New and simple procedure for the determination of muramic acid in chemically complex environments by gas chromatography-ion trap tandem mass spectrometry

A gas chromatographic-ion trap tandem mass spectrometric method was developed for the quantification of muramic acid, a marker of bacterial peptidoglycan, in environmental and clinical specimens. Samples (bacteria, house dust and urine) were heated in methanolic hydrochloric acid overnight and extracted with hexane for removal of hydrophobic compounds. The aqueous phase was evaporated and heated in acetic anhydride and pyridine after which the product, the acetate derivative, was washed with dilute hydrochloric acid and water. The described method is both rapid and simple to apply, and produces a stable derivative. It should become widely used for measuring peptidoglycan in chemically complex environments.

Identification, characterization and purification of the lantibiotic staphylococcin T, a natural gallidermin variant

Staphylococcin T (StT), an antibacterial agent produced by a Staphylococcus cohnii T strain, was purified to homogeneity by ammonium sulphate precipitation, gel filtration, cation exchange and fast performance liquid chromatography (FPLC). The final yield was about 20%, and over a 1000-fold increase in the specific activity was obtained. Mass determination (2166 Da), amino acid sequencing (Ile-Ala-Xaa-Lys-Phe-Leu-Xaa-Xaa-Pro-Gly-Xaa-Ala-Lys-block) and DNA sequencing demonstrated that StT is identical to gallidermin, a lanthionine-containing antimicrobial peptide. StT has a broad spectrum of bactericidal activity against Gram-positive and some Gram-negative bacteria. StT appears to damage cell membrane, and as a result causes an efflux of ions and an immediate block in macromolecular synthesis. Moreover, electron microscopic observations reveal morphological changes, with a loss of ribosomes and condensation of the nucleoid DNA. These changes are followed by a dissolution of the cell contents resulting in a bacterial ghost composed of seemingly intact cell walls with remnants of the cytoplasmic membrane and internal structure. Since StT exhibits antimicrobial activity especially against the Staphylococcus species, this compound may be of use in the treatment of staphylococcal infections.

A method for extraction of high-quality and high-quantity genomic DNA generally applicable to pathogenic bacteria

In this study, we report a modified procedure for extraction of high-quality genomic DNA that is rapid, simple, biologically nonhazardous, and generally applicable to pathogenic bacteria. Bacterial cells were pretreated with 70% ethanol prior to enzymatic digestion with lysozyme. Exposure of bacterial cells to 70% ethanol sterilized the cultures, making the process biologically safe and increased the susceptibility of the cells to lysozyme-induced lysis. Consistently high yields of genomic DNA (mean average yield, 0.5-2.5 mg/ml) were obtained from 465 isolates representing over 30 clinically important bacterial species. Genomic DNA obtained was determined to be suitable for further analysis, including bacterial fingerprinting techniques like restriction endonuclease analysis, Southern hybridization, and repetitive PCR. Availability of a generally applicable procedure for extraction of high-quality and high-quantity genomic DNA would be immensely beneficial for laboratories engaged in molecular surveillance of nosocomial and community-based outbreaks.

HYPER: a hierarchical algorithm for automatic determination of protein dihedral-angle constraints and stereospecific C beta H2 resonance assignments from NMR data

A new computer program, HYPER, has been developed for automated analysis of protein dihedral angle values and C beta H2 stereospecific assignments from NMR data. HYPER uses a hierarchical grid-search algorithm to determine allowed values of phi, psi, and chi 1 dihedral angles and C beta H2 stereospecific assignments based on a set of NMR-derived distance and/or scalar-coupling constraints. Dihedral-angle constraints are valuable for restricting conformational space and improving convergence in three-dimensional structure calculations. HYPER computes the set of phi, psi, and chi 1 dihedral angles and C beta H2 stereospecific assignments that are consistent with up to nine intraresidue and sequential distance bounds, two pairs of relative distance bounds, thirteen homo- and heteronuclear scalar coupling bounds, and two pairs of relative scalar coupling constant bounds. The program is designed to be very flexible, and provides for simple user modification of Karplus equations and standard polypeptide geometries, allowing it to accommodate recent and future improved calibrations of Karplus curves. The C code has been optimized to execute rapidly (0.3-1.5 CPU-sec residue-1 using a 5 degrees grid) on Silicon Graphics R8000, R10000 and Intel Pentium CPUs, making it useful for interactive evaluation of inconsistent experimental constraints. The HYPER program has been tested for internal consistency and reliability using both simulated and real protein NMR data sets.

