Escherichia coli (E. coli) and Staphyloccus aureus (S. aureus) bacteria adhesion to pure and modified poly(vinyl chloride) (PVC) was investigated through classical wettability measurements, captive bubble time dependent measurements, and static adhesion tests. Various chemical modifiers were studied, namely 4-mercaptophenol, 4-mercaptobenzylalcohol, 4-methoxybenzenethiol, 2-naphthalenethiol and 4-mercaptopyridine. The surface thermodynamics of the modified PVC films was investigated via the van Oss, Chaudhury and Good (vOCG) theory and ail increase in the hydrophilic character was deduced from the increase of the contact angle of the air bubble in water with time of immersion. This is ascribed to a water induced Surface reconstruction of the modified PVC surface. E. coli bacteria exhibit a hydrophilic character and strong adhesion, dependence on the nature of the PVC modifier as shown by the remaining attached bacteria. S. aureus which is hydrophobic showed no difference in its adhesion to pure or modified PVC. A slight increase in the adhesion of E. coli is observed with the water induced Surface reconstruction. This work highlights the predominance of the hydrophilic/hydrophobic nature over the acid-base in the bacteria/polymer adhesion mechanism. It also provides, through chemical modification of PVC, a nice route to control the micro-organisms' adhesion to biomedical devices.