Genetic diversity and biofilm formation of Staphylococcus equorum isolated from naturally fermented sausages and their manufacturing environment

S. equorum is often isolated from naturally fermented sausages and from the environment of processing units. The aim of this work was first to characterize the genetic diversity of this species in a single small processing unit manufacturing traditional sausages without the use of starter cultures. One hundred and eighteen S. equorum isolates were collected from meat products and surfaces of this unit. Secondly, the capacity to form biofilm of 57 isolates of S. equorum selected from pulsed-field gel electrophoresis (PFGE) profiles was assessed to determine if this property conferred an advantage for the colonization of surfaces in the processing unit. Characterization of the isolates by PFGE analysis revealed a high diversity of the strains with 52 distinct PFGE patterns detected in this limited environment. It showed also that the exchanges between meat products and environmental surfaces could be limited or that the strains could be adapted to a specific niche as only four strains out of the 52 identified colonized both niches. The majority of the S. equorum strains formed biofilm; this was determined using a validated test on polystyrene microplates. This ability was not correlated with their origin, meat products or environmental surfaces.