How One Becomes a Carrier of Group A Streptococcus
A person becomes a carrier of Group A Streptococcus (GAS) when the organism colonizes their pharynx without causing an immune response or symptoms of infection. 1
Definition and Prevalence of GAS Carriage
- GAS carriers have the bacteria present in their throats but show no evidence of an active immunologic response to the organism, such as rising anti-streptococcal antibody titers 1
- During winter and spring in temperate climates, approximately 20% of asymptomatic school-aged children may be GAS carriers 1
- Carriers may be colonized by GAS for 6 months or longer 1
- The prevalence of asymptomatic GAS carriage is approximately 10.5% in children from high-income countries and 5.9% in children from low/middle-income countries 2
Mechanisms of Becoming a Carrier
- Carriage often develops following an inadequately treated GAS infection, where the organism persists in the pharynx after symptoms resolve 1
- Some individuals become carriers after antibiotic treatment for GAS pharyngitis, as it is more difficult to eradicate GAS from carriers' upper respiratory tracts 1
- Carriers may acquire GAS from family, classroom, or community contacts 1
- The pathogenesis of carriage has been related to the pharyngeal microflora and to special properties of GAS strains, though several aspects remain unclear 3
Distinguishing Features of Carriers
- Carriers have GAS present in the pharynx but no evidence of infection or inflammation 3
- Unlike patients with acute GAS pharyngitis, carriers do not show an immunologic response to the organism 1
- Carriers may experience episodes of intercurrent viral pharyngitis while colonized with GAS, which can be mistaken for recurrent streptococcal infections 1
- When tested during these viral episodes, carriers will have positive throat cultures or rapid antigen detection tests (RADTs) for GAS, mimicking acute streptococcal pharyngitis 1
Clinical Implications of GAS Carriage
- GAS carriers are unlikely to spread the organism to their close contacts 1
- Carriers are at low risk, if any, for developing suppurative complications or nonsuppurative complications (e.g., acute rheumatic fever) 1
- Antimicrobial therapy is not indicated for the majority of chronic streptococcal carriers 1
- It is difficult to eradicate GAS from carriers using standard penicillin therapy 1
Special Circumstances for Carrier Treatment
Eradication of carriage may be desirable in specific situations:
- During a community outbreak of acute rheumatic fever, acute poststreptococcal glomerulonephritis, or invasive GAS infection 1
- During an outbreak of GAS pharyngitis in a closed or partially closed community 1
- In the presence of a family or personal history of acute rheumatic fever 1
- In a family with excessive anxiety about GAS infections 1
- When tonsillectomy is being considered only because of carriage 1
Diagnostic Challenges
- In clinical practice, it is often difficult to differentiate a GAS carrier with an intercurrent viral infection from a patient with acute streptococcal pharyngitis 1
- Helpful clues include the patient's age, season, local epidemiology, and the precise nature of presenting symptoms 1
- Serotyping of repeated streptococcal isolates may assist in determining carrier status, but such studies can only be done in specialized research laboratories 1