Copper nanoparticles (CNPs) were mixed with polyacrylonitrile (PAN) and electrospun into nanofibres (CuPAN nanofibres). PAN nanofibres containing 1.0, 3.0 and 5.0% copper (w/v) displayed beads-on-string morphology with protrusions of copper particles. The diameter of the CuPAN nanofibres differed according to the copper content, ranging from 386 nm (1.0%, w/v, copper) to 922 nm (5.0%, w/v, copper). No chemical interaction of copper with PAN was observed when studied with X-ray diffraction, ATR-FTIR (attenuated total reflection-Fourier transform infrared) spectroscopy and TGA (thermogravimetric analysis). None of the CuPAN nanofibres showed signs of degradation after 7 days in water. Bacteria suspended in random mobility buffer and filtered through a 3% CuPAN nanofibre membrane (25 mm diameter, 75-80 mu m thickness), at a filtration rate of 20 ml min(-1), reduced the cell numbers of enterotoxigenic Escherichia coli (ETEC) from 3.3 x to 2.1 x 10(6) cfu ml(-1) and methicillin-resistant Staphylococcus aureus (MRSA) from 1.2 x 10 to 1.3 x 10(3) cfu ml(-1). Membranes produced with 1.0, 3.0 and 5.0% (w/v) CuPAN inhibited the growth of enteroaggregative E. coli (EAEC), enterohemorrhagic E. coli (EHEC), enteroinvasive E. coli (EIEC), enteropathogenic E. coli (EPEC), ETEC and MRSA, as shown with LIVE/DEAD (TM) BacLight (TM) staining. Real-time bactericidal activity of CuPAN membranes was recorded by staining the cells with SYTO 9 and PI, followed by flow cytometry. Filter membranes made from CuPAN fibres may be used to reduce pathogenic E. coli cell numbers in potable water.