Antibacterial Effect of Zinc Oxide Nanoparticles on Group A β-Hemolytic Streptococci with Macrolide Resistance Isolated from University Student Carriers in North of Iran

The increase in the resistance of group A β-hemolytic streptococci (GABHS) to antibiotics is considered as a serious threat to human health. The current study aimed at determining the antimicrobial effect of zinc oxide nanoparticles (ZnONPs) on the growth of erythromycin-resistant GABHS harboring mef gene isolated from university student carriers. The study was conducted on 100 healthy students from Islamic Azad University, Gorgan Branch. Specimens were collected from the nasopharyngeal region using sterile swab. After biochemical tests to identify GABHS, resistance to various antibiotics was determined using agar disk diffusion test (the Kirby-Bauer method). The minimum inhibitory concentration (MIC) of erythromycin was also determined by broth micro-dilution test. The macrolide resistance gene (mefA) was identified by polymerase chain reaction (PCR) using specific primers, and the antibacterial properties of ZnONPs were evaluated by agar-well diffusion method. The data were analyzed by chi-square and ANOVA tests (P < 0.001). In the current study, the frequency of GABHS carriers was reported 11%. The highest amount of bacterial resistance was correlated with erythromycin with the frequency of 45.4%. Also, 91% of the isolated streptococci were susceptible to cefazolin, followed by cefalexin (82%), penicillin (73%), and amoxicillin (46%). Besides, 43% of the erythromycin-resistant isolates had the MIC of ≥ 1 µg/mL. From the five isolates resistant to erythromycin, 60% harbored the mefA gene. The results of agar-well diffusion test showed that 40% of the strains, which were resistant to erythromycin and harbored mefA gene, were inactivated in the concentration of 50 mg/mL of ZnONPs, and the rest were also inactivated in the concentration of 100 mg/mL. The ZnONPs used in the current study had a high antimicrobial activity against all GABHS isolates that were resistant to erythromycin. It was revealed that the bactericidal property increased upon increasing the concentration of the nanoparticles.