The data is not yet published, but the phenomena has been described in foods and other samples. The bacteria is not actually dead, but in a "dormant" state metabolically.

1. Viable but non-culturable bacteria: their impact on public health

http://www.ias.ac.in/currsci/nov252005/1650.pdf

"The viability of a bacterial cell was traditionally determined by its ability to grow and produce colonies.However, in recent years, many studies have revealed the ability of both Gram-positive and Gram-negative bacteria to go into a viable but non-culturable (VBNC) state. In this state, bacteria are still viable and show metabolic activity
and respiration, but cannot be shown as colony forming units by the conventional plate counts and hence remain hidden1."

2. Viable but non-culturable forms of food and waterborne bacteria: Quo Vadis?

http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6VHY-4CVX484-5&_user=4421&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_version=1&_urlVersion=0&_userid=4421&md5=70669e8045ab0219a3e5b0cb2b8b4664

There is increasing evidence for a viable but non-culturable (VBNC) state in microbes, particularly in the stressing environment presented by modern foods with their varied pre-treatment and packaging strategies. This is a cause for concern because of evidence that microbial pathogens in such a state may retain their capacity to cause infections after ingestion by the consumer despite their inability to grow under the conditions employed in procedures for determining their presence in foods. Heavily stressed pathogenic species of bacteria in a VBNC or not immediately culturable state are potentially dangerous public health problems, particularly as stressed cells may be more virulent than well-fed bacteria. In this viewpoint article, I wish to focus on possible procedures for detecting such organisms and assessing their physiological state.

"Also, when you refer to "flies and other insects" excreting E. coli in their feces, which other insects? Which strain of E.coli?"

They looked at filth flies, blow flies and a couple other species. The preliminary positive results were mostly from filth flies trapped in the fields. They said additional studies are underway to identify the strains of E. coli excreted by the flies.