The spectra of cephalosporins are broader than that of penicillins. Several cephalosporins are excreted biliary and a strong ecological impact can be expected. Enterococci are intrinsically resistant to cephalosporins and their numbers usually increase during administration.
The impact of parenterally administered cephalosporins on the gastrointestinal normal microbiota is summarized in Table 2.
The impact of intravenously administered cefazolin on the gastrointestinal microbiota has been studied in patients at an intensive care unit (33) and in patients undergoing gastrectomy (34). Overgrowth of resistant Pseudomonas species was detected in the first study while increasing numbers of enterococci, reduced numbers of streptococci and also suppressed numbers of some anaerobic species were observed in the second study.
Changes in the intestinal microbiota in connection with short-term administration of cefbuperazone have been studied in patients undergoing colorectal surgery (35). The agent suppressed the aerobic cocci, enterobacteria as well as the anaerobic microbiota.
A selective reduction of the numbers of E. coli has been observed during administration of cefepime in healthy volunteers (36).
Significantly decreased numbers of enterobacteria, bifidobacteria and lactobacilli have been observed in connection with parenteral administration of cefmenoxime in healthy subjects. Furthermore, there was a concomitant increase in numbers of clostridia and Candida species (37).
Cefoperazone is mainly excreted in bile giving rise to high fecal concentrations and thereby major changes in the intestinal microbiota can be expected. The impact of cefoperazone on the fecal microbiota has been evaluated in adult patients (38) and in sick children (39,40). The Gram-negative aerobic rods as well as numbers of staphylococci and streptococci were markedly suppressed in all studies. Overgrowth of resistant enterobacteria, enterococci and Candida species were observed and anaerobic species were also suppressed.
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