Antibacterial activity of florfenicol composite nanogels against Staphylococcus aureus small colony variants

Background: Florfenicol might be ineffective for treating Staphylococcus aureus small colony variants (SCVs) mastitis.Objectives: In this study, florfenicol-loaded chitosan (CS)-sodium tripolyphosphate (TPP) composite nanogels were prepared to allow targeted delivery to SCV infected sites.Methods: The formulation screening, the characteristics, in vitro release, antibacterial activity, therapeutic efficacy, and biosafety of the florfenicol composite nanogels were studied.Results: The optimized formulation was obtained when the CS and TPP were 10 and 5 mg/ mL, respectively. The encapsulation efficiency, loading capacity, size, polydispersity index, and zeta potential of the optimized florfenicol composite nanogels were 87.3% +/- 2.7%, 5.8% +/- 1.4%, 280.3 +/- 1.5 nm, 0.15 +/- 0.03, and 36.3 +/- 1.4 mv, respectively. Optical and scanning electron microscopy showed that spherical particles with a relatively uniform distribution and drugs might be incorporated in cross-linked polymeric networks. The in vitro release study showed that the florfenicol composite nanogels exhibited a biphasic pattern with the sustained release of 72.2% +/- 1.8% at 48 h in pH 5.5 phosphate-buffered saline. The minimal inhibitory concentrations of commercial florfenicol solution and florfenicol composite nanogels against SCVs were 1 and 0.25 mu g/mL, respectively. The time-killing curves and live- dead bacterial staining showed that the florfenicol composite nanogels were concentration -dependent. Furthermore, the florfenicol composite nanogels displayed good therapeutic efficacy against SCVs mastitis. Biological safety studies showed that the florfenicol composite nanogels might be a biocompatible preparation because of their non-toxic effects on the renal tissue and liver.Conclusions: Florfenicol composite nanogels might improve the treatment of SCV infections.

Automated summary

Florfenicol composite nanogels were prepared for targeted delivery to SCV infected sites. The nanogels exhibited sustained drug release, showed good antibacterial activity against SCVs, and had therapeutic efficacy against SCV mastitis. Furthermore, the nanogels demonstrated good biocompatibility and safety.