What causes recurrent streptococcal (strep) infections?

What Causes Recurrent Strep Infections

Most patients with recurrent positive strep tests are actually chronic pharyngeal carriers experiencing repeated viral infections, not true recurrent streptococcal infections. 1

Primary Causes of Apparent Recurrent Strep

Chronic Carrier State with Intercurrent Viral Infections (Most Common)

• Up to 20% of asymptomatic school-aged children are Group A Streptococcus carriers during winter and spring in temperate climates, and these carriers can harbor the bacteria for ≥6 months. 1
• Carriers have GAS present in their pharynx but show no immunologic response to the organism (no rising anti-streptococcal antibody titers). 1
• When carriers develop viral pharyngitis, testing reveals GAS in the throat, mimicking acute streptococcal pharyngitis. 1
• Carriers are at very low risk for developing complications and are unlikely to spread the organism to close contacts. 1

True Recurrent Infections

• New GAS infection acquired from family contacts, classroom contacts, or other community contacts represents a genuine cause of recurrent episodes. 1
• "Ping-Pong spread" within families can cause multiple repeated episodes when family members repeatedly reinfect each other. 1
• Reinfection with a different strain of GAS is more common than relapse with the original strain. 1

Treatment-Related Causes

• Noncompliance with the prescribed antimicrobial regimen is a frequent cause of apparent treatment failure. 1
• Macrolide resistance should be considered, particularly if the patient has had multiple courses of macrolide antibiotics. 2
• True treatment failure with the original infecting strain occurs rarely. 1

Intracellular Bacterial Persistence (Emerging Mechanism)

• Recent research demonstrates that GAS can internalize into epithelial and endothelial cells, creating intracellular reservoirs. 3, 4
• Strains containing the fibronectin-binding protein F1 gene can invade host cells and persist intracellularly, where penicillins do not reach sufficient bactericidal concentrations. 4
• This mechanism may explain treatment failures and persistent throat carriage despite appropriate antibiotic therapy. 4

Distinguishing Carriers from True Infection

Clinical Clues Favoring Carrier State

• Patient's age (school-aged children and adolescents most likely). 1
• Season of the year (winter and spring in temperate climates). 1
• Local epidemiology showing concurrent influenza or enteroviral illnesses. 1
• Lack of robust clinical response to antibiotic therapy in previous episodes. 1
• Absence of GAS during asymptomatic intervals between symptomatic episodes. 1

When to Suspect True Recurrent Infection

• Distinct clinical episodes with clear symptom onset and resolution. 1
• Documented exposure to confirmed GAS cases. 1
• Rising anti-streptococcal antibody titers between episodes. 1

Management Approach

For Single Recurrence

• Retreat with any appropriate antimicrobial agent from standard regimens (penicillin, amoxicillin, cephalosporins, or macrolides). 1
• Consider intramuscular benzathine penicillin G if compliance is questionable. 1

For Multiple Recurrences

• Use antimicrobials with higher rates of pharyngeal eradication: clindamycin (20-30 mg/kg/day in 3 doses for 10 days), amoxicillin-clavulanic acid (40 mg/kg/day in 3 doses for 10 days), or penicillin plus rifampin. 1
• Consider testing all family members simultaneously and treating those with positive cultures if "Ping-Pong spread" is suspected. 1

What NOT to Do

• Do not perform routine post-treatment cultures on asymptomatic patients who have completed therapy. 1
• Do not routinely culture or treat asymptomatic household contacts. 1
• Do not use continuous antimicrobial prophylaxis (except for preventing rheumatic fever recurrence in patients with prior rheumatic fever). 1
• Tonsillectomy is not recommended solely to reduce GAS pharyngitis frequency, as it provides only limited benefit for a short time period. 1

Common Pitfalls

• Misinterpreting a positive test in a carrier with viral pharyngitis as treatment failure leads to unnecessary antibiotic courses. 1, 2
• Hygienic measures (changing toothbrushes, bed linen, washing toys) have no decisive influence on recurrence risk. 5
• Family pets are not reservoirs for GAS and do not contribute to familial spread. 1
• It is much more difficult to eradicate GAS from carriers than from patients with acute infections. 1