Elimination of early Salmonella enteritidis infection after treatment withcompetitive-exclusion culture and enrofloxacin in experimentally infected chicks

The effect of normal avian gut flora (NAGF) and enrofloxacin administration on the early infection of young chicks by Salmonella enteritidis (SE) was determined using day-old White Leghorn chicks. Day-old chicks were divided into two groups, untreated control:and :NAGF-treated, and then infected wit h 10(6) cfu of SE per chick by oral gavage. The untreated, infected chicks were further divided into two groups and were either left untreated or medi cated with a regimen of 10 mg/kg of enrofloxacin in drinking water daily fo r 10 d, followed by two doses of NAGF beginning at 10 and 8 wk bf age in Tr ial 1 and Trial 2, respectively. Liver, spleen, and cecum samples were test ed for the presence of SE, and immunological responsiveness was investigate d up to 12 wk of age. Compared with the untreated group, the cecal coloniza tion of SE was significantly (P < 0.05) decreased in the NAGF-treated group in Trials 1 and 2. No significant differences in organ infection were obse rved in the NAGF-treated vs, untreated birds. although a significant effect of the combined treatment of enrofloxacin treatment and NAGF on the early infection was not shown in Trial 1, compared with enrofloxacin only or the untreated group, a significant reduction (P < 0.05) in the number of infect ed chickens and in the number of SE in the cecal contents was observed at 1 0 wk of age in Trial 2. The enrofloxacin treatment did not increase opportu nistic colonization by SE due to the use of the antibiotic in either trial. The plasma and intestinal immunological responses were not significant at the early age (up to 12 wk) of the birds. The use of enrofloxacin, followed by NAGF, could aid the elimination of SE from young chicks persistently in fected at an early age. The combined treatment, compared with enrofloxacin alone, protected chickens from reinfection by 40%.