Bactericidal substance from Staphylococcus aureus. Biological properties

Antibacterial Peptides: Opportunities for the Prevention and Treatment of Dental Caries

Dental caries is a multifactorial disease that is a growing and costly global health concern. The onset of disease is a consequence of an ecological imbalance within the dental plaque biofilm that favors specific acidogenic and aciduric caries pathogens, namely Streptococcus mutans and Streptococcus sobrinus. It is now recognized by the scientific and medical community that it is neither possible nor desirable to totally eliminate dental plaque. Conversely, the chemical biocides most commonly used for caries prevention and treatment indiscriminately attack all plaque microorganisms. These treatments also suffer from other drawbacks such as bad taste, irritability, and staining. Furthermore, the public demand for safe and natural personal hygiene products continues to rise. Therefore, there are opportunities that exist to develop new strategies for the treatment of this disease. As an alternative to conventional antibiotics, antibacterial peptides have been explored greatly over the last three decades for many different therapeutic uses. There are currently tens of hundreds of antibacterial peptides characterized across the evolutionary spectrum, and among these, many demonstrate physical and/or biological properties that may be suitable for a more targeted approach to the selective control or elimination of putative caries pathogens. Additionally, many peptides, such as nisin, are odorless, colorless, and tasteless and do not cause irritation or staining. This review focuses on antibacterial peptides for their potential role in the treatment and prevention of dental caries and suggests candidates that need to be explored further. Practical considerations for the development of antibacterial peptides as oral treatments are also discussed.

Effect of Bactericidal Substance from Staphylococcus aureus on Group A Streptococci I. Biochemical Alterations

A bactericidal substance isolated from phage type 71 staphylococci has been studied relative to its mechanism of action on streptococcal cells. The substance exerts its effect best at 37 C. No cell lysis occurs as evidenced by lack of alteration in optical density of susceptible cell suspensions. The bactericidal substance results in immediate cessation of protein and deoxyribonucleic acid synthesis as well as degradation of newly and previously formed ribonucleic acid (RNA). The action on RNA seems to be independent of protein synthesis.

Effect of Bactericidal Substance from Staphylococcus aureus on Group A Streptococci II. Structural Alterations

Ultrastructural alterations brought about by treatment of a beta-hemolytic streptococcus with a bactericidal substance from Staphylococcus aureus are described and illustrated. The substance causes an early condensation of nucleoid deoxyribonucleic acid (DNA) and a partial loss of ribosomes. These changes are followed by a dissolution of the cell contents resulting in bacterial "ghosts" composed of empty cell wall and capsule. These morphological findings correlate with known biochemical effects of the bactericidal substance on ribonucleic acid degradation and cessation of DNA and protein synthesis.

Experimental infection of the skin in the hamster simulating human impetigo. III. Interaction between staphylococci and group A streptococci

The interaction between staphylococci and Group A beta hemolytic streptococci in mixed lesions was investigated in an experimental impetigo model. A strain of staphylococcus of phage Type 71, which has been shown in vitro to produce a bacteriocin for streptococci and other Gram-positive organisms, eliminates or reduces Group A streptococci in mixed lesions. In contrast, staphylococcal strains of phage Types 75 and 81, which do not produce a demonstrable bacteriocin in vitro, exhibit no such effect. Some variation was noted in the in vivo response of two different streptococcal M Types to the bactericidal effect of phage Type 71 staphylococci. Bacterial antagonism is more pronounced when staphylococci and streptococci are injected simultaneously into animals than when staphylococci are superimposed on preexisting streptococcal lesions. Marked variations were found in the numbers of viable streptococci (colony-forming units) recovered from individual lesions containing identical mixtures of streptococci and phage Type 71 staphylococci. The frequency of a demonstrable bactericidal effect was related to the number of streptococci injected. With small inocula of streptococci, the tendency towards an all-or-none effect was particularly striking. No evidence of selection of streptococcal or staphylococcal mutants which might explain this phenomenon was obtained. These observations suggest that the bactericidal effect of phage Type 71 staphylococci on other Gram-positive organisms, previously demonstrated in vitro, appears to operate also in vivo.

