Efficacy and quantification of break-point doses of clarithromycin on methicillin-resistant staphylococcus pseudintermedius biofilm growth
Authors: Dicicco, M, S Neethirajan, A Singh, S Weese
Description: Surgical site infections (SSIs) are an inherent risk of any surgical procedure and SSIs caused by Staphylococcus pseudintermedius are becoming the most common nosocomial infections in canines at the Ontario Veterinary College. An important underlying pathogenic factor for the development of SSIs is the ability of the bacteria to form a biofilm. Bacterial biofilms are complex communities of bacteria embedded within a self-produced carbohydrate matrix attached to biological or non-biological surfaces that can greatly impact the ability to treat infections. Clarithromycin eliminates biofilms formed by a wide variety of bacteria and has an effective break-point of 8mg/l on methicillin-susceptible S.pseudintermedius strains. In this study, we investigated the in-vitro efficacy of clarithromycin on 20 methicillin-resistant S.pseudintermedius (MRSP) isolates in-order to test eradication therapies against SSI related infections. MRSP isolates were sub-cultured and inoculated into tryptic soy-broth before addition to microtiter plates. Biofilm formation was quantified first through removal of planktonic bacteria followed by staining, then heat fixing, and finally with elution of biofilm-embedded bacteria before completion of an OD570 reading. To characterize the adhesion, MRSP isolates were grown on stainless steel orthopaedic screws exposed to antibiotics at various time points using Scanning Electron Microscopy (SEM). Visual and image processing evaluation of the SEM images revealed the ability of the MRSPs to form biofilm on the surface and between the screw threads. The quantitative assay results (P > 0.5126) suggest that the influence of clarithromycin in the remediation of MRSP biofilms was insignificant after a 24h growth period. The results of our study indicate that the MRSP biofilms exhibits higher resistance to clarithromycin in therapeutic doses.
Keywords: antibiotic susceptibility, adhesion kinetics, imaging, biofilms
Technical field: technical_fields_app1
Session name: Biological systems