Strep throat

Recurrent Group A Streptococcus Pharyngitis

Reshma Ambaram, MD, and Renu Jain, MD

University of Nevada School of Medicine, Las Vegas

A 9-year-old girl with no significant past medical history presented to the clinic with a 5-day history of persistent sore throat, intermittent headache, nasal congestion, and intermittent fever.

Her vital signs at presentation were normal, including a temperature of 37°C, pulse of 90 beats/min, respiratory rate of 18 breaths/min, and blood pressure of 98/62 mm Hg. Physical examination findings were significant for an erythematous pharynx and uvula with enlarged tonsils, as well as bilateral submandibular lymphadenopathy. Rapid streptococcal antigen test results were positive.

This was the patient’s third occurrence of strep pharyngitis in 3 months. She had been adherent with the previous 2 treatment regimens, each of which had included a 10-day course of amoxicillin. She was confirmed to not be a carrier of group A streptococcus (GAS) via an elevated antistreptolysin O (ASO) titer. She was prescribed a 10-day course of clindamycin and had resolution of the infection.

Discussion

GAS pharyngitis accounts for 20% to 30% of cases of pharyngitis in school-aged children, with peak incidence during the winter and early spring.1 The incubation period for GAS pharyngitis is 2 to 4 days.1 Microbiologic testing includes the rapid streptococcal antigen detection test, which has a specificity of 95% or greater and a sensitivity of 65% to 90%.1 Throat culture is the gold standard, with 90% to 95% sensitivity.1 Complications can include rheumatic fever, poststreptococcal glomerulonephritis, and tonsillopharyngeal cellulitis and abscess.1

Oral penicillin is the antibiotic treatment of choice for GAS pharyngitis because of its efficacy, safety, and narrow spectrum. However, treatment failure has been reported and can occur for a number of reasons, including patients’ difficulty adhering to a 10-day course of oral antibiotics. To address this concern, several antibiotics have been approved for short-course therapy, including a number of cephalosporins and the macrolides azithromycin and clarithromycin.2,3 For less-adherent patients who may not follow up, the use of intramuscular penicillin G benzathine may be preferable.2,3

The M protein coats group A streptococci and acts as the primary antigen, and it is an important virulence factor due to its antiphagocytic properties.3 The emm gene codes for the M protein, and variations in this gene code for more than 130 different types of GAS.3 Thus, in patients with a recurrent pharyngitis due to treatment failure, it may be helpful to determine the serologic group and type of strains to ascertain whether the isolates are the same or different M protein types.3 Such testing, however, is not routine in hospital laboratories, and in these circumstances, contact with a state health department or streptococcal research laboratory will be required.3

Multiple recurrent episodes of GAS pharyngitis in a patient may represent a carrier state in which the bacteria remain in the upper respiratory tract for prolonged periods without provoking an immunologic response.3 Therefore, carriers will have low streptococcal antibody levels as indicated by ASO titers, antideoxyribonuclease B (anti-DNAse B) titers, and the Streptozyme test, which detects antibodies to several streptococcal antigens.3,4

The reason for this prolonged persistence of GAS in the upper respiratory tract is unknown, and whether it is attributable to bacterial factors or host factors is still being studied.3,4 Carriers are less dangerous to others in that they only rarely spread the organism to close contacts.3,4 Furthermore, the risk of developing nonsuppurative sequelae such as rheumatic fever appears to be significantly lower in carriers.3,4 The most effective treatment regimen for eradicating streptococcal carriage is reported to be a 10-day course of clindamycin.2-4 

A high failure rate of penicillins in eradicating GAS in pharyngotonsillitis can serve as sensitive indicator for a high prevalence rate of β-lactamase-producing bacteria in the community.2-4 For these cases, either a 10-day course of clindamycin or penicillin G benzathine plus 10 days of rifampin can be used.2-4 Due to its effective penetration of deep tissue, clindamycin also is used for cases of hypertrophic tonsils, in which GAS may remain in the deep crypts of the tonsillar tissue.

References

1. Langlois DM, Andreae M. Group A streptococcal infections. Pediatr Rev. 2011;32(10):423-430.

2. Berman S, Johnson CE. Sore throat/pharyngitis/tonsillitis. In: Berman S, ed. Pediatric Decision Making. 4th ed. Philadelphia, PA: Mosby Elsevier; 2003:724-727.

3. Kaplan EL, Gerber MA. Group A, group C, and group G beta-hemolytic streptococcal infections. In: Feigin RD, Cherry JD, Demmler-Harrison GJ, Kaplan SL, eds. Feigin and Cherry’s Textbook of Pediatric Infectious Diseases. Vol 1. 6th ed. Philadelphia, PA: Saunders Elsevier; 2009:1225-1238.

4. Shulman ST, Bisno AL, Clegg HW, et al. Clinical practice guideline for the diagnosis and management of group A streptococcal pharyngitis: 2012 update by the Infectious Diseases Society of America. Clin Infect Dis. 2012;55(10):1279-1282.