Experience of the use of probiotics for Salmonellae control in poultry

The Editors of Letters in Applied Microbiology will, at their discretion, publish invited and submitted 'Opinions' on subjects in the general area of Applied Microbiology. They will not be subjected to the normal refereeing procedures and reprints will not be provided. The 'Opinions' will not necessarily represent the views of the Society of Applied Bacteriology or of the Editors. The Editors may invite or readers may submit 'Responses' to published 'Opinions' , provided that they are not merely polemics, and these will also be published at the discretion of the Editors. 'Responses' will be treated precisely like 'Opinions' . They should clearly indicate, in their first sentence, the 'Opinion' to which they are a response.     

Comparison of a competitive enzyme immunoassay kit and the infant mouse assay for detecting Escherichia coli heat-stable enterotoxin

A commercial competitive enzyme immunoassay kit, Escherichia coli ST EIA, was compared with the conventional infant mouse assay for sensitivity and specificity in detecting E. coli heat-stable enterotoxin. Thirty-one of 46 strains of E. coli tested were positive by both assays, while 15 strains were negative. The sensitivity of the ST EIA kit was up to 64-fold lower than the infant mouse assay.     

Enzyme regulation in C4 photosynthesis: purification, properties, and activities of thioredoxins from C4 and C3 plants

Procedures are described for the purification to homogeneity of chloroplast thioredoxins f and m from leaves of corn (Zea mays, a C4 plant) and spinach (Spinacea oleracea, a C3 plant). The C3 and C4f thioredoxins were similar immunologically and biochemically, but differed in certain of their physiochemical properties. The f thioredoxins from the two species were capable of activating both NADP-malate dehydrogenase (EC 1.1.1.37) and fructose-1,6-bisphosphatase (EC 3.1.3.11) when tested in standard thioredoxin assays. Relative to its spinach counterpart, corn thioredoxin f showed a greater molecular mass (15.0-16.0 kDa vs 10.5 kDa), lower isoelectric point (ca. 5.2 vs 6.0), and lower ability to form a stable noncovalent complex with its target fructose bisphosphatase enzyme. The C3 and C4 m thioredoxins were similar in their specificity (ability to activate NADP-malate dehydrogenase, and not fructose-1,6-bisphosphatase) and isoelectric points (ca. 4.8), but differed slightly in molecular mass (13.0 kDa for spinach vs 13.5 kDa for corn) and substantially in their immunological properties. Results obtained in conjunction with these studies demonstrated that the thioredoxin m-linked activation of NADP-malate dehydrogenase in selectively enhanced by the presence of halide ions (e.g., chloride) and by an organic solvent (e.g., 2-propanol). The results suggest that in vivo NADP-malate dehydrogenase interacts with thylakoid membranes and is regulated to a greater extent by thioredoxin m than thioredoxin f.     

Supplemental chloralose anesthesia in morphine premedicated dogs

This study evaluated the cardiorespiratory stability of six dose-regulated, 12-hour, chloralose anesthetic maintenance protocols. Thirty mongrel dogs were premedicated with morphine sulfate (5mg/kg) and anesthetized with an induction dose of chloralose (80mg/kg). Fifteen animals were permitted to breathe spontaneously and 15 animals were ventilated mechanically to maintain a constant arterial pCO2 (40 +/- 5 mmHg). The spontaneously breathing dogs were separated into three groups in which animals (n = 5) were given different bolus doses of supplemental anesthetic. Initially the spontaneously breathing animals were hypoxemic, acidemic and hypercapnic. No consistent hemodynamic difference was noted among these groups. The mechanically ventilated animals were also divided into three groups that received varying doses of supplemental chloralose by constant infusion. Significant (p less than 0.01) myocardial depression was noted in the heavy-dosed animals by the third hour. Systolic pressure decreased 44%, pulse pressure decreased 37% and peak left ventricular dP/dt decreased 52%. All heavy-dosed animals expired before the eighth hour. Although these data suggest that morphine-premedicated, chloralose-anesthetized animals generally provide a stable cardiopulmonary model, high-dose chloralose supplementation depressed ventilation and produced a dose-dependent cardiotoxicity.     

Starch-Ampicillin Agar for the Quantitative Detection of Aeromonas hydrophila

Interest in Aeromonas hydrophila as a food-borne and human pathogen is increasing. Isolation media from the clinical laboratory were evaluated for food use and either did not give quantitative recovery of A. hydrophila or did not permit ready differentiation of A. hydrophila from the background microflora. A new medium was developed which permitted quantitative recovery of A. hydrophila from foods. The medium consisted of phenol red agar base (Difco Laboratories), soluble starch (10 g/liter), and ampicillin (10 mg/liter). All foods surveyed contained A. hydrophila. Foods sampled included red meats, chicken, raw milk, and seafood (fish, shrimp, scallops, crab, and oysters). The count of A. hydrophila at the time of purchase ranged from 1 × 10²/g (lower limit of detection) to 5 × 10⁵/g. In most instances, the count of A. hydrophila increased during 1 week of storage at 5°C. The starch-ampicillin agar developed permitted rapid quantitative recovery of A. hydrophila from foods in the presence of very large numbers of competing microflora.     

Frequency among Enterobacteriaceae of the DNA sequences encoding type 1 pili.

Type 1 pili, characterized by mannose-inhibitable agglutination of fowl or guinea pig erythrocytes, have been found throughout the family Enterobacteriaceae. A radiolabeled probe was prepared from a restriction endonuclease-digested fragment of the Escherichia coli pil operon and used to detect homologous DNA sequences in 236 bacteria representing 11 genera of Enterobacteriaceae. Only isolates identified as E. coli or Shigella spp. exhibited homology. In contrast, mannose-sensitive hemagglutination was observed in nine genera. Probe DNA did not hybridize to plasmid DNA, indicating a chromosomal location for the pil operon. Analysis of restriction nuclease-digested whole-cell DNA from 60 E. coli and two Shigella sp. isolates indicated that internal sequences were conserved in most strains, but that changes in flanking sequences in the chromosome were common.     

