Effect of Carbohydrates on Hemolysin Production by Escherichia coli

The production of hemolysin by Escherichia coli after adding various carbohydrates to starved cultures was investigated.

Identification of antigenic sites on staphylococcal enterotoxin B and toxoid

The staphylococcal enterotoxins (SEs) are capable of causing both food poisoning and a toxic shock-like illness in man. In addition, SEs are known to act as superantigens, stimulating T-cells according to their T-cell receptor Vbeta type. Relatively little is known of their antigenic determinants and how these may relate to the structure and function of the toxins. As a step in the study of these relationships, the entire molecule of SEB was synthesized in duplicate as a series of octapeptides overlapping by seven residues. This series thus represented all the potential linear epitopes of eight residues or less. The reactivity of the octapeptide series with antisera raised to purified SEB and to formaldehyde-inactivated SEB has been used to locate several antigenic sites on native SEB and to identify antigenic differences in the toxoid. Three antigenic peptides identified from the antigenic profile were synthesized and characterized. These represented amino acids 21-32, 93-107 and 202-217 of SEB. None of these peptides affected SEB-induced T-cell proliferation. However, the occurrence or absence of cross-reactivity of these peptides with antibodies to native SEB corresponds to the degree of exposure and/or the rigidity of these regions within SEB.

Stimulation of rat spleen cells by staphylococcal enterotoxins

There is much interest in staphylococcal enterotoxins as T cell mitogens in humans, mice and rabbits. Rat spleen cells were shown to proliferate in response to staphylococcal enterotoxins A and B and toxic shock syndrome toxin-1 at concentrations (5 to 500 ng ml-1) which also stimulate mouse spleen cells. The proliferative response to all these enterotoxins was inhibited by cyclosporin A, indicating the response to be predominantly that of T cells. These results indicate that the rat provides another convenient model for the analysis of T cell responses to enterotoxins.

Investigation of microbial growth in vivo: evaluation of a novel in vivo chamber implant system

An intraperitoneal chamber implant system has been used to investigate the phenotype of Staphylococcus aureus growing in the rat and the effect of the antibiotic flucloxacillin on bacterial growth in vivo. Titanium chambers were implanted in the peritoneum: a period of 3-4 days equilibration allowed diffusion of host proteins into the chamber fluid prior to inoculation with bacteria. S. aureus inoculated into the chamber fluid, grew rapidly over a 72 h period, reaching counts of > 10(9) per ml. Organisms harvested from chambers were analysed by SDS-PAGE and showed significant differences in polypeptide profiles from the same strain grown in nutrient broth in vitro. Analysis of whole cell extracts by Western-blotting revealed that protein A expression was repressed in S. aureus grown in vivo. Following subcutaneous administration, flucloxacillin levels in serum peaked earlier and were higher than those detected in chamber fluid. The inhibitory effect of the antibiotic on the growth of S. aureus in chambers in treated animals could be monitored easily by sequential sampling of the chamber fluid. These results indicate the potential of the chamber implant model for investigation of microbial phenotype in vivo and development of alternative methods for assessment of antimicrobial efficacy in vivo.

Cell envelope proteins of Staphylococcus epidermidis grown in vivo in a peritoneal chamber implant

Staphylococcus epidermidis was grown in vivo in chambers implanted intraperitoneally in rats. The cell wall and cytoplasmic membrane protein profiles of the in vivo-grown organisms were compared with those of S. epidermidis grown in vitro in nutrient broth (NB), in iron-restricted NB, or in pooled human peritoneal dialysate (HPD). Compared with growth in broth and in common with growth in HPD, growth in vivo in chambers resulted in the repression of many S. epidermidis wall proteins, with proteins of 27, 42, 54, and 70 kDa predominating. Growth in vivo also resulted in the induction of two iron-repressible cytoplasmic membrane proteins of 32 and 36 kDa, which were also present in staphylococci grown in HPD and in iron-restricted NB. Immunoblotting experiments revealed that in sera taken 21 days after inoculation of the intraperitoneal chambers, the predominant antibody response to cell envelope proteins was directed against the 32- and 36-kDa iron-repressible membrane proteins.

