CHITOSAN AND CLOXACILLIN COMBINATION IMPROVE ANTIBIOTIC EFFICACY ON DIFFERENT LIFESTYLE GROWTH OF BACTERIAL ISOLATES FROM CHRONIC BOVINE MASTITIS

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

Congreso; REUNIÓN CONJUNTA DE SOCIEDADES DE BIOCIENCIAS; 2017

Bovine mastitis is the most common pathology that affects dairycows around the world. Staphylococcus spp are the most frequentlybacteria isolates in intramammary infections (IMI). In our work, weselected seven isolates from chronic IMI, refractory to all protocolsfor bovine mastitis. We found that 85%, 71% and 57% of isolatespresent resistance to more than two, three and four antibiotics, respectively.The higher cure-rates to mastitis antibiotic therapy areduring the dry period, in which cloxacillin (Clx) are the most frequentlyused. By other side, chitosan (Ch) exhibit important properties asantimicrobial and pharmaceutical agent. The aim of this work wasfocused on the design of a new formulation that can improve conventionalantibiotic therapy. For that, combinations of Clx and Chwere applied to different lifestyle of bacterial growth. In the presentwork, we analyzed Clx effect on pre-stablished biofilm and invasionof bovine mammary epithelial cells by bacteria from chronic isolates.Accordingly, we found that biofilms and intracellular survival disruptionneeded between 16-128 and 4-32-folds more Clx concentrationthat their planktonic counterparts, respectively. Ch incorporation toantibiotic therapy can improve antibiotic efficacy in planktonic, biofilmsand intracellular survival, reducing Clx concentration in 16-64,5-16 and 4-32-folds, respectively. In fact, Ch addition to conventionaltherapy cannot only reduce bacterial viability, but also inhibits anew biofilm formation and could eradicate pre-established bacterialbiofilms (CFU/mL, Cristal Violet and CLSM). These findings showedthat biofilms and intracellular growth represent a strong protectionagainst antibiotic therapy. However, combined therapy representsan efficient, safer and greener strategy that can be applied duringthe dry period, which could help to improve antimicrobial treatmentagainst multiresistant bacteria and reduce generation and propagationof them.