Physicochemical properties of Shiga toxigenic Escherichia coli.
OBJECTIVE
To investigate the physicochemical surface properties, such as cellular surface charge, hydrophobicity and electron donor/acceptor potential of a selection of Shiga toxigenic Escherichia coli (STEC) isolates grown in broth and agar culture.


RESULTS
Cellular surface charge was determined using zeta potential measurements. Hydrophobicity of the isolates was determined using bacterial adhesion to hydrocarbons assay, hydrophobic interaction chromatography and contact angle measurements. Microbial adhesion to solvents was used to determine the electron donor/acceptor characteristics. No differences of surface charge measurements were found between broth and agar grown cultures. Isolates belonging to serogroup O157 and serotypes O26:H11 and O111:H- were significantly (P < 0.05) less negatively charged than other STEC serotypes tested. All strains were hydrophilic with most methods and demonstrated a lower hydrophobicity in agar culture compared with broth culture. All strains demonstrated a strong microbial adhesion to chloroform indicating that STEC possess an electron donor and basic character. A relationship between serogroup O157 and other STEC serotypes was apparent using principal-component analysis (PCA).


CONCLUSIONS
Combining the results for physicochemical properties using PCA differentiated between strains belonging to the O157 serogroup and other STEC/non-STEC strains. PCA found similar results for broth and agar grown cultures.


CONCLUSIONS
Particular serotypes of STEC possess similar physicochemical properties which may play a role in their pathogenicity or potential attachment to various surfaces.
Rivas
L
L
Food Science Australia, Brisbane, Queensland, Australia. lucy.rivas@csiro.au
Fegan
N
N
Dykes
G A
GA
D001422:Bacterial Adhesion / Q000502:physiology; D002725:Chloroform / Q000378:metabolism; D002845:Chromatography / Q000379:methods; D003470:Culture Media; D004583:Electrons; D004926:Escherichia coli / Q000502:physiology*; D019453:Escherichia coli O157 / Q000502:physiology; D006838:Hydrocarbons / Q000378:metabolism; D057927:Hydrophobic and Hydrophilic Interactions; D025341:Principal Component Analysis / Q000379:methods; D022603:Shiga Toxins / Q000737:chemistry*; D012997:Solvents / Q000378:metabolism; D013499:Surface Properties
D003470:Culture Media; D006838:Hydrocarbons; D022603:Shiga Toxins; D012997:Solvents; D002725:Chloroform