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Updated: Jun 19, 2025
A Murine Model of Group B Streptococcus Vaginal Colonization
Published on: November 16, 2016
Characterization of group A streptococci causing invasive diseases in Sri Lanka
Madumali Weerasekara1, Gihani Vidanapathirana1,2, Carmen Li3
1Department of Medical Laboratory Science, Faculty of Allied Health Sciences, University of Peradeniya, Peradeniya, Sri Lanka.
Abstract:
Group A β haemolytic streptococcus (GAS) or Streptococcus pyogenes is a human pathogen that causes an array of infections, including pharyngitis, cellulitis, impetigo, scarlet fever, toxic shock syndrome, and necrotizing fasciitis. The present study characterizes 51 GAS isolates from invasive infections in Sri Lanka, focusing on resistance profiles, genetic determinants of resistance, and virulence markers. Isolates were tested for sensitivity to penicillin, erythromycin, clindamycin, and tetracycline. The presence of erm(A), erm(B), and mef(A) was detected in erythromycin-resistant isolates, while tet(M) was detected in the tetracycline-resistant isolates. PCR was used to identify SpeA, SpeB, SpeC, SpeF, SpeG, smez, and ssa as virulence markers. Selected GAS isolates were emm-typed using the updated CDC protocol. All 51 isolates were susceptible to penicillin. The number of isolates non-susceptible to erythromycin was 16. The commonest resistance determinant identified was erm(B) (11/16). Tetracycline non-susceptibility was found in 36 (70.6 %) isolates and 26 of them contained the tet(M) gene. Thirteen (25.5 %) isolates were resistant to both tetracycline and erythromycin, while 12 (23.5 %) isolates were sensitive to both antibiotics. The commonest virulence markers detected among the isolates were SpeB (44, 86.3 %), SpeG (36, 70.6 %), and SpeF (35, 68.6 %), while SpeJ (15, 29.4 %), SpeA (10, 19.6 %), and ssa (5,9.8 %) were less common. The emm types were diverse. In conclusion, the GAS isolates studied showed resistance to erythromycin and tetracycline, while retaining universal susceptibility to penicillin. Additionally, these isolates exhibited diverse genetic backgrounds, displaying varying patterns of virulence genes and emm types.
Insights
Group A Streptococcus (GAS) isolates in Sri Lanka show resistance to erythromycin and tetracycline but remain susceptible to penicillin. Virulence gene profiles and emm types were diverse among these invasive strains.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Epidemiology
Background:
- Group A Streptococcus (GAS), or Streptococcus pyogenes, is a significant human pathogen responsible for various infections.
- Invasive GAS infections pose a substantial public health concern globally and in regions like Sri Lanka.
Purpose of the Study:
- To characterize 51 GAS isolates from invasive infections in Sri Lanka.
- To determine antibiotic resistance profiles, identify genetic determinants of resistance, and analyze virulence markers.
- To investigate the diversity of emm types among these isolates.
Main Methods:
- Antibiotic susceptibility testing for penicillin, erythromycin, clindamycin, and tetracycline.
- Polymerase Chain Reaction (PCR) to detect resistance genes (erm(A), erm(B), mef(A), tet(M)) and virulence markers (SpeA, SpeB, SpeC, SpeF, SpeG, smez, ssa).
- emm-typing using the updated CDC protocol.
Main Results:
- All 51 isolates were susceptible to penicillin.
- 16 isolates (31.4%) were non-susceptible to erythromycin, with erm(B) being the most common determinant (11/16).
- 36 isolates (70.6%) were non-susceptible to tetracycline, with tet(M) detected in 26 (70.6%).
- 13 isolates (25.5%) were resistant to both erythromycin and tetracycline.
- Common virulence markers included SpeB (86.3%), SpeG (70.6%), and SpeF (68.6%).
- Diverse emm types were observed among the isolates.
Conclusions:
- GAS isolates from invasive infections in Sri Lanka exhibit significant resistance to erythromycin and tetracycline.
- Universal susceptibility to penicillin was maintained, highlighting its continued importance in treatment.
- The observed diversity in virulence genes and emm types suggests varied genetic backgrounds and potential for different pathogenic potentials within the GAS population in Sri Lanka.
