Antibacterial potential of Forsythia suspensa polysaccharide against resistant Enterobacter cloacae with SHV-12 extended-spectrum β-lactamase (ESBL)

In this study, a homogenous polysaccharide (FSP), with an average molecular weight of 9.08 × 10⁴ Da, was isolated from Forsythia suspense and its antibacterial potential against Enterobacter cloacae producing SHV-12 ESBL was investigated. Growth kinetics, in vitro competition and biofilm formation experiments demonstrated that SHV-12 ESBL contributed to a fitness benefit to E cloacae strain. The antibacterial activity of FSP (2.5, 5.0 and 10.0 μg/mL) was tested against E cloacae bearing SHV-12 ESBL gene using bacterial sensitivity, agar bioassay and agar well diffusion assays. It was found that the addition of FSP demonstrated potent antibacterial activities against this bacterial as showed by the decrease of bacterial growth and the increase of the inhibition zone diameter. Furthermore, SHV-12 ESBL gene expression was decreased in E cloacae strain following different FSP treatment in a concentration-dependent manner. In conclusion, these data showed that FSP exhibited potent good antibacterial activity against E cloacae producing SHV-12 ESBL via inhibition of SHV-12 ESBL gene expression, which may promote the development of novel natural antibacterial agents to treat infections caused by this drug-resistant bacterial pathogen.

Keywords: Enterobacter cloacae producing SHV-12 ESBL; Forsythia suspense polysaccharide; antibacterial activity.