Increasing Vegetable Intake by Emphasizing Tasty and Enjoyable Attributes: A Randomized Controlled Multisite Intervention for Taste-Focused Labeling

Healthy food labels tout health benefits, yet most people prioritize tastiness in the moment of food choice. In a preregistered intervention, we tested whether taste-focused labels compared with health-focused labels increased vegetable intake at five university dining halls throughout the United States. Across 137,842 diner decisions, 185 days, and 24 vegetable types, taste-focused labels increased vegetable selection by 29% compared with health-focused labels and by 14% compared with basic labels. Vegetable consumption also increased. Supplementary studies further probed the mediators, moderators, and boundaries of these effects. Increased expectations of a positive taste experience mediated the effect of taste-focused labels on vegetable selection. Moderation tests revealed greater effects in settings that served tastier vegetable recipes. Taste-focused labels outperformed labels that merely contained positive words, fancy words, or lists of ingredients. Together, these studies show that emphasizing tasty and enjoyable attributes increases vegetable intake in real-world settings in which vegetables compete with less healthy options.

Evaluation of the chick embryo for the determination of relative virulence of Neisseria meningitidis

The chick embryo model was evaluated as a method to compare virulence between selected strains of Neisseria meningitidis. Inoculation of 13-day-chick embryos via the egg yolk distinguished strains having an LD50 of 10(3) colony forming units (CFU) or greater (low virulence) from those having an LD50 of approximately 10(1) or less (high virulence). A strain of serogroup B and a spontaneous nonpiliated strain of group C were found to be of relatively high virulence while a strain of N. lactamica, a serogroup A carrier strain, and certain nongroupable strains were found to be of low virulence. Strains having an LD50 of 10(2) were not differentiated from either of these. Alternatively, inoculation of the chorioallantoic membrane (CAM) of 9-day-old chick embryos statistically differentiated most strains of N. meningitidis although inoculation via this route was less sensitive.

Immunogold labelling of Listeria monocytogenes virulence-related factors within Caco-2 cells

We demonstrated by immunoelectron microscopy that listeriolysin O (LLO), phospholipases and other putative virulence-related proteins produced by Listeria monocytogenes were primarily cell-wall-associated when the bacterium infected Caco-2 tissue culture cell monolayers. Antibodies made to LLO, serogroup 1/2a reacted poorly with serogroup 4b cells and vice-versa, indicating fundamental structural differences in the two proteins. Finally, comet-tail pseudopod structures shown to be involved in cell-to-cell passage of Listeria in Caco-2 cells did not possess detectable Listeria antigens on their anterior surface or within their structure, suggesting that the phagocytic process is primarily host-cell-dependent once it is initiated by the bacterial cell.

A filamentous-like mutant of Listeria monocytogenes with reduced expression of a 60-kilodalton extracellular protein invades and grows in 3T6 and Caco-2 cells

We describe a spontaneous rough mutant of Listeria monocytogenes that produces reduced amounts of a 60-kilodalton major extracellular polypeptide (p60) as shown by sodium dodecyl sulfate--polyacrylamide gel electrophoresis and Western blot analysis. The cells of this mutant are filamentous, do not give rise to smooth wild-type colonies, and produce listeriolysin O in amounts equal to that of the wild-type cells, but they show a reduced virulence in the mouse LD50 model and in the Caco-2 tissue culture virulence assay. Light and electron microscopic studies show that this mutant invades and remains filamentous during in vivo growth in both Caco-2 and 3T6 tissue culture monolayers. The reduced virulence of the rough mutant is not due to the inability of its filamentous forms to invade or to grow in nonprofessional phagocytes since invasion and growth of the smooth wild-type and the rough mutants are comparable in both Caco-2 and 3T6 monolayers.

Cytopathogenic effects in enterocytelike Caco-2 cells differentiate virulent from avirulent Listeria strains

We have developed a simple test that differentiates between virulent and avirulent Listeria species as defined by the mouse 50% lethal doses (LD50S). The assay is based on trypan blue-revealed cytopathogenic effects that are produced during the infection of the human enterocytelike cell line Caco-2. These effects were elicited only by Listeria strains that had an intraperitoneal mouse LD50 less than 10(8) and were not produced by nonhemolytic, avirulent strains of Listeria monocytogenes generated spontaneously or by Tn916 mutagenesis or by avirulent Listeria species. A negative test was also obtained with hemolysin-producing, avirulent L. monocyotogenes NCTC5105 and Listeria ivanovii KC1786. The test was negative with avirulent L. monocytogenes strains which are strong inducers of opacity in egg yolk agar. However, a strain which has a low LD50, such as 10(4), may show less severe cytopathogenic effects than a strain having a higher LD50, such as 10(6). The test has been effectively used to screen for virulent listerial isolates, spontaneous mutants, and transposon-induced mutants.

The type strain(s) of Listeria monocytogenes: a source of continuing difficulties

The type strain of Listeria monocytogenes differs from wild-type L. monocytogenes strains in more characteristics than just the previously reported deficiency in hemolytic activity and virulence in the murine infection model. The type strain from the American Type Culture Collection (strain ATCC 15313) produces lecithinase, is hemolytic on rabbit (but not sheep) blood agar, lacks motility, and shows limited cytopathogenic effects on Caco-2 monolayers, whereas the type strain from the Special Listeria Culture Collection (strain SLCC 53) is unable to produce lecithinase, is nonhemolytic on rabbit or sheep blood agar, is motile, and shows no cytopathogenic effects on Caco-2 monolayers.