Genetic analysis of the bacteriocin-encoding plasmids pRJ6 and pRJ9 of Staphylococcus aureus by transposon mutagenesis and cloning of genes involved in bacteriocin production

pRJ6 and pRJ9, small Staphylococcus aureus plasmids which code for bacteriocins, exhibited a bactericidal activity against several lactic acid bacteria and strains of Listeria monocytogenes, an important food-borne pathogen. Filter-mating experiments using plasmid derivatives tagged with either Tn551 or Tn917-lac showed that pRJ6, but not pRJ9, could be mobilized by staphylococcal conjugative plasmids. Transposon mutagenesis of both plasmids was also performed. The bacteriocin and immunity structural genes of pRJ6 are part of the same operon, which is located around co-ordinate 4.0, being transcribed from right to left. However, gene cloning experiments using a staphylococcal vector showed some evidence for the involvement of additional functions of pRJ6 in bacteriocin expression. One function involved in pRJ6 mobilization mapped around co-ordinate 5.2, and it appears to be transcribed from left to right. The bactericidal action exerted by strains harbouring pRJ9 appears to reflect the activity of at least two bacteriocins, whose combined action results in a broader spectrum of activity and in a higher antagonistic activity. Gene cloning experiments also supported these assumptions.

Two-component anti-Staphylococcus aureus lantibiotic activity produced by Staphylococcus aureus C55

Staphylococcus aureus C55 was shown to produce bacteriocin activity comprising three distinct peptide components, termed staphylococcins C55alpha, C55beta, and C55gamma. The three peptides were purified to homogeneity by a simple four-step purification procedure that consisted of ammonium sulfate precipitation followed by XAD-2 and reversed-phase (C8 and C18) chromatography. The yield following C8 chromatography was about 86%, with a more-than-300-fold increase in specific activity. When combined in approximately equimolar amounts, staphylococcins C55alpha and C55beta acted synergistically to kill S. aureus or Micrococcus luteus but not S. epidermidis strains. The N-terminal amino acid sequences of all three peptides were obtained and staphylococcins C55alpha and C55beta were shown to be lanthionine-containing (lantibiotic) molecules with molecular weights of 3,339 and 2,993, respectively. The C55gamma peptide did not appear to be a lantibiotic, nor did it augment the inhibitory activities of staphylococcin C55alpha and/or C55beta. Plasmids of 2. 5 and 32.0 kb are present in strain C55, and following growth of this strain at elevated temperature (42 degreesC), a large proportion of the progeny failed to produce strong bacteriocin activity and also lost the 32.0-kb plasmid. Protoplast transformation of these bacteria with purified 32-kb plasmid DNA regenerates the ability to produce the strong bacteriocin activity.

Staphylococcin 1580 is identical to the lantibiotic epidermin: implications for the nature of bacteriocins from gram-positive bacteria

Staphylococcin 1580 was purified to homogeneity from culture supernatants of Staphylococcus epidermidis 1580 by means of adsorption to XAD 2, cation exchange chromatography, and high-performance liquid chromatography on reversed-phase C18. The purified active substance migrated in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent M(r) of approximately 2,000. Amino acid analysis, mass determination (2,165 Da) and N-terminal sequencing (Ile-Ala-Xaa-Lys-Phe-Ile-Xaa-Xaa-Pro-Gly-Xaa-Ala-Lys-block) demonstrated that staphylococcin 1580 is identical to epidermin, a lanthionine-containing antibiotic peptide (lantibiotic).

Effect of various inducing agents on bacteriocin (klebocin) production by Klebsiella pneumoniae

The influence of various inducing agents on growth, synthesis and release of klebocin by Klebsiella pneumoniae was studied. A significant level of klebocin was detected only after induction. The highest level of klebocin was achieved with mitomycin C followed by rifampicin and polymyxin B. Chloramphenicol and UV irradiation did not show any effect on klebocin production. Maximum klebocin release occurred after 8 h of induction with all the agents. Concentration of mitomycin C did not show any significant effect on klebocin production.

Production of a bacteriocin, ulceracin 378, by Corynebacterium ulcerans

The production of the bacteriocin ulceracin 378 by Corynebacterium ulcerans 378 was demonstrated during the growth of the organism on solid medium. Ulceracin 378 was not found in broth cultures and could not be extracted from the organisms by various solvents and salt solutions. Ulceracin 378 was not inducible by UV irradiation or mitomycin C treatments. Ulceracin 378 was active against all of the C. ulcerans strains tested and some related species, but it was not autoinhibitory. The active material was not phage related and was extracted from cultures grown on semisolid media composed of proteose peptone, Tween 80, Casamino Acids, glycerol, and sodium chloride. The yield was significantly reduced by either increasing the agar concentration or omitting Tween 80. Ulceracin 378 was resistant to DNase, RNase, phospholipases C and D, and alkaline phosphatase but was susceptible to proteolytic enzymes. This suggests that the active principle of ulceracin is protein in nature. Ulceracin 378 was partially purified by ammonium sulfate fractionation, dialysis, and chromatography on DEAE-cellulose.

