Appraisal of the Epidemiology and Antimicrobial Resistance Characteristics of Asymptomatic Group A Streptococcus Carriage Among Children in Anambra, Nigeria

Abstract

Group A Streptococcus (GAS, Streptococcus pyogenes) is a significant human pathogen causing a spectrum of diseases from mild pharyngitis to severe invasive infections and post-streptococcal sequelae such as rheumatic heart disease. In Nigeria, particularly in Anambra State, data on asymptomatic GAS carriage and antimicrobial susceptibility patterns among children remain scarce, hindering effective public health interventions. This cross-sectional study aimed to determine the throat carriage rate, associated factors, and antimicrobial susceptibility patterns of GAS among healthy school children in Anambra State, Nigeria. A total of 100 healthy school children aged 5–17 years were randomly selected from three secondary schools across the three senatorial zones of Anambra State. Throat swab samples were collected and processed using standard bacteriological techniques, including culture on blood agar, Gram staining, catalase and bacitracin susceptibility testing, and a panel of biochemical tests. Molecular confirmation of selected isolates was performed using 16S rRNA gene sequencing and PCR. Antimicrobial susceptibility testing was conducted using the Kirby-Bauer disk diffusion method against eight antibiotics. Data on socio-demographic characteristics, hygiene practices, symptoms, and healthcare-seeking behavior were collected using a structured questionnaire. The prevalence of asymptomatic GAS carriage was 2.0% (2/100), with both isolates confirmed as S. pyogenes by 16S rRNA sequencing. Total bacterial counts ranged from 1.5×10³ to 1.88×10⁴ CFU/ml, while Streptococcus spp. counts ranged from undetectable to 5.1×10³ CFU/ml. Antimicrobial susceptibility testing revealed variable resistance patterns: one GAS isolate (B3a) was sensitive to ciprofloxacin and streptomycin but resistant to levofloxacin, gentamicin, and rifampicin; the other GAS isolate (D5a) showed resistance to erythromycin, norfloxacin, levofloxacin, and, notably, amoxicillin. Commensal isolates (S. oralis and S. mitis) exhibited multidrug resistance, with S. mitis resistant to all tested antibiotics. Questionnaire analysis revealed suboptimal awareness (only 72% had heard of streptococcal infections), inadequate hygiene practices (only 39% always washed hands before eating), high rates of sharing personal items (46%), and poor healthcare-seeking behavior (27% of symptomatic children received no treatment). No statistically significant differences in knowledge or practices were observed across grade levels (SIG >0.05). The study concludes that asymptomatic GAS carriage occurs at an intermediate rate (2.0%) among healthy school children in Anambra State, with the unexpected finding of amoxicillin resistance challenging the dogma of universal β-lactam susceptibility. Multidrug resistance in commensal streptococci suggests they may serve as resistance gene reservoirs. Suboptimal hygiene practices, sharing of personal items, and poor healthcare-seeking behavior are prevalent and likely facilitate sustained GAS transmission. These findings provide essential baseline data for local surveillance, empiric treatment guidelines, school-based health education, and antimicrobial stewardship frameworks in southeastern Nigeria. Further research using larger sample sizes, MIC testing for β-lactams, and molecular characterization of resistance genes is recommended to confirm these findings and guide policy formulation