Nonhemolytic Listeria monocytogenes mutants that are also noninvasive for mammalian cells in culture: evidence for coordinate regulation of virulence

We identified nonhemolytic mutants of Listeria monocytogenes that were severely deficient in their ability to invade mammalian nonprofessional phagocytes. These mutants were generated spontaneously or by means of transposon Tn916 mutagenesis. In terms of their extracellular proteins, the noninvasive mutants were deficient not only in the sulfhydryl-activated hemolysin (listeriolysin) but also in an antigenically unrelated extracellular protein with an apparent molecular weight of 32,000 which could induce opacity in egg yolk and is considered to be a phospholipase. Our results suggest the existence of a common genetic control between the expression of listeriolysin and that of other determinants, including a phospholipase and determinants involved in the ability of L. monocytogenes to enter mammalian cells.

Listeria monocytogenes intragastric and intraperitoneal approximate 50% lethal doses for mice are comparable, but death occurs earlier by intragastric feeding

The intraperitoneal (i.p.) and intragastric (i.g.) mouse approximate 50% lethal dose values (ALD50S) were determined for 15 food and clinical isolates of Listeria monocytogenes. Although all strains gave i.g. ALD50S comparable to or less than their i.p. ALD50S, the i.g. feeding of most strains produced more deaths within the first 3 days of the 6-day test than did i.p. injection. ALD50S ranged from 50 to 4.4 x 10(5) cells with approximately 1-log 95% confidence intervals. Of five strains tested by suspension in milk or by growth in milk, none gave i.g. ALD50S that were lower than those of washed cells. Results with 10- to 21-g mice supported the use of 15-g mice for i.g. testing; 21-g mice were more resistant to i.g. infection. These results indicate that i.g. feeding permits an evaluation of the role of the carrier (such as milk) in the determination of listerial virulence, permits strain characterization by i.p. and i.g. ALD50S, and emphasizes a potentially more rapid infection when the bacterium is introduced i.g.

Analyses of fermentation products of Listeria species by frequency-pulsed electron-capture gas-liquid chromatography

Aerobic fermentation broths of eight Listeria monocytogenes strains, two or more strains of the remaining six Listeria species, and one strain of Jonesia denitrificans were examined by frequency-pulsed electron-capture gas-liquid chromatography for carboxylic acids, alcohols, amines, and hydroxy acids. All species produced acetic, isobutyric, butyric, isovaleric, phenylacetic, lactic, 2-hydroxybutyric, 2-hydroxyvaleric, and 2-hydroxyisocaproic acids. Propionic acid was not formed, and traces of isocaproic acid were observed. Of the alcohol and amine derivatives observed, only acetylmethylcarbinol, butylamine, and putrecine were identified. Recognition of the products of glucose and amino acid metabolism serves to further characterize the members of the genus Listeria both taxonomically and physiologically.

Physiological studies on the growth and utilization of sugars by Listeria species

Experiments, relevant to growth in milk, were done to delineate the aerobic and anaerobic growth of Listeria species on selected sugars in several media. All species grew on glucose aerobically, forming lactic acid and (or) acetic acid. Anaerobically, only lactic acid was formed; cell yields were 80% of those obtained aerobically. When incubated aerobically, small amounts (1.5 microns/mL) of isovaleric acid, 2-hydroxyisovaleric acid, and trace amounts of isobutyric acid were formed. These products were characteristically formed by 26 strains representing all the species of Listeria. Added leucine stimulated isovaleric acid formation. Anaerobic fermentations of glucose could be followed by 60 to 80% cell lysis; less lysis occurred in air. Anaerobically, only hexoses and pentoses supported growth; aerobically, maltose and lactose supported growth of some strains, but sucrose did not support growth of any strain tested. Listeria grayi and Listeria murrayi utilized the galactose and glucose moieties of lactose for growth; Listeria monocytogenes and Listeria innocua used only the glucose moiety. Glucosamine and N-acetylglucosamine supported aerobic and anaerobic growth as well as glucose, and their presence stimulated the utilization of lactose by "lactose-negative" strains. Analyses of cultures grown at 5 degrees C in sterile milk treated with glucose oxidase supported the conclusion that the glucose of the milk was the major, if not the limiting, substrate that supported growth.

The Swedish medical care programs: an interim assessment

The medical care program (MCP) concept emerged from a conviction that it would be possible to combine biomedical knowledge about a certain disease, principles of care and an efficient organization into a holistic approach to care. The purpose of the present review of nine MCPs was to: (1)provide and overview of MCP development and and evaluation in the Stockholm County; (2) present different perspectives regarding the current status of the MCP policy and future developments; and (3) contribute to a discussion of factors which enhance or block the effectiveness of MCPs. Information was gathered during interviews with 32 representatives of professionals and interest groups. The majority of MCPs were initiated by medical professionals while two, the program for alcohol disorders and that for rheumatoid diseases, were initiated by politicians or the rheumatoid patients. Three central problems were identified: (1) the original desire for standardization and the emergent demand for local variation; (2) ambiguities about specific roles of the newly developing general practitioners; and (3) lack of resources to develop, implement and evaluate MCPs to the standards of the original concept. The experience of the MCPs certainly has increased understanding of the policy-program-implementation-outcome process and inevitable gaps that materialize as policy struggles towards implementation.

