Streptococcus pyogenes, or Group A Streptococcus (GAS), is a highly transmissible human pathogen responsible for a wide range of infections, from pharyngitis and skin diseases to life-threatening invasive diseases. Since 1998, our team has conducted nationwide surveillance in Taiwan through the TSAR (Taiwan Surveillance of Antimicrobial Resistance) program to monitor the molecular epidemiology of GAS.
Our study identified a transient but alarming emergence of high-level levofloxacin-resistant emm12/ST36 GAS strains between 2012 and 2018. These isolates exhibited high clonality, carried double mutations in GyrA and ParC, and had levofloxacin MICs ≥32 mg/mL. Whole-genome multilocus sequence typing (wgMLST) showed that the Taiwanese emm12 strains shared over 96% genetic similarity with epidemic scarlet fever strains from Hong Kong and China.
In addition, we observed the increasing prevalence of invasive emm58 strains, especially among adults and the elderly. These isolates showed a higher tendency to cause bloodstream infections and carried resistance genes such as tetM, along with virulence factors like IdeS, suggesting increased pathogenicity and drug resistance.
Our findings emphasize the evolving landscape of GAS infections and the public health implications of antimicrobial resistance and clone emergence. They also highlight the need for continuous genomic surveillance and reappraisal of vaccine design, particularly for high-risk adult populations.
References
1. Huang YC, Lai JF, Wu CJ, Huang IW, Kuo SC, Liao CL, Huang TW, Lauderdale TL. High-level levofloxacin-resistant emm12 group A Streptococcus, 2012–2018: A multicenter study in Taiwan. J Microbiol Immunol Infect. 2023 Aug;56(4):875–879. https://doi.org/10.1016/j.jmii.2023.04.010