Antibiotic Resistance and Genotypic Characteristics of Group A Streptococci Associated with Acute Pharyngitis in Korea

Global Streptococcus pyogenes strain diversity, disease associations, and implications for vaccine development: a systematic review

The high strain diversity of Streptococcus pyogenes serves as a major obstacle to vaccine development against this leading global pathogen. We did a systematic review of studies in PubMed, MEDLINE, and Embase that reported the global distribution of S pyogenes emm-types and emm-clusters from Jan 1, 1990, to Feb 23, 2023. 212 datasets were included from 55 countries, encompassing 74 468 bacterial isolates belonging to 211 emm-types. Globally, an inverse correlation was observed between strain diversity and the UNDP Human Development Index (HDI; r=-0·72; p<0·0001), which remained consistent upon subanalysis by global region and site of infection. Greater strain diversity was associated with a lower HDI, suggesting the role of social determinants in diseases caused by S pyogenes. We used a population-weighted analysis to adjust for the disproportionate number of epidemiological studies from high-income countries and identified 15 key representative isolates as vaccine targets. Strong strain type associations were observed between the site of infection (invasive, skin, and throat) and several streptococcal lineages. In conclusion, the development of a truly global vaccine to reduce the immense burden of diseases caused by S pyogenes should consider the multidimensional diversity of the pathogen, including its social and environmental context, and not merely its geographical distribution.

A global snapshot on the prevalent macrolide-resistant emm types of Group A Streptococcus worldwide, their phenotypes and their resistance marker genotypes during the last two decades: A systematic review

Watchful epidemiological surveillance of macrolide-resistant Group A Streptococcus (MRGAS) clones is important owing to the evolutionary and epidemiological dynamic of GAS. Meanwhile, data on the global distribution of MRGAS emm types according to macrolide resistance phenotypes and genotypes are scant and need to be updated. For this, the present systematic review analyses a global set of extensively characterized MRGAS isolates from patients of diverse ages and clinical presentations over approximately two decades (2000 to 2020) and recaps the peculiar epidemiological features of the dominant MRGAS clones. Based on the inclusion and exclusion criteria, 53 articles (3593 macrolide-resistant and 15,951 susceptible isolates) distributed over 23 countries were dissected with a predominance of high-income countries over low-income ones. Although macrolide resistance in GAS is highly variable in different countries, its within-GAS distribution seems not to be random. emm pattern E, 13 major emm types (emm12, 4, 28, 77, 75, 11, 22, 92, 58, 60, 94, 63, 114) and 4 emm clusters (A-C4, E1, E6, and E2) were significantly associated with macrolide resistance. emm patterns A-C and D, 14 major emm types (emm89, 3, 6, 2, 44, 82, 87, 118, 5, 49, 81, 59, 227, 78) and 3 well-defined emm clusters (A-C5, E3, and D4) were significantly associated with macrolide susceptibility. Scrutinizing the tendency of each MRGAS emm type to be significantly associated with specific macrolide resistance phenotype or genotype, interesting vignettes are also unveiled. The 30-valent vaccine covers ~95% of MRGAS isolates. The presented data urge the importance of comprehensive nationwide sustained surveillance of MRGAS circulating clones particularly in Low and Middle income countries where sampling bias is high and GAS epidemiology is obfuscated and needs to be demystified.

Epidemiological study of erythromycin-resistant Streptococcus pyogenes from Korea and Japan by emm genotyping and multilocus sequence typing

Background

We determined the epidemiological characteristics of erythromycin (EM)-resistant Streptococcus pyogenes (group A streptococci, GAS) strains isolated from Korea and Japan, using emm genotyping and multilocus sequence typing (MLST).

Methods

Clinical isolates of GAS had been collected from 1992 to 2012 in Korea and from 2004 to 2009 in Japan. EM resistance was determined by the microdilution method, and resistance genotypes were assessed by PCR. The emm genotyping and MLST were performed by DNA sequencing.

