Abstract

Background:
Group A Streptococcus (GAS) is a human pathogen that causes several nonsuppurative complications, such as acute rheumatic fever, leading to rheumatic heart disease (RHD).

Aim:
To determine the prevalence of GAS isolates, M-protein genotypes, antimicrobial susceptibility profiles, and superantigen characteristics in Limpopo Province, South Africa.

Methods:
GAS isolates were obtained from throat swabs (n = 466) of patients with pharyngitis at selected hospitals in Limpopo Province. Clinical GAS isolates (n = 122) were also collected from the NHLS-Polokwane Provincial laboratory. The susceptibility profiles of penicillin, erythromycin, and clindamycin were determined. The M-protein (emm) typing and superantigen (SAg) gene profiles of the isolates were determined. The emm types were correlated with those found in the 30-valent vaccine.

Results:
The prevalence of GAS isolates in throat swabs was 7.1% (33/466). Of the 155 isolates, 45 (29%) were invasive, 108 (70%) were noninvasive, and 2 (1%) were unknown. All isolates exhibited 100% susceptibility to penicillin; however, 15% erythromycin and 16% clindamycin resistance were observed. Thirty-five emm types were identified, with emm77 (21%) being the most prevalent, followed by emm92 (14%). The potential vaccine coverage was 61%. Twenty-seven SAg profiles were identified, of which 22.6% belonged to profile K, comprising 5 emm types, of which only 2 (emm11, emm77) were vaccine types.

Conclusion:
A high diversity of emm types was found, with emm77 and emm92 being the most prevalent. The estimated direct vaccine coverage was 61%, with a theoretical coverage of 76%. The causes of RHD clinical progression need further investigation, particularly regarding genetic factors such as human leukocyte antigen variation.

Key words: Emm type; GAS; M-proteins; Superantigen; Vaccine type.