GAS pharyngitis is a self-limiting disease in most cases, however, it can cause suppurative and nonsuppurative complications [1,2]. In our patient both, peritonsillar abscess and poststreptococcal reactive arthritis occurred as a complication of acute GAS tonsillitis. Although microbiological examination was not performed at the time the patient presented with tonsillitis, the reappearance of sore throat within 4 days after completing a 5-day antibiotic therapy with amoxicillin/clavulanic acid and the presence of GAS in throat swab cultures at the time she presented with PTA, strongly suggest GAS aetiology of antecedent tonsillitis. Moreover, the isolation of GAS strains with identical susceptibility patterns from both, throat swabs and abscess aspirate, leaves no doubt that GAS strain that caused tonsillitis participated in the development of PTA. From the majority of PTA aspirates polymicrobial mixture of aerobic and anaerobic bacteria is recovered, however, GAS along with Fusobacterium necrophorum are commonly regarded to be the primary pathogens [4,5]. In our patient three bacterial species were detected in abscess aspirate: GAS, Prevotella oralis, and H. parainfluenzae. There are no uniform recommendations regarding PTA antibiotic therapy, thus treatment options vary greatly between clinicians and are based mainly on their preferences [4,8,9]. In most cases antibiotics of choice include penicillin combined with metronidazole, amoxicillin with clavulanic acid, clindamycin, cefuroxime, or metronidazole [8-10]. In our department cefuroxime combined with metronidazole is administered as empiric antimicrobial therapy in most cases, our patient was treated with these drugs as well.

PSRA is defined as arthritis associated with proven streptococcal infection but not fulfilling the modified Jones criteria for the diagnosis of acute rheumatic fever (ARF). It is still not clear whether this entity represents a distinct syndrome or is a manifestation of ARF [2,3]. ARF has now become rare in developed countries. Its incidence in Western Europe is currently less than 1 case per 100 000 population, whereas PSRA is relatively more frequent with the annual incidence of approximately 2 cases per 100 000 people [11]. There is a mean interval of 14 days between the onset of GAS pharyngitis symptoms and the occurrence of PSRA [3]. Age distribution appears to be bimodal, with two incidence peaks, at ages 8–14 and 21–37 years, respectively [3]. Joint involvement is typically non-migratory and affects large joints, particularly those of lower limbs. Knee and ankle joints are regularly involved, although small joints and axial involvement occurs as well. Mono-, oligo- and polyarthritis are equally represented. Unlike the self-limiting and exquisitely responsive to salicylates arthritis of ARF, PSRA responds relatively poorly to salicylates and nonsteroid anti-inflammatory drugs. Carditis is a rare event. The disease resolves within weeks [3,11,12]. Discrimination between ARF and PSRA is ambiguous due to the lack of generally accepted set of criteria for the diagnosis of PSRA [11]. In our patient non-migratory monoarthritis, localized in the left ankle, without fever or known cardiac involvement occurred approximately 20 days after the onset of tonsillitis while the patient was still on antibiotic therapy due to PTA. Although joint oedema resolved within 4 days, arthralgia, moderately responsive to nonsteroid anti-inflammatory drugs, persisted for about 5–6 weeks. Antecedent GAS throat infection was confirmed by cultures as well as serologically. However, the modified Jones criteria were not fulfilled, thus PSRA was diagnosed. Similarly to what was noted by Jansen et al. [13], clinical findings of PSRA in our patient had subsided before ASO titre reached its maximum value. At present, there are no evidence-based guidelines whether patients with PSRA, similarly to those with ARF, should receive long-term antibiotic prophylaxis [11]. Recent data indicate no increased risk of valvular heart disease in adults with PSRA [14]. Accordingly, our patient did not receive secondary antibiotic prophylaxis.

Some European guidelines, among them British, Scottish, Dutch and Belgian, consider GAS pharyngitis to be a mild, self-limiting disease that does not require a specific diagnosis or antimicrobial treatment except in high-risk patients, such as those with a history of valvular heart disease or acute rheumatic fever, immunosuppressed or severely ill [15-18]. Recently issued recommendations of European Society of Clinical Microbiology and Infectious Diseases represent similar approach [19]. However, the remaining European and North American guidelines recommend that all cases of acute streptococcal pharyngitis/tonsillitis should be appropriately treated to prevent both, suppurative and nonsuppurative poststreptococcal complications [20]. According to Polish recommendations, phenoxymethyl penicillin, 2–3 million units twice daily for 10 days, is currently antibiotic therapy of choice for GAS pharyngitis. Second and third-line drugs include: first generation cephalosporin in patients with penicillin allergy who do not have immediate hypersensitivity to beta-lactam antibiotics or macrolides (erythromycin, azithromycin, clarithromycin) in those with hypersensitivity to beta-lactam antibiotics. Azithromycin is the only drug that is given in a 5-day course as opposed to a 10-day course for all the other antibiotics [21]. Currently, American Heart Association/American Academy of Pediatrics and Infectious Diseases Society of America recommend amoxicillin once or twice daily for 10 days as alternative first-line therapy, since in comparative clinical trials once-daily amoxicillin (50 mg/kg, to a maximum of 1000 mg) for 10 days has been shown to be effective for GAS pharyngitis [2,22]. However, the treatment of tonsillitis in our patient did not comply the recommendations, particularly with respect to the duration of therapy. Five-day treatment with amoxicillin/clavulanic acid resulted in the lack of GAS eradication, which in turn caused both PTA and PSRA.