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F A Kapral

Publications and source records attributed to F A Kapral.

At least 19 recordsLinked to original sources
PubMed1993

Growth cycle-induced changes in sensitivity of Staphylococcus aureus to bactericidal lipids from abscesses.

Three Staphylococcus aureus strains (303, 18Z and TG), exhibiting various patterns of survival within abscesses, were significantly more sensitive to the bactericidal activity of oleic acid during the log phase of growth than at other stages of the growth cycle. Cells entering the stationary phase showed diminished sensitivity to the fatty acid. These changes were reflected by changes in the LD50 and also by differences in the rate of killing by oleic acid. Additional changes were noted: the rate of killing by oleic acid declined over a 4-day period; a progressively greater proportion of the staphylococcal population became resistant to even high concentrations of oleic acid; from the fourth day onwards c. 50-55% of the cocci were totally resistant to the fatty acid. Strains 303 and 18Z became more sensitive to mono-olein during the log phase of growth, but strain TG was very resistant to mono-olein throughout the growth cycle. Growth in the presence of glycine 6% to reduce cross-links in the peptidoglycan did not alter bacterial sensitivity to oleic acid. However, all three S. aureus strains exhibited significant increases in membrane fluidity during the log phase of growth, but upon entering the stationary phase membrane fluidity again decreased. Concomitant changes in carotenoid content occurred during the growth cycle, but these changes did not appear to be solely responsible for the changes in sensitivity to the lipids.

Abscess↗
PubMed1993

Host response to coagulase-negative staphylococci in abscesses induced within mice.

A model whereby a known number of coagulase-negative staphylococci were packed into capillary tubes and implanted into the peritoneal cavity of mice proved to be a satisfactory method for generating abscesses that could be easily removed free of extraneous host tissue, and that permitted measurement of the survival of the organisms and accumulation of lipid in the lesion. Strains of S. epidermidis, S. schleiferi and S. lugdunensis, differing in their ability to produce fatty acid modifying enzyme (FAME) and lipase, were packed into either glass or plastic capillary tubes and used to generate abscesses. Abscesses produced by S. aureus served as comparators. Lipids accumulated within the abscesses caused by S. aureus in the same manner as previously described for the organism inoculated without tubes. Lipids also accumulated within abscesses produced by all the coagulase-negative staphylococci, but the rate of accumulation was slower and the lipid droplets were smaller than seen with S. aureus. The mobilisation of lipid did not differ in response to cocci in plastic or glass tubes. Strains of S. epidermidis and S. schleiferi producing FAME and lipase were better able to survive within abscesses than strains unable to produce these enzymes. However, FAME and lipase production did not appear to be the sole determinants of survival within abscesses. Regardless of whether they produced FAME and lipase, the two S. epidermidis strains were significantly better able to survive within plastic tubes than in glass tubes. No such difference was seen with S. aureus between plastic and glass tubes.

Abscess↗
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↗
PubMed1981

Generalized exfoliation associated with Staphylococcus aureus infection.

A 67-year-old man presented with a rash that was refractory to systemic corticosteroid therapy. Physical examination revealed sloughing skin on his hands, soles, and lower extremities. Stroking involved and uninvolved skin produced Nikolsky's sign. Skin biopsies revealed the plane of cleavage to be in the basal epidermal layer. Cultures of the patient's skin, blood, nose, and throat grew Staphylococcus aureus. These isolates produced an epidermal toxin that caused Nikolsky's sign in neonatal mice. The toxin caused cleavage in the basal epidermal layer of neonatal mice, was heat labile, and was not neutralized by exfoliatin antitoxin.

Aged↗
PubMed1981

Survival of Staphylococcus aureus in intraperitoneal abscesses.

An examination of 10 strains of Staphylococcus aureus for survival within abscesses developing in the peritoneal cavity of mice revealed three distinct patterns of survival. Although non-haemolytic mutants were destroyed more rapidly than were their parent strains, this difference could not be attributed to any particular haemolysin. In abscesses generated with mixtures of non-haemolytic variants and their parent strains, the former were preferentially eliminated; this suggests that the non-haemolytic variants were inherently more sensitive to the conditions within these lesions. Subsequent studies confirmed that abscess homogenates were cidal for staphylococci and that this activity resided in the insoluble fraction of the homogenates. Staphylococci added to abscess homogenates were killed, but only after a lag. This lag could be shortened or eliminated by incubating homogenates before adding the test organism. After development of a suitable assay, it was found that the cidal activity in abscess homogenates could be increased 3-20-fold by pre-incubation. Staphylococcal strains differed in their relative sensitivities to the cidal material; those strains rapidly destroyed within abscesses were the most sensitive and strains capable of better survival were more resistant. The results support the concept that the cidal material is responsible for destruction of staphylococci within such lesions.

Abscess↗
PubMed1981

Binding of radiolabeled Staphylococcus aureus delta-toxin to human erythrocytes.

The addition f [3H]isoleucine to a chemically defined medium resulted in the production of delta-toxin (DT) with a high specific radioactivity (0.47 microCi/mg). The purified tritium-labeled toxin ([3H]DT) was found to migrate in sodium dodecyl sulfate-polyacrylamide gel electrophoresis as a single band with a molecular weight of 1,600. Upon electrofocusing, [3H]DT yielded one major peak (pI = 5.90) and two minor peaks (pI = 5.10, 6.95) of radioactivity. The percentage of [3H]DT associated with pelleted fractions of intact erythrocytes or erythrocyte ghosts remained fairly constant over a 100-fold range of toxin concentrations. Erythrocyte ghosts, however, bound more [3H]DT than did intact erythrocytes when exposed to the same concentration of toxin. Erythrocytes maintained in isotonic sucrose were more susceptible to toxin than erythrocytes suspended in saline, but did not bind more [3H]DT. The binding of [3H]DT to erythrocyte ghosts was found to be temperature dependent from 0 to 20 degrees C but was constant from 20 to 50 degrees C.

Bacterial Toxins↗
PubMed1981

Hydrophobic interaction chromatography of Staphylococcus aureus delta-toxin.

Staphylococcus aureus delta-toxin bound avidly to agarose gels containing phenyl, octyl, or decyl ligands, but less so to agarose with hexyl groups. Agarose with ethyl or butyl moieties did not bind any more toxin than did agarose without attached ligands. About 10% of the applied toxin preparation did not bind to gels and eluted with the starting buffer. The nonadsorbed material was not hemolytic, did not react with anti-delta-toxin immunoglobulin G, and did not appear to be a peptide. Toxin bound to phenyl-Sepharose was not eluted with water, solutions containing chaotropic ions or ethylene glycol, or by increasing the pH, but was eluted with 50% ethanol. The ethanol-eluted delta-toxin (EEDT) was soluble in water, ethanol, 10% sucrose, or 6 M urea, but was poorly soluble in aqueous salt solutions at neutral pH. Regardless of whether the soluble or insoluble form of delta-toxin was applied to the gel, the resultant EEDT fraction was water soluble. The hemolytic activity of EEDT was markedly reduced when assayed in saline, but was the same as that of the original toxin preparation when assayed in isotonic sucrose. A significant portion of EEDT, when rechromatographed on phenyl-Sepharose, did not bind to the gel. This unbound fraction may represent toxin aggregates in which the hydrophobic regions of the toxin monomers are interiorized within the aggregates.

Bacterial Toxins↗