The anti-shigellosis activity of the methanol extract of Picralima nitida on Shigella dysenteriae type I induced diarrhoea in rats

BACKGROUND Picralima nitida Stapf (Apocynaceae) is a medicinal plant used traditionally in Cameroon to cure various ailments such as gastrointestinal disorders and dysentery. This study reports the in vitro and in vivo anti-shigellosis activity of the methanol extract of this plant on rats. METHODS The antimicrobial activity of the extract against pathogenic strains was evaluated using the disc diffusion assay and broth microdilution method. After oral administration of a suspension of Shigella dysenteriae type I (sd1), diarrheic rats were divided into 5 groups; the control group received the vehicle of the extract and the four others 125, 250, 500 mg/kg of the plant extract and ciprofloxacin (20 mg/kg) respectively for 7 days. The frequency of faeces emission as well as the weight of normal and diarrheic faeces was recorded. The presence of stools containing mucus or blood and the number of sd1 in faeces were also recorded. RESULTS In vitro, the extract had an antimicrobial effect on 11 out of the 17 pathogenic strains tested. The values of CMI and CMB obtain against Shigella dysenteriae type I were 800 and 6400 μg/ml respectively. In vivo, diarrhoea induction was effective and we notice an increase in faeces frequency and weight (p < 0.05), increase in the percentage of diarrheic stool released as well as the mucus contained in stool (p < 0.05), an increase in bacterial population in stool (p < 0.05). Picralima nitida extract, like ciprofloxacin markedly reduces the frequency faeces released and sd1 density from 100% (diarrheic rats) to 47.22 and 61.69% (500 mg/kg) respectively. It also slowed down the movement of charcoal meal through gastro-intestinal tract with the percentage of intestinal length covered of 60.54 (500 mg/kg). CONCLUSION This anti-shigellosis activity in vitro and in vivo attests the usefulness of Picralima nitida in the traditional treatment of gastrointestinal disorders such as dysentery.