Impact of Sub-Minimal Inhibitory Concentrations of Ciprofloxacin, Amikacin and Gentamicin on the Production of Staphylococcus aureus β- Toxin ʺThe Biofilm Ligaseʺ

Abstract

Beta toxin (β- toxin) plays an important role in Staphylococcus aureus infections by two mechanisms: sphingomyelinase cytotoxic activity and biofilm ligase activity. The biofilm ligase activity is considered as a promising property for biofilm matrix establishment. The present study investigated the influence of sub minimal inhibitory concentrations (sub-MICs) of ciprofloxacin, amikacin and gentamicin on the capacity of S. aureus (wound isolates) to produce β-toxin and form biofilm. After determination of the MIC for each antibiotic, bacteria were grown in sub-MICs of these antibiotics then the ability of beta hemolysin production and biofilm formation were evaluated. The results indicated that 1/8 MICs of all antibiotics have induced  β- toxin  and biofilms whereas  the 1/2 MICs were inhibitory and a high correlation between the  β- toxin  production and biofilm formation has been observed in all isolates under the influence of antibiotics, when the  β- toxin decrease, the biofilm also decrease.

Keywords: S aureus, β- toxin, biofilm, sub-MIC, ciprofloxacin, amikacin, gentamicin.