Treatment Streptococcus pneumoniae ATCC49619 TIGR4 R6 MIC (μg/mL) MIC (μg/mL) MIC (μg/mL) Erythromycin 0.25 0.25 0.12 FeNPs-PEG No found No found No found FeNPs-PEG-Eri 0.12 0.12 0.12

Table 1: Antimicrobial activity of eri, FeNPs-PEG and FeNPs-PEG-eri on three strains of S. pneumoniae.