ABSTRACT

The use of antibiotics in poultry production has been implicated in the high level of resistance to antibiotics among Avian pathogenic Escherichia coli (APEC) isolates. Medicinal plants with reported antibacterial properties are promising alternatives to the use of antibiotics in poultry production. The aim of this study was to investigate the antibacterial activities of selsected medicinal plants (Thevetia nerifolia, Zingiber officinale, Asystecia giganticum, Alchornea cordifolia, Dalium guineense) against APEC isolated from poultry farms in Umuahia and Afikpo. Forty eight (48) E. coli isolates were obtained from 46 faecal and 20 entrail samples obtained from 12 poultry farms. Twenty (62.5%) of the isolates were positive to in-vitro (Congo red) and in-vivo pathogenicity (day old chicks lethality) test which were designated as APEC. The antibiotic susceptibility testing of the APEC isolates to common antibiotics was carried out. The antibacterial activity of the extracts of the medicinal plants was investigated against the APEC isolates and a type culture of APEC. Percentage resistance of the APEC isolates to routine antibiotics was in the order, Ampicillin (100%), Cephalexin (95%), Pefloxacin (85%), Nalidixic acid (80%), Augmentin (80%), Streptomycin (80%), Septrin (70%), Gentamycin (65%), Ciprofloxacin (65%)  and Ofloxacin (35%). The isolates showed multiple antibiotics resistance (MAR) with MAR Index in the range of 0.3 to 1.0 and accompanying frequencies range of 1.0 to 5.0. The antibacterial susceptibility test of the plant extract showed that T. nerifolia and Z. officinale had no antibacterial activity against the APEC isolates while A. giganticum, A. cordifolia and D. guineense possessed some antibacterial activity with the highest significant (p<0.05) activity obtained with A. giganticum (17.76mm). The antimicrobial activity of the plant extracts was in the order: Asystecia giganticum>Alchornea cordifolia >Dialium guineense. Their MIC was noted as 250mg/ml. the photochemical screening of the plant extracts using semi-quantitative (chemical) method showed the varying presences of alkaloids, tannins, phenols, steroid, terpenoid and glycosides. The study reveals that Alchornea cordifolia, Asystecia giganticum and Dialium guineense possess antibacterial activity against APEC and could be a possible source of antimicrobial agents for use on the poultry farms.