Epidemiological analysis of Group A streptococcus infection diseases among children in Beijing, China under COVID-19 pandemic

Streptococcus pyogenes (GAS) is vital human pathogen responsible for a wide spectrum of infectious diseases, not only infection on skin and respiratory, but also invasive diseases, such as streptococcal toxic shock syndrome, necrotizing fasciitis as well as triggered autoimmune diseases [1, 2]. Human immunity to GAS may be related with disease manifestations after GAS infection [3]. Severe GAS infection diseases account for 18.1 million cases around the world, with 1.78 million new cases and 500,000 deaths every year [4, 5]. Li analyzed epidemiological characteristics and changes in incidence of GAS infection diseases in China after SARS outbreak. The yearly incidence was 2.44 cases per 100,000. Case-fatality ratios was 0.03 case per 1000 people. Significant seasonal features were May to June and November to December. Scarlet fever in children was high incidence and case-fatality [6]. Comparing with USA, GAS infection in China was usually presented in non-invasive GAS infection [7, 8]

Antibiotic resistance increases gradually, causing global concern [9]. Resistance of isolates to antibiotic varies in different countries and regions [10, 11]. In China, GAS was high frequent resistance to macrolides and clindamycin [12]. M protein is an important virulence factor of GAS coded by emm gene. Depending on variation of N-terminal, more than 250 emm types have been identified. Surveillance on GAS emm types in a long period can give a valuable clue for prediction of future emm clones [13]. The prevalent emm types vary over time in different countries and regions [14]. In China, in the year of 2011, emm12 was the most prevalent type in scarlet fever, with high resistance to erythromycin, tracycline, and clindamycin. However, epidemiological characteristics of M protein changed with time [15].

Sixteen known sAgs have been identified in GAS, including speA, speC, speG-M, smeZ, ssa, speQ, and speR [16], responsible for GAS virulence and successful infection pathogenesis [17].

Researches on GAS epidemiological features have been attracted great attention around the world. Relationship among GAS infection diseases, emm types, and sAgs distribution has not been identified [18‐20]. Because COVID-19 pandemic has changed our lifestyle, molecular characteristics of GAS isolated from Chinese children may be different.

In this study, we analyzed emm types, sAgs, and antimicrobial susceptibility resistance of GAS isolates as well as GAS infection categories to find differences among GAS infected cutaneous diseases before and under COVID-19 pandemic.

Streptococcus pyogenes is bacterial pathogen worldwide responsible for a broad spectrum of infection diseases as well as autoimmune sequelae [1, 4]. Epidemiological and molecular features of GAS isolates are quite different in different countries. COVID-19 pandemic has already changed our lifestyle. People pay more attention to protective social distance, wearing masks, personal hygiene, and frequent hand washing [24]. Respiratory infection diseases have been reduced dramatically as well as GAS-related respiratory infection diseases. Because of these, isolates collected in our study were much fewer compared with our previous study. Our present study offered insights into antibiotic resistance, virulence genes of GAS under COVID-19 pandemic.

In our present research, male-to-female ratio was 1.65:1. Kim analyzed children suffered scarlet fever in Jeju in Korea between 2002 and 2016. He presented male-to-female ratio was 1.3:1[25]. In Shanghai, during 2011 to 2015, scarlet fever usually affected children aged three to nine [12]. Patients from our present study, aged from 22 days to 11 years old, with median 6.58 years old.

Resistance rate of macrolides in our present study was still high compared with our previous studies from 2016 to 2017, and 2019. Yu found that from 2016 to 2018, 342 GAS strains were highly susceptible to penicillin, levofloxacin, and chloramphenicol, whereas most of strains were resistant to azithromycin, erythromycin, clarithromycin, clindamycin, and tetracycline [9]. Since 1990, the resistance rate of GAS against clindamycin and macrolides has been high [7]. Chinese strains mainly harbored ermB gene. In our study, 93.86% stains harbored ermB gene. Distribution of ermB gene in our GAS strains among scarlet fever, impetigo, psoriasis, allergic purpura, and suppurative tonsillitis was 95.24%, 100%, 80%, 100%, and 100% respectively (Table 3). In our previous study from 2016 to 2017, 97.64% GAS strains harbored ermB gene. In the year of 2019, we found 89.67% isolates harbored ermB gene.

M protein is immune-dominant GAS protein, locating on surface of bacterial cell wall [26], which adhering to host cell and block phagocytosis, aiding GAS colonization [27]. Macrolide resistance in GAS links to some emm types. In our study, emm12.0 and emm1.0 were predominant types in macrolide resistance GAS. Emm12.0 carried ermB was the most frequent macrolide resistance isolates, which was consistent with Liang’s study between 2005 and 2008 as well as our study in 2009 [22].

