Prevalence of Salmonella and Shigella Spp on Lettuce and Green Pepper and their Drug Resistance Pattern
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Date
2008-07-03
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Addis Ababa University
Abstract
The microbial load of lettuce and green pepper purchased from different supermarkets in Addis Ababa, Ethiopia, was analyzed. A total of 80 vegetable samples consisting of 40 lettuces and 40 green peppers were included in the study. More than 90% of the lettuce and the green pepper samples had aerobic mesophilic counts of ≥ log 6 cfu/g. Enterobacteriaceae were frequently encountered in these samples and about 97% of the lettuce and 58% of the green pepper samples had enterobacteraceae counts of ≥ log 5 cfu/g. Over 48% of the lettuce and 35% of the green pepper samples had coliform counts ≥ log 4 cfu/g. All vegetable samples harbored staphylococci and more than 92% of the lettuce samples and 80% of the green pepper samples harbored staphylococci with counts ranging from log 4 to log 6 cfu/g. About 42% of lettuce and 30% of green pepper samples had spore counts ≤ log 2 cfu/g. The majority of lettuce and green pepper samples harbored yeasts and mold and more than 88% of lettuce and 18% of green pepper samples had counts ≥ log 4 cfu/g.
The aerobic mesophilic flora of both lettuce and green pepper samples were dominated by Gram positive organisms, with Bacillus and Micrococcus being the most dominant species in the lettuce and green pepper, respectively. Salmonella was isolated from six (10%) samples consisting of two lettuce and four green pepper samples. Shigella was also isolated from fifteen (18.75%) samples of five lettuces and ten green peppers samples.
Resistance to antibiotics was seen in all isolates from the vegetable samples. All of the Salmonella and 97% of Shigella isolates showed resistance to penicillin. The majority of the Salmonella isolates showed susceptibility to polymixin B., gentamicin and ciproflaxin. Ampicillin resistance was observed in 42% of Salmonella and 79% of Shigella isolates. Multiple drug resistance (MDR) was observed in 8 and 24 isolates of Salmonella and Shigella isolates.
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Keywords
Addis Ababa, Lettuce, Green Pepper, Quality, Safety, Salmonella, Shigella, Super Market, Vegetables