Biomedical subjects

F A Kapral

Publications and source records attributed to F A Kapral.

At least 19 recordsLinked to original sources

PubMed1992

The production of bactericidal fatty acids from glycerides in staphylococcal abscesses.

Staphylococcal abscesses contain two types of lipids which are bactericidal for Staphylococcus aureus. These include a group of long chain unsaturated free fatty acids and another as yet unidentified lipid with unique properties. When abscess homogenates are incubated with S. aureus culture filtrates, the amount of bactericidal activity is increased. This phenomenon is called activation. To determine the source of increased bactericidal activity during activation, individual types of lipid were isolated from abscess homogenates and examined for their ability to be activated. Activation was found to result from the release of long chain unsaturated fatty acids from glycerides, presumably by the action of staphylococcal lipase.

Abscess↗

PubMed1992

Modification of bactericidal fatty acids by an enzyme of Staphylococcus aureus.

Certain strains of Staphylococcus aureus produce an enzyme capable of inactivating the bactericidal fatty acids produced in staphylococcal abscesses by esterification to various alcohols. The enzyme, called FAME (fatty acid modifying enzyme), has a pH optimum between 5.5 and 6.0 and a temperature optimum of about 40 degrees C. Enzyme activity is not affected by edetic acid or by the presence or absence of sodium and potassium ions. Although FAME can utilise methanol, ethanol, 1-propanol, 2-propanol, 1-butanol or cholesterol as substrates, cholesterol appears to be the preferred substrate. FAME esterifies without being an esterase operating in reverse. Strains capable of producing the enzyme can synthesise it in trypticase soy broth and in a chemically defined medium, but not necessarily in equal amounts. FAME production is correlated with the ability of a strain to grow and survive within the tissues.

Abscess↗

PubMed1992

The accumulation of bactericidal lipids in staphylococcal abscesses.

Abscesses were generated in the peritoneal cavity of mice by the inoculation of 10(9) staphylococci. Abscess weight increased rapidly, reaching about 200 mg by the fourth day; for the next 60 days, abscess weight increased only slightly. The amount of total lipid increased during abscess development, attaining a peak level of about 19 mg per abscess at 7 days before decreasing. Almost all of this lipid resulted from the accumulation of neutral lipids. The small increases seen in the phospholipid and glycolipid fractions could be accounted for through the accumulation of host cellular elements in the abscess. Leucocytes containing cytoplasmic lipid droplets were first seen 4-12 h after infection and these cells were widely scattered around the periphery. During the next 2 days, the number of cells with lipid droplets increased markedly and lipid droplets were also found in the deeper portions of the abscesses. Although lipid droplets were found subsequently throughout the abscess, the greatest amounts always occurred in the leucocyte zone immediately proximal to the connective tissue capsule. During abscess development, the bactericidal activity also increased rapidly, reaching a maximum by the seventh day and declining thereafter.

Abscess↗

PubMed1992

Effect of capsulation on the resistance of Staphylococcus aureus to the bactericidal lipids produced in abscesses.

Staphylococcus aureus strains differ in their sensitivity to some of the bactericidal lipids produced by the host in staphylococcal abscesses. To evaluate whether the presence of a capsule might account for these differences, capsulate and non-capsulate S. aureus strains were compared for their sensitivity to staphylococcal abscess homogenates and the neutral lipid fraction derived from such material. Although the presence of a capsule appeared to reduce sensitivity, two non-capsulate mutants were only about three-to-four times more sensitive than their capsulate parent strains. Another strain, known for its resistance to these bactericidal lipids, was not capsulate. This suggests that mechanisms other than capsule formation must also determine sensitivity to the lipids.

Abscess↗

PubMed1992

Carotenoid pigment levels in Staphylococcus aureus and sensitivity to oleic acid.

Staphylococcus aureus mutants lacking pigment, or expressing only low levels of pigment, were more sensitive to oleic acid than were the parent strain and mutants making more pigment than the parent. One class of mutants (colour index 5), although possessing significant levels of pigment, were nevertheless quite sensitive to oleic acid. This suggested that only certain carotenoids in the biosynthetic pathway were capable of imparting resistance to fatty acids. The phenotypic expression of pigment also affected the sensitivity of a strain to oleic acid. The parent S. aureus strain 18Z, when grown to express its maximal pigment potential, was more resistant to oleic acid than when it was grown to express minimal levels of pigment.

Carotenoids↗

PubMed1992

The production of fatty acid modifying enzyme (FAME) and lipase by various staphylococcal species.

