Norfloxacin Sub-Inhibitory Concentration Affects Streptococcus suis Biofilm Formation and Virulence Gene Expression

Abstract

Streptococcus suis (S. suis) is a major pathogen causing economic losses to the swine industry. Norfloxacins are usually used at sub-MIC (Minimum Inhibitory Concentration) doses to prevent S. suis infection. This study demonstrates the effect of norfloxacin sub-MIC on biofilm formation and virulence gene expression in S. suis.It was found that 1/4 MIC of norfloxacin increased biofilm formation in S. suis, the biofilms formed contained a higher number of viable bacteria. Additionally, bacterial growth rates were inhibited at 1/2 MIC of norfloxacin. Furthermore, the mRNA level of S. suis virulence gene cps, ef, sly, fpbs, gdh and gapdh increased by real-time PCR, while the virulence gene mrp decreased at 1/4 MIC. In conclusion, Norfloxacin sub-MICs affects biofilm formation and virulence gene expression in S. suis. These findings suggest that investigating the effect of the administration of antibiotics sub-MICs on bacterial biofilms and infection may lead to the development of future antibiotic treatments modalities.

Sub-Inhibitory Concentrations of Amoxicillin and Tylosin Affect the Biofilm Formation and Virulence of Streptococcus suis

“…Additionally, studies have shown that a sub-inhibitory concentration of antibiotics may affect the virulence genes of bacteria, such as Panton-Valentine-leucocidin (PVL), alpha-hemolysin (Hla), and phenol-soluble-modulin alpha (PSMα) [ 16 , 17 ]. The previous experiments of our research group confirmed this view [ 18 ]. Norfloxacin can significantly down-regulate the key virulence genes of S. suis , such as capsular polysaccharide (CPS), extracellular factor (EF), hemolysin (SLY), fibronectin and fibrinogen binding protein (FBPS), glutamate dehydrogenase (GDH), and glycerophosphate deoxygenase (GAPDH).…”

“…Furthermore, the results of tissue HE staining ( Figure 5 ) showed that, after treatment with 1/4MIC Amoxicillin and Tylosin, respectively, the damage degree of each tissue was significantly lower than that of the control group, which indicates that 1/4MIC Amoxicillin and Tylosin might be involved in the expression of multiple genes that regulate bacterial virulence [ 36 ]. We selected seven virulence-related genes in S. suis for verification, which were ef , fbps , gapdh , gdh , mrp , and sly [ 18 ]. Compared with the control group, 1/4MIC Amoxicillin and Tylosin can significantly down-regulate the gene expression of ef , fbps , gapdh , gdh , mrp , and sly .…”

“…We have similar findings in S. suis . Norfloxacin at sub-inhibitory concentrations could enhance the ability of S. suis biofilm formation, increase the number of viable bacteria in the biofilm, and significantly reduce the expression levels of virulence factors ef , fbps , gapdh , gdh , mrp , and gapdh , resulting in persistent infection [ 18 ]. As commonly used drugs for the treatment of swine streptococcus, it is currently unknown whether Amoxicillin and Tylosin can affect the formation of S. suis biofilm and regulate virulence at sub-inhibitory concentrations.…”

Effect of Biofilm Formation on the Escherichia coli Drug Resistance of Isolates from Pigs in Central China

“…It is well known that bacteria growing in a biofilm are intrinsically resistant to many antibiotics (Li et al, 2020). The improvement of bacterial resistance can cause the disease to prolong and the formation of biofilm is one of the important reasons for the improvement of drug resistance (Wang et al, 2019).…”

Influence of Acupuncture on Expression of Mitochondrial Fusion and Fission Mediators in Rat Liver

“…Melting curve analysis was performed at 95C for 10 sec and 65C for 5 sec. Results are expressed as the fold changes calculated using the comparative 2 -ΔΔCt method (Liu et al, 2020). Liver tissues (50 mg) were lysed using protein extraction solution (iNtronbio, Korea) and quantified using a bicinchoninic acid assay kit (Pierce, USA).…”