[The patient as a source of bacteria in intensive care units: influence of antibiotics and tracheal intubation (author's transl)].

133 patients in an intensive care unit, who prior to admission had not shown any signs of bacterial infection and had not received antibiotic treatment, were assigned to two groups at random. One group received antibiotic prophylaxis with penicillins or cephalosporins (+Pat.), the other group did not receive antibiotics (-Pat.). Staph. aureus was the most frequent facultative pathogen in tracheal secretions and in the environment of "-Pat.". This organism was significantly more frequent in "-Pat." than in "+Pat." in both the tracheal secretions and the environment. Klebsiella spp. outnumbered all other species in "+Pat.". They were significantly more frequent in tracheal secretions of "+Pat." than of "-Pat.". In the first week of hospitalisation marked changes were seen in bacterial flora of tracheal secretions of "+Pat.". Colonization with grammnegative bacteria rose to nearly 100%, the frequency of Staph. aureus diminishing at the same time. Monitoring by contact cultures revealed that gramnegative rods were significantly more numerous in the environment of "+Pat." than of "-Pat.". Matching bacterial strains cultured from tracheal secretions and from the environment of the patients proved that "+Pat. spread significantly higher numbers of their gramnegative bacteria into the environment. The same is true of "-Pat." for Staph. aureus. Intubation had no noticeable effect on the degree of contamination of the surroundings with Staph. aureus. Gramnegative rods were significantly more frequent in tracheal secretions of patients with intubation than in patients without. The same trend was observed for environmental contamination. As the clinical results of this study have shown, antibiotic prophylaxis does not protect patients from infections to the extent expected. Patients, and particularly intubated patients, receiving antibiotic treatment have to be considered as sources of highly resistant gramnegative organisms.