Listeria monocytogenes ATCC 35152 and NCTC 7973 contain a nonhemolytic, nonvirulent variant

Listeria monocytogenes NCTC 7973 and this same strain deposited as ATCC 35152 contain two phenotypes: hemolytic virulent colonies and nonvirulent colonies that show no zones of hemolysis when streaked on heart infusion agar containing 5% rabbit blood. Results of examinations of these virulent and nonvirulent strains by investigators at the Centers for Disease Control, Atlanta, Ga., the Pasteur Institute, Paris, France, and the University of Würzburg, Federal Republic of Germany, support the conclusion that the avirulent strain is a nonhemolytic mutant of the virulent strain and that hemolysin is a virulence factor for L. monocytogenes.

Role of keto acids and reduced-oxygen-scavenging enzymes in the growth of Legionella species

Keto acids and reduced-oxygen-scavenging enzymes were examined for their roles in supporting the growth of Legionella species and for their potential reactions between the chemical components of the media. When grown in an experimental ACES (2-[(2-amino-2-oxoethyl)-amino] ethanesulfonic acid)-buffered chemically defined (ABCD) broth, the presence of keto acids shortened the lag periods, increased the rates of growth, and gave maximum cell yields. In addition, keto acids affected the specific activities of reduced-oxygen-scavenging enzymes determined during growth. The specific activities of superoxide dismutase of Legionella pneumophila (Knoxville) and L. dumoffii (TEX-KL) were increased three- to eightfold, while that of L. bozemanii (WIGA) was not affected. All strains appeared to be equally sensitive to the effects of superoxide anion (O2-) generated by light-activated riboflavin, and all were equally protected by the presence of keto acids in the ABCD broth. Production of trace amounts of acetate and succinate in pyruvate- and alpha-ketoglutarate-containing media exposed to light suggested that hydrogen peroxide was formed. Pyruvate and alpha-ketoglutarate were products of growth on amino acids, and there was no quantitative evidence that these keto acids were metabolized when they were added to the medium. The rate of cysteine oxidation in ABCD broth was increased by the presence of ferric ion or by exposure to light or by both, and keto acids reduced the rate of this oxidation. ACES buffer was a substrate for the production of O2- in the presence of light, and the combined addition of Fe2+ ions, cysteine, and either keto acid to the medium strongly inhibited the production of O2-. Thus, keto acids inhibited the rate of cysteine oxidation, they stimulated rapid growth by an unknown process, and, in combination with added Fe2+ ions and cysteine, they reversed the toxic effects of light by inhibiting O2- production.

Guanine is a growth factor for Legionella species

Evaluation of previously described chemically defined media for the growth of Legionella pneumophila showed that these media supported poor growth of several strains of L. pneumophila and did not support growth of certain of the Legionella species described later. Growth was stimulated by the dialysate from yeast extract but not by the nondialyzable fraction. Further investigations indicated that the active factors from the yeast extract dialysate were purine or pyrimidine derivatives, and certain known purines and pyrimidines were found to stimulate growth. Of these, guanine universally stimulated growth of all Legionella strains and was a growth requirement for several of the species tested. A balanced, N-(2-acetamido)-2-aminoethanesulfonic acid-buffered, chemically defined medium having guanine or a purine-pyrimidine mix is presented for the general growth of Legionella species.

Actinomyces and the intrauterine contraceptive device: aspects of the fluorescent antibody stain

Using fluorescein-conjugated globulins specific for Actinomyces israelii and Arachnia propionica, we observed large dispersed actinomycete populations in vaginal smears of several asymptomatic women. Mycelial granules, commonly revealed by the Papanicolaou stain, were not seen. These observations are discussed in regard to the threat of infection and sensitivity of the fluorescent stain.

Presence of toxic shock toxin in toxic shock and other clinical strains of Staphylococcus aureus

Toxic shock toxin (TST), also known as pyrogenic exotoxin C (Schlievert et al., J. Infect. Dis. 143:509-516, 1981) and staphylococcal enterotoxin F (Bergdoll et al., Lancet i:1017-1021, 1981), was purified from toxic shock strains of Staphylococcus aureus by preparative isoelectric focusing and by chromatofocusing. Neither method produced an absolutely pure protein as determined by silver staining of sodium dodecyl sulfate-acrylamide gels, although chromatofocusing was the better method of the two. Three molecular weight variants of the protein were found in the two toxic shock syndrome strains that were studied, regardless of the purification method that was used. An isoelectric point of 7.15 and molecular weights of 21,400, 22,100, and 23,200 were determined for the different forms of the protein from electrophoresis data. A sedimentation coefficient of 2.3S was determined by sucrose gradient centrifugation, and a Stokes radius of 2 X 10(-7) cm was determined by gel filtration. An average molecular weight of 18,900 for all of the TST forms was calculated from these data by the Stokes-Einstein equation. A survey for TST in 32 control and 46 toxic shock strains of S. aureus by isoelectric focusing and by agarose gel double immunodiffusion with specific rabbit antiserum revealed that the isoelectric focusing method tends to overestimate the number of TST-positive strains because of the detection of non-TST, neutral staphylococcal proteins. Based on immunodiffusion data, the association of TST with toxic shock strains was found to be 100% in vaginal isolates and 62% in non-vaginal isolates. In the control strains, TST was found in 16% of the vaginal strains and 23% of the non-vaginal strains. The value of this toxin as a marker for toxic shock and its relationship to the pathogenesis of this disease are discussed.

