Chitosan enhances the antimicrobial effect of cloxacillin against Staphylococcus spp. isolated from chronic bovine mastitis

BRESER ML; FELIPE V; ORELLANO MS; BOHL LP; CONESA A; ISAAC P; PORPORATTO C

Mar del Plata

Congreso; LXIV Reunión Anual de la Sociedad Argentina de Inmunología (SAI); 2016

Staphylococcal mastitis is a major and costly problem of dairy cattle all over the world, and persistent infections are often attributable to biofilm growth of bacteria. The main treatment to attend this infections is the antibiotic therapy, although in many cases has a partial efficacy and cannot completely remove this process. The higher cure rates of antibiotic therapies are during the dry period, in which one of the most commonly used is cloxacillin (Clx). Cationic polymers such chitosan (Ch) have important properties such as antimicrobial agent, so they are a good supplement for use in biomedical applications. In the present work, we analyzed minimum bactericidal concentration (MBC and CFU/mL), metabolic activity (MTT assay) and biofilm eradication (Crystal Violet assay) of chronic bovine isolates, after beingcultured in planktonic and biofilm form. Bacteria were cultivated in the presence of different concentrations and combinations of Clx and Ch. Our results indicated that MBC for Clx was higher for biofilm growth than in planktonic cultures (between 20 to 65 times more) (MBC, CFU/mL and MTT assay). The Clx showed no significant inhibition effects over formation and eradication of preformed biofilms (Crystal Violet assay and CFU/mL). The combination of Ch and Clx significantly reduces the antibiotic needed to remove planktonic and biofilm growth (16 -60 and 4-5 times, respectively). This combination significantly inhibited biofilm formation and increased eradication of this on dose-dependent manner. In conclusion, our results showed that, bacteria inside biofilms needed significantly higher concentrations of Clx than those in planktonic conditions. However, we observed that combination of Clx and Ch could significantly reduce the concentration of antibiotic required to remove bacteria in biofilms, suggesting that the combined administration can be a great strategy for intramammary treatment of chronic bacterial infections.