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OBJECTIVES: To quantify the relative contribution of premorbid and episode specific factors in determining the long term persistence of disabling symptoms of low back pain. DESIGN: Prospective cohort study. SETTING: Two general practices in the south Manchester area. PARTICIPANTS: 180 patients, who previously participated in a cross sectional population survey, who consulted because of low back pain during the study period. They were followed at 1 week and 3 and 12 months after consultation. MAIN OUTCOME MEASURE: Persistent disabling low back pain in the 12 months after the consultation. RESULTS: Disabling low back pain persisted in one third of participants after consultation and was more common with increasing age, among those with a history of low back pain, and in women. Persistence of symptoms was associated with "premorbid" factors (high levels of psychological distress (odds ratio 3.3; 95% confidence interval 1.5 to 7.2), poor self rated health (3.6; 1.9 to 6.8), low levels of physical activity (2.8; 1.4 to 5.6), smoking (2. 1; 1.0 to 4.3), dissatisfaction with employment (2.4; 1.3 to 4.5)) and factors related to the episode of low back pain (duration of symptoms, pain radiating to the leg (2.6; 1.3 to 5.1), widespread pain (6.4; 2.7 to 15), and restriction in spinal mobility). A multivariate model based on six factors identified groups whose likelihood of persistent symptoms ranged from 6% to 70%. CONCLUSIONS: The presence of persistent low back pain is determined not only by clinical factors associated with pain but also by the premorbid state.

Clostridium septicumNCTC 282 was cytotoxic for CACO-2 and HEp-2 cells. However, HEp-2 cells were more resistant than CACO-2 cells toC. septicumcytotoxin. Short motile rod forms were considerably more cytotoxic than swarming bacteria. Bacterial adhesion only occurred with HEp-2, and short motile rod forms adhered in significantly greater numbers than swarming bacteria. Removal of bacterial flagella by mechanical shearing had little effect on adherence, demonstrating that these surface structures did not act as adhesins. Addition of a variety of monosaccharides (sucrose,D-fucose,L-fucose, mannose) to HEp-2 cell monolayers had little effect on bacterial adhesion, although maltose effected a 50% reduction. Invasion of HEp-2 cells byC. septicumoccurred with short motile rods, but not with swarming bacteria, suggesting that the initial stages of infection by this organism may be affected by the abilities of different cell forms to adhere to and invade epithelial cells. Since cytotoxicity, adherence and epithelial cell invasion byC. septicumis dependent on bacterial form, differentiation of the organism into swarm cells in response to environmental factors will influence the pathogenesis of infection.

There have been recent reports of substantial increases occurring in the incidence of and/or mortality from tongue and mouth cancers in several countries. In this paper using data from Scotland (1960–89) we report on time trends in pharyngeal cancer. Similar increases in rates are evident for cancers of the oropharynx and hypopharynx while there has been little change in the occurrence of nasopharyngeal cancer (which has distinct aetiological factors). It therefore seems that reported changes in the incidence of and mortality from oral cancer may be real, and in Scotland, this is most probably due to changes in alcohol consumption.

Studies showed that the plant cell wall polysaccharide arabinogalactan supported growth of Bifidobacterium longum in batch culture. Galactose was also utilized, but not arabinose, the other major constituent sugar of the polymer. Enzymes required for hydrolysis of arabinogalactan ('arabinogalactanase', α-arabinopyranosidase, β-galactosidase) were inducible and cell-associated in B. longum, and their expression was repressed by glucose. Considerable amounts of α-arabinopyranosidase and β-galactosidase were synthesized during growth on arabinogalactan, but only low levels of arabinogalactanase were detected. B. longum only grew on arabinogalactan in continuous culture under putative carbon-excess conditions. In C-limited chemostats, the bifidobacterium could not establish unless Bacteroides thetaiotaomicron was present in co-culture. The relationship between the two organisms was not simply commensal; at low specific growth rates, bacteroides cell population densities were approximately 30% lower than those recorded in axenic culture, indicating the existence of competitive interactions with the bifidobacterium. In contrast, at high specific growth rates, a mutualistic association was observed, in that Bact. thetaiotaomicron was maintained in the chemostats at high dilution rates if bifidobacteria were also present. Measurements of residual carbohydrate in spent culture fluid from C-limited chemostats indicated that a large part of the arabinogalactan molecule could not be broken down by either B. longum or Bact. thetaiotaomicron alone, or in co-culture. Formate and acetate were the major fermentation products of B. longum cultured in the presence of high concentrations of arabinogalactan, confirming that these bacteria were growing under energy-limited conditions. Copyright 1995, 1999 Academic Press