Determination of catalase, peroxidase, and superoxide dismutase within the genus Legionella

We examined 40 strains of Legionella for reduced-oxygen scavenging enzymes. Using a simple reaction chamber with a Swinney filter for the Beers and Sizer assay, we determined the catalase activity of live cells grown on buffered charcoal-yeast extract agar. For 29 strains of Legionella pneumophila, the apparent first-order rate constants for catalase ranged from 0.000 to 0.005. Similarly, low values ranging from 0.001 to 0.005 were observed for Legionella wadsworthii, Legionella oakridgensis, and Legionella gormanii. High catalase activities were found for Legionella jordanis, Legionella longbeachae, Legionella micdadei, and Legionella bozemanii, with first-order rate constant values of 0.010 to 0.035. Cell-free extracts were analyzed for catalase, peroxidase, and superoxide dismutase. Cell-free extracts of all strains had superoxide dismutase levels ranging from 8.2 to 30.5 U per mg of protein. The species could be characterized by their catalase and peroxidase since L. pneumophila and L. gormanii had only peroxidase (relative molecular weight [Mr], 150,000); L. dumoffii had a peroxidase (Mr, 150,000) plus a catalase (Mr, 174,000); and all remaining species had catalase only (Mr, 300,000, 220,000, or 150,000).

Whole-cell peroxidase test for identification of Legionella pneumophila

A simple combined peroxidase-catalase test has been developed which is applicable to live bacterial cells. Known strains of Legionella pneumophila were differentiated from other species of Legionella by being peroxidase positive and catalase negative.

Heated histoplasmin as a control for non-specificity in the complement fixation test for histoplasmosis

We present data in support of the use of a heated histoplasmin control for the complement fixation (CF) test for histoplasmosis to assist in the detection of the presence of h or m antibody.

Factors influencing the reactivity of Legionella antigens in immunofluorescence tests

We examined several factors for their effects on the serological reactivity of Legionella antigens used for direct or indirect fluorescent-antibody tests. These factors included media, methods of killing, strain differences, and the nature of the reactivity with diverse human sera. The maximum serological reactivities were obtained with charcoal-yeast extract agar; the relative antigenicity of cells grown on a chemically defined medium could be fourfold less than those grown on the charcoal-yeast extract agar. Cells grown at 25 degrees C showed only small antigenic differences from those grown at 35 degrees C but had better morphological and staining characteristics. Cells killed by 1% Formalin or 37% Formalin vapors showed a 20% less relative antigenicity than those killed by heat, but their cell walls stained more clearly and they had fewer aberrations. As tested with several human sera, cells of Philadelphia 1 showed great variation in relative antigenicity with changes in media or methods of preparation; Bellingham 1 was quite stable under these same conditions. The data suggest that Bellingham 1 had serogroup 1-specific antigens, reactive with human sera, which were not present in Philadelphia 1.

Absence of siderophore activity in Legionella species grown in iron-deficient media

Growth of Legionella species in a defined medium deficient in iron did not result in the production of phenolic or hydroxamate siderophores which could be detected by chemical or biological assay methods. Growth of a variety of other gram-negative organisms under the same conditions resulted in the production of both hydroxamate and phenolate siderophores. The iron-deficient medium limited growth of the Legionella species more severely than it did the growth of the other gram-negative organisms. We have concluded that Legionella species do not make the commonly recognized siderophores, probably because they are restricted in their growth to those environments in which inorganic iron is readily available or is supplied in a form bound to an unknown carrier.

Production of superoxide and hydrogen peroxide in medium used to culture Legionella pneumophila: catalytic decomposition by charcoal

The difficulties associated with the growth of Legionella species in common laboratory media may be due to the sensitivity of these organisms to low levels of hydrogen peroxide and superoxide radicals. Exposure of yeast extract (YE) broth to fluorescent light generated superoxide radicals (3 microM/h) and hydrogen peroxide (16 microM/h). Autoclaved YE medium was more prone to photochemical oxidation than YE medium sterilized by filtration. Activated charcoals and, to a lesser extent, graphite, but not starch, prevented photochemical oxidation of YE medium, decomposed hydrogen peroxide and superoxide radicals, and prevented light-accelerated autooxidation of cysteine. Also, suspensions of charcoal in phosphate buffer and in charcoal yeast extract medium readily decomposed exogenous peroxide (17 and 23 nmol/ml per min, respectively). Combinations of bovine superoxide dismutase and catalase also decreased the rate of photooxidation of YE medium. Medium protected from light did not accumulate appreciable levels of hydrogen peroxide, and autoclaved YE medium protected from light supported good growth of Legionella micdadei. Various species of Legionella (10(4) cells per ml) exhibited sensitivity to relatively low levels of hydrogen peroxide (26.5 microM) in challenge experiments. The level of hydrogen peroxide that accumulated in YE medium over a period of several hours (greater than 50 microM) was in excess of the level tolerated by Legionella pneumophila, which contained no measurable catalase activity. Strains of L. micdadei, Legionella dumoffi, and Legionella bozmanii contained this enzyme, but the presence of catalase did not appear to confer appreciable tolerance to exogenously generated hydrogen peroxide.

