Dan, microbes are microbes -- they don't differentiate between the stuff they break down. You don't have to buy any, just add some decent soil or existing compost.
Joseph Jenkins, author of The Humanure Handbook [entire book available online at
http://www.weblife.org/humanure/default.html ] calls the people who insist on disposing of human and animal waste by flushing it into the groundwater with drinking water 'fecophobes', an excellent term, IMHO. (Well, IMO...)
From the Center for Disease Control in Atlanta, GA, regarding composting: "Complete pathogen destruction is guaranteed by arriving at a temperature of 62C (143.6F) for one hour, 50C (122F) for one day, 46C (114.8F) for one week or 43C (109.4F) for one month."
Sure, you have to pay attention to what you're doing. Jenkins says to add the humanure to the center of the compost pile, where the most biological activity and highest temperatures are found.
Many of the people who offer info to the public are looking to include the lowest common denominator, AND they are trying to protect all the people, all the time, from all possible problems, under all possible circumstances. It isn't possible, but they continue to do it. But in doing so, they tend to skip over a lot of information that people of average intelligence and education could use.
Sue