emm 基因并对该基因的 5' 部分进行测序，对 GAS 分离株进行 emm 基因分型。将 emm 类型与疫苗中的类型进行关联。
共收集到 54 株 GAS 分离株，包括 19 株咽炎分离株和 35 株临床分离株。在成功测序的 43 株 GAS 分离株中，我们发现了 15 种不同的 emm 类型。11 株分离株（20%）无法分型。最常见的 emm 类型是 92（占比 26%），它是 30 价疫苗的一部分。其次是 emm 25 和 75，各占分离株的 12%。30 价疫苗未涵盖高达 67%的 emm 类型。
鉴定出 15 种 emm 类型，其中 92 最为常见。令人担忧的是，目前正在开发的疫苗未涵盖 67%的 emm 类型。建议将监测研究扩展至该国其他地区，以扩大对流行的 emm 类型的了解。
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