[Evolution of the intestinal flora in patients under preventive treatment with cephalosporins].

The evolution of the intestinal flora has been studied in 20 patients undergoing chemoprophylaxis with cephalosporins. The patients, admitted to the Cantonal Hospital of Geneva for heart surgery, all received intravenous treatment initiated on the day of admission. Subsequently, one group continued to receive a cephalosporin orally while prophylaxis was discontinued in a second group. Microbiological analysis of aerobic bacteria in faeces demonstrated in both groups (1) a significant increase in resistance to beta-lactamines (ampicillin); (2) a parallel though lesser increase in resistance to other antibiotics (which shows the probable role of plasmids carrying drug resistance markers); and (3) an increase in bacteria known for their resistance to beta-lactamines (klebsiella, enterobacter, pseudomonas). These results demonstrate that a single intravenous administration of beta-lactamines has a selective effect on the intestinal flora and notably on bacteria which are known to be the cause of infectious diseases acquired in hospitals.