M protein and sAgs play an important role in GAS infection pathogenesis. There is a close relationship between emm types and sAgs [28]. In this study, we presented distribution of emm types including 13 emm types and 11 sAgs. Types emm12.0 and emm1.0 exhibited higher polymorphism rate which were similar with our previous study as well as Yu’ study from 2016 to 2018 [9]. They were responsible for about 73.81% of scarlet fever cases in our present study. Tsai collected 320 GAS strains from 339 children in Southern Taiwan. Emm12 (63.8%) was dominant type, following emm1 (16.9%), emm4 (11/0.9%) during 2000 to 2019 [29].

The dominant emm12.0, emm1.0, emm12.19, and emm12.67 types in this study were similar to those in Southeast Asia, UK and Southern Taiwan [30], but were different from results presented in Portugal and Canada. Ana exhibited markers of invasive GAS were emm1 and emm64, speA, and speJ independently, However, GAS carried emm4, emm75, ssa, speL/M genes were independent markers in pharyngitis [31]. In Canada, since 2010, emm1 has been the most frequent type. Epidemic scarlet fever has been reported in China, United Kingdom. In China, UK. GAS isolates were emm1, emm12, emm3, and emm4 respectively carrying speA, speC, ssa [32]. Our research was a little different from previously epidemic reports. Emm12 strains had been major epidemic isolates.

GAS M protein has been surveillance in Beijing from 2011 to 2018, meanwhile, M 12 stains began to decrease from 2011, and the lowest point was in 2014. Meanwhile, M 1 stains began to raise, and reached to the highest point in 2014, and then exceed M 12 from 2013 to 2014 [33]. However, our present research was different form Yu’ research. During 2019–2021, 2016–2017, we found GAS from scarlet fever and impetigo carried emm12, predominantly. In psoriasis, GAS carried emm1 in 2019 (Table 4), however, between 2020 and 2021, the isolates carried emm12, emm12.29 and emm89 predominantly [21, 22]. Patricia found emm70, emm33, emm25, emm93.3,and emm11 were the most frequent emm types among impetigo, pharyngitis, and asymptomatic throat [3].

Liang and Luca found emm1.0 isolates harbored speA, speC with similar frequencies, meanwhile, emm12.0 carried low frequencies speA, and high frequencies speC. The frequencies of speA, speC among emm1.0, emm12.0 isolates in present study were consistent with Liang’s results[20], while that in our previous study were in agreement with Luca’s results[34].

In our present study, 11 sAgs were detected in GAS isolates. SmeZ, ssa, speC were the most common sAgs. Emm1 carried speG, ssa, smeZ, speC, and speA. However, content of speH, speI, and speM was less. Emm12 harbored speG, ssa, smeZ and speG, with little speA, speJ and speM. Both emm1.0 and emm12.0 had no speK, speL. Lu found among invasive or not GAS isolates harbored speB, and slo, meanwile, smeZ, speC, and speF were determined in more than 90% isolates from 2009 to 2016 in 7 cities in China. These isolates carried emm12.0 (42.9%) and emm1.0 (30.7%) [35].

Liang found scarlet fever isolates carried speA (52.4%), and speC (79.3%) from 2005 to 2008 in mainland China [20]. SAg distribution was varied in different geographic areas. In France, Plainvert exhibited GAS strains carried speA (59%), speC (37%), ssa (13%), and smeZ (92%) in meningitis from 2003 to 2013. During 2006 to 2009, Friaes presented more than 90% GAS isolates carried speG and smeZ. In Ireland, Mary exhibited invasive emm types were emm1, emm3, meanwhile, in non-invasive GAS isolates were emm4, emm28, and emm3. SpeA, speG and speJ were related with invasive GAS isolates, whereas speC, speI, and ssa with non-invasive GAS infections [36]. According to our present data, we found scarlet fever isolates harbored speC (94.05%), and smeZ (98.81%), psoriasis isolates carried speC (80%), and smeZ (100%). Impetigo isolates carried speC (88.89%), ssa (88.89%), and smeZ (88.89%). In our previous study from 2016 to 2017, we found that the most prevalent scarlet fever isolates carried smeZ (96.97%), speC (92.59%) and speG (91.58%), presented in Table 6. However, in our study of 2019, the most prevalent GAS carried smeZ (94.46%), speC (91.14%) and ssa (74.91%). Scarlet fever isolates prevalently harbored smeZ (93.6%), speC (90.4%). Psoriasis isolates harbored smeZ (100%), speC (100%), and impetigo isolates harbored smeZ (100%), ssa (89.7%), and speC (89.7%) [22]. Catarina collected 303 GAS strains from scarlet fever, tonsilla-pharyngitis patients between 2002 and 2008. Isolates from scarlet fever carried smeZ, ssa, speG and speC. Strains from pharyngitis carried smeZ, speG, speC, and ssa [37].

Our study has several limitations. Firstly, our research was conducted at a single center, which could have made biases to occurrence of GAS infected cutaneous diseases. Under COVID-19 pandemic, outpatients deceased dramatically. Atypical symptoms might have been misdiagnosed. Secondly, our study had small GAS isolates which might not fully represent GAS types under COVID-19 pandemic.

The study sponsors had no role in study design; collection, analysis, and interpretation of data; writing the report; or the decision to submit the report for publication.