Characterization of antibody responses in legionellosis with an immunofluorometric assay

A solid-phase immunofluorometric assay was used to qualitatively characterize and precisely measure human immunoglobulin class-specific antibody responses in legionellosis. Stable antigen preparations consisted of cells grown at 25 degrees C that were killed, fixed with Formalin vapors, washed, and lyophilized. Working-curve material consisted of dilutions of selected convalescent sera. Linear regressions of logit transformations of relative fluorescence intensities versus the logarithm of the relative concentrations of sera were determined to give immunoglobulin class-specific antibody levels from uninfected and infected individuals. Each fluorescence intensity obtained with immunoglobulin class-specific antibody was converted to a multiple of the median fluorescence intensity obtained with sera from uninfected individuals. A presumptive-positive acute-phase legionellosis serum was defined for each immunoglobulin class by a multiple of the normal median fluorescence intensity that was greater than the multiple of the normal median from approximately 97% of the uninfected population.

Actinomyces in the vaginas of women with and without intrauterine contraceptive devices

Either Actinomyces israeli, A. naeslundii, or Arachnia propionica was found, by immunofluorescence studies, in cervicovaginal mucus from 36% of 50 women. One or more of these organisms were found in a surprising 27% of those with neither intrauterine contraceptive devices (IUDs) nor intravaginal foreign bodies. The only common finding was abundant vaginal mucus, and no clinical features were more serious than vaginal itching, odor, or vague discomfort. Among those women who harbored actinomycetes, the average duration of continuous IUD use was 5.3 years; the comparable figure for those with no infection was 2.1 years.

Relationship of phospholipid chemistry to serological reactivity in the Venereal Disease Research Laboratory slide test antigen

A total of 13 egg lecithins, 12 beef heart lecithins, and 15 beef heart cardiolipins were assayed for the ability to function in the Venereal Disease Research Laboratory microflocculation test, as well as for purity, fatty acid composition, free amines, metals, and products of oxidation. We found that the presence of peroxides and oxidation-related ultraviolet-absorbing chromophores showed a close inverse relationship to acceptable serological activity. The degree of purity of the lipids had only a slight influence on serological activity, whereas fatty acid composition, saturation, and configuration had none at all. We did not detect contaminating iron, copper, cobalt, nickel, or free amines in these lipids. We discuss the implications of our findings for improving the chemical standards for these lipids.

Metal requirements of Legionella pneumophila

Serial passage of six strains of Legionella pneumophila and one strain of Pseudomonas aeruginosa in a liquid chemically defined medium deficient in trace metals resulted in the death of five L. pneumophila strains and very limited growth in the remaining strain and the P. aeruginosa strain. Addition of either iron or magnesium restored growth to almost normal levels in all of the strains when early-passage inocula were used. A low concentration of magnesium stimulated growth with cobalt, copper, iron, manganese, molybdenum, vanadium, or zinc. When a complete defined medium containing trace metals was used, growth was inhibited by adding the chelators ethylenediaminetetraacetic acid, citrate, or 2,2'-bipyridyl. Chelator inhibition was partly or fully relieved with either calcium, cobalt, copper, iron, magnesium, molybdenum, nickel, vanadium, or zinc. P. aeruginosa differed from L. pneumophila in that it required higher concentrations of each chelator to inhibit growth and that its growth was stimulated by only four metals: calcium, iron, magnesium, and zinc. A trace-metal supplement for L. pneumophila was designed which included all metals stimulating growth in these experiments and which proved to be sufficient for optimal growth of all the strains.

Studies on the thermal degradation of the H and M antigens of lyophilized histoplasmin

Lyophilized histoplasmin for the agar gel microimmunodiffusion test has been prepared as a candidate World Health Organization Biological Reference Reagent. It was subjected to elevated temperature for given periods of time and analyzed by the capillary precipitin test and the single radial immunodiffusion test to determine the stability of the H and M antigens. H antigen showed no fall in relative potency when incubated at 48 degrees C for 20 days. M antigen showed a fall in relative potency after storage at 37 degrees C and 48 degrees C, but the extent of the fall was greater in the radial immunodiffusion test than in the capillary precipitin test. Half-lives of the antigens could not be calculated from the Arrhenius equation because the response curves at each temperature followed different kinetics. However, as based on zero time data, M antigen of the lyophilized histoplasma showed a 20% drop in relative potency when stored at -20 degrees C for 2 years. Other analyses suggested that M antigen of liquid histoplasmin stored at 5 degrees C and of lyophilized histoplasma stored at -20 degrees C was degraded at equal rates.

Demonstration of Actinomyces and Arachnia species in cervicovaginal smears by direct staining with species-specific fluorescent-antibody conjugate

For direct observation of microaerophilic actinomycetes by fluorescent antibody, a procedure was developed in which pepsin treatment and rhodamine conjugate of normal serum were used to reduce nonspecific staining in cervicovaginal smears. Actinomyces israelii, Actinomyces naeslundii, and Arachnia propionica were observed in cervicovaginal smears from women who did use and who did not use an intrauterine contraceptive device. A. israelii was found more commonly in women with an intrauterine contraceptive device, but no evidence was obtained that the use of an intrauterine contraceptive device influenced the presence of either A. propionica or A. naeslundii.

