Do streptococcal (Group A Streptococcus) throat carriers exist and can they spread infection to others?

Group A Streptococcal Throat Carriers

Yes, streptococcal throat carriers absolutely exist—these are individuals who harbor Group A β-hemolytic streptococci in their pharynx without evidence of an immunologic response to the organism, and they do not ordinarily require antimicrobial therapy. 1

Definition and Characteristics

Carriers are distinguished from acute infections by the absence of an immunologic response (no rising anti-streptococcal antibody titers) despite having Group A streptococci present in their throats. 1, 2 These individuals remain colonized for extended periods—often 6 months or longer—without developing symptoms or being diagnosed with strep throat. 2

The key distinction: carriers have the organism present but show no evidence of active infection or immune response to it. 1, 2

Epidemiology and Prevalence

• Up to 20% of asymptomatic school-aged children may be streptococcal carriers during winter and spring in temperate climates. 1, 2
• The carrier rate is highest in the 6-14 year age group, with some studies showing rates as high as 11.7% for Group A streptococci specifically. 3
• Research from various settings confirms carrier rates ranging from 6% to 16% in school-aged populations. 4, 5

Clinical Significance and Risk Profile

Streptococcal carriers pose minimal clinical risk and do not require treatment in most circumstances:

• Carriers are unlikely to spread the organism to their close contacts. 1, 2
• They are at very low risk, if any, for developing suppurative complications (like peritonsillar abscess) or nonsuppurative complications (like acute rheumatic fever or post-streptococcal glomerulonephritis). 1, 2
• Carriers may develop intercurrent viral pharyngitis during their colonization period, which can confuse the clinical picture when they test positive for Group A streptococci. 1

Common Clinical Pitfall

The major diagnostic challenge occurs when a carrier develops a viral upper respiratory infection. When tested, these patients have Group A β-hemolytic streptococci in their pharynges and appear to have acute streptococcal pharyngitis, but they are actually experiencing a viral illness superimposed on their carrier state. 1 This scenario accounts for approximately one-fourth of school children with culture-positive pharyngitis who are not truly infected but are carriers with concurrent non-streptococcal sore throat. 3

Helpful clues to distinguish carriers from acute infection include: patient age, season, local epidemiology (presence of influenza or enteroviral illnesses), and the precise nature of presenting signs and symptoms (viral features like cough, congestion, and rhinorrhea suggest carrier state with viral infection). 1, 6

Management Approach

Do not treat asymptomatic carriers in routine circumstances. 1, 2 The Infectious Diseases Society of America explicitly recommends against testing or treating asymptomatic household contacts of patients with GAS pharyngitis. 2

Eradication of the carrier state is more difficult than treating acute infection—this has been demonstrated with penicillin therapy and likely applies to other antimicrobials as well. 1, 2 Many published studies showing high penicillin failure rates were likely "contaminated" with carriers. 1

Rare Indications for Treating Carriers

Treatment may be warranted in specific circumstances: 2

• "Ping-pong" spread of GAS occurring within a family
• Communities experiencing outbreaks of acute rheumatic fever or post-streptococcal glomerulonephritis
• Patients with personal or family history of rheumatic fever

When eradication is necessary, clindamycin is particularly effective for eliminating streptococci in carrier states (7 mg/kg three times daily, maximum 300 mg/dose, for 10 days), or amoxicillin-clavulanate can be used. 6

Testing Recommendations

Do not perform routine throat cultures or rapid antigen testing for asymptomatic patients after completion of antibiotic therapy for group A streptococcal pharyngitis unless special circumstances are present. 1, 6 Post-treatment testing should only be performed for patients who remain symptomatic, whose symptoms recur, or who have had rheumatic fever and are at unusually high risk for recurrence. 6

It is not necessary to perform throat cultures or provide treatment for household contacts of patients with Group A streptococcal pharyngitis, except in specific situations with increased risk of frequent infections or nonsuppurative sequelae. 1