Effect of Brine Concentration on Bacteria Isolated from Leafy Vegetables (Talinum triangulare, Telfairia occidentalis and Vernonia amygdalina)

Abstract

The effect of brine on bacteria isolated from leafy vegetables was evaluated. Fresh waterleaf (Talinum triangulare), Pumpkin leaves (Telfairia occidentalis) and Bitter leaves (Vernonia amygdalina) including cooking salt were bought from vendors in Mile 3 market, Port Harcourt, Rivers State. Brine concentrations of 1, 2, 3, 4 and 5% were prepared by dissolving appropriate grams of salt in distilled water. Nine millilitres of the respective concentrations were transferred into clean test tubes, labelled, stoppered with foil and autoclaved at 121℃ for 15 minutes at 15psi. Sterile distilled water served as a control. The test isolates were standardized based on 0.5McFarland and 1mL each was introduced into different brine concentrations. The standard plate count was used to monitor brine effects on isolates and this was done hourly for six hours. Inoculated plates were incubated at 37℃ for 24 hours. After incubation, enumerated colonies were used to deduce isolate mortality. The total heterotrophic bacterial (THB) load of bitter, Pumpkin and water leaves were 3.49±0.4×106, 3.25±0.4×106 and 1.99±0.2×106 CFU/g, respectively. The staphylococcal counts for bitter, Pumpkin and water leaves were 1.65±0.3×104, 3.13±0.5×104 and 1.55±0.4×104 CFU/g, respectively. Total coliform counts for bitter, Pumpkin and water leaves were 1.52±0.8×105, 2.85±0.1×105 and 1.75±0.6×105 CFU/g, respectively. Staphylococcal counts of pumpkin leaves were significantly (P≤0.05) higher than those obtained for bitter leaf and water leaf. There was no significant difference(P>0.05) in the THB and Coliform counts of all samples. E. coli was predominant in Pumpkin and water leaves while Staphylococcus sp was predominant in bitter leaves. The LC50 values for E. coli, Klebsiella, Staphylococcus, and Bacillus sp were; 5.39, 3.88, 1.62, and -0.41mg/ml, respectively. The LC50 showed that the brine was very lethal on Bacillus sp and Staphylococcus sp. High brine concentration is recommended to achieve reduced bacterial load.