Streptococcus pyogenes or Group A Streptococcus (GAS) is a strict human pathogen, sometimes found in oropharyngeal or cutaneous carriage [1]. It is responsible for infections, which can be complicated by autoimmune post-infectious pathologies, such as acute glomerulonephritis (ANG), acute rheumatic fever (ARF), rheumatic carditis, or various neuropsychiatric disorders [2]. There are more than 34 million cases and more than 350,000 deaths each year [3].

In 2018, the World Health Organization (WHO) highlighted the need to strengthen control strategies, including the development of a GAS vaccine [4]. Initial efforts to develop it focused on the M protein. This protein is not only involved in bacterial attachment but also allows microorganisms to escape phagocytosis by leukocytes [5]. This approach has been limited by two factors. First, more than 100 types of M proteins are described; second, similarities between the M protein and host proteins can trigger cross-reactivity [6]. Although the vaccine potential of this region is under investigation, interest in recent years has shifted to other GAS antigens such as cysteine protease and C5a peptidase [7]. Faced with these obstacles to vaccine prevention, antimicrobial resistance is nowadays a heavy burden [8]. Thus, it is necessary to monitor the behavior of GAS with respect to antibiotics. We conducted this study to determine the prevalence of GAS in skin and ENT infections and to study their antibiotic sensitivity profile.

This was a prospective, descriptive study conducted in the Bacteriology and Virology Department of Albert Royer National Children’s Hospital over a 9-month period from January 1^st, 2024 to October 30^th, 2024, in patients aged from 0 to 18 years, seen for consultation and with a dermatosis suspected of GAS infection (superficial skin infections or bacterial dermohypodermitis) or an ENT infection.

This study has been approved by the National Ethics Committee for Health Research (CNERS) of the Cheikh Anta Diop University of Dakar (CER/UCAD/AD/MSN/034). Free and informed consent was obtained from the patient or guardian and a survey form was completed from the interview to collect patient information such as age, sex, address, mother’s education level and antibiotic use before consultation. Samples were taken under strict aseptic conditions with sample processing according to standard bacteriology techniques. The isolation of GAS was done by inoculation on CVBA (Crystal Violet Blood Agar) and GSO (Ordinary Blood Agar), the identification took into account the demonstration of Gram-positive, catalase-negative cocci, grouped in a chain, the presence of beta hemolysis completed by a latex agglutination test with the Streptex™ kit and the antibiotics susceptibility was carried out according to the recommendations of CASFM 2020. The data were entered with Excel 2010 software and analyzed by Epi info 7.2 software.

Sociodemographic Characteristics

A total of 245 patients (children and adults) were included, with a mean age of 5.49 years and a standard deviation of 3.9. The proportion of male patients was higher (51%) (Table 1). By age group, there was a predominance of patients aged from 0 to 3 years (40.69%), followed by those aged from 5 to 10 years (25.52%) (Figure 1).

Table 1. Sociodemographic characteristics.

Figure 1. Distribution of the population according to age group.

Distribution by Origin

The proportion of individuals living in Dakar was the majority at 94.48%, or 232 individuals (Figure 2).

Figure 2. Distribution of the population by origin.

Ethnicity Distribution

Regarding ethnicity distribution, the Wolofs formed the majority, with 108 individuals (44.14%), followed by the Fulani (29.87%) (Figure 3).

Figure 3. Population distribution by ethnicity.

Distribution byMaternal Education Level

Figure 4. Distribution by mother’s education level.

The population constituted mainly of patients whose mothers were not in school (54.48%) (Figure 4).

Distribution of Patients by Sample Type

Skin samples were more numerous (135; 55.11%) than ENT samples (Table 2).

Table 2. Distribution by sample type.

Distribution byTreatment ConceptbeforeConsultation

The majority of patients (44.14%) had not received any antibiotic treatment before the consultation. Only 20.00% were receiving antibiotic therapy (Figure 5).

Figure 5.Distribution of patients according to antibiotic use before consultation.

Prevalence ofStreptococcus pyogenesInfections

Among the 245 patients included, 71.43% (175) had a bacterial infection, and GAS was present in 17 subjects, for a prevalence of 6.93% (17/245) (Table 3).

Table 3. Prevalence of GAS infections.

Germ Distribution

The distribution of isolated germs shows a predominance of Streptococcusspp (41.29%) followed by S. aureus (27.96%), Streptococcus pneumoniae (8.60%) and Streptococcus pyogenes (6.93%) (Figure 6). Are included in Streptococcusspp, all the streptococci that could not be grouped or identified.

Figure 6. Frequency of bacteria isolated in skin infections.

Distribution of GASStrainsbyClinical Form

According to the clinical form, S. pyogenes strains were found most frequently in impetigo (47.05%), followed by tonsillitis (23.52%) (Table 4).

Table 4. Distribution of SGA strains according to clinical form.

AntibioticSusceptibility Profileof GASStrains

Figure 7. Sensitivity of SGA strains to the antibiotics tested.

