Influence of the oral administration of different lactic acid bacteria on intestinal microflora and IgA-secreting cells in mice treated with ampicillin

Abstract

It is well known that ampicillin induces an important change in the ecological balance of normal intestinal microflora. The present paper studies the effect of Lactobacillus casei, L. acidophilus, L. delbrueckii subsp bulgaricus and Streptococcus salivarius subsp thermophilus administered orally to mice treated with ampicillin, on the intestinal microflora, on the number of immune cells associated with the gut mucosa and on the IgA-secreting cells of the small intestine. The animals received 75 mg kg -1 of ampicillin orally per day over 3 consecutive days. A quantity of 1.2 x 109 bacteria/day/mouse of the different lactic acid bacteria (LAB) was administered over 2 consecutive days; one group received the LAB on days 0 and 1 and the other on days 2 and 3 following the start of antibiotic treatment. Viable enterobacteria and strict and facultative anaerobic bacteria were determined in faeces and liver, in all the groups, at various intervals. The IgA-secreting cells in histological sections of small intestine were counted by immunofluorescence test. It was observed that ampicillin therapy produced a decrease in the number of strictly anaerobic bacteria with both a remarkable overgrowth of enterobacteria and translocation to the liver. The study demonstrated that the oral administration of L. casei, L. delbrueckii subsp bulgaricus and L. acidophilus improved the intestinal microflora avoiding the bacterial translocation and increasing the number of IgA-secreting cells which reach values similar to those in control mice (ampicillin untreated). This effect was more evident when the LAB were administered together with ampicillin (on days 0 and 1). S. thermophilus was not effective in any case. These results suggest that the oral administration of some LAB species could produce beneficial effects in preventing ampicillin-associated gastrointestinal side-effects, especially in the immuno-compromised host.