Escherichia coli and Staphylococcus aureus Contaminations of Carrots Sold within Zaria, Nigeria and their Antibiotic Susceptibility Profiles

摘要

Carrots ( Daucus carota ) are root vegetable containing carotene, vitamins and mineral salts. Carrots maybe purple, red, white or yellow in color depending on their varieties and can be eaten fresh, mixed in salad or cooked. Carrots are prone to faecal contamination and often subjected to poor/rough handling in Nigeria. Upon purchase, many people consume them without proper washing. Hence, instead of serving nutritive purposes, they may turn to be a source of food poisoning/infections. Escherichia coli have caused a number of diarrheal diseases and Staphylococcus aureus is an important agent of food poisoning. Forty (40) fresh carrot samples were randomly purchased from different vendors in Zaria metropolis. Then, 10g of epidermal (layer) scrapings of each sample was aseptically collected, homogenized in 90ml of buffered peptone water and serially diluted. From 10~(-4) dilution, 0.1ml was spread-plated on EMB and MSA plates, followed by 24hrs incubation at 37~(o)C. Characteristic colonies of E. Coli and S. Aureus were Gram-stained and biochemically identified. A susceptibility testing of the isolates to some selected antibiotics was performed using disc diffusion method. Twenty (20) out of the 40 carrot samples were positive for E. Coli (50.0%), whereas S. Aureus were isolated from 26 samples (65.0%) with a total mean staphylococcal count of 4.3 x 10~(5) CFU/g. All the Escherichia coli isolates were susceptible to Streptomycin (30μg) and Tarivid (10μg), but Septrin (30μg) and Amoxicillin (30μg) had the least activities against them. Staphylococcus aureus isolates were most susceptible to Ciprofloxacin (10μg), followed by Gentamycin (10μg) and Streptomycin (30μg), but resistant to Ampiclox (30μg) and Amoxicillin (30μg).