Studies on plating efficiency and estimation of viability of suspensions of Paracoccidioides brasiliensis yeast cells

Mild sonication was used to obtain single cell suspensions of Paracoccidioides brasiliensis. These cells were intact by microscopic criteria. Direct cell counts in a given inoculum and colony formation on various media were used to determine plating efficiency. Sonicated and nonsonicated cell suspensions were used to study plating efficiency and to estimated viability by means of vital dyes. Methylene blue Erythrosin B, and Janus green were unreliable when used with P. brasiliensis, but vital dyes were accurate when tested with Candida albicans. Acridine orange gave more meaningful results of viability. Estimates of viability, however, changed significantly as a result of relatively minor alterations in the composition of the suspending medium. In initial experiments, the plating efficiency of P. brasiliensis was dismally low. It descended abruptly with increasing dilution of inoculum. Efficiency was much improved if horse serum was added to brain heart infusion plates or if glucose glycine yeast extract (GGY) plates were incubated at room temperature and mycelial colonies were counted. With the technique we report, current plating efficiency of sonicated suspensions is of the order of 25%. Our results and procedures have an important bearing upon those studies concerned with in vitro killing of P. brasiliensis in suspensions or with isolating this fungus from clinical or environmental specimens.

Amino acid requirements of Legionella pneumophila

The amino acids required for growth and as energy sources by 10 strains of Legionella pneumophila were determined by using a chemically defined medium. All strains required arginine, cysteine, isoleucine, leucine, threonine, valine, methionine, and phenylalanine or tyrosine. Most strains (7 of 10) required serine, and two strains had to be supplied proline before growth could be established. All 10 strains used serine and, to a lesser extent, threonine as the sole sources of carbon and energy. The Y serine calculated was 94.9 +/- 8.5 g (dry weight) of cells/mol of serine. Assuming that the value of Y adenosine 5'-triphosphate is 10.5, these results indicate that oxidative catabolism of 1 mol of serine yielded approximately 9 mol of adenosine 5'-triphosphate. This high yield suggests that although serine was the major source of carbon, other amino acids may also be metabolized.

Development of a chemically defined liquid medium for growth of Legionella pneumophila

A chemically defined liquid medium has been developed for the study of the physiology and antigen production of the Legionnaires disease bacterium. The medium contains basal salts, vitamins, alpha-ketoglutaric acid, pyruvate, 0.05% l-cysteine, 0.05% glutathione, and a mixture of 20 additional amino acids, each of 0.01% final concentration, except serine, which was at 0.1%. The medium in shake culture at 37 degrees C with increased CO2 at pH 6.5, supports the maximum rate of growth, the highest cell yields, and the maximum cell surface antigen as distinguished by specific fluorescein isothiocyanate-conjugated antibody. Studies during the development of this medium showed that CO2, pyruvate, and alpha-ketoglutarate strongly stimulated growth; that cysteine and methionine were required for growth; and that serine, threonine, histidine, tyrosine, and tryptophane were energy sources. Glutathione substituted for cysteine, but cystine did not. The organisms did not use glucose and polysaccharides, as judged by cell yields when these carbohydrates were present or absent. The chelators malate, citrate, and ethylenediaminetetraacetic acid totally inhibited growth. Beta-mercaptoethanol, thioglycolate, dithiothreitol, and Tween 80 (0.05%) inhibited growth strongly or completely. Catalase activity was extremely weak or absent. Morphology varied, depending upon conditions and phases of growth. In general, filamentous forms became chains of cigar-shaped bacilli fragmenting to pairs and becoming coccoidal in the late stationary pha-e of growth. The organism grew at 25, 30, and 37 degrees C. Although they varied in their growth characteristics, 10 isolates were passed for five transfers in the chemically defined broth, giving maximum rates of growth, cell yields, and antigen production.

Biochemical and serological characteristics of soluble yeast phase antigens of Histoplasma capsulatum

Soluble antigens of whole yeast-phase cells were extracted with a 0.1 M phosphate buffer containing 0.1 M sodium chloride and 0.02% iodacetate. After being separated by differential filtration into fractions less than or greater than 50,000 daltons these antigens were purified by molecular sieve and chromatographic separations on ionic exchange resins. Two high molecular weight fractions obtained from diethylaminoethyl-cellulose (DEAE) at pH 8.0 and 7.0 with tris (hydroxymethyl) aminomethane (Tris) buffer were M antigens; those obtained at pH 4.0 and 4.0 with salt were H antigens. The four fractions had protein to carbohydrate ratios of 7.3, 14.0, 8.4, and 6.5 respectively, and all had essentially the same amino acid composition with no methionine and tyrosine and little histodine, arginine, phenylalanine and lysine. They had high concentrations of glucose, less mannose and traces of galactose. The low molecular weight fractions had the new complex "Y antigen", M antigen with protein to carbohydrate ratios of 1.4, 1.4 and 0.3 respectively. The amino acid and sugar composition of Y antigen strongly resembled the composition of the low molecular weight H and M antigens. Unlike the high molecular weight antigens, these low molecular weight antigens had methionine in relatively high concentrations; they had the same sugars as their respective high molecular weight counterparts. The yeast phase antigens differed from their respective mycelial counterparts in the following ways: glucose was the major sugar in the yeast phase with less amounts of mannose and traces of galactose, whereas in the mycelial antigens, mannose was the major sugar, with lesser amounts of galactose, and hexosamine. The H and M antigens of the yeast phase had high concentrations of glycine and alanine, whereas in the mycelial phase, these antigens had high concentrations of threonine and proline; the H and M antigens of the yeast phase had 5 to 16 times the protein to carbohydrate ratio observed for the same antigens of histoplasmin.