We noted very good susceptibility of Streptococcus pyogenes strains to penicillin G (100%), cefotaxime (100%), ceftriaxone (100%), ceftazidime (100%), chloramphenicol, and vancomycin (100%). Erythromycin activity was good (87%), as was that of ampicillin (86%), lincomycin (75%), rifampicin (71%), and pefloxacin (67%). However, poor activity was noted for cotrimoxazole (43%), norfloxacin (33%), and resistance to gentamicin was observed in all strains (Figure 7).

This study assessed the role of Streptococcus pyogenes in the infectious etiologies of pediatric skin and ENT diseases at the Albert Royer Children’s Hospital. It included 245 patients with a mean age of 5.49 years, predominantly male. The majority of our study population residing in Dakar (92%) were Wolof and had uneducated mothers (54.48%). We found a prevalence of GAS infection of 6.93%. This prevalence is lower than noted in 2015 among schoolchildren in Bamako with a rate of 22.3% [9]. Another study carried out in Ethiopia had reported a prevalence of 10.6% [10]. Still, a higher prevalence (17.1%) was found in India in 2014 among children aged from 5 to 15 years with acute tonsillopharyngitis [11].

The distribution of clinical forms shows a predominance of impetigo (47.05%) followed by tonsillitis (23.5%). In another study conducted by Coulibaly etal., in 2012, impetigo has been the most observed affection [12]. However, the results of Teclessou etal., 2022 in Togo showed a predominance of folliculitis [13]. In our study, GAS infections were more frequent in children aged from 5 to 10 years. This could be explained by the fact that this is the school age group with promiscuity and frequent contact between children. Paradoxically, other studies on Streptococcus pyogenes skin infections had shown a predominance in children aged from 2 to 5 years [14]. GAS infections were also more common in males, with a rate of 61.54%. The same observation was noted in studies conducted in Mali (2000) and in Burkina Faso (2002) [8][10].

We noted that 20% of patients were already receiving antibiotics before their presentation, and only one of them had a GAS infection. This low frequency of GAS infections in patients receiving antibiotics may be due to the decapitation of the infection, but also to the fact that they are a minority in the study population.

The distribution of isolated micro-organisms shows a predominance of Streptococcusspp (41.29%), followed by S.aureus (27.96%), Streptococcus pneumoniae (8.60%), and Streptococcus pyogenes (6.93%). The results of a study on microbial etiologies in a community setting in India showed a clear predominance of S.aureus(73%) followed by Streptococci (12%) [15].

Regarding antibiotic susceptibility, we noted a good activity of penicillin G and third-generation cephalosporins (3GC) with 100% susceptibility rates of GAS strains. These results are similar to those of Camara etal. in a study on the antibiotic susceptibility of Streptococcus pyogenes where all strains were susceptible to penicillin, amoxicillin and cephalosporins [16]. Another study on the susceptibility of S.pyogenes showed a good susceptibility to beta-lactams [17].

Regarding glycopeptides, all strains were susceptible to vancomycin. A similarity is noted with the results of Camara etal., who found a 100% susceptibility rate to vancomycin and teicoplanin [16].

Macrolide activity was also good: 87% of strains were susceptible to erythromycin. Gashaw etal. found an activity rate of 87.75% of erythromycin on GAS strains in a study on the carriage rate of Streptococcus pyogenes, associated factors, and antimicrobial susceptibility profiles in urban and rural schoolchildren in Gondar City, northwest Ethiopia [18]. A higher activity, 98%, was noted in a study on antimicrobial resistance and epidemiological profile of Streptococcus pyogenes in Türkiye [19].

Regarding fluoroquinolones, we noted a fairly good activity for pefloxacin (67%), in contrast to that of norfloxacin, which was low (33%). These values are lower than those of the results of Beyala etal., 2021 in Yaoundé, who noted 96.4% of susceptibility to pefloxacin and norfloxacin and 100% to levofloxacin [20].

All Streptococcus pyogenes isolates were sensitive to chloramphenicol. A similarity is noted with the results of a study on the antimicrobial susceptibility of invasive Streptococcus pyogenes isolates in Germany between 2003 and 2013, with a susceptibility of 99.1% of strains to chloramphenicol [21]. Similarly, a value close to our results was found in an Ethiopian study with a susceptibility rate of 95.5% [22]. In an Indian study investigating the prevalence and antibiotic susceptibility of Streptococcus pyogenes strains isolated from pyoderma in a tertiary care hospital, 76.9% of S.pyogenes isolates were susceptible to chloramphenicol [23].

This single-center, cross-sectional study includes potential selection bias (cultured patients may not represent all clinical cases), limited sample size, lack of molecular resistance characterization (e.g., resistance genes, emm typing), incomplete control for prior antibiotic exposure, and reliance on phenotypic susceptibility testing without MIC data. These constraints limit generalizability and causal inference; we recommend cautious interpretation and prospective, multicenter studies with integrated genomic analysis to validate and extend these findings.

We noted a low prevalence of Streptococcus pyogenes infections (6.93%). Good antibiotic susceptibility was noted for beta-lactams, chloramphenicol, and macrolides. However, fluoroquinolone activity remained low.