Results

The emm genotypes and sequence types (STs) were concordant in 143 (85.1%) of 168 EM-resistant GAS strains from Korea. ST36/emm12 (35.1%), ST52/emm28 (22.6%), and ST49/emm75 (16.1%) were the most common types. Most of the ST36 (93.9%) and ST52 (95.8%) strains harbored erm(B), whereas strains ST49, ST42, and ST15 contained mef(A). The concordance between emm genotypes and STs was 41 (93.2%) among 44 EM-resistant GAS strains from Japan. ST36/emm12 (34.1%), ST49/emm75 (18.2%), and ST28/emm1 (15.9%) were the major types. ST36 isolates harbored either erm(B) (56.3%) or mef(A) (37.5%), whereas isolates ST28, ST49, and ST38 carried only mef(A). The proportion of erm(B) and mef(A) was 66.1% and 33.3% in Korea and 22.7% and 68.2% in Japan, respectively.

Conclusions

The common STs in Korea and Japan were ST36 and ST49, whereas ST52 was present only in Korea and ST28 only in Japan. Genotype erm(B) was predominant in Korea, whereas mef(A) was frequent in Japan. There were differences between Korea and Japan regarding the frequencies of emm genotypes, STs, and EM resistance genes among the EM-resistant GAS.

Genetic Diversity among Group A Streptococcus Isolated from Throats of Healthy and Symptomatic Children

BACKGROUND

Group A streptococcus (GAS) is the commonest bacterial cause of pharyngitis. Children in the age group of 5-15 years are most commonly affected. It can also colonize throats of healthy children in this age group. Both cases and carriers can transmit it in the community.

METHODS

Throat swab samples were collected from 1849 asymptomatic and 371 symptomatic children.

RESULTS

The rate of isolation of GAS was 1.41% among the asymptomatic group and 7.55% among the symptomatic group. Nine different emm types were encountered in the asymptomatic children and 14 among the symptomatic children.

CONCLUSION

Throat swab cultures must be used in all cases of pharyngitis. Early and appropriate antibiotic therapy will prevent complications. Asymptomatic throat carriage of GAS in children was low in our study. However, they can still act as reservoirs. Emm typing helps in understanding epidemiology and finding new types.

Macrolide-resistant Streptococcus pyogenes: prevalence and treatment strategies

Although penicillin remains the first-choice treatment for Streptococcus pyogenes infection, macrolides are important alternatives for allergic patients and lincosamides are recommended together with β-lactams in invasive infections. S. pyogenes may exhibit macrolide resistance because of active efflux (mef genes) or target modification (erm genes), the latter conferring cross resistance to lincosamides and streptogramin B. Worldwide, resistance is restricted to a limited number of genetic lineages, despite resistance genes being encoded on mobile genetic elements. For reasons that are not completely clear, resistance and the associated phenotypes are highly variable across countries. Although resistance remains high in several countries, particularly in Asia, an overall decreasing trend of resistance has been noted in recent years, mostly in Europe. This decrease is not always accompanied by declines in macrolide consumption, suggesting significant roles of other factors in determining the dynamics of macrolide-resistant clones. Continued surveillance is needed to obtain further insights into the forces governing macrolide resistance in S. pyogenes.

Differences between macrolide-resistant and -susceptible Streptococcus pyogenes: importance of clonal properties in addition to antibiotic consumption

A steady decline in macrolide resistance among Streptococcus pyogenes (group A streptococci [GAS]) in Portugal was reported during 1999 to 2006. This was accompanied by alterations in the prevalence of macrolide resistance phenotypes and in the clonal composition of the population. In order to test whether changes in the macrolide-resistant population reflected the same changing patterns of the overall population, we characterized both macrolide-susceptible and -resistant GAS associated with a diagnosis of tonsillo-pharyngitis recovered in the period from 2000 to 2005 in Portugal. Pulsed-field gel electrophoresis (PFGE) profiling was the best predictor of emm type and the only typing method that could discriminate clones associated with macrolide resistance and susceptibility within each emm type. Six PFGE clusters were significantly associated with macrolide susceptibility: T3-emm3-ST406, T4-emm4-ST39, T1-emm1-ST28, T6-emm6-ST382, B3264-emm89-ST101/ST408, and T2-emm2-ST55. Four PFGE clusters were associated with macrolide resistance: T4-emm4-ST39, T28-emm28-ST52, T12-emm22-ST46, and T1-emm1-ST28. We found no evidence for frequent ongoing horizontal transfer of macrolide resistance determinants. The diversity of the macrolide-resistant population was lower than that of susceptible isolates. The differences found between the two populations suggest that the macrolide-resistant population of GAS has its own dynamics, independent of the behavior of the susceptible population.