Evaluation of purified H and M antigens of histoplasmin as reagents in the complement fixation test

Complement-fixation (CF) tests were performed with purified H and M antigens, histoplasmin, and Histoplasma capsulatum whole cell yeast phase antigen using sera of 126 patients with proven or suspected histoplasmosis. Specific titers for either H or for M antibody were obtained with the individual purified antigens; the highest titers were comparable to those obtained with histoplasmin. However, in sera containing only anti-M antibody, the titers obtained with the purified M antigen were 2 to 16 times those obtained with the histoplasmin or yeast phase antigens. The CF test for either H or M antibody was 4 to 32 times as reactive as the agar-gel microimmunodiffusion test; in general precipitin lines were obtained with either H or M antigens from sera with CF titers greater than or equal to 8. With sera containing H antibody, there was an excellent correlation between the CF titers obtained with purified M antigen and histoplasmin. The correlations of CF titers with H antigen and either histoplasmin or yeast phase antigen were very low.

Solid-phase competitive-binding radioimmunoassay for detecting antibody to the M antigen of histoplasmin

A radioimmunoassay (RIA) was designed and compared with complement fixation and immunodiffusion tests for their relative ability to detect antibodies in sera of histoplasmosis patients. M antigen, purified from histoplasmin, was fixed to microtiter wells as the solid phase, and specific rabbit 125I-labeled anti-M globulin was the source of indicator antibodies. The optimal concentrations for the competitive-binding assay were 1.6 ng per well for M antigen and 650 ng per well for the 125I-labeled anti-M globulin. A panel of sera from 29 histoplasmosis patients and from patients with other mycoses was screened for RIA activity and in complement fixation and immunodiffusion tests that used histoplasmin and Histoplasma capsulatum yeast-form antigens. The sera of 22 histoplasmosis patients reacted in the RIA, 21 in the complement fixation, and 16 in the immunodiffusion tests. Sera of patients with other mycotic infections did not react in the RIA, with the exception of those of one blastomycosis patient and one candidiasis patient. The RIA could be modified to quantitate M antigen; as little as 125 pg could be detected. The evaluation of this panel of histoplasmosis patients' sera showed that the RIA was about equivalent in sensitivity to the complement fixation test. Some advantages of the RIA over the complement fixation test were that RIA was less prone to cross-reactions and gave better quantitation of low-titered sera. The RIA was a 1-day test, was not hindered by the anti-complementary activity of some sera, and could be modified to quantitate minute amounts of M antigen.

Evaluation of histoplasmin for the presence of H and M antigens: some difficulties encountered in the production and evaluation of a product suitable for the immunodiffusion test

The development of a single histoplasmin suitable for use in immunodiffusion testing of a variety of human histoplasmosis sera depends not only upon the presence of both antigens, but on relative concentration of one to the other, and perhaps on the chemical characteristics of the H and M antigens of a given strain.

Characterization and evaluation of a soluble antigen complex prepared from the yeast phase of Histoplasma capsulatum

Soluble yeast-phase (YPS) antigen preparations (Reeves et al., 1972) were obtained from three strains of Histoplasma capsulatum. These were analyzed by agar-gel diffusion and complement fixation tests with human sera from known cases of histoplasmosis. Two of the preparations contained the H and M antigens normally found in histoplasmin, whereas the third preparation contained the H but not the M antigen. In addition, a group of unknown antigens, designated as the Y (yeast) antigens, were demonstrated in all three YPS preparations. On the basis of Sephadex gel filtration data, the molecular weight of the YPS M antigen was estimated to range from 117,000 to greater than 200,000; that of the YPS H antigen was estimated to range from about 60,000 to greater than 200,000; and that of the Y antigens was estimated to range from less than 10,000 to 100,000. Complement fixation tests with human homologous and heterologous sera showed that the Y antigens were specific for H. capsulatum; Y antigens were not detected in the single lot of histoplasmin used in this study. When 60 human histoplasmosis sera and serum samples from nine animals experimentally infected with H. capsulatum were analyzed, it was found that antibodies to the Y antigens occurred with about the same frequency as antibodies to the H antigen but with less frequency than that of antibodies to the M antigen. When used in rabbits as immunogens for the preparation of specific antisera to H. capsulatum, the components of the YPS preparations caused the formation of numerous cross-reacting antibodies. The data from this study show that the value of the YPS preparations for the serological diagnosis of histoplasmosis rests on the specificity of the H, M, and Y antigens and on the fact that the primary production of antibodies is restricted to these antigens in the course of natural infections. The YPS preparations were found to be stable for a period of at least 11 months under a variety of storage conditions and temperatures. Data obtained with various killing agents and metabolic inhibitors suggest an improved method for preparing the YPS antigens by using a suitable strain and killing the cells with iodoacetate.

Purification, composition, and serological characterization of histoplasmin-H and M antigens

To obtain purified H and M antigens suitable as primary standards in the serological diagnosis of histoplasmosis by agar gel double-diffusion tests, H and M reactive components of histoplasmin were fractionated by column chromatography by using Sephadex G-100, Sephadex G-200, and diethylaminoethyl cellulose. Six fractions from diethylaminoethyl cellulose were reactive in agar gel double-diffusion, complement fixation, and capillary precipitin tests. When examined by electrophoresis on acrylamide gel, one M antigen (fraction 2, molecular weight greater than 200,000) and two H antigens (fractions 5 and 6, molecular weight greater than 200,000) each gave essentially a single protein band. In agar gel double-diffusion and complement fixation tests with sera from patients with proven cases of histoplasmosis, blastomycosis, or coccidioidomycosis, these two fractions of H antigen and the one of M antigen reacted only with sera from proven or suspect cases of histoplasmosis and showed reactivity with those sera known to contain only the anti-H or anti-M antibody, respectively. Fraction 2 (M antigen) and fractions 5 and 6 (H antigens) had carbohydrate-to-protein ratios of 1.60, 0.77 and 0.78, respectively. Both antigens contained galactose, glucose, mannose, and hexosamine, with mannose being the predominant sugar. Fraction 2 was characterized by a high proline and glucose content, whereas fractions 5 and 6 contained higher concentrations of galactose, mannose, glycine, and alanine. Each of these products appeared to separate into two active fractions, one of a molecular weight greater than 200,000 and one of a molecular weight less than 35,000. The M antigen component of fraction 2 was still characterized by a high proline content, whereas the H antigen components of fractions 5 and 6 had a high content of glutamic acid, serine, glycine, and proline.

