Increasing antibiotic resistance of veterinary importance is of global health significance and concerns, due to antibiotic-resistant bacteria originating from animals; therefore, easily obtainable and cheap alternatives to antibiotic use in prophylaxis and also as growth promoters are imperative. Antibiotic resistance of 73 and 51 gram-negative, indicator bacterial strains isolated from 68 crop and 51 gizzard contents of layer hens respectively, and identified as Citrobacter, Enterobacter, Escherichia coli, Klebsiella, Proteus, Salmonella, Shigella and Vibrio species were determined. The bacterial flora exhibited in vitro resistance to one or more antibiotics but the most generally resisted antibiotics (discs) were amoxycillin (66.7 to 100%; 71.4 to 100%), augmentin (64.3 to 100%; 50.0 to 100%), cotrimoxazole (42.6 to 100%; 42.1 to 100%), nitrofurantoin (32.1 to 66.7%; 25.0 to 100%) and tetracycline (36.4 to 60.0%; 42.1 to 100%) respectively; while 31 different antibiotic resistant patterns were recorded. Essential oils of Eugenia aromatica (90.9 to 100%), Ageratum (27.3 to 100%), Chrysophyllum albidum juice (22.2 to 100%), lactic acid (100%), acetic acid (72.7 to 100%) and carvone (33.3 to 100%) were however, inhibitory towards the multi-drug resistant Gram-negative bacteria. This study is the first to conclude that essential oils of Ageratum, Eugenia, Anacardium, as well as carvone, Chrysophyllum albidum juice, lactic and acetic acids can serve as easily-produced, natural bio-antibacterial agents of poultry importance instead of antibiotics, in Nigeria.
Key words: Antimicrobial resistance, avian health, essential oils, veterinary public health, zoonosis.
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