Influence of cefotaxime on microbial colonization resistance in healthy volunteers.

The influence of cefotaxime 1000 mg given intravenously bd on microbial colonization resistance was investigated in six healthy volunteers. Administration of cefotaxime allowed colonization of the bowel by a resistant challenge strain of Enterobacter cloacae in all volunteers. The faecal concentration of aerobic flora increased significantly in five of six volunteers. In one the numbers of Gram-negative bacilli, enterococci and yeasts also increased. In the other four the faecal concentration of enterococci and yeasts increased, but Gram-negative bacilli did not rise above pre-treatment level. It is concluded that cefotaxime impairs colonization resistance, although to a variable degree. Therefore the term 'selective decontamination' is not fully justified for prophylactic regimens that include cefotaxime.