From the Guidelines
Diagnosing chronic Group A Streptococcus (GAS) carriers involves throat cultures as the primary method, with a person considered a chronic carrier when they have a positive throat culture for GAS but no symptoms of infection and no immunologic response to the organism. To confirm carrier status, obtain a throat swab for culture during a period when the person is asymptomatic, and consider performing an anti-streptolysin O (ASO) or anti-DNase B antibody test, which would remain normal in carriers but elevated in those with active infection 1. Multiple positive cultures over time (at least 2-3 weeks apart) without symptoms strongly suggest carrier status. It's essential to distinguish carriers from those with recurrent infections, as carriers typically don't require treatment unless they're implicated in disease outbreaks or have a history of rheumatic fever. Carriers harbor the bacteria in the throat or tonsils but don't show an immune response or develop complications like rheumatic fever. The carrier rate is approximately 10-20% in children and lower in adults. When testing, proper technique is crucial - swab both tonsillar pillars and the posterior pharynx, avoiding the tongue and buccal mucosa, to maximize detection accuracy.
Some key points to consider when diagnosing chronic GAS carriers include:
- The importance of throat cultures in diagnosing carrier status
- The need to distinguish carriers from those with recurrent infections
- The role of anti-streptolysin O (ASO) or anti-DNase B antibody tests in confirming carrier status
- The proper technique for obtaining a throat swab to maximize detection accuracy
- The carrier rate in different populations, such as children and adults
According to the Infectious Diseases Society of America (IDSA) guidelines, antimicrobial therapy is not indicated for the large majority of chronic streptococcal carriers, but there are special situations in which eradication of carriage may be desirable, such as during a community outbreak of acute rheumatic fever or in a family with a history of acute rheumatic fever 1. In these situations, treatment with antibiotics such as clindamycin, penicillin, or amoxicillin-clavulanic acid may be considered. However, it's crucial to weigh the benefits and risks of treatment and to consider the potential for antibiotic resistance.
In terms of treatment regimens, the IDSA guidelines recommend the following:
- Clindamycin: 20-30 mg/kg/day in 3 doses for 10 days
- Penicillin and rifampin: penicillin V 50 mg/kg/day in 4 doses for 10 days, and rifampin 20 mg/kg/day in 1 dose for the last 4 days of treatment
- Amoxicillin-clavulanic acid: 40 mg amoxicillin/kg/day in 3 doses for 10 days
- Penicillin G benzathine and rifampin: penicillin G benzathine 600,000 U for <27 kg and 1,200,000 U for ≥27 kg, and rifampin 20 mg/kg/day in 2 doses for 4 days 1.
It's essential to note that these treatment regimens are only recommended in specific situations and that the decision to treat should be made on a case-by-case basis, taking into account the individual patient's circumstances and the potential risks and benefits of treatment.
From the Research
Diagnosing Chronic Group A Strep Carriers
To diagnose chronic Group A strep carriers, the following steps can be taken:
- Identify individuals with a history of recurrent streptococcal pharyngitis or those who are asymptomatic but have a positive throat culture for Group A beta-hemolytic streptococci (GABHS) 2
- Use clinical decision rules to assess the risk of Group A beta-hemolytic streptococcal infection, followed by rapid antigen testing if a diagnosis is unclear 3
- If rapid antigen testing is negative, a throat culture is recommended in children and adolescents to confirm the presence of GABHS 3
Characteristics of Chronic Group A Strep Carriers
Chronic Group A strep carriers often have:
- Prolonged presence of GABHS in the pharynx without evidence of infection or inflammation 2
- A low risk of immune-mediated complications 2
- Persistent pharyngeal carriage, which can raise management issues 2
Management of Chronic Group A Strep Carriers
The management of chronic Group A strep carriers depends on whether the individual belongs to a 'high-risk' group and may benefit from eradication regimens or not 2.