Autoimmune Thyroid Disease

An Unfortunate and Lengthy Adventure in Misdiagnosis

Normal gut bacteria produce amines

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Different strains of amine producing bacteria grow under different circumstances:

Dimethylamine, methylamine, propylamine, and pyrrolidine were the major amines formed by Bacteroides fragilis NCDO 2217 during the active phase of growth in batch culture. Production of these metabolites was strongly pH dependent and was optimal under acidic conditions (pH 6.0). Low pH also favored the formation of pyrrolidine, cadaverine, and dimethylamine by Clostridium perfringens C523, but the reverse was the case with putrescine, butylamine, and propylamine, where production was maximal at neutral pH. B. fragilis was grown in continuous culture under either starch or casein limitation. Amine formation was influenced by carbohydrate availability and was greatest when the bacteria were grown at high growth rates (dilution rate, 0.20/h) under starch limitation, where they constituted about 18% of the total fermentation products measured. Amine production was optimal and increased concomitantly with growth rate when C. perfringens was grown in glucose-limited continuous culture. Under conditions of high growth rate and glucose limitation, amines accounted for approximately 27% of the fermentation products measured. When glucose in the feed medium was increased from 5 to 15 g/liter, amine production was repressed, and under these nutritional conditions the growth rate had little effect on the process. Influence of pH, nutrient availability, and growth rate on amine production by Bacteroides fragilis and Clostridium perfringens

Acute laminitis has been associated with the overgrowth of gram-positive bacteria within the equine hindgut, causing the release of factor(s) leading to ischemia-reperfusion of the digits. The products of fermentation which trigger acute laminitis are, as yet, unknown; however, vasoactive amines are possible candidates. The objectives of this study were to use an in vitro model of carbohydrate overload to study the change in populations of cecal streptococci and lactobacilli and to establish whether certain species of these bacteria were capable of producing vasoactive amines from amino acids. Cecal contents from 10 horses were divided into aliquots and incubated anaerobically with either corn starch or inulin (fructan; both at 1 g/100 ml). Samples were taken at 6-h intervals over a 24-h period for enumeration of streptococci, lactobacilli, and gram-negative anaerobes by a dilution method onto standard selective growth media. The effects of the antibiotic virginiamycin (1 mg/100 ml) and calcium hydrogen phosphate (CaHPO4; 0.3 g/100 ml) were also examined. Fermentation of excess carbohydrate was associated with increases in numbers of streptococci and lactobacilli (2- to 3.5-log unit increases; inhibited by virginiamycin) but numbers of gram-negative anaerobes were not significantly affected. A screening agar technique followed by 16S rRNA gene sequence analysis enabled the identification of 26 different bacterial strains capable of producing one or more vasoactive amines. These included members of the species Streptococcus bovis and five different Lactobacillus spp. These data suggest that certain bacteria, whose overgrowth is associated with carbohydrate fermentation, are capable of producing vasoactive amines which may play a role in the pathogenesis of acute laminitis. Identification of Equine Cecal Bacteria Producing Amines in an In Vitro Model of Carbohydrate Overload

Bacteroides fragilis and many species of lactobacillus are normal inhabitants of the gut. They produce amines when they are allowed to feed on poorly digested protein, particularly in the presence of carbohydrate fermentation. Bacteria can even liberate phenols from phenol containing amino acids like tyrosine and phenylalanine. It seems that undigested starch and protein can both play a role in the production of amines. I have yet to find any information that implicates fat, since bacteria don’t really digest fat.


Written by alienrobotgirl

25 April, 2006 at 1:16 pm

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