The effect of long-term ethanol feeding on efficacy of doxycycline plus rifampicin in the treatment of experimental brucellosis caused by Brucella melitensis in rats.

A model of Brucella melitensis infection was used in the setting of long-term ethanol administration to study the effects of ethanol on antibiotic therapy of B. melitensis infection. Wistar rats received a liquid diet containing maximally 42.2% of total calories as ethanol. Controls were pair-fed a liquid diet without ethanol. Diets began 15 days pre- and continued post-infection. Rats were infected intraperitoneally with B. melitensis. Doxycycline (10 mg/kg/day) plus rifampicin (6 mg/kg/day) were administered intragastrically starting days 7 to 14 following B. melitensis inoculation. The cure rate was 64.71% in ethanol-fed and 100% in control groups. Although the number of B. melitensis in spleens and livers was reduced, cure was unsuccessful in 6 ethanol-fed rats and this was not explained by the appearance of resistance, since none of the strains isolated following a 7-day course of therapy showed an increase in the minimum inhibitory concentration (MIC) of antibiotics. This study suggests that long-term ethanol ingestion diminishes the efficacy of doxycycline plus rifampicin combination therapy of rat brucellosis in an experimental design.