Purification of the viridicin produced by Aerococcus viridans

A new bacteriocin produced by Aerococcus viridans was purified. Bacteria grown on liquid medium synthesized a bacteriocin, viridicin, which can be extracted from the cells by treatment with 0.86 M NaCl solution. Viridicin production was not induced by ultraviolet irradiation or by treatment with mitomycin C. The bacteriocin was purified by ultrafiltration, gel filtration, and preparative polyacrylamide disc gel electrophoresis. The molecular weight was between 100,000 and 120,000. The purified viridicin was homogeneous on polyacrylamide gel electrophoresis. The viridicin was composed of protein, carbohydrate, and lipid.

Production and properties of a staphylococcin genetically controlled by the staphylococcal plasmid for exfoliative toxin synthesis

Previous data from this laboratory showed that certain phage group 2 staphylococci contain a large 56S virulence plasmid containing genes that code for both exfoliative toxin (ET) and a specific staphylococcin. Optimal cultural conditions for bacteriocin production were similar to those found for ET production. The bacteriocin is an extracellular product produced in small quantities that can be neither extracted from cell pellets with 1 M NaCl nor induced with mitomycin C. The staphylococcin is active against a wide variety of gram-positive organisms and also against group 2 staphylococcal strains that have been cured of the plasmid carrying the staphylococcin marker. The bacteriocin is not inactivated by oxidation, mechanical agitation, or boiling for 15 min. It is sensitive to the action of trypsin and Pronase but not lysostaphin and is stable within a pH range of 4 to 9. It has an isoelectric point of approximately 7.7. Removal of the ampholytes and glycerol from electrofocused staphylococcin preparations resulted in total loss of bacteriocin activity.

Viridins, bacteriocins of alpha-hemolytic streptococci: isolation, characterization, and partial purification

Bacteriocin-like activities were detected in 78% of 120 alpha-hemolytic streptococcal isolates. Inhibitory substances from three such isolates (one Streptococcus sanguis strain and two S. mitis strains) were investigated further and termed viridins (A, B, and C). The viridins were unique among bacteriocins of gram-positive bacteria in that they inhibited many gram-negative bacteria in addition to inhibition of a variety of gram-positive organisms. Viridins were obtained in a cell-free state only after mechanical disruption of bacteriocinogenic cells but could not be isolated from supernatant fluids of cultures of such bacteria or from freeze-thaw liquor of agar on which the bacteria had been grown. Viridin B could be partially purified by ammonium sulfate precipitation and by gel filtration on a Sephadex G-100 column. This bacteriocin had some unusual properties including heat lability, a narrow pH range of activity, and lack of adsorptive capacity to susceptible bacteria. Although viridin B was bactericidal to a Neisseria sicca strain, it was only bacteriostatic against a coagulase-negative staphylococcus.

Effect of ethidium bromide on elimination of exfoliative toxin and bacteriocin production in Staphylococcus aureus

The scalded skin syndrome has been associated with phage group II staphylococci. The clinical manifestations of scalded skin syndrome, Ritter's disease, scarlatiniform erythema, and localized bullous impetigo, are due to the production of an extracellular protein, designated exfoliative toxin. Phage group II staphylococci can also produce an extracellular protein, bacteriocin, which is bacteriocidal for specific gram-positive microorganisms. Strain UT 0007 produces both bacteriocin and exfoliative toxin which appear to be products of extrachromosomal genes. These genes are jointly eliminated from strain UT 0007 after growth in either ethidium bromide or at high temperatures.