Staphylococcal surface display of immunoglobulin A (IgA)- and IgE-specific in vitro-selected binding proteins (affibodies) based on Staphylococcus aureus protein A

An expression system designed for cell surface display of hybrid proteins on Staphylococcus carnosus has been evaluated for the display of Staphylococcus aureus protein A (SpA) domains, normally binding to immunoglobulin G (IgG) Fc but here engineered by combinatorial protein chemistry to yield SpA domains, denoted affibodies, with new binding specificities. Such affibodies, with human IgA or IgE binding activity, have previously been selected from a phage library, based on an SpA domain. In this study, these affibodies have been genetically introduced in monomeric or dimeric forms into chimeric proteins expressed on the surface of S. carnosus by using translocation signals from a Staphylococcus hyicus lipase construct together with surface-anchoring regions of SpA. The recombinant surface proteins, containing the IgA- or IgE-specific affibodies, were demonstrated to be expressed as full-length proteins, localized and properly exposed at the cell surface of S. carnosus. Furthermore, these chimeric receptors were found to be functional, since recombinant S. carnosus cells were shown to have gained IgA and IgE binding capacity, respectively. In addition, a positive effect in terms of IgA and IgE reactivity was observed when dimeric versions of the affibodies were present. Potential applications for recombinant bacteria with redirected binding specificity in their surface proteins are discussed.

Development and evaluation of an indirect ELISA for detection of exfoliative toxin ExhA, ExhB or ExhC produced by Staphylococcus hyicus

Immunoblot analysis and enzyme-linked immunosorbent assay (ELISA) confirmed previous reports that the Staphylococcus hyicus exfoliative toxins ExhA and ExhB are metalloproteins, and further indicated that ExhC is also a metalloprotein. An indirect ELISA was developed for the detection of toxigenic strains as an alternative method to the use of phage typing for selection of S. hyicus isolates to be used in autogenous vaccine against exudative epidermitis in pigs. The indirect ELISA was evaluated by investigating the presence of toxin among a total of 655 S. hyicus isolates from 69 pig skin samples, one from each of the 69 pig herds with outbreak of exudative epidermitis. Toxigenic S. hyicus were detected in 74% of the cases by ELISA. From each of the five cases, in which initially no toxigenic S. hyicus were found, a further 40 S. hyicus-like colonies were tested in ELISA. Testing of this number of colonies has a >99% probability of disclosing toxigenic S. hyicus. Toxin-producing isolates were found in only two of the five cases investigated. This may indicate the existence of one or more variants of the exfoliative toxin of S. hyicus that are not detected in the indirect ELISA or that S. hyicus may be displaced from lesions of exudative epidermitis.

Staphylococcus schleiferi subsp. schleiferi expresses a fibronectin-binding protein

Staphylococcus schleiferi subsp. schleiferi is associated with a range of nosocomial infections, but the pathogenic mechanisms by which these occur are poorly understood. This study provides phenotypic and genotypic evidence for the expression of a cell wall-anchored fibronectin-binding protein by this species.

Serum amyloid A, cytokines, and corticosterone responses in germfree and conventional mice after lipopolysaccharide injection

To determine why germfree mice are less susceptible to lipopolysaccharide (LPS) than conventional mice, we studied serum levels of serum amyloid A (SAA), tumor necrosis factor (TNF), interleukin 1 (IL-1), IL-6, and corticosterone in mice after treatment with LPS. A single injection of LPS caused an elevation of SAA, an acute-phase protein in the mouse, in both conventional and germfree IQI mice, and the response was significantly less in germfree mice. LPS-induced elevations of serum TNF, IL-1, and IL-6 levels were also significantly less in germfree mice, while serum corticosterone levels were greater in germfree mice than in conventional mice. These results suggest that the lower susceptibility to LPS and a smaller response of SAA elevation by LPS in germfree mice may result from less elevation in serum of these cytokines in these mice, which are known to mediate the acute phase response of SAA. High levels of serum corticosterone in germfree mice may be partly responsible for the lower responsiveness of these inflammatory cytokines to LPS in these mice.

