response of group b streptococcus to the combination of gold nanoparticles-erythromycin as a nanoweapon

Background: group b streptococcus (gbs) causes a wide range of adverse effects in both mothers and infants during pregnancy and after delivery. objectives: this studyaimedto evaluate the effects of erythromycin either alone or in combination with gold nanoparticles (aunps) on the clinical gbs isolated from pregnant women. methods: this descriptive cross-sectional studywas performedon106womenaged 16 - 48 years. after identification of gbsstrains by phenotypic and genotypic methods (pcr), erythromycin-resistant isolates were identified using the kirby-bauer test and broth microdilution method according to clsi-2015 guidelines. the antibacterial properties and minimum inhibitory concentration (mic) of erythromycin (either alone or combined with aunps) were assessed by the agar well-diffusion and broth microdilution methods, respectively. results: the frequency of gbs isolates was significantly high in the pregnant women aged less than 40 years (73.9%) (p = 0.0251), those with a history of abortion (60.9%) (p = 0.038), and residents of rural areas (60%) (p = 0.038). moreover, 65.2% of the isolates were resistant to erythromycin. the mic of aunps-erythromycin combination required to inhibit the growth of 50% of gbs isolates (mic50 = 0.25 g/ml) was significantly lower than the concentration of aunp-erythromycin required to inhibit the growth of 90% of the isolates (mic90 = 1 g/ml) (p = 0.02), indicating a 16-fold lower dose than the values for erythromycin and aunps alone. in the agar well-diffusion method, the average diameter of the growth inhibition zone of aunps-erythromycin was 2.5-fold greater than that of free erythromycin (p = 0.037). conclusions: the results showed that the combination of erythromycin with aunps increased the antibacterial effects of erythromycin against gbs isolates.