Hi, Jerry -
" I would like to hear some more definitive data about this."
From the Merck manual at http://www.merckmanuals.com/professional/gastrointestinal_disorders/gastroenteritis/overview_of_gastroenteritis.html, see below (please note that all specific references to E. coli refer to pathogenic strains, not the normal flora, and that there are no references to E. coli garden variety acting on the upper digestive system to cause illness).
The bacteria most commonly implicated are
Escherichia coli (especially serotype O157:H7)
Bacterial gastroenteritis is less common than viral. Bacteria cause gastroenteritis by several mechanisms. Certain species (eg, Vibrio cholerae, enterotoxigenic strains of E. coli) adhere to intestinal mucosa without invading and produce enterotoxins. These toxins impair intestinal absorption and cause secretion of electrolytes and water by stimulating adenylate cyclase, resulting in watery diarrhea. C. difficile produces a similar toxin (see Anaerobic Bacteria: Clostridium difficile–Induced Diarrhea).
Some bacteria (eg, Staphylococcus aureus, Bacillus cereus, Clostridium perfringens) produce an exotoxin that is ingested in contaminated food. The exotoxin can cause gastroenteritis without bacterial infection. These toxins generally cause acute nausea, vomiting, and diarrhea within 12 h of ingestion of contaminated food. Symptoms abate within 36 h.
Other bacteria (eg, Shigella, Salmonella, Campylobacter, some E. coli subtypes) invade the mucosa of the small bowel or colon and cause microscopic ulceration, bleeding, exudation of protein-rich fluid, and secretion of electrolytes and water. The invasive process and its results can occur whether or not the organism produces an enterotoxin. The resulting diarrhea contains WBCs and RBCs and sometimes gross blood.
Salmonella and Campylobacter are the most common bacterial causes of diarrheal illness in the US. Both infections are most frequently acquired through undercooked poultry; unpasteurized milk is also a possible source. Campylobacter is occasionally transmitted from dogs or cats with diarrhea. Salmonella can be transmitted by consuming undercooked eggs and by contact with reptiles, birds, or amphibians. Species of Shigella are the 3rd most common bacterial cause of diarrhea in the US and are usually transmitted person to person, although foodborne epidemics occur. Shigella dysenteriae type 1 (not present in the US) produces Shiga toxin, which can cause hemolytic-uremic syndrome (see Thrombocytopenia and Platelet Dysfunction: Thrombotic Thrombocytopenic Purpura (TTP) and Hemolytic-Uremic Syndrome (HUS)).
Several different subtypes of E. coli cause diarrhea. The epidemiology and clinical manifestations vary greatly depending on the subtype: (1) Enterohemorrhagic E. coli is the most clinically significant subtype in the US. It produces Shiga toxin, which causes bloody diarrhea (hemorrhagic colitis). E. coli O157:H7 is the most common strain of this subtype in the US. Undercooked ground beef, unpasteurized milk and juice, and contaminated water are possible sources. Person-to-person transmission is common in the day care setting. Outbreaks associated with exposure to water in recreational settings (eg, pools, lakes, water parks) have also been reported. Hemolytic-uremic syndrome is a serious complication that develops in 2 to 7% of cases, most commonly among the young and old. (2) Enterotoxigenic E. coli produces two toxins (one similar to cholera toxin) that cause watery diarrhea. This subtype is the most common cause of traveler's diarrhea in people visiting the developing world. (3) Enteropathogenic E. coli causes watery diarrhea. Once a common cause of diarrhea outbreaks in nurseries, this subtype is now rare. (4) Enteroinvasive E. coli causes bloody or nonbloody diarrhea, primarily in the developing world. It is rare in the US.
In the past, C. difficile infection occurred almost exclusively in hospitalized patients receiving antibiotics. With the emergence of the hypervirulent NAP1 strain in the US in the late 2000s, many community-associated cases are now occurring.
Several other bacteria cause gastroenteritis, but most are uncommon in the US. Yersinia enterocolitica can cause gastroenteritis or a syndrome that mimics appendicitis. It is transmitted by undercooked pork, unpasteurized milk, or contaminated water. Several Vibrio species (eg, V. parahaemolyticus) cause diarrhea after ingestion of undercooked seafood. V. cholerae sometimes causes severe dehydrating diarrhea in the developing world and is a particular concern after natural disasters or in refugee camps. Listeria causes food-borne gastroenteritis. Aeromonas is acquired from swimming in or drinking contaminated fresh or brackish water. Plesiomonas shigelloides can cause diarrhea in patients who have eaten raw shellfish or traveled to tropical regions of the developing world."
I do at least somewhat know whereof I speak, at least on some subjects. :)
As far as moving normal E. coli directly upstream, it does happen in severe cases of vomiting, where the upper intestinal contents are vomited as well as stomach contents. But it apparently causes no problems above and beyond that which was already causing the individual to vomit so severely.
Many years ago (like 30? ugh) I was told by someone that Montezuma's revenge could be caused by "normal" E. coli that were "new" to the traveler's system, but I cannot find any reference to that on the web so it's likely that knowledge on the enteropathogenic strains of E. coli has just advanced over the years, replacing the older theory.