Influence of oral doxycycline therapy on the diversity and antibiotic susceptibility of human intestinal bifidobacterial population.
OBJECTIVE
To evaluate the influence of doxycycline therapy on the composition and antibiotic susceptibility of intestinal bifidobacteria.


RESULTS
Faecal samples were collected from nine subjects receiving doxycycline therapy and ten control subjects, and analysed for bifidobacteria by culturing and PCR-DGGE (denaturing gradient gel electrophoresis). A marked decrease in the diversity (average number of amplicons detected by PCR-DGGE 0.8 in the antibiotic vs 4.3 in the control group) of Bifidobacterium populations was observed during doxycycline therapy. The proportion of a tetracycline-resistant bifidobacterial population was higher in the antibiotic group than in the control group (83%vs 26%). Based on the tet gene PCR, resistance could be associated with the presence of tet(W). In two subjects, strains representing highly similar genetic fingerprints but different tetracycline susceptibilities were detected. A mutation causing lack of functionality in the tet(W) was observed in one of the susceptible strains.


CONCLUSIONS
Doxycycline therapy had a drastic effect on the diversity and tetracycline susceptibility of intestinal Bifidobacterium populations.


CONCLUSIONS
The use of broad-spectrum antibiotics increased the pool of tetracycline-resistant commensal bacteria in the intestine. The detection of resistance genes alone is not sufficient for the evaluation of bacterial antibiotic resistance.
Mättö
J
J
VTT Biotechnology, VTT Technical Research Centre of Finland, Espoo, Finland.
Maukonen
J
J
Alakomi
H-L
HL
Suihko
M-L
ML
Saarela
M
M
D000284:Administration, Oral; D000900:Anti-Bacterial Agents / Q000008:administration & dosage* / Q000627:therapeutic use; D001431:Bacteriological Techniques; D001644:Bifidobacterium / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D016022:Case-Control Studies; D004318:Doxycycline / Q000008:administration & dosage* / Q000627:therapeutic use; D005243:Feces / Q000382:microbiology; D014644:Genetic Variation / Q000187:drug effects; D006801:Humans; D007422:Intestines / Q000382:microbiology*; D008826:Microbial Sensitivity Tests / Q000379:methods; D009154:Mutation; D016133:Polymerase Chain Reaction / Q000379:methods; D013753:Tetracycline Resistance / Q000235:genetics
D000900:Anti-Bacterial Agents; D004318:Doxycycline