Eighty-six strains encompassing 11 species of coagulase-negative staphylococci were examined for the production of fatty acid modifying enzyme (FAME) and lipase. Staphylococcus schleiferi and S. saprophyticus most closely resembled S. aureus in that 80% of the strains produced both enzymes. In contrast, no strains of S. lugdunensis and S. haemolyticus tested produced these enzymes. S. simulans was unusual in that eight of 10 strains produced FAME, but only one produced lipase. Among the other species the proportion of strains producing both enzymes ranged from 10 to 60%. Generally there was a strong correlation between FAME and lipase production.

Acyltransferases↗

PubMed1992

The esterification of fatty acids by Staphylococcus aureus fatty acid modifying enzyme (FAME) and its inhibition by glycerides.

Fifty-five randomly selected Staphylococcus aureus strains were examined for fatty acid modifying enzyme (FAME) production. Of these, 20.4% did not elaborate the enzyme. Amongst the remaining strains, the lowest level produced in culture was 0.1 unit/10(9) cocci and the maximum was 2.01 U/10(9) cocci; the median level was 0.4 U/10(9) cocci. In a series of straight-chain saturated fatty acids with 11-24 carbons, all could be esterified by FAME. However, those with 15-19 carbons were generally better substrates than the others. For a particular chain length, the unsaturated forms were better substrates than the saturated form. Triglycerides with unsaturated fatty acid side chains were potent inhibitors of FAME. Diglycerides were almost as active as triglycerides, but monoglycerides were much less inhibitory. FAME was purified by gel filtration followed by hydrophobic interaction chromatography on hexyl agarose. FAME and lipase may have a role in determining the survival of S. aureus in lesions.

Acyltransferases↗

PubMed1992

The production of a bactericidal monoglyceride in staphylococcal abscesses.

The treatment of abscess homogenates with calcium ionophores stimulated the production of a bactericidal lipid with properties indistinguishable from those of a previously unidentified bactericidal lipid that had been detected in staphylococcal abscesses. The lipid was identified as a monoglyceride by thin layer chromatography. It resembled the unidentified lipid in that it had a high specific activity, exhibited differential activity, was inhibited by Staphylococcus aureus delta toxin, lecithin and Ca++, and its activity was reduced by oxidation. Stimulation of monoglyceride production by calcium ionophore requires the joint presence of components from the sedimented and supernatant fractions of abscess homogenates, and was not produced if boiled homogenate was used. The addition of verapamil interfered with the production of monoglyceride in homogenates treated with calcium ionophore. Monoglyceride was produced only in abscess homogenates and not in homogenates of other normal tissues or tissues taken from mice infected with S. aureus. Calcium ionophore could be replaced by inositol triphosphate, suggesting that monoglyceride production involved the release of calcium from intracellular stores. The 2-monoglyceride was the form originally produced in abscess homogenates, but this spontaneously isomerized to the 1-monoglyceride. The fatty-acid moiety of the monoglyceride consisted primarily of 16:0 and 16:1 fatty acids.

Abscess↗

PubMed1991

Correlation of carotenoid production, decreased membrane fluidity, and resistance to oleic acid killing in Staphylococcus aureus 18Z.

Staphylococcus aureus is susceptible to killing by host-derived fatty acids. Studies were performed to test for a correlation between carotenoid production by S. aureus and protection against oleic acid. Oleic acid killing of cells grown in carotenoid expression medium was determined as the dosage of oleic acid in 2 M NaCl-2 mM EDTA that would kill 20% of the cells in 60 min at 37 degrees C (i.e., the 20% lethal dose). Compared with the wild-type strain (18Z), a carotenoid-deficient mutant strain (18Z-76) and strain 18Z grown in a medium that suppressed carotenoid production both showed increased sensitivity to oleic acid. Spontaneous revertants of strain 18Z-76 that regained the ability to produce carotenoids were as resistant to oleic acid as the wild-type strain. Oleic acid was shown by fluorescence polarization to decrease polarization values. Lower polarization values indicate a more-fluid membrane. To determine whether protection against oleic acid killing might depend on carotenoid stabilization of membranes, fluorescence polarization values were determined for strains showing different levels of carotenoid production. An indirect correlation was found between membrane fluidity and carotenoid production. We were able to conclude that there is a direct correlation between carotenoid production (i.e., cell pigmentation), cell membrane stability, and resistance to oleic acid-induced cell killing.

Carotenoids↗

PubMed1985

Staphylococcus aureus delta toxin as an enterotoxin.

