Effect of freezing of human fecal specimens upon the isolation of nuclear dehydrogenating clostridia

Bacterial populations associated with different regions of the human colon wall

The microorganisms associated with the undiseased human colon wall were examined in material obtained from four sudden-death victims. In traffic accident subjects (aged 45 and 16 years) the anaerobe-aerobe ratio was about 10(4):1 in all areas of the colon examined, whereas in acute heart failure subjects (aged 74 and 46 years) the ratio was as low as 1.2:1. The flora of each individual was distinct and complex. Although the predominant anaerobes isolated were Bacteroides and Fusobacterium spp., which composed over 50% of the flora in some samples, the species isolated (indicated by morphology and glucose fermentation products) varied between individuals. Other major types observed were gram-positive nonsporing rods, including Bifidobacterium spp., and anaerobic cocci (between 8 and 20% of isolates). Clostridia were only isolated in significant numbers from one individual. Scanning electron microscopy showed that most of the organisms were present below the top surface of the mucin layer overlying the mucosa. The use of several different preparative procedures for microscopy showed a complex microbial structure within the mucus, but major variations in the bacterial populations in different areas of the colon were not found. Spiral-shaped organisms up to 60 mum long in the form of double helices were found in two subjects by scanning electron microscopy but were not isolated during the parallel bacteriological investigation. The differences between this and previous studies are discussed in relation to experimental procedures and also in contrast to results with animals that showed a particularly specialized flora associated with the colon wall.

Metabolic epidemiology of large bowel cancer: fecal bulk and constituents of high-risk North American and low-risk Finnish population

The dietary pattern and fecal constituents of two populations with distinct risk for the development of colon cancer, a high-risk population in New York Metropolitan area and a low-risk population in rural Kuopio, were studied. The average daily intake of dietary fat and protein was the same in the two groups, but the sources of fat were different, a greater portion coming from dairy products in rural Kuopio and from meat in the New York Metropolitan area. Not only the frequency of bowel movements was higher, but also the daily total stool output as well as the fecal fiber excretion were greater in Kuopio compared with New York due to high dietary intake in rural Kuopio of cereal products rich in fiber. The concentration of fecal secondary bile acids and bacterial beta-glucuronidase activity was lower in rural Kuopio, but the total daily excretion of these constituents was the same in two populations. The daily fecal excretion of bacterial nuclear dehydrogenase activity and of neutral sterols was higher in rural Kuopio, and the concentration of these constituents was the same in the two groups. The high daily excretion of cholesterol metabolites in Kuopio might be due to high dietary intake of dairy products. The data suggest that one of the factors contributing to the low-risk of large bowel cancer in Finland, in spite of high dietary intake of fat, appears to be the fact that a high dietary fiber leads to an increase in stool bulk, thus diluting bile acids, which have promoting activity.