Testing for Streptococcal Carrier State

Understanding Streptococcal Carriers

Streptococcal carriers are individuals who have Group A β-hemolytic streptococci present in their throats but show no evidence of immunologic reaction to the organism 1
During winter and spring in temperate climates, up to 20% of asymptomatic school-aged children may be streptococcal carriers 1
Carriers may be colonized by Group A streptococci for several months and may experience intercurrent viral pharyngitis during this period 1
Carriers are unlikely to spread the organism to close contacts and are at low risk for developing suppurative or nonsuppurative complications (e.g., acute rheumatic fever) 1

It is difficult in clinical practice to differentiate between a carrier with an intercurrent non-Group A streptococcal infection and a patient with true acute streptococcal pharyngitis 1, 2
Helpful clues for differentiation include patient's age 2, season of the year 2, local epidemiology (e.g., presence of influenza or enteroviral illnesses) 2, and nature of presenting signs and symptoms 1, 2

Performing throat cultures during asymptomatic intervals may help distinguish persistent carriage from repeated episodes of streptococcal pharyngitis 2
Serotyping of repeated streptococcal isolates from an individual patient may assist in determining carrier status, but such studies can only be performed in specialized research laboratories 2
The clinical significance of the number of Group A streptococcal colonies on throat culture plates is limited - while carriers tend to have fewer colonies than those with acute infection, there is too much overlap for reliable differentiation 3, 4

Streptococcal carriers do not ordinarily require antimicrobial therapy 1
It is more difficult to eradicate Group A streptococci from the upper respiratory tract of carriers compared to those with acute infections 1
Many published studies showing high failure rates of penicillin therapy were likely "contaminated" with carriers 1, 2
For patients with multiple episodes of culture-positive pharyngitis, information about clinical response to antibiotics and presence/absence of Group A streptococci during asymptomatic intervals is helpful 2

Routine throat cultures after completion of antibiotic therapy for Group A streptococcal pharyngitis are not necessary unless special circumstances exist 1
Continuous antimicrobial prophylaxis for Group A streptococcal infection is not recommended except for preventing recurrences of acute rheumatic fever 2