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

Congreso; LXI REUNIÓN ANUAL DE LA SOCIEDAD ARGENTINA DE INVESTIGACIÓN CLÍNICA (SAIC); 2016

Staphylococcal mastitis is a major and costly problem of dairycattle all over the world, and persistent infections are often attributableto biofilm growth of bacteria. The main treatment to attendthis infections is the antibiotic therapy, although in many caseshas a partial efficacy and cannot completely remove this process.The higher cure rates of antibiotic therapies are during the dryperiod, in which one of the most commonly used is cloxacillin (Clx).Cationic polymers such chitosan (Ch) have important propertiessuch as antimicrobial agent, so they are a good supplement foruse in biomedical applications. In the present work, we analyzedminimum bactericidal concentration (MBC and CFU/mL), metabolicactivity (MTT assay) and biofilm eradication (Crystal Violet assay)of chronic bovine isolates, after being cultured in planktonic andbiofilm form. Bacteria were cultivated in the presence of differentconcentrations and combinations of Clx and Ch. Our resultsindicated that MBC for Clx was higher for biofilm growth than inplanktonic cultures (between 20 to 65 times more) (MBC, CFU/mL and MTT assay). The Clx showed no significant inhibition effectsover formation and eradication of preformed biofilms (CrystalViolet assay and CFU/mL). The combination of Ch and Clx significantlyreduces the antibiotic needed to remove planktonic andbiofilm growth (3-5 and 4-10 times, respectively). This combinationsignificantly inhibited biofilm formation and increased eradicationof this on dose-dependent manner. In conclusion, our resultsshowed that, bacteria inside biofilms needed significantly higherconcentrations of Clx those in planktonic conditions. However, weobserved that combination of Clx and Ch could significantly reducethe concentration of antibiotic required to remove bacteria in biofilms,suggesting that the combined administration can be a greatstrategy for intramammary treatment of chronic bacterial infections.