[Consensus document on the diagnosis and treatment of acute tonsillopharyngitis]

Acute tonsillopharyngitis is one of the most common childhood diseases. Viruses are the most frequent origin. Group A Streptococcus (Streptococcus pyogenes) is the main bacterial cause. A culture or a rapid antigen-detection test of a throat-swab specimen should only be done on the basis of clinical scores, in order to avoid over-diagnosis of bacterial origin and unnecessary antibiotic prescription. The objectives of treatment are: the reduction of symptoms, reduce the contagious period, and prevent local suppurative and systemic complications. Ideally, only confirmed cases should receive antibiotics. If there is no possibility to perform a rapid antigen-detection test, or in some cases if the result is negative, it is recommended to perform a culture and, if there is high suspicious index, to prescribe antibiotics. Penicillin is the treatment of choice, although amoxicillin is also accepted as the first option. Amoxicillin/clavulanate is not indicated in any case as empirical treatment. Macrolides are not a first choice antibiotic, and should be reserved for those patients with immediate penicillin allergy reaction or for the treatment of streptococcal carriers. It is of primordial importance to adapt the prescribing of antibiotics to the scientific evidence.

Differences among group A streptococcus epidemiological landscapes: consequences for M protein-based vaccines?

Group A streptococcus (GAS) is a bacterial pathogen responsible for a wide array of disease pathologies in humans. GAS surface M protein plays multiple key roles in pathogenesis, and serves as a target for typing and vaccine development. In this review, we have compiled GAS epidemiological studies from several countries around the world to highlight the consequences on the theoretical efficacy of two different M protein-based vaccine strategies.

Phenotypes and genotypes of macrolide-resistant Streptococcus pyogenes isolated in Seoul, Korea

The mechanisms of resistance to macrolides in 51 erythromycin-resistant clinical isolates of Streptococcus pyogenes collected from 1997 through 2003 in Seoul, Korea were evaluated. They were characterized by their antimicrobial susceptibility, phenotype (using triple-disc and induction tests), resistance genotype, emm genotyping (M typing) and phylogenetic analysis. Erythromycin resistance was observed in 23 % of isolates. Inducible phenotype was the most common (iMLS, 51 %, 26 strains), followed by the constitutive phenotype (cMLS, 31 %, 16 strains) and the M phenotype (18 %, 9 strains). Eight of twenty-six iMLS isolates exhibited the iMLS-C phenotype. The remaining 18 isolates gave small inhibition zones (<12 mm) around all three discs, and mild blunting of the spiramycin and clindamycin zones of inhibition proximal to the erythromycin disc. They showed remarkable inducibility in erythromycin and clindamycin resistance. The MIC90 of erythromycin and clindamycin rose from 8 to >128 μg ml−1 and from 0.5 to >128 μg ml−1, respectively. Their resistance characteristics did not fit into any known iMLS subtype reported so far in the literature. So, it was named as an iMLS-D, new subtype. All of these iMLS-D strains harboured the erm(B) gene, demonstrated the emm12 genotype, except one, and formed a tight cluster in a phylogenetic tree, with 89.2 to 100 % sequence homology, suggesting that they are closely related. Nine of sixteen cMLS strains had the emm28 genotype, which had been reported to be associated with multiple drug resistance.

Genetic diversity and exotoxin A production of group A streptococci causing sepsis

The M protein and streptococcus pyrogenic exotoxin (SPE A) are important virulence factors in group A streptococci (GAS) infections. The emm types of GAS strains isolated from patients with sepsis were determined by sequencing the 5' N-terminus of the emm gene, encoding the M protein, and clonality analysis using pulsed-field gel electrophoresis. The presence of speA and production of SPE A were also examined. There were no predominant GAS clones. The emm genotypes were variable, and the most common genotype was emm13 (17.9%). The production prevalence of SPE A was 21.4%. The low mortality rate (7.1%) of GAS sepsis might be attributable to the low incidence of virulent strains such as emm1 (10.7%) and emm3 (7.1%), as well as to low production rate of SPE A.