Characterization of staphylococcal gamma-lysin

gamma-Lysin was purified from Staphylococcus aureus strains Smith 5R and PG23 (a toxic shock syndrome isolate) by a combination of heparin-agarose and hydroxylapatite chromatography. Both strains produced two haemolytic components, designated gamma 1 and gamma 2. Though each component was weakly haemolytic they acted synergistically to potentiate haemolysis on rabbit, sheep and human blood. Rabbit and sheep erythrocytes were more sensitive to lysis by gamma-lysin than human erythrocytes. The molecular mass of gamma 1 was 32 kDa and its pI value was 9.4. gamma 2 had a molecular mass of 36 kDa and a pI value of 9.3. While both trypsin and papain acted synergistically with gamma 2 to induce increased haemolysis, no such synergism was seen with gamma 1. Also, protease inhibitors acted to inhibit synergism between gamma 1 and gamma 2. These findings suggest that gamma 1 could be a protease.

Development and design of a novel in vivo chamber implant for the analysis of microbial virulence and assessment of antimicrobial therapy

An accurate reflection of the pathogenicity of microorganisms and the therapeutic effects of antimicrobial agents on their growth necessitates testing within an in vivo environment. We have developed a novel diffusion chamber, incorporating two 0.22 microns membrane filters, for the growth of in vivo organisms. The chamber, which is implanted intraperitoneally into the rat, has an external sampling portal. This portal allows multiple and sequential sampling of the microbial inoculum without killing the rat, thus significantly reducing the total number of animals used in such studies. In addition, the chamber is superior to other reported implants since it is well tolerated, reusable, easily constructed and can be used within two days of implantation. Staphylococcus epidermidis and a toxic shock syndrome toxin-1 (TSST-1) producing strain of S. aureus have been successfully grown within in vivo chambers, with 10(8)-10(9) organisms per millilitre being recovered within 48 h. Scanning electron microscopy revealed clusters of staphylococci and fibrous material adhering to the inner surface of the filters, with numerous phagocytic cells attached to the outer side. Western immunoblotting indicated that higher levels of TSST-1 were produced by S. aureus grown in vivo as opposed to cells grown in vitro.

A toxic shock syndrome toxin mutant of Staphylococcus aureus isolated by allelic replacement lacks virulence in a rabbit uterine model

The gene coding for toxic shock syndrome toxin-1 in S. aureus was inactivated by allelic replacement in two TSS-associated strains. One mutant derived from FRI1169 (a non-enterotoxigenic strain) lacked virulence in the rabbit uterine chamber infection model. This suggests that TSST-1 is the only determinant produced by this strain that can induce the symptoms of shock in rabbits. A novel method for allelic replacement involving transduction of plasmid integrants is described.

Staphylococcus aureus bacteriophages mediating the simultaneous lysogenic conversion of beta-lysin, staphylokinase and enterotoxin A: molecular mechanism of triple conversion

A new group of serotype F bacteriophages of Staphylococcus aureus has been found which mediates the simultaneous triple-lysogenic conversion of enterotoxin A, staphylokinase and beta-lysin. The phages were recovered fro methicillin-resistant strains of S. aureus isolated in Irish hospitals between 1971 and 1988 and from strain PS42-D, which has been used as the propagating strain for the S. aureus typing phage 42D since before 1965. The molecular mechanism of triple conversion mediated by three of these phages was determined by molecular cloning, restriction endonuclease site mapping and hybridization analysis, and compared with the mechanism of beta-lysin and staphylokinase conversion mediated by the serotype F, double-converting phase phi 13. THe genetic determinants mediating expression of enterotoxin A (entA) and staphylokinase (sak) were cloned from the DNA of the triple-converting phage and expression of the cloned determinants detected in Escherichia coli and S. aureus. The entA and sak determinants were closely linked in the phage DNA adjacent to the phage attachment site (attP) in each case and furthermore, the sak determinant of phage phi 13 was also located near its attP. The restriction maps of the entA-, sak- and attP-containing DNA regions of the three triple-converting phages were very similar to each other and to the corresponding sak- and attP- containing DNA region of phage phi 13. Hybridization analysis using a cloned beta-lysin determinant (hlb) and cloned attP-containing DNA fragments as probes demonstrated that beta-lysin conversion mediated by the triple-converting phages and phage phi 13 was caused by insertional inactivation of the chromosomally encoded hlb determinant by orientation-specific integration of phage DNA following lysogenization.

