Abstract:
A study was conducted in Morogoro Municipality, Tanzania to investigate the bacterial
load found on African indigenous leafy vegetables, their sources and their sensitivity to
commonly used antibiotics. A total of 126 samples of fresh African indigenous leafy
vegetables (amaranth, nightshade and sweet potato leaves), water used for irrigation from
rivers and shallow wells and manure fertilised soils were collected at farm sites and
market outlets for bacteriological analysis. Bacterial counts were calculated as colony
forming units (CFU) per millilitre (CFU/ml) of vegetable washing. The isolates sensitivity
or resistances to antibiotics were determined on Muller – Hinton agar plates by the disk
diffusion technique. Data was subjected to Analysis of Variance (ANOVA) using SAS
Statistical software. Results showed that microorganisms were abundant on the surfaces of
the African indigenous leafy vegetables, with nightshade having 1.8 × 105 CFU/ml while
amaranth and sweet potato leaves having 1.7 × 105 CFU/ml and 1.5 × 105 CFU/ml
respectively. The water used for irrigation from the lower section of the river had
significantly (P = 0.03) higher bacterial loads 1.8 × 105 CFU/ml than water from the
higher sections. Biochemical tests indicated bacterial isolates from the studied vegetables
to be Escherichia coli, Enterobacter aerogenes, Proteus spp, Staphylococcus albus and
Bacillus spp. The results show that Escherichia coli, Enterobacter aerogenes and Proteus
spp (coliforms) were highly sensitive (>75 %) to enrofloxacin, sulphamethoxazole and
ofloxacin antibiotics but resistant to rifampicin. The observed bacterial loads, and
sensitivity patterns to commonly used antibiotics reveal the potential adverse health
impact of the vegetables on consumers. Proper handling and preparation of vegetables
before consumption is highly recommended. Further research covering different African
indigenous leafy vegetables in wider agro-ecological areas and sensitivity patterns to
commonly used antibiotics is also strongly recommended.
