Characteristics and Antibiogram Studies of Bacteria Associated with Vegetables Stored In Raffia Baskets in Nigeria

Abstract

Raffia baskets are used in rural communities to preserve fresh vegetables for a given period of time. This method of storage is aimed at extending the shelf life of the vegetables until they are used. Thus, this study was aimed at determining the microbial succession during storage and susceptibility pattern of bacterial isolates from stored leafy vegetables to various antibiotics. Five (5) leafy vegetables namely, Bitter leaf (Vernomia anydalira), Water leaf (Talinum triangulare), Fluted pumpkin leaf, (Telfairia occidentalis), Okazi leaf (Gnetum africana) and Scent leaf (Ocimum gratissimum) were obtained from the Nigerian Stored Products Research Institute (NSPRI) farm, Port Harcourt. These vegetables were stored in a raffia basket for fourteen (14) days while another set of the vegetables were left in the open air as control. This set up was monitored for changes to occur. Standard microbiological techniques were employed for the various analyses of the vegetable samples. Both cultural and molecular characterizations of the isolates were done. The disc diffusion method was used in determining the susceptibility pattern of the bacterial isolates. The results of the predominant microorganisms identified were of the genus; Bacillus, Pseudomonas, Enterococcus, Enterobacter, Bordetella, Staphylococcus, Myroides, Escherichia, Serratia, Micrococcus and Acetobacter. Also, Bacillus species occurred in all the vegetables while Enterococcus faecalis, Acetobacter orientalis, Bordetella pertussis, Myroides xuanwuensis and Bacillus flexus were isolated on the third day of storage from the vegetables. The total heterotrophic bacterial counts ranged from 1.8 x106 cfu/g to 1.25 x107 cfu/g (bitter leaf), 9x105 cfu/g to 9.0 x106 cfu/g (Scent leaf), 7 x105 cfu/g to 1.88 x107 cfu/g (Okazi), 3.2x106 cfu/g to 1.05x107 cfu/g (Fluted pumpkin leaf) and 8.4 x106 cfu/g to 2.04 x107 cfu/g (water leaf). Antibiogram of bacterial isolates revealed that they were resistant to Augmentin and Ceftazidime according to Clinical Laboratory Standard Institute schemes. Combination of the antibiotics showed that most of the isolates were 100% susceptible to ciprofloxacin + erythromycin, and ciprofloxacin + ceftriaxone. The study revealed that for all the vegetables, those stored in the basket lasted longer and were fresher compared to those kept in the open space. This study revealed that the raffia baskets are suitable for storage and preservation of leafy vegetables, but microbial succession occurred as a result of increase in the period of storage leading to the proliferation of microorganisms. This could be from aerosols or by chance inoculation, through handling or materials used or other microorganisms which are inherent in the vegetables because of their contact with the soil or water used in the washing of the leaves.