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.

Prevalence, Antibiotic Susceptibility Profile and Associated Factors of Group A Streptococcal pharyngitis Among Pediatric Patients with Acute Pharyngitis in Gondar, Northwest Ethiopia

Background

Streptococcus pyogenes (S. pyogenes) or group A streptococcus is a common cause of bacterial pharyngitis in children. Since it is difficult to distinguish between viral and bacterial pharyngitis using solely signs and symptoms, culture-based diagnosis and treatment are critical for avoiding serious complications. Therefore, this study aimed to determine the prevalence, antimicrobial susceptibility patterns, and associated factors of S. pyogenes among pediatric patients with acute pharyngitis.

Methods

A hospital-based cross-sectional study was conducted at the University of Gondar Comprehensive Specialized Hospital from April to June 2021. Standard microbiological procedures were used to collect and process throat swabs and to isolate and identify S. pyogenes. The disc diffusion method was used for antimicrobial susceptibility testing (AST).

Results

A total of 215 children with acute pharyngitis were included in this study. Of these, 23 (10.7%) were culture positive for S. pyogenes. The presence of an inflamed tonsil, tonsillar exudate, scalariform rash, and dysphagia were associated with streptococcal pharyngitis. Children aged 5 to 15 were more susceptible to streptococcal throat infection than younger children. Penicillin, vancomycin, chloramphenicol, clindamycin, and ceftriaxone were effective against 100%, 95.7%, 95.7%, 91%, and 87% of isolates, respectively. In contrast, 56.5%, 39.1%, and 30.4% of isolates showed at least reduced susceptibility to tetracycline, erythromycin, and azithromycin, respectively.

Conclusion

Streptococcus pyogenes is responsible for 10.7% of acute pharyngitis cases among pediatric patients in the study area. Although all isolates remain sensitive to penicillin, many showed reduced susceptibility to tetracycline and macrolides. Therefore, prior to antibiotic prescription, screening children with acute pharyngitis for S. pyogenes and testing the antibiotic susceptibility of isolates is recommended.

Streptococcal Pharyngitis and Rheumatic Fever

Streptococcus pyogenes (Group A Streptococcus) causes a variety of diseases, from benign self-limiting infections of the skin or throat to lethal infections of soft tissue accompanied by multi-organ failure. GAS is one of significant species among Gram-positive pathogens which is responsible for several suppurative infections and non-suppurative sequelae. They also cause pharyngitis, streptococcal toxic shock syndrome (STSS), necrotizing fasciitis and other diseases. Currently, global burden of RF / RHD is undervalued. In 2010, RF and RHD were estimated as 15.6 million cases and deaths around 200,000 annually. Laboratory diagnosis includes cultural techniques, serology, PYR test, Bacitracin susceptibility test and antibiotic resistance testing helps in differentiating the Streptococcus pyogenes from other groups of Streptococci. Most of the Acute Rheumatic Fever cases gets missed or does not present in the initial stage rather it has been developed into advanced Rheumatic Heart Disease condition. Modified Jones criteria in 2015 will be helpful especially to the low risk population as it is challenging because of limited access to primary health care, diagnosis of streptococcal disease. In addition to this revised criteria, diagnosis still relies on clinical diagnostic algorithm. Vaccines based on M protein and T antigens are continuing to evolve with different results. Ongoing vaccine development is still challenging for the GAS research community, it will make a positive and lasting impact on the peoples globally.