ABSTRACT
Consumption of fresh vegetables is very common in Nigeria. One of the methods of increasing the availability of vegetables all year round is drying. There is need to determine the microbial quality/safety of the dehydrated vegetables in order to determine the risk of food borne diseases. The microorganisms associated with three dehydrated vegetables (bitter leaf, bell pepper and okra) were isolated, identified and enumerated. The moisture contents of the vegetables were determined and the effects of varying temperature levels on growth of microbial isolates recovered from the samples were studied. A total of nine bacteria, namely: Staphylococcus aureus, Acinetobacter iwoffi, Corynebacterium sp., Bacillus pumilus, Micrococcus sp., Pseudomonas aeruginosa, Flavobacterium sp., Bacillus sp., Micrococcus kristianae and eleven fungi: Aspergillus niger, A. flavus, Aspergillus spp., Penicillium spp., Cladosporium sp., Fusarium spp. were isolated. The mean for total colony forming units (cfu/g) for bacteria were 2.1x107cfu/g, 6.1x105cfu/g, 2.2x106 cfu/g for bell pepper, bitter leaf and okra, respectively while the mean for total colony forming unit (cfu/g) for fungi were highest (1.3 x 106cfu/g) in bell pepper while bitter leaf recorded the least (7 x 103cfu/g) mean for total colony unit for fungi. The mean for percentage (%) moisture content ranged between 16.6-25.8%.The optimum growth was recorded for all the bacteria and fungi at 37ºC and 30ºC; nearly all the isolates had their growth retarded at 45ºC. The recovery of several harmful microorganisms in this study suggest the need for proper handling of vegetables during processing and storage to minimize microbial contamination in order to protect consumers’ health.
ABSTRACT
The antimicrobial activity of the leave of Acalypha wilkesiana methanolic extract and its four derivative fractions were determined on human pathogenic bacteria namely strains of Staphylococcus aureus, Streptococcus pyogenes, Enterococcus faecalis, Pseudomonas aeruginosa, Proteus vulgaris and Escherichia coli and fungi; Aspergillus niger, A. flavus, A. carbonerium, Trichophyton mentagrophytes and Candida albicans. Methanolic extract (200 mg/ml) and its fractions were tested on the bacteria and fungi using the disc diffusion method. In vitro antibacterial and antifungal activity were screened by using Mueller Hinton Agar (MHA) and Potato Dextrose Agar (PDA) respectively. The minimum inhibitory concentration for the bacteria and fungi were also determined. Results showed broad spectrum antimicrobial activity against the Gram-negative and Gram-positive bacteria but same cannot be said about its activity against the fungi. The ethyl acetate fraction inhibited the growth of more bacteria and fungi compared to the other fractions; however, the aqueous extract was more effective on the bacteria isolates as it showed the lowest MIC for more bacteria compared to the other fractions. The extract and its fractions were active against bacteria which some standard antibiotics were not able to inhibit. Methanolic extract of A. wilkesiana leaves and its fractions showed a better antibacterial activity than antifungal activity. The fact that the plant was active against both clinical and laboratory isolates is an indication that it can be a source of very potent antibiotic substances that can be used against drug resistant microorganisms. The search for new drugs to counter the challenges posed by resistant strains of bacteria and some fungi might have started yielding results as the investigation of this plant has demonstrated enormous therapeutic potential.