Group A β-hemolytic Streptococcus (GABHS), also called Streptococcus pyogenes, is the most frequently identified during acute pharyngitis. Moreover, Streptococcus pyogenes tonsillitis is estimated to be 20-40% of cases in children and 5-15% in adults [1,2]. Every year streptococcus pyogenes causes 600 million pharyngitis cases in children [3]. The most common symptom of pharyngitis is a sore throat and pharyngitis or tonsillitis can be defined as an acute inflammation of the tonsil, pharynx or both. Suppurative infection with Gas can causes multiple complications, including retropharyngeal, sinusitis, mastoiditis, acute otitis media cervical lymphadenitis and abscess. On the other hand, a non-suppurative infection can lead to rheumatic heart disease, acute rheumatic fever, acute glomerulonephritis, toxic shock syndrome and scarlet fever [4]. 

Acute rheumatic fever is an autoimmune disease caused by Streptococcus pyogenes leading to severe damage to the heart valves. Annually there is (233,000) death in children and adolescents due to rheumatic heart disease [5].

Clinical criteria are unreliable enough to diagnose pharyngitis caused by group A Streptococcus (GAS). Hence, the throat swab culture is considered the gold standard for detecting GAS but with significant disadvantages with time; the culture requires 1-3 days to obtain the result, while rapid antigen detection at the point of care requires 5-10 minutes [6]. Another limitation of a throat culture is that it cannot distinguish the carrier from the confirmed infection with intermediator viral pharyngitis [7]. Approximately 10-15% of asymptomatic children are carriers of GAS without immune response to (Anti-DNase and Anti-streptolysin O antigen) [8]. Rapid Antigen Detection Test (RADTs) is widely used in the health care point with a reported sensitivity of 85% [9], 66% [10], 99% [11] and high stable specificity of 95% [9]. Annually, 53.2% of 1000 children aged 3-9 years get antibiotic prescriptions due to pharyngitis caused by Streptococcus pyogenes [12]. Consistent with guidelines, confirmed cases with GAS pharyngitis typically received antibiotics, usually amoxicillin or penicillin). On the other hand, symptomatic not confirmed aetiology of pharyngitis also receive antibiotic treatment [13]. Studies data estimated that 20-30% of children and 5-15% of adults with sore throat have pharyngitis caused by Streptococcus pyogenes and 56% of children and 72 of adults receive antibiotics [13]. Age-specific prevalence of GAS pharyngitis is shown in Figure 1 [12].

All rapid antigen tests, also called rapid chromatographic immunoassay, detect cell wall carbohydrates of group A Streptococcus pyogenes [9]. Many other techniques detect Streptococcus pyogenes antigen, like latex agglutination assay, enzyme immunoassay and optical immunoassay [6].

Figure 1: The specific-Age Prevalence of Gas Pharyngitis Shows Three Studies' Colonization and Assumed Etiological Cases

The image was adapted from Harbeck et al. [11]

One hundred fifty clinical swabs were collected from children aged 2-12. Patients visited the otolaryngologist outpatient clinic at Al-Habooby teaching hospital. Two swabs were collected from each patient, one for rapid antigen test and the other for culture. Amies transport medium was used to transport samples before culture. All children suffered from sore throat, fever, nausea and headache. Samples swabs were collected by the otolaryngologist directly from the tonsils and were tested using the Rapid antigen detection kit.

A rapid antigen detection kit was used to detect the carbohydrates antigen of the group A Streptococcus pyogenes. Steps were followed according to the manufacturer’s instructions. The quick antigen detection principle relies on the fast chromatographic immunoassay technique and the cassette contains the anti-Streptococcus pyogenes cell wall carbohydrates antibodies. According to the manufacturer’s instructions, buffers A and B were prepared by adding four drops from buffer A and four drops from buffer B and mixing well. Collected swabs were extracted by stirring ten times in mixed buffer and incubated for one minute at room temperature. The strip was immersed in the mixture and placed on a dry surface for ten minutes before reporting the result. Results were considered positive when the control and test lines were solid at the same time, they were considered negative when the control line was visible and the test line was invisible (Figure 2). Results with no control line were discarded.

Figure 2: Elucidate the Positive Results of GAS Antigen

Both the control and the test lines are visible

Streptococcus pyogenes Culture

On the other hand, all collected swabs were transported by Amie’s transport media swabs. Swabs were inoculated and stabbed on a 5% blood agar plate and incubated overnight at 37°C. The next day the culture was investigated and the morphology of the colonies was observed-small white pinpoint colonies with beta hemolysis. Streptolysin O toxin showed hemolysis underneath the agar, a specific feature of Streptococcus pyogenes. Furthermore, Bacitracin disk (0.04 U) was used to distinguish susceptible Streptococcus group A from other Beta-hemolytic Streptococcus groups.

Antibiotic Susceptibility Test (AST)

A susceptibility test for an antibiotic was conducted using (VITEK 2 bioMerieux system). All steps were followed according to the manufacturer's instructions. McFarland standard (0.5) was prepared from the culture and inoculated to the AST card. Antibiotics tested involved Benzylpenicillin, Ampicillin, Cefotaxime, Ceftriaxone, Levofloxacin, Erythromycin, Clindamycin, Linezolid, Vancomycin, Tetracycline, Trimethoprim/ Sulphamethoxazole.