Enterotoxin production by Staphylococcus aureus isolates from cases of septicaemia and from healthy carriers

In a prospective study, 52 Staphylococcus aureus isolates from individual patients with septicaemia and 27 nasal strains from separate, healthy carriers were compared for production of a range of extracellular proteins and toxins. Whereas there was no difference (p greater than 0.05) between septicaemic and nasal isolates with respect to incidence of alpha, beta, gamma and delta haemolysins, toxic shock syndrome toxin-1 or staphylokinase production, the incidence of enterotoxin A, B, and C production was higher among isolates from septicaemia (p less than 0.01). Of the isolates from septicaemia, 33 (63%) produced enterotoxins A, B, C or D alone or in combination. Only three (11%) of the nasal isolates produced a single enterotoxin, enterotoxin D. Of the isolates from septicaemia, 67% were hospital-acquired and greater than 25% of these were endemic, methicillin-resistant (MRSA) strains. All MRSA strains produced either enterotoxin A, or enterotoxin B, or both. These findings suggest a possible role for enterotoxins in the pathogenesis of S. aureus disease other than food poisoning.

Damaging effect of toxic shock syndrome toxin 1 on chick embryo cells in vitro

The lethal effect of staphylococcal toxic shock syndrome toxin 1 (TSST-1) on rabbits and chick embryos is enhanced in the presence of lipopolysaccharide (LPS). In an investigation of the mode of action of TSST-1, its effect-both singly and in combination with LPS-on tissue culture cell lines was examined. Of a variety of cell lines examined for sensitivity to TSST-1 treatment, only primary chick embryo cells were susceptible. At a critical concentration (0.2 microgram/mL), TSST-1 alone caused detachment of the cell monolayer. In contrast, LPS per se had no visible effect on the cells at any concentration tested. TSST-1 in combination with LPS caused monolayer detachment at all concentrations of TSST-1 employed; thus detachment was independent of TSST-1 concentration in the presence of LPS. The ability of TSST-1 to disrupt the monolayer was neutralized in the presence of polyclonal rabbit antiserum to TSST-1. In a time course study over 24 hours, the effect of the toxin on the cells was initially visible by light microscopy after 4-7 hours. Clear differences in cellular morphology between TSST-1 treated monolayers and untreated controls were observed by scanning electron microscopy. Treated cells lost their normal spindle-shaped appearance before detachment.

A new methicillin- and gentamicin-resistant Staphylococcus aureus in Dublin: molecular genetic analysis

In June 1985 two new strains of methicillin- and gentamicin-resistant Staphylococcus aureus (MGRSA) were isolated in a Dublin hospital. Of these, one strain spread rapidly, affecting a total of 65 patients during the following 18 months, and subsequently spread to a second Dublin hospital. Detailed laboratory studies, including plasmid screening, plasmid restriction enzyme digest pattern analysis, hybridisation analysis, location of resistance determinants, and bacteriophage typing with a set of experimental S. aureus typing phages, demonstrated that the "new" MGRSA organisms, termed Phenotype III Dublin isolates, were completely distinct from, and unrelated to, the MGRSA strains responsible for serious nosocomial infections in Dublin hospitals during the decade before June 1985. These Phenotype III isolates were very similar to MGRSA organisms isolated in a Baghdad hospital during 1984. Data from plasmid curing, plasmid transfer and hybridisation experiments indicated that 20% of the Phenotype-III isolates expressed chromosomally encoded, high level resistance to ethidium bromide (MIC 120 micrograms/ml), and that this was possibly due to chromosomal integration of a penicillinase-like plasmid.

