Microbial colonization of prosthetic devices. II. Scanning electron microscopy of naturally infected intravenous catheters.

Forty two nonselected naturally infected intravenous catheters were investigated by Scanning Electron Microscopy (SEM) and usual bacteriological methods. In many catheter samples an amorphous deposited substance could be detected by SEM investigation, mostly associated with the isolation of staphylococci, Acinetobacter calcoaceticus and Pseudomonas aeruginosa. The thickest layers of such a substance were found in catheters infected by coagulase-negative staphylococci. The bacteria seemed to be closely packed and cemented by this matrix. It's possible protective role against the defence mechanisms of the host and chemotherapeutic agents was discussed.