Copper kills diarrhoeagenic bacteria growth medium as mentioned in methods (Ta- ble 1). In the control glass bottles, on the other hand, the number of bacteria inoculated either remained the same or slightly increased (Table 1). After incubation in the enrichment broth, there was no visible turbidity in the test samples, and no bacteria could be recovered when the enriched cultures were streaked onto selective media. With controls, turbidity in enrichment medium and subsequent growth of bacteria on selective me- dium were observed (Table 1), where VC exhib- ited as typical yellow colony on TCBS medium, SF as typical small green colonies on HEA medi- um, and Salmonella species as pink colonies with/ without black centre on XLD medium whereas ETEC and EPEC exhibited typical metallic sheen colonies on EMB agar medium. This indicates that the bacteria in the test samples were either completely killed or had lost their culturabili- ty on media. Sudha VBP et al. antibacterial activity of copper against pathogenic strains of SF, EPEC, and SPT. Copper pot is as active in regular drinking-water (pH 7.83±0.4) as that report- ed by us earlier (12) in distilled water (pH 6.7±0.05), and the level of copper leached in the former is far less (177±16 ppb) than that in distilled water (~420 ppb). Other studies have shown that copper ves- sel is lethal to E. coli in water at different pH and temperature conditions, with the fastest inacti- vation occurring as the pH shifts away from neu- trality and 35 oC (15). Copper has also been shown to act, to a greater or lesser extent, on E. coli in the presence of organic and inorganic constituents in water (16). In laboratory experiments, copper has been shown to kill meticillin-resistant Staphylococ- cus aureus (17), Campylobacter jejuni, and S. enterica (18). Findings of these studies suggest that copper can act on a range of organisms under different conditions. It is still important to test the effect of copper on various sources of drinking-water under Table 1. Effect of overnight storage of tap-water inoculated with diarrhoeagenic bacteria in copper pots and glass bottles Before Copper pots Glass bottles incubation After incubation After incubation Bacteria inoculated Dose Bacterial count Enrichment Bacterial count Enrichment (CFU/mL) (CFU/mL) culture (CFU/mL) culture V. cholerae O1 IDH 2474 506±11 No growth Not detected 516±11 Detected S. flexneri 2a IDH 02196 533±28 No growth Not detected 530±26 Detected ETEC IDH 01254 513±23 No growth Not detected 866±83 Detected EPEC E2347 506±11 No growth Not detected 600±10 Detected S. enterica Typhi 500865 170±53 No growth Not detected 109±66 Detected S. Paratyphi A 453±109 No growth Not detected 361±67 Detected CFU=Colony-forming unit; EPEC=Enteropathogenic Escherichia coli; ETEC=Enterotoxigenic Escherichia coli Physical and chemical parameters The level of copper that had leached into the test samples was 177±16 ppb which was well within the WHO limit of 2000 ppb (Table 2). TDS, alkalin- ity, hardness, contents of chlorides and sulphates remained the same before and after incubation in both test and control samples, except that the pH had slightly increased from 7.83±0.4 to 7.93±0.3 in the test samples (copper pot) after incubation for 16 hours (Table 2). DISCUSSION None of the test pathogens was recovered from drinking-water stored in copper pots even after enrichment culture. This is the first report on the Volume 30 | Number 1 | March 2012 different field conditions. Safety of leached copper does not appear to be an issue since studies have shown that the current WHO guideline of 2 mg Cu/L is safe (19,20), and the levels leached in the study were ~1/20th of the permissible limits. It has been observed in the present study that the other physicochemical parameters of drinking-water re- main unchanged after copper intervention, which makes them amenable for public use. We observed that the unrecovered bacteria in the test samples did not get resuscitated even after enrichment and plating on selective media. This indicates that they have lost culturability on non- selective medium and on enrichment and selective media. However, we still need to confirm whether 19