Molecular cloning and genetic analysis of the determinant for gamma-lysin, a two-component toxin of Staphylococcus aureus

The gamma-lysin determinant of Staphylococcus aureus strain Smith 5R has been cloned in phage lambda and plasmid vectors in Escherichia coli. Genetic evidence is presented which demonstrates that gamma-lysin requires the co-operative action of two polypeptides expressed by the closely linked hlgA and hlgB genes. Recombinants expressed haemolytic activity in agarose medium but not in agar, a known property of gamma-lysin. Haemolysis was inhibited by antiserum raised against the 32 kDa component of gamma-lysin, but not by anti-alpha-, anti-beta- or anti-delta-lysin serum. Subcloning and transposon Tn5 mutagenesis identified a 3.5 kb region which was necessary for gamma-lysin expression in E. coli. Two genes (hlgA and hlgB) were mapped and their polypeptide products identified. Non-haemolytic Tn5 mutants fell into two groups based upon complementation tests done between extracts of mutants in vitro and also between extracts of mutants and components of gamma-lysin purified from S. aureus culture supernates. Immunoblotting showed that some mutants in group A (defective in expression of hlgA) did not express a 32 kDa polypeptide which was synthesized by the parental haemolytic recombinant and by mutants in group B. Minicell analysis suggested that the products of the hlgB gene were proteins of 38 kDa and 36 kDa. The smaller molecule co-migrates with a protein in a fraction of the S. aureus culture supernate containing component B of gamma-lysin. The 38 kDa polypeptide is probably an unprocessed precursor. Southern hybridization demonstrated that the hlgA and hlgB genes are closely linked in the chromosome of several strains of S. aureus.

Induction of tumour necrosis factor by staphylococcal toxic shock toxin 1

Staphylococcal toxic shock syndrome toxin 1 (TSST1) induced the release of tumour necrosis factor (TNF) from human and rabbit monocytes in vitro. Nanogram amounts of TSST1 were sufficient to induce TNF release. There was considerable variation in response between cells from different rabbits and different donors. Rabbit monocytes were slightly more sensitive to TSST1 than were human monocytes. Release of TNF in vivo could explain many of the symptoms of toxic shock syndrome.

Toxic shock syndrome: a multisystem conundrum

First described in 1978, toxic shock syndrome (TSS) emerged as cause for public concern in 1980 as an acute multisystem disease syndrome associated with Staphylococcus aureus. Epidemiological, clinical and microbiological studies have revealed most of the pieces of the puzzle: a new toxin TSST-1, low antibodies in susceptible individuals, the presence of a focus of S. aureus infection. In menstrual TSS, the role of tampons has generated much controversy. Exactly how the pieces fit together to explain the pathophysiology of TSS at the cellular and molecular levels remains to be elucidated.

Colonial dissociation and susceptibility to phagocytosis of Pseudomonas aeruginosa grown in a chamber implant model in mice

Pseudomonas aeruginosa strains were grown in 1-cm plastic chambers sealed at both ends with porous Millipore filters and implanted in the peritonea of mice. Mucoid and nonmucoid strains of P. aeruginosa isolated from a patient with cystic fibrosis largely retained their phenotypes when grown for up to 1 year in this in vivo system, although colonial dissociation occurred, as observed in chronic lung infections of patients with cystic fibrosis. In the absence of added opsonins, P. aeruginosa M2 cells taken directly from the in vivo system were significantly more susceptible to phagocytosis than were the same P. aeruginosa cells after being washed in buffer. Phagocytosis of in vivo-grown P. aeruginosa cells could be further enhanced by using a porin protein F-specific monoclonal antibody.

Cloning and expression in Escherichia coli and Staphylococcus aureus of the beta-lysin determinant from Staphylococcus aureus: evidence that bacteriophage conversion of beta-lysin activity is caused by insertional inactivation of the beta-lysin determinant

The beta-lysin determinant (Hlb) from Staphylococcus aureus CN6708 was cloned in Escherichia coli K-12 using the bacteriophage replacement vector lambda L47.1. The Hlb determinant was localised to a 1250 base pair DNA sequence by cloning fragments from a Hlb+ recombinant phage into the plasmid vectors pACYC184 and pBR322 in E. coli K-12, and by the subsequent construction and analysis of several sub-clones, in vitro deletion and Tn5 insertion mutations. E. coli cells harbouring Hlb+ plasmids expressed readily detectable levels of beta-lysin and sphingomyelinase activity, which were located in the cytoplasm. Two polypeptides of molecular weight 38,000 and 33,000 which were encoded by the Hlb determinant were detected in E. coli minicells, but only the 33,000 dalton protein was detected in immunoblotting experiments with specific anti-beta-lysin serum. Hybridisation analysis with probes made from the cloned Hlb determinant and from DNA of the staphylokinase-converting phage phi 13, indicated that bacteriophage conversion of S. aureus to loss of beta-lysin activity is due to insertion of phi 13 DNA into or adjacent to the beta-lysin determinant. A shuttle plasmid was used to transfer the cloned Hlb determinant into a beta-lysin negative strain of S. aureus where the wild-type chromosomal determinant was inactivated by lysogenic conversion. Beta-lysin activity was readily detected in supernatants of S. aureus harbouring the cloned determinant.

