A comparison study of different methods used in the detection of Giardia lamblia.

OBJECTIVE: The purpose of this study was to compare results obtained using a single fecal specimen for O&P examination, direct immunofluorescent assay (DFA), and three immunodiagnostic techniques. DESIGN: Sixty-eight human fecal specimens were collected and examined by each method. The O&P and the DFA were used as the reference method. SETTING: The study was performed at the research laboratory in the Medical Technology Department at The University of Southern Mississippi. PATIENTS OR OTHER PARTICIPANTS: The fecal specimens were collected from individuals with a suspected Giardia lamblia infection. INTERVENTIONS: None. MAIN OUTCOME MEASURES: The amount of agreement and disagreement between methods. 1. The sensitivity and specificity of each method. 2. The working time and cost per specimen for each method. RESULTS: There was complete agreement among methods on 52 specimens (21 positive, 31 negative). Eight specimens were positive by all immunologic methods, but negative by O&P. The remaining eight specimens (12%) demonstrated discrepancies among methods. Sensitivity and specificity of each assay ranged from 91% to 100% and 89% to 100%, respectively. The cost per specimen ranged from $11.62 for the DFA method to $32.54 for the O&P method. The average cost per specimen for ELISA and EIA averaged $26.86. CONCLUSION: The study supported findings of other investigators who concluded that immunologic methods have the greater sensitivity. The immunologic methods were more efficient, quicker, and economical than the conventional O&P method.

Re-examination of the metabolic potentials of the acetogens Clostridium aceticum and Clostridium formicoaceticum: chemolithoautotrophic and aromatic-dependent growth.

Both Clostridium formicoaceticum and Clostridium aceticum grew chemolithoautotrophically on carbon monoxide plus CO2 in defined medium in the absence of carbohydrates, amino acids, or other carbon and energy sources. Formate supported the growth of both organisms as well in both defined and undefined media (both of which also contained CO2). Hydrogen was stimulatory to the growth of C. formicoaceticum upon first transfer into H2-enriched formate medium; however, neither chemolithoautotrophic growth at the expense of H2 plus CO2 nor hydrogenase could be demonstrated with this acetogen. Consistent with recent findings with other acetogens, numerous aromatic compounds were utilized by C. aceticum and C. formicoaceticum: (i) aromatic methoxyl groups were O-demethylated; (ii) aromatic acrylates were reduced; and (iii) aromatic aldehydes were oxidized. These findings demonstrate that the metabolic potentials of these two acetogens are greater than previously recognized.

Expression of an aromatic-dependent decarboxylase which provides growth-essential CO2 equivalents for the acetogenic (Wood) pathway of Clostridium thermoaceticum.

The acetogen Clostridium thermoaceticum generates growth-essential CO2 equivalents from carboxylated aromatic compounds (e.g., 4-hydroxybenzoate), and these CO2 equivalents are likely integrated into the acetogenic pathway (T. Hsu, S. L. Daniel, M. F. Lux, and H. L. Drake, J. Bacteriol. 172:212-217, 1990). By using 4-hydroxybenzoate as a model substrate, an assay was developed to study the expression and activity of the decarboxylase involved in the activation of aromatic carboxyl groups. The aromatic-dependent decarboxylase was induced by carboxylated aromatic compounds in the early stages of growth and was not repressed by glucose or other acetogenic substrates; nonutilizable carboxylated aromatic compounds did not induce the decarboxylase. The decarboxylase activity displayed saturation kinetics at both whole-cell and cell extract levels, was sensitive to oxidation, and was not affected by exogenous energy sources. However, at the whole-cell level, metabolic inhibitors decreased the decarboxylase activity. Supplemental biotin or avidin did not significantly affect decarboxylation. The aromatic-dependent decarboxylase was specific for benzoates with a hydroxyl group in the para position of the aromatic ring; the meta position could be occupied by various substituent groups (-H, -OH, -OCH3, -Cl, or -F). The carboxyl carbon from [carboxyl-14C] vanillate went primarily to 14CO2 in short-term decarboxylase assays. During growth, the aromatic carboxyl group went primarily to CO2 under CO2-enriched conditions. However, under CO2-limited conditions, the aromatic carboxyl carbon went nearly totally to acetate, with equal distribution between the carboxyl and methyl carbons, thus demonstrating that acetate could be totally synthesized from aromatic carboxyl groups. In contrast, when cocultivated (i.e., supplemented) with CO under CO2-limited conditions, the aromatic carboxyl group went primarily to the methyl carbon of acetate.

Biotransformations of aromatic aldehydes by acetogenic bacteria.

Vanillin was subject to O demethylation and supported growth of Clostridium formicoaceticum and Clostridium thermoaceticum. Vanillin was also stimulatory to the CO-dependent growth of Peptostreptococcus productus. The aldehyde substituent of vanillin was metabolized by routes which were dependent upon both the acetogen and a co-metabolizable substrate (e.g. carbon monoxide [CO]). C. formicoaceticum and C. thermoaceticum oxidized the aldehyde group of vanillin to the carboxyl level, while P. productus reduced the aldehyde group of vanillin to the alcohol level. In contrast, during CO-dependent growth, C. thermoaceticum reduced 4-hydroxybenzaldehyde to 4-hydroxybenzyl alcohol while P. productus both reduced and oxidized 4-hydroxybenzaldehyde to 4-hydroxybenzyl alcohol and 4-hydroxybenzoate, respectively. These metabolic potentials indicate aromatic aldehydes may affect the flow of reductant during acetogenesis.

Biotransformations of carboxylated aromatic compounds by the acetogen Clostridium thermoaceticum: generation of growth-supportive CO2 equivalents under CO2-limited conditions.

Clostridium thermoaceticum ATCC 39073 converted vanillate to catechol. Although carboxylated aromatic compounds which did not contain methoxyl groups were not by themselves growth supportive, protocatechuate and p-hydroxybenzoate (nonmethoxylated aromatic compounds) were converted to catechol and phenol, respectively, during carbon monoxide-dependent growth. Syringate is not subject to decarboxylation by C. thermoaceticum (Z. Wu, S. L. Daniel, and H. L. Drake, J. Bacteriol. 170:5705-5708, 1988), and sustained growth at the expense of syringate-derived methoxyl groups was dependent on supplemental CO2. In contrast, vanillate was growth supportive in the absence of supplemental CO2, and 14CO2 was the major 14C-labeled product during [carboxyl-14C]vanillate-dependent growth. Furthermore, the decarboxylation of protocatechuate and p-hydroxybenzoate supported methanol- and 1,2,3-trimethoxybenzene-dependent growth (CO2 is required for growth at the expense of these substrates) when supplemental CO2 was depleted from the growth medium, and the decarboxylation of protocatechuate was concomitant with improved cell yields of methanol cultures. These findings demonstrate that (i) C. thermoaceticum is competent in the decarboxylation of certain aromatic compounds and (ii) under certain conditions, decarboxylation may be integrated to the flow of carbon and energy during acetogenesis.