The fecal microflora and bile acids in children with cystic fibrosis.

Fecal fat, bile acids, and the rectal microflora were studied in seven 
control children and in three groups of patients with cystic fibrosis 
(CF). Seven were off antibiotics, ten on oral cloxacillin, and six 
on i.v. triple therapy (cloxacillin, gentamycin, and carbenicillin) for at least 
2 weeks. Controls had lower concentrations (milligrams per gram dry stool) 
of both fat (P < 0.005) and vile acids (P < 
0.025) than CF children off antibiotics. Antibiotics had little or no 
effect on fat but led to a striking decrease (P < 
0.01) of bile acids in the triple therapy group. Concomitantly, there 
was reduced deconjugation of bile acids (P < 0.01) and formation 
of secondary bile acids (P < 0.005). This was associated with 
a 5-fold increase in the percentage of bile acids found in 
the aqueous phase of stools and with a marked reduction (P 
< 0.001) of the anaerobic flora (log counts per gram wet 
stool) in children on triple therapy (4.3 plus or minus 1.9) 
when compared to controls (9.8 plus or minus 0.1), CF off 
antibiotics (9.1 plus or minus 0.1) and CF on cloxacillin (9.6 
plus or minus 0.2). The close relationship between the anaerobic flora, 
the extent of bile acid microbial transformation, and fecal bile acid 
concentrations suggest that reduction of the anaerobic flora decreases adsorption of 
bile acids to dietary residues and microbes, favors bile acid absorption, 
and leads to a decreased fecal loss of bile acids in 
CF. 