Changes in aerobic faecal bacterial flora of severely ill patients during antibiotic treatment.

The stool of patients both undergoing and not undergoing antibiotic treatment was examined for aerobic faecal bacterial flora (quality and quantity) in an intensive care unit. The bacterial flora in the stool of patients not undergoing antibiotic treatment was generally normal. In patients undergoing antibiotic treatment the faecal bacterial flora showed changes as a result of the use of the antibiotic. Under cephalosporin treatment alone (cefotaxime, cefazolin) E. coli was still to be found. In patients being treated with a combination of two or three antibiotics the frequency of occurrence of E. coli was markedly reduced. Pseudomonas aeruginosa were however substantially more often detected showing increased resistance. The wider the antibiotic spectrum, the more facultative pathogenic microorganisms in the faeces increase, especially Pseudomonas aeruginosa, which can then become an important source for nosocomial infections.