[Bacterial etiology of hospital-acquired infections].

During the last decades the spectrum of microorganisms causing nosocomial infections has changed. The frequency of Streptococci group A decreased and bacteria formerly considered as apathogen now cause serious infections. More and more "new" organisms are responsible for nosocomial infections. Especially in immunocompromised patients Legionella pneumophila causes infections with often severe and fatal course. Clostridium difficile can be isolated in 6% to 48% in the stool of patients with antibacterial treatment. Up to 36% of all hospitalized patients excrete Clostridium difficile asymptomatically. Acinetobacter species are responsible for 1% to 3% of all nosocomial infections. These changes are probably due to selection by antibiotics and an increase of invasive medical procedures even in immunocompromised patients.