Molecular typing of methicillin and gentamicin resistant Staphylococcus aureus in Dublin

The high incidence of infection in Dublin hospitals caused by non-typable strains of methicillin- and gentamicin-resistant Staphylococcus aureus (MGRSA) has created an important epidemiological problem as conventional methods of sub-dividing these organisms have not been useful. This report describes a novel approach to the typing and analysis of MGRSA strains, particularly non-typable isolates, by comparing restriction endonuclease HindIII digest patterns of total cellular DNA; and by using Southern hybridization analysis to detect size variations or polymorphisms in restriction endonuclease cleavage fragments within small regions of the chromosome. Non-typable MGRSA strains and isolates belonging to two phenotypically related groups of phage-type 77 and 77/84 strains were readily subdivided on the basis of molecular size differences in high molecular weight DNA fragments generated by the enzyme HindIII. Restriction endonuclease fragment size polymorphisms were readily detected in many of the non-typable strains tested in hybridization experiments, and these were used for strain sub-division. Both techniques were useful tools for the separation of closely related MGRSA strains.

Expression of the cloned toxic shock syndrome toxin 1 gene (tst) in vivo with a rabbit uterine model

Toxic shock syndrome (TSS) toxin 1 (TSST1) is produced by strains of Staphylococcus aureus associated with TSS. Purified TSST1 induces in rabbits a shock-like illness with many features similar to TSS in humans. These symptoms were also induced by TSST1-producing bacteria in diffusion chambers implanted in the rabbit uterus. Naturally occurring TSST1+ strains and a TSST1- strain harboring a pE194-derived plasmid carrying the cloned TSST1 determinant tst gave the same symptoms. TSST1- strains and a TSST1- strain carrying a pE194-tst plasmid with a deletion of the tst gene had no effect in rabbits. The results with the plasmid-carrying TSST1+ and TSST1- strains, which were isogenic apart from tst, show that the toxin is responsible for the illness in rabbits and suggest that it is a major factor in the pathogenesis of TSS.

Effect of toxic shock syndrome toxin 1 on chicken embryos

Staphylococcus aureus strains associated with toxic shock syndrome produce toxic shock syndrome toxin 1 (TSST1). This toxin has a variety of biological effects, including enhanced lethality in rabbits in the presence of sublethal amounts of lipopolysaccharide (LPS). Because chicken embryos are highly susceptible to LPS, the synergistic effect of TSST1 and LPS was examined in this system. Although TSST1 per se had no effect on chicken embryos, it potentiated the lethal effect of LPS. The 50% lethal dose of LPS was greatly reduced in the presence of up to 10 micrograms of TSST1 per ml. However, at high doses of TSST1 (greater than 100 micrograms/ml), no enhanced lethality was observed. The lowest dose of TSST1 tested which potentiated lethality was 10 ng/ml.

Toxicity of staphylococcal toxic shock syndrome toxin 1 in rabbits

Strains of Staphylococcus aureus associated with toxic shock syndrome produce toxic shock syndrome toxin 1 (TSST 1), which is lethal to conventional rabbits and acts synergistically with gram-negative lipopolysaccharide. The lethal effect of TSST 1 was examined in specific-pathogen-free rabbits on the basis that these rabbits, being less colonized by gram-negative bacteria, would be less susceptible than conventional animals. Although there was no significant difference in mortality between specific-pathogen-free and conventional rabbits in response to 100 micrograms of TSST 1, there was a difference in response between Dutch belted rabbits and New Zealand white rabbits. Both specific-pathogen-free and conventional New Zealand white rabbits were more susceptible to TSST 1 than the Dutch belted strain. Pretreatment of conventional New Zealand white rabbits with polymyxin B neutralized the lethal effect of TSST 1.