The classical enterotoxins are known primarily for their ability to cause emesis and diarrhoea in cases of staphylococcal food poisoning but they also exhibit other biological activities. The seven antigenic types of toxin have molecular weights in the range 25 000-35 000. All types induce emesis in man and monkey and are of comparable potency. The enterotoxins seem to induce emesis by stimulating neural receptors in the intestine rather than acting on the medulla directly. The mechanism whereby diarrhoea is produced is unclear. Another product of Staphylococcus aureus which meets the more recent definition of an enterotoxin is the delta toxin. This toxin is an amphipathic peptide having an Mr of 2977 and possessing the ability to interact with a variety of hydrophobic substances. It is cytotoxic, can increase vascular permeability in guinea-pig skin, and can increase cellular cyclic AMP levels in guinea-pig ileum. In the ileum delta toxin also inhibits water absorption, apparently by increasing the bidirectional movement of Na+ and Cl- across the mucosa. This response does not appear to be mediated by cyclic AMP since the changes in ion fluxes precede the increases in cellular cyclic AMP levels. In high doses delta toxin also elicits a positive response in the neonatal mouse after intragastric inoculation.

Animals↗

PubMed1983

Exfoliative dermatitis in an infant. Association with enterotoxin F-producing staphylococci.

A 2-month-old premature infant had an extensive exfoliative dermatitis with flaccid bullae, mucous membrane involvement, thrombocytopenia, and an elevated creatinine kinase level. A subepidermal cleavage plane with numerous necrotic epidermal cells and a polymorphonuclear cell infiltrate were present on a skin biopsy specimen. The isolates of Staphylococcus aureus obtained at the onset of her disease had a 29/52 bacteriophage lysis pattern and produced enterotoxins C and F and epidermal toxin, but no exfolliatins. In toxic shock syndrome (TSS), subepidermal blister formation has been described and a new toxin, epidermal toxin, which causes subepidermal cleavage in the newborn mouse model, has been identified. In some infants, exfoliative dermatitis may be a variant of the well-described TSS in older children and adults.

Bacterial Toxins↗

PubMed1980

Partial characterization of a bactericidal system in staphylococcal abscesses.

Since leukocytes comprise a major portion of staphylococcal abscesses, the properties of the bactericidal material in abscess homogenates were compared with those of bactericidal systems associated with leukocyte lysosomes. The bactericidal material in abscess homogenates was distinguished from the myeloperoxidase system by its resistance to heat (100 degrees C, 30 min), lack of solubility in dilute acid (0.005 N HCl), resistance to strong acid (pH 1), and insensitivity to catalase. It was differentiated from the cationic proteins by its lack of solubility in dilute acid, insensitivity to iron (0.1 mM) or trypsin (5 mg/ml), and greater activity in solutions of increased ionic strength. These characteristics, together with its sensitivity to Ca2+ or albumin, suggested that the material might be lipid. Subsequent studies revealed that all the bactericidal activity resided in the lipid fraction recovered after extraction of abscess homogenates by the Dole procedure.

Abscess↗

PubMed1979

Levels of exfoliatin antitoxin in pooled human serum globulin.

The potential value of human serum globulin for treatment of patients with the staphylococcal scalded-skin syndrome was determined by measuring the exfoliatin antitoxin content of globulin pools. Of 16 lots tested, only four had detectable antitoxin activity, and in these the levels were minimal. These findings suggest that pooled serum globulin is not a practical source of exfoliatin antitoxin.

Animals↗

PubMed1978

Increased tissue conductance and ion transport in guinea pig ileum after exposure to Staphylococcus aureus delta-toxin in vitro.

Prior studies had shown that Staphylococcus aureus delta-toxin was able to inhibit water absorption in guinea pig ileum and to elevate the cyclic AMP content of this tissue, but was unable to elicit certain cyclic AMP-mediated changes in Y-1 adrenal or Chinese hamster ovary cells. Because water movement passively follows the net movement of electrolytes in the gut, this study investigated the effect of delta-toxin on ion transport in guinea pig ileum maintained in vitro. The transmural potential difference (PD) of guinea pig ileum was measured and nullified with an automatic voltage clamp. The short circuit flowing under these conditions (I(sc)) was measured, and the conductance was calculated (I(sc)/PD). Unidirectional (22)Na(+) and (36)Cl(-) fluxes were measured. In a glucose-free Ringer solution, delta-toxin caused an immediate spike in PD and I(sc), and the extent and duration of the spike generally increased with increasing toxin concentration. The conductance of ileum was increased by delta-toxin, and this effect on conductance could be blocked by lecithin, a known inhibitor of delta-toxin. Tissue in the presence of glucose did not exhibit a spike in PD or I(sc) when exposed to delta-toxin. In a glucose-free medium, delta-toxin caused a 1.5- to 2.5-fold increase in both the unidirectional absorption and secretion of Na(+) and Cl(-), whereas the net secretion of Na(+) increased above basal levels. The observation that delta-toxin causes a prompt increase in intestinal ion flux lends credence to the concept that the elevation in cellular cyclic AMP, which occurs later, is a secondary response to the toxin. The rapid increase in ion flux may reflect the ability of delta-toxin to augment intercellular movement of ions across the mucosa rather than the stimulation of transcellular processes.

