Submitted to: PLoS One
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 24, 2013
Publication Date: August 9, 2013
Citation: Nicholson, T.L., Shore, S.M., Smith, T.C., Fraena, T.S. 2013. Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) isolates of swine origin form robust biofilms. PLoS One. 8(8):e73376. Interpretive Summary: Methicillin-resistant Staphylococcus aureus (MRSA) colonization of livestock animals is common and prevalence rates for pigs have been reported to be high. In this report we demonstrate that MRSA swine isolates can form biofilms. Biofilms are adherent communities of bacteria that are protected from environmental stresses such as antimicrobial compounds and other clearance mechanisms. We also demonstrate that two different compounds can destroy the biofilms formed by these strains. Collectively, these findings provide critical information needed to design intervention strategies to control or eliminate MRSA in swine herds.
Technical Abstract: Methicillin-resistant Staphylococcus aureus (MRSA) colonization of livestock animals is common and prevalence rates for pigs have been reported to be as high as 49%. One hypothesis to explain the high prevalence of MRSA in swine herds is the ability of these organisms to exist as biofilms. To investigate the ability of MRSA swine isolates to form biofilms, a microtiter crystal violet assay was used to quantify and compare biofilm formation by several swine and human isolates. The contribution of known biofilm matrix components, polysaccharides, proteins and extracellular DNA (eDNA), was tested in all strains as well. All MRSA swine isolates formed robust biofilms similar to human clinical isolates. The addition of Dispersin B had no inhibitory effect on swine MRSA isolates when added at the initiation of biofilm growth or after pre-established mature biofilms formed. In contrast, the addition of proteinase K inhibited biofilm formation in all strains when added at the initiation of biofilm growth and was able to disperse pre-established mature biofilms. Of the LA-MRSA strains tested, we found ST398 strains to be the most sensitive to both inhibition of biofilm formation and dispersal of pre-formed biofilms by DNaseI. Collectively, these findings provide a critical first step in designing strategies to control or eliminate MRSA in swine herds.