Cloning, and expression in Escherichia coli K-12, of the chromosomal hemolysin (phospholipase C) determinant of Pseudomonas aeruginosa

A hemolysin determinant was cloned from Pseudomonas aeruginosa PA103 by inserting Sau3a-generated DNA fragments between the BamHI sites of the lambda replacement vector WL47.1. A 9.5-kilobase HindIII fragment encoding the hemolysin was subcloned from this phage and inserted into the plasmid vector pHC79 to generate the recombinant plasmid pKC95. Escherichia coli K-12 strains harboring pKC95 exhibited zones of hemolysis after several days of growth on blood agar plates. Hemolysis was shown to be due to phospholipase C activity by using the chromogenic substrate p-nitrophenylphosphorylcholine. Deletion mutants of pKC95 were isolated, and polypeptides expressed from these plasmids were examined by using the E. coli minicell system. A polypeptide of 78,000 daltons was associated with phospholipase C activity. The hemolytic activity was cell associated when expressed in E. coli.

Properties of Escherichia coli grown in vivo using a chamber implant system

Strains of Escherichia coli were examined for their ability to grow in diffusion chambers implanted into the peritoneal cavities of mice and rabbits. In rabbit chambers E. coli K12 strains grew poorly, whereas isogenic strains harbouring ColV plasmids and wild-type isolates from extra-intestinal infections grew well. The difference was much less marked with strains grown in mouse chambers. Differences in sensitivity to the bactericidal action of human or rabbit serum were found in some cases between organisms of the same strain grown in vivo or in vitro. Host immunoglobulins were bound to the surface of all in vivo bacteria. Comparison of the polypeptide composition of bacterial cell envelope preparations on SDS-PAGE gels revealed differences between in vivo and in vitro grown E. coli growing in vivo may possess properties significantly different from the same organisms growing on laboratory medium.

Staphylococci associated with toxic shock syndrome in the United Kingdom

Only 15 cases of menstrual toxic shock syndrome were reported in the United Kingdom by 31 October 1981. The women affected used tampons of various brands. Staphylococcus aureus was isolated from the vaginas of 12 women. Two distinct strains were isolated from three women. Most strains were phage group I or nontypable strains related to them and were resistant only to penicillin, cadmium, and arsenate. Enterotoxin F was produced by strains from 10 of 12 patients and by 20% to 30% of strains from other sources--including healthy people. Its production was particularly common among control phage group I vaginal isolates. The reason for the rarity of toxic shock syndrome in the United Kingdom as compared to the United States is still unknown. There does not seem to be a low prevalence of toxigenic strains, but factors such as immunity to toxin and a difference in tampon use may be important and need further study.

Prevalence of epidermolytic toxin in clinical isolates of Staphylococcus aureus

One hundred and sixteen strains of Staphylococcus aureus isolated from exfoliative skin lesions were screened for their ability to produce different serotypes of epidermolytic toxin (ET). Toxin production was assessed by immunodiffusion, analytical isoelectric focussing and examination for the Nikolsky sign in mice. Of 84 strains of phage group II, 72 (85.7%) were toxinogenic as were 10 of 32 (31.3%) non-group-II strains. The ability to produce ET serotypes A and B was not confined to a particular phage group.

Plasmids in epidermolytic strains of Staphylococcus aureus

Thirty-four epidermolytic toxin-producing strains of Staphylococcus aureus obtained from a variety of sources were screened for the presence of plasmid DNA. All serotype ii toxin producers harboured a large 42 kilobase pairs (kb) plasmid. Elimination of these plasmids resulted in the simultaneous loss of a bacteriocin determinant (Bac+) and type ii toxin production (Toxii+). Some strains producing serotype i toxin (Toxi+) contained similar 42 kb plasmids. Elimination of these plasmids resulted in the loss of only bacteriocin production. Strains producing both toxin serotypes readily lost Toxii+ and Bac+, which were carried on the same plasmid, but Toxi+ could not be eliminated. Thus Toxi+ was probably chromosomally determined, while Toxii+ was a plasmid-encoded marker. In some strains cadmium resistance was also linked to the 42 kb plasmid. The 42 kb plasmids from seven strains with different phenotypes were analysed with restriction endonucleases EcoRI and HindIII. The plasmids shared 19 of 22 HindIII fragments indicating that they are closely related to each other.