Other Etiological Agents and Streptococcus pyogenes Pharyngitis

The current study showed that out of 150 suspected samples, 60 (40%) were positive for Streptococcus pyogenes antigen, while 90 (60%) were negative. These results show that the other etiologic agent is more frequently causing pharyngitis than bacterial pharyngitis caused by Streptococcus pyogenes group A. In addition, all culture swabs were positive for streptolysin O and Bacitracin antibiotic disk 0.04 U (Figure 3).

Figure 3: Elucidate the Pharyngitis Caused by Gas and Pharyngitis Caused by Other Etiologic Agents

Antibiotics Susceptibility Test

Data of the result showed the sensitivity of Streptococcus pyogenes to different antibiotics. Streptococcus pyogenes was sensitive (100%) to vancomycin, (90%) to linezolid, (80%) to levofloxacin, (70%) to clindamycin, (60%) to Trimethoprim/Sulfamethoxazole (50%) to Benzylpenicillin, (40%) to erythromycin, (30%) to ampicillin and Cefotaxime and (20%) to ceftriaxone (Figure 4, Table 1).

Table 1:

Figure 4: Elucidate Antibiotic Sensitivity for Streptococcus Pyogenes using the VITEK System

MIC: Minimum inhibitory concentration, R: Resistant, S: Sensitive

In the current study, we investigated children with acute pharyngitis and evaluated the prevalence of Streptococcus pyogenes as a causative agent of the disease. Complications of Streptococcus pyogenes pharyngitis can lead to serious health issues, including rheumatic heart disease, scarlet fever and post-streptococcal nephritis. Proper diagnosis of bacterial pharyngitis could prevent these complications and the spread of the infection. The rapid antigen detection method is used to differentiate bacterial from viral pharyngitis. Our data study showed that the rate of streptococcal pharyngitis was 60 (40%) and for other etiological agents, 90 (60%) out of 150 samples. Our data was closed to a study in Korea that involved 377 participants with a median age of 3.5 years and a total of 45.4% were less than three years old.

Data showed that the rate of streptococcal pharyngitis is 11.4% using RADT with a specificity of 75.0% and a sensitivity of 97.9%. Children in the age group 3-14 years recorded 194% of GAS pharyngitis, while in children less than three years was 1.8%[14]. Another study reported that viral pharyngitis is 63% in patients aged 3- 21 years [15]. Furthermore, another study in the USA recorded a GAS pharyngitis rate of 19.1% among outpatients [12]. Growth on the blood agar plate showed beta hemolysis and Bacitracin susceptibility for Streptococcus group A.

A meta-analysis of 285 studies showed the prevalence rate of GAS pharyngitis at 24.1% and children with sore throats have been confirmed serologically by detecting anti-streptococcus antibodies in their blood [16]. Moreover, a study in Paris tested 785 children with acute pharyngitis by RADT. The study data showed that 36% of pharyngitis was caused by group A Streptococcus pyogenes [17].

Streptococcus pyogenes showed resistance to different antibiotics. Study results by [18] showed the prevalence of resistance to ceftriaxone, clindamycin, levofloxacin, tetracycline, erythromycin and Cefotaxime was 5.3%, 40%, 8.9%, 51%, 83%, 4.2% respectively. Another study conducted in Hawaassa, southern Ethiopia, revealed the resistance (0.0%), (25.7%), (2.9%), (2.9%), (2.9%), (57.1%) to penicillin, vancomycin, erythromycin, ceftriaxone, amoxicillin, tetracycline respectively.

Interestingly, a study conducted in Dakar city, Senegal, revealed a 100% resistance of Streptococcus pyogenes to tetracycline, while macrolides are still active against the bacteria with reduced susceptibility to spiramycin. Furthermore, isolations were sensitive to levofloxacin, vancomycin, chloramphenicol and teicoplanin [19]. The current results of the study revealed the sensitivity of antibiotics (100%) to vancomycin, (90%) to linezolid, (80%) to levofloxacin, (70%) to clindamycin, (60%) to Trimethoprim/Sulfamethoxazole (50%) to Benzylpenicillin, (40%) to erythromycin, (30%) to ampicillin and Cefotaxime and (20%) to ceftriaxone. The difference in the results of the antibiotic among studies is because of the different geographical areas and types of strain.

These results showed the prevalence of Streptococcus pyogenes as a causative agent of acute pharyngitis that might if untreated, cause a serious complication leading to life-threatening complications like rheumatic fever and kidney disease. On the other hand, prescribing antibodies at the proper diagnosis and the right time is very important during the infection, which prevents complications.

Our current data revealed the prevalence of Streptococcus pyogenes as a cause of acute pharyngitis in children. Most cases of acute pharyngitis are caused by a viral infection, including adenovirus, coronavirus and rhinoviruses. Most health office clinics use the rapid antigen detection kit for fast diagnosis to distinguish between the two causative agents.

Prescribing antibiotics for viral infection leads to incorrect treatment and misleading the correct treatment options, in addition to the cost. Using the RADT as a rapid test increases the chance of the proper treatment.

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