Antimicrobial resistance is one of the 21st century’s major global public health challenge which calls for search for newer sources of antimicrobials. Escherichia coli (E. coli) is gram negative straight rod, non-spore forming bacteria, widely distributed in nature and commonly found in lower gastro intestinal tracts of most warm-blooded animals. The bacteria are associated with dysentery and hemolytic uremic syndrome in humans and colibacillosis in poultry. Pathogenic E. coli associated diseases are a major problem in Tanzania due to low hygienic practices which in turn results into high incidence of diseases. Development of antimicrobial resistance among bacteria including E. coli has increased the need for searching alternative therapy. The availability and accessibility of medicinal plants in most resource poor countries have made medicinal plant products to be a preferred solution. This study was carried out to evaluate the anti- E. coli activity of ethanolic seeds extracts of Carica papaya against E. coli isolates. A total of 50 swab samples were collected from toilets around university campuses between May and July 2018. Agar well diffusion method was used to evaluate anti- E. coli activity of C. papaya seed extracts. A suspension of 0.05 g/ml ciprofloxacin made by dissolving 500 mg ciprofloxacin tablet into 10ml of distilled water and Dimethyl sulfoxide (DMSO) were used as a positive and negative control respectively. C. papaya seed extracts was diluted at 50% and 100% concentration levels using DMSO. Results from this study showed that C. papaya seeds extracts have anti- E. coli activity. Zone of inhibition was wider (average 18.75 mm (SD 1.95) in diameter) in 100% concentration of the extracts than in 50% (average 7.5 mm (SD 3.88) in diameter) indicating a direct relationship between efficacy and extracts concentration. Therefore, C. papaya seeds have potential to be used as a source of natural remedy for the treatment of E. coli associated disease conditions. However, further studies are needed to establish active compounds that inhibit the growth of Escherichia coli and its therapeutic dose.

Keywords: Medicinal-plants, natural-products, E. coli-infections, anti- E. coli activity, Carica papaya