A comparative study of two serotypes of epidermolytic toxin from Staphylococcus aureus

Two serotypes of epidermolytic toxin were purified from culture filtrates of different strains of Staphylococcus aureus. The amino acid composition of the proteins is similar, each containing no cystine and one methionine, but type ii contains no tryptophan, whereas type i has 1 mol/mol protein. The molecular weights of type i and type ii toxins were 30,000 and 29,500, respectively, as found by SDS-polyacryamide gel electrophoresis and confirmed by studies of CNBr fragments and tryptic peptides. Dansylation gave a single different N-terminal amino acid for each toxin; the C-terminus of each is lysine. Peptide mapping of tryptic digests showed that very few peptides are common to the two amino acid sequences.

Experimental staphylococcal infections in newborn mice: inhibition of weight gain as an index of virulence

We attempted to evaluate the neonatal mouse model as an indicator of the virulence of staphylococcal strains freshly isolated from human patients in hospital. In preliminary studies with two previously characterised clinical isolates of Staphylococcus aureus and one of S. epidermidis, three indices of infection were studied. These were: mortality rate, multiplication of organisms in the skin, and the effect on weight gain. Of these inhibition of normal weight grain by mice given subcutaneous injections when 3 days old was the most convenient and easily applied test. At a challenge dose of 10(6) c.f.u., the multiplication of organisms in the skin was correlated with the inhibition of normal weight gain. Weight gain was used to compare the virulence of a small series of clinical isolates from different types of staphylococcal infection. Strains isolated from severe infections caused a greater inhibition of weight gain than did strains from milder infections or environmental sources.

Age-related susceptibility of mice to staphylococcal infection

The virulence of six strains of staphylococci in experimental subcutaneous infection in mice of three age groups (3, 10 and 21 days) was studied. The results showed an age-related susceptibility to infection, in that the newborn mice were more susceptible than older mice to death and lesion formation. Resistance, i.e., ability to survive challenge of 10(7) c.f.u., developed at about 5 days. The strains used varied in toxin and enzyme pattern and there were marked differences in response to challenge as measured by mortality and lesion development. The Staphylococcus epidermidis strain was least virulent, while some strains of S. aureus produced lesions at low doses (10(4) c.f.u.). Two distinct types of lesion were observed, abscesses and necrotic lesions. Development of necrotic lesions appeared to be correlated with the ability to produce toxin in vitro.

Effect immunization with highly purified alpha- and beta-toxins on staphylococcal mastitis in rabbits

Experiments were carried out to determine whether immunization of female rabbits with highly purified staphylococcal alpha- or beta-toxins would protect them against intramammary challenge with staphylococci. High circulating anti-alpha-toxin titers reduced the lethal hemorrhagic edematous form of the disease ("blue-breast") produced by strains BB and Compton 201 to a localized chronic abscess form. No such protection was afforded by high anti-beta-toxin titers. Immunization with alpha- or beta-toxins produced no change in the clinical picture of the disease produced by CN.6708, a strain of Staphylococcus responsible for a natural outbreak of abscess-type rabbit mastitis. From these experiments it would appear that alpha-toxin is a key antigen in the blue-breast form of rabbit mastitis. Since the abscess form of the disease was not prevented by immunization with either alpha- or beta-toxin, other virulence factors must be acting to produce this more localized disease.

Effects of staphylococcal products on locomotion and chemotaxis of human blood neutrophils and monocytes

The effects of staphylococcal products as chemo-attractants for human blood neutrophils and monocytes and as inhibitors of locomotion of these cells were studied with bacterial cells, culture filtrates and isoelectrically focused fractions from culture filtrates of nine strains of Staphylococcus aureus. Little direct chemotactic activity of staphylococcal products for neutrophils was observed, although a chloroform-soluble extract of the whole organisms contained such activity. The major chemotactic effect of staphylococci for neutrophils was indirect, i.e., generated when the organisms or their products were incubated with plasma, perhaps due to activation of complement. In contrast, direct chemotactic activity for monocytes was found in a large number of staphylococcal fractions. Staphylococci also produced inhibitors of locomotion of both neutrophils and monocytes. Isoelectric focusing showed more fractions inhibitory for neutrophils than for monocytes. Some of the inhibitors could be identified. Staphylococcal alpha-toxin inhibited migration of both neutrophils and monocytes. Sphingomyelinase C (beta toxin) inhibited migration of monocytes but not of neutrophils. Leucocidin-rich strains were strongly active as inhibitors of neutrophil locomotion but less so as inhibitors of monocyte locomotion.