Group A streptococcal bacteriocin. Production, purification, and mode of action

A bacteriocin, streptocin A, was isolated from the supernatant fluid of tryptic soy broth cultures of Group A streptococcus strain FF-22. Evidence was obtained which supports the view that the failure to recover active streptocin A after growth of the producer strain in certain fluid media is due to the inactivation of the bacteriocin by concomitantly synthesized streptococcal proteinase. The bacteriocin was purified 139-fold and the active product appeared to be of uniform size, having a molecular weight of approximately 8,000. Streptocin A was bactericidal, but not lytic, for a susceptible Group A streptococcus and the lethal effect was markedly temperature dependent. The bacteriocin inhibited the synthesis of DNA, RNA, and protein, and also prevented the uptake and incorporation of glucose by the sensitive cells. Degradation of RNA occurred, but appeared to be less than that produced by a staphylococcal bacteriocin. This effect may be due to differences in the killing potency of the two bacteriocins in preparations having similar inhibitory activity when measured by lawn culture assays.

Isolation and characterization of a bacteriocin from a homofermentative Lactobacillus

Nearly 100 isolates of Lactobacillus were obtained from human and animal sources. Screening tests with the isolates revealed seven possible bacteriocinogenic strains and 26 strains sensitive to one or more of these inhibitory strains. Three homofermentative strains were selected for additional study after it was shown that their inhibitory substances differed in activity spectrum and in susceptibility to inactivation by proteolytic enzymes. One of these, L. helveticus strain LP27, was shown to produce a potent bacteriocin called lactocin 27. The lactocin was isolated from the culture supernatant fluid as a protein-lipopolysaccharide complex. In the presence of sodium dodecyl sulfate the complex was dissociated, and the activity was found to reside in a small glycoprotein (molecular weight 12,400). The amino acid composition of purified lactocin 27 is similar to that of the L. fermenti bacteriocin; neither requires disulfide bonds for activity.

Bacteriocin of a group A streptococcus: partial purification and properties

The production of bacteriocin-like inhibition by certain strains of group A streptococci was demonstrated during the growth of these organisms on solid nutrient media. Active bacteriocin could not be recovered from broth cultures, possibly because of its inactivation by streptococcal proteinase. The bacteriocin, streptocin A, produced by Streptococcus pyogenes strain FF-22 was partially purified by chemical precipitation and chromatography on carboxymethyl-cellulose. Streptocin A inhibited the growth of various gram-positive organisms but none of a wide range of different gram-negative strains. The bacteriocin was inactivated by proteolytic enzymes and, although labile in alkali, it was extremely stable to heating in mild acids.

Kinetic studies on the interaction of bacteriophage type 71 staphylococcal bacteriocin with susceptible bacteria

Kinetic studies on the interaction of the bacteriocin produced by phage type 71 Staphylococcus aureus with susceptible bacterial cells were undertaken. Survivors among susceptible bacteria to which the bacteriocin has been added can be rescued after trypsin treatment. The bacteriocin adsorbs very rapidly to susceptible streptococcal cells at a time when killing of the cells is only minimal. Heat-killed or mechanically disrupted cells are also effective in adsorbing the bacteriocin. Adsorption is comparable at 37 C and 25 C, but is less pronounced at 4 C. Elution of adsorbed bacteriocin could not be achieved by heating, by varying pH, or by using different concentrations of sodium chloride solutions. Surface M protein of streptococcal cells plays no role in the adsorptive process. Adsorption is specific in that only susceptible bacteria, but not resistant ones, are capable of adsorbing the bacteriocin.

Mode of action of a Staphylococcus epidermidis bacteriocin

Staphylococcin 1580, a bacteriocin produced by Staphylococcus epidermidis 1580, is bactericidal to sensitive cells of many gram-positive bacteria and stable staphylococcal L-forms. The bacteriocin inhibited simultaneously the syntheses of deoxyribonucleic acid, ribonucleic acid, and protein, and caused neither degradation of deoxyribonucleic acid nor induction of phages in lysogenic, sensitive cells. After 1 hr of treatment, extensive degradation of ribonucleic acid occurred, which was accompanied by leakage of ultraviolet-absorbing material out of the cell. The incorporation of glucose in acid-precipitable and glycogenlike material was inhibited. Furthermore, the staphylococcin inhibited the transport of glucose, glutamic acid, rubidium ions, and o-nitrophenyl-beta-galactoside. The uptake of oxygen was only gradually affected, but the intracellular adenosine triphosphate level fell rapidly to 15% of the control value. The motility of sensitive Bacillus subtilis cells was markedly reduced on treatment. Staphylococcin 1580 exhibited no phospholipase activity. The phenomena are interpreted as resulting from an altered conformation and composition of the membrane, from an inhibition of transport through the membrane, or from a combination of these effects.

