stomach acids kill most lower gut bacteria, so it ussually takes high concentrations to make a person sick. With bacteria like salmonella, its the preformed toxin that makes you sick. One of the more pernicious organisims that people have to worry about is giardia. The 0157:H7 is one strain of E. coli that gets alot of press because of the severity of the disease it causes. we all have E. coli growing in our lower gut though not the 0157 strain. But because of the scare that the 0157 strain has produced, everyone is scared of E. coli now.

On a side note, recent studies have produced evidence that people today arent exposed to enough germs. And this might be the cause of some run away allergies, and immune disorders.

you can always have the water and/or soil tested to make sure its not contaminated. just get in touch with your local state health unit. Personaly, if there wasnt sewage or animal watse running into it, i wouldnt worry about it