Infections of pacemaker electrodes and/or aggregate pockets are usually caused by staphylococci, primarily Staphylococcus epidermidis. From in vitro experiments it can be demonstrated that staphylococci are able to adhere to the plastic electrode sheath, to multiply there, and to form microcolonies. Furthermore, the staphylococci produce a slimy amorphous substance with which they are completely covered after a 24-hour incubation. No difference was noticed between the in vitro experiment situation and that occurring in pacemaker infection in humans. This slimy material may be responsible for the maintenance of the infection and the protection of the enclosed bacterial cells against natural host defense mechanisms and antibiotic treatment.

On 12 different, chemically pure polymers attachment and "slime"-production of the coagulase-negative staphylococcal strain KH 11 were studied. According to their behaviour the polymers investigated could be arranged into three groups: Group 1 with good attachment of staphylococci, but missing "slime"-production; group 2 with good attachment and moderate "slime"-production; group 3 with both properties strongly developed. According to the results presented, attachment of staphylococci and "slime"-production seem to be independent of the presence of organic additives in biomaterials.

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.

Ten commercially available unused intravenous catheters were investigated by Scanning Electron Microscopy (SEM). Different types of irregularities in the external and internal surface could be detected in all catheters examined. Representative examples were demonstrated in 6 SEM-photos. The possible role of such irregularities in favouring bacterial attachment to catheter surfaces was discussed.

Intravenous catheters, artificially infected with staphylococci by perfusion experiments were investigated by Scanning Electron Microscopy (SEM), to demonstrate the mode of adhesion. It seemed to be clear, that the first step of bacterial attachment was associated with the different irregularities of the inner surface of the catheter. With longer perfusion times and/or heavier inoculum cell adherence took place also in apparently smooth regions of the catheter lumen. The possible utilization of catheter material was discussed.