[Investigation of hydrophobic characteristics of biofilm producer and non-producer Staphylococcus aureus clinical isolates].

The ability of staphylococcus to adhere certain structures and to form biofilm (slime) layer plays an important role in the pathogenesis of staphylococcal infections. Hydrophobic interactions and hydrogen bonds are important factors that play role in adherence. This study was designed to compare the hydrophobic properties of slime positive and negative Staphylococcus aureus strains isolated from blood cultures. Ten methicillin-resistant S. aureus isolates (five of them being slime positive) obtained from blood cultures of patients at intensive care unit of a university hospital, between May 2006 and June 2007, were included in the study. Slime production of the isolates was determined by Christensen's method. Methicillin resistance was determined by cefoxitin disc test and oxacillin salt agar test. It was determined that the test strains did not exhibit any autoaggregation. The adherence of strains to the three different hydrocarbons as solid phases (butyl-sepharose, octyl-sepharose and phenyl-sepharose; Amersham Bioscience, Sweden) were studied by using hydrophobic interaction chromatography (HIC) method. After butyl- and octyl-sepharose chromatography, it was determined that slime negative S. aureus strains were separated into three fractions eluted with phosphate buffered saline (PBS), 40% and 96% ethanol, while slime positive strains were separated into two fractions eluted with 40% and 96% ethanol, respectively. By phenyl-sepharose chromatography analysis; both slime negative and positive strains were separated into two fractions eluted in 40% and 96% ethanol. Hydrophobicity tests were repeated at 4 degrees C and pH 6-9 to evaluate the effect of changing conditions on hydrophobicity. However, no changes we re observed at these temperature and pH values. According to these analysis it was concluded that; (a) S. aureus strains consist heterogeneous fractions with distinct hydrophobic binding strengths; (b) hydrophobic surface protein secretion may be different in heterogeneous groups, and (c) slime positive S. aureus strains were more hydrophobic than non-slime producing strains. Further research is required in order to characterise the eluted fractions and to evaluate their pathogenic capacities.