The staphylococcal alpha-toxin pore has a flexible conformation

The alpha-toxin from Staphylococcus aureus undergoes several conformational changes from the time it is released from the bacterium to the moment it forms a channel in the plasma membrane of its target cell. It is initially a soluble monomer, which undergoes membrane binding and oligomerization into a heptameric ring and finally inserts into the lipid bilayer to form a pore. Here we have analyzed the stability of different forms of the alpha-toxin (monomer as well as heptamers in solution, bound to the membrane and membrane-inserted) by differential scanning calorimetry and limited proteolysis. Data presented here show that, in contrast to both the membrane-bound prepore complex and the monomer in solution, the membrane-inserted alpha-toxin channel does not undergo cooperative unfolding and is highly susceptible to proteases. These observations suggest that the channel has a looser conformation. Interestingly, resistance to proteases could be recovered upon solubilization of the channel, indicating that the loss of rigid tertiary packing only occurred upon membrane insertion. Far-UV CD data, however, suggest that the transmembrane beta-barrel must be stably folded and that therefore only the Cap and Rim domains of the channel are loosely packed. All together, our data show that the alpha-toxin channel is not a rigid complex within the membrane but adopts a rather flexible conformation.

The staphylococcal transferrin-binding protein is a cell wall glyceraldehyde-3-phosphate dehydrogenase

Staphylococcus aureus and Staphylococcus epidermidis possess a 42-kDa cell wall transferrin-binding protein (Tpn) which is involved in the acquisition of transferrin-bound iron. To characterize this protein further, cell wall fractions were subjected to two-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis blotted, and the N-terminus of Tpn was sequenced. Comparison of the first 20 amino acid residues of Tpn with the protein databases revealed a high degree of homology to the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Analysis of staphylococcal cell wall fractions for GAPDH activity confirmed the presence of a functional enzyme which, like Tpn, is regulated by the availability of iron in the growth medium. To determine whether Tpn is responsible for this GAPDH activity, it was affinity purified with NAD+ agarose. Both S. epidermidis and S. aureus Tpn catalyzed the conversion of glyceraldehyde-3-phosphate to 1,3-diphosphoglycerate. In contrast, Staphylococcus saprophyticus, which lacks a Tpn, has no cell wall-associated GAPDH activity. Native polyacrylamide gel electrophoresis of the affinity-purified Tpn revealed that it was present in the cell wall as a tetramer, consistent with the structures of all known cytoplasmic GAPDHs. Furthermore, the affinity-purified Tpn retained its ability to bind human transferrin both in its native tetrameric and SDS-denatured monomeric forms. Apart from interacting with human transferrin, Tpn, in common with the group A streptococcal cell wall GAPDH, binds human plasmin. Tpn-bound plasmin is enzymatically active and therefore may contribute to the ability of staphylococci to penetrate tissues during infections. These studies demonstrate that the staphylococcal transferrin receptor protein, Tpn, is a multifunctional cell wall GAPDH.

Heptameric structures of two alpha-hemolysin mutants imaged with in situ atomic force microscopy

Atomic force microscopy has been used to study self-assembled structures of two alpha-hemolysin mutants. For a mutant (alphaHL-H5) that was locked into the prepore state on fluid phase egg-PC membranes, we visualized, for the first time, heptameric prepores and showed that the 7-fold axis in the prepore lies perpendicular to the membrane surface. For another mutant (TCM) with the transmembrane domain, the self-assembled oligomer that assumes the conformation of the fully assembled pore is also a heptamer. These results show that heptamers are the preferred oligomerization state of alpha-hemolysin.

Effect of proteolytic starter cultures of Staphylococcus spp. on biogenic amine formation during the ripening of dry fermented sausages

The effect of proteolytic starter cultures of Staphylococcus carnosus and Staphylococcus xylosus on biogenic amine production was examined during the fermentation process of dry sausages. Microbial counts (lactic acid bacteria, Micrococcaceae and Enterobactenaceae), pH, moisture and proteolysis-related parameters were also studied. The polyamines spermine and spermidine were the main amines found in the raw material and they only showed slight fluctuations during the fermentation. The four elaborated batches presented a significant (P < 0.001) formation of tyramine and putrescine. The main rate of amine production was during the first three days, when a sharp pH decrease and the development of lactic acid bacteria occurred. Sausages fermented with starters had lower amounts of tyramine than naturally fermented sausages (control), but differences in the Micrococcaceae counts were only significant during the first week of the ripening process. A slight formation of diaminopropane, cadaverine, agmatine, tryptamine and phenylethylamine was observed. The amounts of histamine were constant and remained below 0.5 mg/kg of dry matter, while serotonin, octopamine and dopamine were not detected. The sausages with Staphylococcus as starter culture showed strong proteolysis that was correlated with higher pH values than those of the control sausages. However, no positive correlation was found between the proteolysis index and biogenic amine production. Since proteolysis was stronger during the second half of the ripening process, the release of free amino acids as amine precursors occurred later than the early amine production.