Nitrate dissimilation in chemostat grown cultures ofClostridium butyricum SS6 has been investigated. Sucrose limited cultures grown on nitrate produced nitrite as the principal end-product of nitrate reduction whilst under nitrate-limiting conditions ammonia accumulated in the spent media. Nitrate reduction was accompanied by the synthesis of a soluble nitrate reductase (123 nmol·NADH oxidised · min-1 · mg protein-1) and in addition, under N-limiting conditions, a soluble nitrite reductase (56 nmol NADH oxidised min-1 · mg protein-1). Corresponding ammonia grown cultures synthesised neither enzyme. Concurrent with the dissimilation of nitrate to nitrite and ammonia cell population densities increased by 18% (C-limitation) and 32% (N-limitation). Spent media analyses of the fermentation products from ammonia and nitrate grown cells showed the accumulation of acetate in nitrate dissimilating cultures. Molar ratios of acetate/butyrate increased by a factor of 5 (C-limitation) to 12 (N-limitation) upon adding nitrate to the growth medium. In C-limited cultures, grown on nitrate, hydrogenase activity was 340 nmol · min-1 · mg protein-1 and under N-limitation this increased to 906 nmol · min-1 · mg protein-1. Since N-limited cultures are electron acceptor limited, the increase in hydrogenase activity enables excess electrons to be spilled by this route.

High levels of amines were present in large intestinal material taken from five persons who had died suddenly. Mean total concentrations of simple aliphatic amines were approximately 22 mmol/kg in the proximal colon and 16 mmol/kg in the distal bowel, with propylamine, piperidine and methylamine predominating in all regions. Amine concentrations in faeces from six healthy donors ranged from 1·8 to 41·5 mmol/kg (mean 13·3, S.E.M. 5·9). A wide range of these metabolites was found in intestinal contents, of which trimethylamine and propylamine were quantitatively most important. Although considerable inter-individual variation was seen in faecal amine excretion, methylamine and dimethylamine were never detected in fresh faeces, indicating these substances were rapidly absorbed from the rectum. Net production rates of different amines in faecal material incubatedin vitrovaried from approximately 0·01 μmol/h/g for methylamine, cadaverine, histamine and tryptamine, to 1·26 μmol/h/g in the case of propylamine. Amines were further metabolised by colonic bacteria, especially in the presence of a fermentable carbohydrate source. Amine formation by faecal bacteria was maximal at near neutral pH, while culture in the presence of a fermentable carbohydrate source reduced net amine production by 80%.Confirmatory evidence for the importance of pH and carbohydrate availability on amine production was obtained in experiments with 16 pure cultures of intestinal bacteria. Most probable number (MPN) counts of amine producing bacteria in faeces from four healthy donors showed that high numbers of methylamine, dimethylamine and propylamine forming bacteria were present in every sample. However, considerable variability was seen in carriage rates of bacteria forming other amines, especially with respect to histamine, butylamine and phenylethylamine. Measurements of individual amine concentrations in MPN tubes showed that propylamine constituted about 70% of total amine production at all sample dilutions, and that while high populations of histamine forming bacteria were present in faecal samples, very small amounts of this product were formed.