STANDARDIZATION AND COMPARISON OF METHODS EMPLOYED FOR MICROBIAL CELL-SURFACE HYDROPHOBICITY AND CHARGE DETERMINATION

Whilst there are a number of methods available to characterise the cel l surface hydrophobicity (CSH) and cell surface charge (CSC) of microo rganisms, there is still debate concerning the correlation of results between individual methods. In this study, the techniques of bacterial adherence to hydrocarbons (BATH) and hydrophobic interaction chromato graphy (HTC) were used to measure CSH. Electrostatic interaction chrom atography (ESIC) and zeta potential (ZP) measurements were used to det ermine CSC. To allow meaningful comparisons between the BATH and HIC t ests, between ESIC and ZP and also between CSH and CSC, the buffer sys tems employed in each test were standardised (phosphate buffered salin e, pH 7.3, 0.01 mM). Isolates of Staphylococcus epidermidis derived fr om microbial biofilm were used as the test organism in this study. The isolates examined exhibited primarily medium to high CSH and a highly negative CSC. Good correlation of CSH measurement was observed betwee n the BATH and HIC tests (r = 0.89). Good correlation was observed bet ween ESIC (anionic exchange column) and ZP measurements. No correlatio ns were observed between isolate CSC and either increased or decreased CSH. It is recommended that whenever comparisons of various methods t o determine either CSC or CSH (by partitioning methods), the buffer sy stems should remain constant throughout to achieve consistency of resu lts.