Natural history of impetigo. II. Etiologic agents and bacterial interactions

Intensive observations on 37 children in a population with endemic skin infections provided an opportunity to study the interrelationships between and the significance of the bacterial genera commonly associated with impetigo. Cultures of the respiratory tract, three normal skin sites, and lesions, when present, were taken three times weekly from July to October 1969. Impetigo developed in all 37 children. Group A streptococci alone were recovered from 21% of 361 lesions, Staphylococcus aureus alone from 8%, Staphylococcus epidermidis alone from 5% and mixtures of streptococci and staphylococci from 61%. Vesicular or pustular lesions were more often pure streptococcal than pure staphylococcal. Streptococci alone were more often recovered from early stage lesions rather than from later ones. The pure staphylococcal lesions characteristically occurred early in the season whereas streptococcal or mixed lesions had later peaks.Serial observations on 74 lesions revealed longer persistence of streptococci than staphylococci in mixed lesions. In 85% of the instances the same streptococcal serotype was recovered repeatedly from an individual lesion, whereas staphylococcal types changed in 57% of instances. Phage type 75 accounted for the majority of staphylococcal isolates from all sites, whereas phage type 54 was recovered only from skin lesions. In contrast to streptococci, the site sequence of staphylococcal spread was from the nose to normal skin to skin lesions. These studies reveal important differences in the migration of staphylococci (as compared with streptococci) to various body sites and suggest a subsidiary role for staphylococci in nonbullous impetiginous lesions yielding both organisms.

Production and purification of a Staphylococcus epidermidis bacteriocin

Liquid cultures of Staphylococcus epidermidis 1580 contained rather small amounts of a bacteriocin, staphylococcin 1580, which was found both in the supernatant fluid and in the cell pellet. It could be extracted from the cells with 5% NaCl solution. The staphylococcin production could not be induced by ultraviolet irradiation or treatment with mitomycin C. Bacteria grown on semisolid medium produced a much larger amount of the compound with a high specific activity. The staphylococcin was purified by ammonium sulfate precipitation, ultracentrifugation, and chromatography on Sephadex columns. The purified material was homogeneous on polyacrylamide gel electrophoresis. The molecular weight was between 150,000 and 400,000. The bacteriocin was composed of protein, carbohydrate, and lipid and consisted of subunits exhibiting a molecular weight of about 20,000.

Nature and properties of a Staphylococcus epidermidis bacteriocin

Staphylococcin 1580, produced by Staphylococcus epidermidis 1580, consisted of 41.8% protein, 34% carbohydrate, and 21.9% lipid. In the protein fraction, the acidic amino acids, glutamic and aspartic acid, and the neutral amino acids, glycine and alanine, predominated. Neutral sugars consisted of glucose, galactose, and fucose in a molar ratio of 6:3:1. The purified bacteriocin was not inactivated by heating for 15 min at 120 C in the presence of 0.5% serum albumin and was stable in the pH range from 3.5 to 8.5. The compound was sensitive to the action of the proteolytic enzymes trypsin, Pronase, and chymotrypsin. All gram-negative bacteria tested were resistant; a large number of gram-positive bacteria were sensitive to staphylococcin 1580 action. Growth of stable staphylococcal L-forms was inhibited by the bacteriocin to the same extent as their parent strains. The staphylococcin was adsorbed to cell walls, cell membranes, and resistant cells. The effect of staphylococcin 1580 appeared to be bactericidal but not bacteriolytic.

Structural changes in Clostridium botulinum type E after treatment with boticin S5 1

Treatment with boticin S5(1), a bacteriocin produced by a nontoxigenic organism closely related to Clostridium botulinum type E, caused extensive changes in the structure of a sensitive C. botulinum type E strain. Nucleoid deoxyribonucleic acid, normally seen as fine filaments scattered throughout the cell, was aggregated into dense deoxyribonucleic acid masses. Mesosomes appeared to undergo structural rearrangement from lamellar to vesicular configuration. Eventual dissolution of cell contents left bacterial ghosts composed of seemingly intact cell walls with remnants of the cytoplasmic membrane and internal structures. The morphological changes observed in boticin-treated strain 070 cells were very similar to those produced by a bacteriocin-like substance from phage type 71 Staphylococcus aureus on sensitive beta-hemolytic streptococci. A similarity in the mode of action of the two bactericidal agents is suggested.