Isolation of a new soluble antigen from the yeast phase of Histoplasma capsulatum

A method is described by which a soluble antigen was prepared from the yeast phase of Histoplasma capsulatum. This soluble preparation had a specificity greater than that of whole-cell yeast-phase antigens. In complement fixation tests with sera from human cases of histoplasmosis, blastomycosis, and coccidioidomycosis, the soluble antigen reacted in 12.1% of 141 tests with heterologous sera, whereas conventional whole-cell yeast antigens reacted in 47.3% of 91 tests with heterologous sera. The reactivities of the two types of antigens with homologous sera were essentially the same.

Correlation of M protein production with those factors found to influence growth and substrate utilization of Streptococcus pyogenes

In the absence of proteinase formation, factors reported to influence the growth or fermentation by streptococci have been evaluated to determine their quantitative effect upon the production of M protein during the growth of Streptococcus pyogenes. Buffers, amino acids, peptides, gross organic additions, and carbohydrate substrates were tested under a variety of cultural conditions. The M protein content was remarkably constant throughout the late logarithmic period of growth, i.e., when the cell population doubled, the M protein doubled. However, several factors affected the M protein content per milligram of cells (dry weight). When types 1, 12, and 22 were grown aerobically in a semidefined medium, the M protein content of the cell population essentially doubled; in Todd-Hewitt broth, this aerobic effect on M protein synthesis was not observed. When cells grown on Todd-Hewitt broth were transferred to medium containing 0.1% starch and no added glucose, the M protein content per milligram of cells (dry weight) increased as much as fourfold. When growth was initiated in glucose, the rate of M protein formation was at a maximum in the early logarithmic phase of growth and was comparatively greater than the rate of cellular multiplication. When the amount of substrate fermented was greater than 0.2%, increased M protein was not observed. An evaluation of the effects of medium or conditions of growth showed the units of M per milligram of cells (dry weight) were not influenced by a shift in the stoichiometry of either the anaerobic or aerobic fermentation, substrate used, or adenosine triphosphate utilized for growth. These results show that M protein synthesis is subject to limited glucose repression or substrate catabolite repression.

Factors influencing the production of H and M antigens by Histoplasma capsulatum: effect of physical factors and composition of medium

Stagnant culture methods have permitted only limited physiological studies of the production of H and M antigens by Histoplasma capsulatum because, with such methods, antigen production is uncontrolled. In this investigation, a shake culture method was used to convert yeast-phase inoculum to mycelialphase growth at 25 C. Results strongly suggest that the release of H and M antigens relates to autolysis of the cells. Among the factors influencing production of H and M antigens under shaking conditions, choice of strain was the most important. Alterations of carbon or nitrogen source or variations in amino acid to carbohydrate ratios had limited influence on antigen production. With a strain that produced both H and M antigens, however, proportions of titers of M to H antigens could be made to vary considerably by changes in the medium, the pH, and the temperature. Results suggest that the source of M antigen during autolysis is enzymatic dissolution of the cell wall. The source of H antigen is more obscure. Production of both antigens may be differentially controlled under conditions of good reproducibility by a correct choice of strain and manipulation of culture medium.

Factors influencing the production of H and M antigens by Histoplasma capsulatum: development and evaluation of a shake culture

Studies were undertaken to improve the production of histoplasmin for use in complement-fixation tests and in the determination of H and M antibodies. A shake culture method performed at 25 C was developed with a yeast-phase inoculum. Eight strains of Histoplasma were tested in three synthetic media to evaluate the effects of strain and medium on H and M antigen production. Intrastrain variation was negligible, and antigen production was reproducible. All of the strains produced H antigen; six strains produced both H and M antigens, and two produced only H antigen. The time of H and M antigen appearance varied with the medium; M antigen appearance was dependent upon the strain and medium used. Titers of M antigen appeared to be greater in stagnant culture.

Evaluation of methods used to purify acid-extracted group A streptococcal M protein

The literature includes descriptions of both acid-soluble and acid-insoluble M protein in the preparation of "hot acid-extracted group A streptococcal M protein." We present evidence for the contamination of crude type 1 acid-insoluble M protein. The purification of preparations of crude and partially purified acid-soluble type 1 and type 12 M protein is described. Our quantitative criteria for purification were recovery of M precipitin activity, improvement in specific activity, and removal of carbohydrate. Exclusion of nucleic acid is also discussed. Greater purification in a single passage was found with a carboxymethylcellulose column (with acidic elution) than with hydroxyapatite, diethylaminoethyl-Sephadex, or carboxymethyl-cellulose (with neutral elution) columns or with ammonium sulfate fractional precipitation. Carboxymethylcellulose with acidic elution was found to be a satisfactory standard laboratory procedure for the preparation of purified acid-extracted (acid-soluble) group A streptococcal M protein.