Effect of heavy metals on growth and biofilm formation by gram negative pathogens

High concentration of metals and other trace elements could restrict bacterial growth and modify their metabolic pattern. Bacteria use various types of resistance mechanisms in response to heavy metal toxicity. In this study, the susceptibility patterns of gram negative pathogens, E.coli, Klebsiella sp. and Pseudomonas aeuroginosa to different levels of metals (Zinc, Cadmium and Silver) was determined. Susceptibility was assayed by using an agar well assay and a crystal violet biofilm assay in 96 well ELISA titre plate. The toxicity of the metal ions followed an order of Zn>Cd>Ag in both the assays. All the pathogens were observed to tolerate 1x10-3 molar concentration of heavy metals. All the test organisms lost their ability to form biofilm at higher concentrations of Zinc sulphate. Further work is warranted to determine the minimum inhibitory concentration of heavy metal against the pathogen and to study the resistance mechanism in P. aeuroginosa.