Qualitative and quantitative methods for detecting staphylococcal epidermolytic toxin

Concentrated supernates of cultures of 98 strains of Staphylococcus aureus were screened for the production of epidermolytic toxin by (1) biological tests in 3-day-old mice, (2) double-diffusion precipitation tests against specific antiserum, and (3) the appearance of characteristic protein bands on thin-layer-gel isoelectric focusing. Positive results were obtained in all three of these tests with supernates from 11 of these cultures; the same 11 strains, and no others, produced epidermal splitting when newborn mice were challenged with viable organisms. Of the 14 phage-group II strains included in the survey, eight (58%) produced epidermolytic toxin. Three toxinogenic strains belonged to phage groups other than group II. A radial-immunodiffusion test employing antiserum to purified epidermolytic toxin proved satisfactory for measuring amounts of epidermolytic toxin in excess of 200 mug per ml. The results of immunodiffusion tests indicated that six of the 11 positive strains produced two serologically distinct forms of epidermolytic toxin and that the remainder produced only one of these. A striking correlation was observed between the presence of toxin of serotypes i and ii and the occurrence of protein bands i and ii in thin-layer isoelectric-focusing gels. These tests should facilitate the qualitative and quantitative assessment of the production of different serotypes of epidermolytic toxin by S. aureus in future surveys of strains isolated from toxic epidermal necrolysis of Ritter's type and impetigo. The two forms of epidermolytic toxin previously designated ETA (pI=7-0) and ETB (pI=6-0) were detected by preparative isoelectric focusing of sero-type-i toxin. Evidence suggests that studies of the effect of heat should provide a means of investigating the relationship between the different molecular forms of epidermolytic toxin.

Action of staphylococcal epidermolytic toxin on mouse skin: an electron microscopic study

The ultrastructure of the skin of 3-day-old mice challenged with small doses of highly purified staphylococcal epidermolytic toxin was examined at various time intervals. Up to 130 min few changes were evident, but at this time wide gaps developed between cells in the horizontal planes of the stratum granulosum, and "bubbles" normally present in the intracellular spece were no longer apparent. Splitting of the desmosomes occurred after the development of distended intercellular spaces. After 20 hr, that is, in the "healing" phase, the appearance suggested that normal maturation of keratinocytes was altered. Also at this time a degree of cell separation was still apparent in the outermost actively maturing layer of the stratum granulosum. The proteinase inhibitor Trasylol was tested for its effect on the toxin when administered up to 45 min after challenge.

Interaction of Clostridium perfringens theta-haemolysin, a contaminant of commercial phospholipase C, with erythrocyte ghost membranes and lipid dispersions. A morphological study

Commercially available preparations of phospholipase C from Clostridium perfringens are commonly contaminated with theta haemolysin, one of a group of bacterial haemolysins called oxygen labile (O-labile) haemolysins. Treatment of erythrocyte ghosts and a mixed lipid dispersion containing cholesterol with commercially available phospholipase C in the absence of Ca-2+ and the presence of phosphate buffer and/or EDTA resulted in the formation and release of ring or arc-shaped structures. Highly purified phospholipase C, free of theta-haemolysin, produced no changes in the morphology of erythrocyte ghosts or lipid dispersions in the presence of phosphate or EDTA, but caused the formation of typical diglyceride droplets in the presence of Ca-2+ in the absence of these inhibitors. Ring structures, identical to those caused by commercial phospholipase C, were formed on addition of highly purified theta-haemolysin to erythrocyte ghost membranes, lipid dispersions containing cholesterol and cholesterol dispersions, but not on treatment of membranes from Micrococcus lysodeikticus. Heat-inactivated O-haemolysin (60 degrees C for 10 min) produced no such effects. The dimensions of rings and arcs displayed heterogeneity. The outside diameters in various preparations varied from approx. 27-58 nm with border thickness of 4.1-7.8 nm.