Antibiotic resistance patterns and resistance-associated genes in Streptococcus pneumoniae: insights from healthy children.

BACKGROUND

The emergence of resistance to β-lactam and macrolide antibiotics, the main therapeutic agents for Streptococcus pneumoniae infections, poses a major public health challenge. This study aimed to investigate antibiotic resistance patterns and characterize the resistance-associated genes in pneumococcal isolates.

METHODS

Nasopharyngeal swab specimens were collected from 318 healthy children younger than 16 years of age. S. pneumoniae isolates were identified using conventional culture, Gram staining, and biochemical tests. Antimicrobial susceptibility was determined by the disk diffusion method, and the minimum inhibitory concentration (MIC) of erythromycin was measured using the E-test. Molecular PCR assays were performed to confirm pneumococcal identification and detect antibiotic resistance genes.

RESULTS

Nasopharyngeal carriage of S. pneumoniae was detected in 25 of 318 children (7.86%). Penicillin showed the highest resistance rate (92%), whereas vancomycin exhibited the lowest (8%). Based on the E-test results, seven isolates (28%) were non-susceptible to erythromycin, including four (16%) resistant and three (12%) intermediate isolates. Therefore, 13 isolates (52%) were classified as multidrug-resistant (MDR). Among the 25 isolates, the pbp2b and ermA genes were each detected in one isolate (4%), whereas ermB, mef(A/E), and tetM were identified in 8 (32%), 16 (64%), and 23 (92%) isolates, respectively. The tet(O) gene was not detected in any isolate.

CONCLUSION

These findings highlight the importance of continuous surveillance of pneumococcal carriage and antimicrobial resistance in pediatric populations to support evidence-based treatment strategies and public health interventions.