Animals↗

PubMed1978

Pulmonary infection of mice with Staphylococcus aureus.

The survival of Staphylococcus aureus in the lungs of mice was studied under various conditions. Doses of 10(7) to 10(9) washed staphylococci were quantitatively introduced into the lungs after intratracheal inoculation in mice under either ether or sodium pentobarbital anesthesia. Mice were sacrificed at intervals, the lungs were excised and homogenized, and the cocci were enumerated by plate count. The 50% lethal dose was 6 x 10(8) cocci per mouse, and mice died within 24 h but without proliferation of the inoculum. Mice given 10(8) cocci intratracheally under pentobarbital anesthesia regularly survived and eliminated the organisms over a 48-h period. The use of ether anesthesia resulted in persistence of the inoculum for up to 48 h, but the organisms were then eliminated. Inability to proliferate did not appear to result from a lack of iron because pretreatment of the mice with ferric ammonium citrate or Imferon did not alter inoculum survival. Staphylococci inoculated intratracheally in mice infected with influenza virus 3 to 21 days previously showed no enhanced persistence or multiplication. Cocci preclumped with fibrinogen, inocula mixed with 10 times the number of Formalin-killed staphylococci, or inocula of the encapsulated Smith strain did not survive any better than conventional inocula, suggesting that phagocytosis might not be the sole mechanism for elimination. However, a sedimentable fraction from normal or infected lung homogenates proved either inhibitory or cidal for staphylococci in vitro.

Animals↗

PubMed1977

Effect of Staphylococcus aureus delta toxin on Chinese hamster ovary cell morphology and Y-1 adrenal cell morphology and steroidogenesis.

Since Staphylococcus aureus delta toxin previously had been shown to increase the cyclic adenosine 3',5'-monophosphate (cAMP) content of guinea pig ileum, the effect of delta toxin on such cAMP-mediated responses as morphogenesis and steroidogenesis in cultured tissue cells was examined. In contrast to cholera toxin, delta toxin did not cause spindling of Chinese hamster ovary cells. Unlike adrenocorticotropin or cholera toxin, delta toxin was unable to cause rounding of Y-1 adrenal cells or to promote steroid production by the cells. S. aureus alpha toxin and enterotoxin B were also unable to cause rounding of Y-1 adrenal cells. Omission of Ca2+ from the media still allowed for increased steroid production by adrenocorticotropin but not by delta toxin. Delta toxin at concentrations greater than 10 micrograms/ml did cause lysis of both Chinese hamster ovary and Y-1 adrenal cells. These findings suggest that the increase in intestinal cAMP levels caused by delta toxin is mediated through a mechanism different from that initiated by cholera toxin.

Adrenal Gland Neoplasms↗

PubMed1976

Effect of fatty acids on Staphylococcus aureus delta-toxin hemolytic activity.

The lysis of human erythrocytes by Staphylococcus aureus delta-toxin proceeded without a lag and was directly proportional to toxin concentration and temperature of incubation. Lysis was complete within 8 min. Addition of saturated, straight-chain fatty acids of 13 to 19 carbons increased the activity of delta-toxin, whereas those with 21 to 23 carbons were inhibitory. Palmitic acid was the fatty acid most active in augmenting delta-toxin, but its effect could be abolished by the simultaneous addition of either tricosanoic acid or egg lecithin.

Fatty Acids↗

PubMed1976

Inhibition of water absorption in the intestine by Staphylococcus aureus delta-toxin.

Water absorption in intestinal segments was monitored by measuring the concentration of polyethylene glycol, a nonabsorbable reference marker, in a balanced salt solution continuously perfused through the lumen. Staphylococcus aureus delta-toxin inhibited water absorption in rabbit jejunum and ileum perfused in vivo and in guinea pig ileum perfused in vitro. Cholera toxin also interfered with water absorption in guinea pig ileum maintained in vitro, but S. aureus enterotoxin B had no demonstrable effect on this tissue.

Animals↗