[Bacteriological study of chronic maxillary sinusitis in adults and observation of susceptibility to antibiotics]

The unilateral mucosal samples were taken from 42 patients and were cultured for bacteria. Meanwhile, the antimicrobial susceptibility was determined for 11 antibiotics and the beta-lactamase-producing bacteria(beta LPB) were examined. In 85.71% of all samples, bacterial growth was present. Anaerobic bacteria were present in 21.43% of cases. Predominant aerobic bacteria were alpha-hemolytic streptococci and coagulase-negative staphylococci. Predominant anaerobic bacteria were peptostreptococcus species and bacteroides species. The beta LPB were isolated from 40% patients, which were responsible for the resistance to some antibiotics. The antimicrobial susceptibility testing showed that the antibiotics containing beta-lactamase inhibitor, third-generation cephalosporins and third-generation quinolones had good efficacy. Our findings indicated the bacterial infection may not play the key role in the development of chronic sinusitis and the bacterial infection may not play the key role in the development of chronic sinusitis and the resistance to some antibiotics due to the high prevalence of beta-lactamase production must be considered when the antibiotics therapy is taken.

Toxohormone-like factor from microorganisms with impaired respiration

A substance that significantly depresses liver catalase values when injected into mice has been isolated from biochemical mutants of yeasts and staphylococci with impaired respiration. This is considered as an important argument in support of the Warburg hypothesis on the origin of cancer cells.

Detection of rare apoptotic T cells in vivo

The flow cytometric analysis of apoptosis in lymphocytes from in vivo samples has been difficult because of the low frequency of apoptotic events. To overcome this obstacle, many investigators have relied on in vitro incubations to increase the number of apoptotic cells before analysis. In this report, we show that an adaptation of the terminal deoxynucleotidyl transferase (TdT)-mediated dUTP-digoxigenin nick-end labeling (TUNEL) assay for use in flow cytometry can be used to detect rare apoptotic lymphocytes from freshly harvested LN suspensions. This approach is both specific and extremely sensitive. This method also is amenable to multiparameter analyses and allows a phenotypic analysis of these rare apoptotic cells. However, we observed that some monoclonal antibodies can stain apoptotic-but not viable-cells nonspecifically. Therefore, the specificity of all antibodies to stain apoptotic cells was confirmed in competition assays.

Studies on the chemistry and immunochemistry of cell walls of Staphylococcus aureus

The cell walls of an 80/81 strain of Staphylococcus aureus (NYH-6) contain alanine, glycine, glutamic acid, lysine, muramic acid, glucosamine, and ribitol phosphate. 94 per cent of the phosphorus and 41 per cent of the glucosamine are removed by extraction of the cell walls with hot 5 per cent TCA, but significant amounts of the other constituents are not extracted by this procedure. The residue after hot TCA extraction (mucopeptide) is susceptible to lysozyme whereas the intact cell walls are resistant. Staphylococcus aureus cell walls are agglutinated by S. aureus antisera. Agglutination of the cell walls of one S. aureus strain is inhibited by absorption of antisera with cell walls of other S. aureus strains but not by absorption with S. albus cell walls. The ribitol teichoic acid can be isolated from cold TCA extracts of the cell walls. This compound consists almost entirely of ribitol phosphate and glucosamine. The isolated teichoic acid of strain NYH-6 is readily fixed to tanned sheep erythrocytes and these sensitized cells are agglutinated by S. aureus antisera. Cold TCA extracts of cell walls of other strains of S. aureus inhibit hemagglutination whereas extracts of S. albus walls do not. Studies on the inhibition of both hemagglutination and precipitation indicate that the antigenic determinant of S. aureus NYH-6 teichoic acid is beta-N-acetylglucosamine.