Concentrations of Homovanillic Acid and 5-Hydroxyindoleacetic Acid in Cerebrospinal Fluid from Human Infants in the Perinatal Period

To assess maturation of central serotonin and catecholamine pathways at birth, we measured lumbar CSF homovanillic acid (HVA) and 5-hydroxyindoleacetic acid (5-HIAA), stable acid metabolites of dopamine and serotonin, using HPLC with electrochemical detection. CSFs from 57 neonates (38 premature and 19 at term) and 13 infants 1-6 months old were studied. HVA levels increased with maturity (p less than 0.05; ANOVA), whereas 5-HIAA levels were similar in all these subjects. HVA/5-HIAA ratios increased markedly from 1 +/- 0.12 in the most premature neonates to 1.98 +/- 0.17 in the older infants (p less than 0.01; t test). There were no sex differences for these values.     

Pancreatic polypeptide immunoreactivity in medullary carcinoma of the thyroid: identification and characterisation by radioimmunoassay, immunocytochemistry and high performance liquid chromatography

Pancreatic polypeptide immunoreactivity has been identified in primary medullary carcinoma of thyroid using radioimmunoassay and immunocytochemistry and subsequently characterised by HPLC. Two region-specific PP antisera were used in the study; one C-terminal and one non-C-terminal. These antisera demonstrate variable cross-reactivity with the molecular species of PP identified in the tumours. The immunoreactive material in the tumours corresponded to human PP and not PYY or NPY on the basis of immunoreactivity and HPLC behaviour. It was identified in all patients with familial-type disease but not in the two sporadic cases examined. We propose that estimation of the PP content of medullary carcinoma of thyroid may be a useful means of differentiating familial and sporadic types.     

Enterotoxin A production in Staphylococcus aureus: inhibition by glucose

In this study, we investigated the relationship between carbohydrate metabolism and repression of staphylococcus enterotoxin A (SEA) in Staphylococcus aureus 196E and a pleiotrophic mutant derived from strain 196E. The mutant, designated at strain 196E-MA, lacked a functional phosphoenolpyruvate phosphotransferase system (PTS). The mutant produced acid, under aerobic conditions, from only glucose and glycerol. The parent strain contained an active PTS, and aerobically produced acid from a large number of carbohydrates. Prior growth in glucose led to repression of SEA synthesis in the parent strain; addition to the casamino acids enterotoxin production medium (CAS) led to more severe repression of toxin synthesis. The repression was not related to pH decreases produced by glucose metabolism. When S. aureus 196E was grown in the absence of glucose, there was inhibition of toxin production as glucose level was increased in CAS. The inhibition was related to pH decrease and was unlike the repression observed with glucose-grown strain 196E. The inhibition of SEA synthesis in mutant strain 196E-MA was approximately the same in cells grown with or without glucose and was pH related. Repression of SEA synthesis similar to that seen with glucose-grown S. aureus 196E could not be demonstrated in the mutant. In addition, glucose-grown S. aureus 196E neither synthesized -galactosidase nor showed respiratory activity with certain tricarboxylic acid (TCA) cycle compounds. Glucose-grown strain 196E-MA, however, did not show supressed respiration of TCA cycle compounds; -galactosidase was not synthesized because the mutant lacked a functional PTS. Cyclic adenosine-3, 5-monophosphate did not reverse the repression by glucose of SEA or -galactosidase synthesis in glucose-grown S. aureus 196E. An active PTS appears to be necessary to demonstrate glucose (catabolite) repression in S. aureus.Abbreviations SEA staphylococcal enterotoxin A - SEB staphylococcal enterotoxin B - SEC staphylococcal enterotoxin C - PTS phosphoenolpyruvate phosphotransferase system - CAS casamino acids salts medium - TCA tricarboxylic acid cycle     

Feeding and the control of volume within the tests of regular sea-urchins

The rigid, fluid filled, echinoid test presents problems of internal volume control when the vital functions of the animal involve the introduction of material, from outside the test, into the internal fluid systems. The volume of food in the guts of echinoids can be shown to vary considerably in the short term, to an extent which demands considerable capabilities for internal volume compensation. This is achieved by adjusting the quantity of fluid held within the gut so that, although the volume of food may vary widely, the total volume of the gut remains constant within narrow limits. The volume of gut fluid varies inversely with the quantity of food, and ingestion of food through the mouth is compensated by ejection of an equal volume of fluid from the anus. Defaecation is compensated by intake of fluid into the gut. On starvation, the gut becomes completely fluid filled and free from food.
The food of regular urchins is habitually compacted into regularly sized subpherical pellets covered with a tough mucus coating. The formation of coated pellets takes place in the buccal cavity and pharynx. The pellets remain discrete throughout their passage along the gut. The mucus coating resists digestion and remains intact even after defaecation. The functional morphology of the buccal cavity and pharynx is described in detail.
It is suggested that the functional significance of the pellets is associated with the gut fluid, volume compensation mechanism, which requires free flow of fluid throughout the length of the gut. It is also suggested that the siphon may be implicated in volume control, where fine adjustment of gut volume can be achieved by balancing ejection of fluid from the anus with intake of water through the mouth, but that the water intake is by the siphonal route, thus avoiding the necessity of flushing and diluting the enzyme rich digestive stomach region.