Isolation and characterization of Streptococcus pyogenes from Iraqi children with pharyngotonsillitis

Abstract

Background: Streptococcus pyogenes known as group A streptococci (GAS) is the main causative agent of pharyngotonsillitis in children younger than 12 years old. The infection appears mostly in winter and spring. Signs and symptoms of patients with a beta-hemolytic GAS infection, include tonsillar exudate, fever, painful anterior cervical adenopathy, and the lack of a cough. Penicillin and ampicillin are the preferred clinical therapy choice for GAS pharyngitis treatment. Objectives: Isolate and identify GAS in throat swabs among children suffering from acute pharyngotonsillitis to estimate the prevalence rate of bacterial isolates associated with age, sex, and months variation of GAS infection. Also, it is to determine the antibiotic sensitivity patterns such as penicillin, ampicillin, erythromycin, azithromycin, ofloxacin, clindamycin, and rifampicin, which are used for the treatment of GAS associated with the acute pharyngotonsillitis in children. Materials and Methods: Four hundred and ten throat swabs have been obtained from patients who were clinically diagnosed as having acute pharyngotonsillitis of age ranging from (1–12) years of both sexes were admitted to various hospitals and enrolled in a sequential manner from November 2021 to April 2022 in two Governorates (Baghdad and Babylon), Iraq. These throat swabs were exposed to the bacterial culturing, and some other tests. Streptococcus pyogenes isolates were identified depending on the colony properties, beta-hemolysis on sheep blood agar plate, Gram’s stain, catalase production test, in addition to a sensitivity to bacitracin and Pyrrolidinyl arylamidase test to confirm the identification of GAS. Results: The prevalence of identifying GAS isolates was 140 (34.1%) out of 410 samples. GAS strains can cause acute pharyngotonsillitis in children of all ages, but it most frequently occurred between 1 and 6 year age groups, and it was more in men 80 (57.1%) than in women 60 (42.9%). Likewise, it was found that GAS associated with acute pharyngotonsillitis with a high incidence in winter and in early spring, in which the peak of GAS infection has been seen in January (30.7%). On the other hand, some antibiotics were used to show their effect on these GAS isolates. The findings revealed that all isolates were sensitive (100%) to penicillin and ampicillin, and (83.6%) of isolates were sensitive to clindamycin, whereas some isolates shown a lesser degree of sensitivity (75% and 60%) to rifampicin and ofloxacin. However, only 49.3% of the isolates were sensitive to erythromycin, and (46.4%) were sensitive to azithromycin. Conclusion: GAS strains can cause acute pharyngotonsillitis in children of all ages, but it most frequently occurred in the age groups (1–6) year, and more predominant in men than in women. High percentage of infections with GAS have been noticed in winter and spring to reach its peak in January. Additionally, penicillin and ampicillin are preferred antibiotic for treatment, whereas in the most serious cases clindamycin was added to the treatment plan.

Keywords

• antibiotic resistance
• beta-hemolytic streptococci
• streptococcus pyogenes
• pharyngotonsillitis