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PubMed1997

alpha-Hemolysin, gamma-hemolysin, and leukocidin from Staphylococcus aureus: distant in sequence but similar in structure.

alpha-Hemolysin from Staphylococcus aureus assembles from a water-soluble, monomeric species to a membrane-bound heptamer on the surface of target cells, creating water-filled channels that lead to cell death and lysis. Staphylococcus aureus also produces the gamma-hemolysin and leukocidin toxins, which function as two component toxins in the disruption and lysis of erythrocytes and leukocytes. Analysis of the aligned sequences of alpha-hemolysin, gamma-hemolysin, and leukocidin in the context of the alpha-hemolysin heptamer structure supports the conclusion that even though the level of sequence identity between alpha-hemolysin and the gamma-hemolysin and leukocidin toxins is in the so-called twilight zone, the three-dimensional structures of the protomers are probably conserved. By analogy with alpha-hemolysin, gamma-hemolysin and leukocidin may also form oligomeric, transmembrane channels in which an antiparallel beta-barrel constitutes the primary membrane-embedded domain.

Amino Acid Sequence↗
PubMed1997

A single amino acid substitution in Staphylococcus aureus dihydrofolate reductase determines trimethoprim resistance.

A single amino acid substitution, Phe98 to Tyr98, in dihydrofolate reductase (DHFR) is the molecular origin of trimethoprim (TMP) resistance in Staphylococcus aureus. This active site amino acid substitution was found in all S. aureus TMP-resistant clinical isolates tested. In order to explore the structural role of Tyr98 in TMP-resistance the ternary complexes of the chromosomal S. aureus DHFR (SaDHFR) with methotrexate (MTX) and TMP in the presence of nicotinamide adenine dinucleotide phosphate (NADPH) as well as that of mutant Phe98Tyr DHFR SaDHFR(F98Y) ternary folate-NADPH complex have been determined by X-ray crystallography. Critical evidence concerning the resistance mechanism has also been provided by NMR spectral analyses of 15N-labelled TMP in the ternary complexes of both wild-type and mutant enzyme. These studies show that the mutation results in loss of a hydrogen bond between the 4-amino group of TMP and the carbonyl oxygen of Leu5. This mechanism of resistance is predominant in both transferable plasmid-encoded and non-transferable chromosomally encoded resistance. Knowledge of the resistance mechanism at a molecular level could help in the design of antibacterials active against multi-resistant Staphylococcus aureus (MRSA), one of todays most serious problems in clinical infectology.

Binding Sites↗
PubMed1996

Rapid assay for detection of methicillin-resistant Staphylococcus aureus using multiplex PCR.

The presence or absence of the mecA gene, the determinant of resistance to all beta-lactam antibiotics, was examined in clinical isolates of Staphylococcus aureus by multiplex polymerase chain reaction (MPCR). Two pairs of primers were used, which yielded two specific products; a 280-bp nuc- based PCR fragment (amplification product of the nuc gene encoding specific Staphylococcus aureus nuclease) and a 533-bp mecA-based PCR fragment (amplification product of the mecA gene). The MPCR system was designed to be incorporated into the work flow in clinical diagnostic laboratories as a routine analysis.

Genes, Bacterial↗
PubMed1999

Simultaneous detection of erythromycin-resistant methylase genes ermA and ermC from Staphylococcus spp. by multiplex-PCR.

A comparative analysis of the two most dominant erythromycin-resistance determinant genes in Staphylococcus sppnamely, the ermA and ermC genes, was carried out. Sixty erythromycin-resistant strains of Staphylococcus spp. were tested, of which 24 were avian and 36 were clinical isolates. Our results indicated the prevalence of ermA over the ermC gene as opposed to the widely held opinion of the ermC gene being the most dominant resistance determinant gene. A multiplex-PCR assay was developed to detect the presence of ermA and ermC genes. Two pairs of primers, specific for the detection of ermA and ermC genes, were used in a multiplex-polymerase chain reaction (PCR) assay to yield amplified DNA products of 610 and 520 bp, respectively. Their digestion with restriction enzyme FokI that yielded a 477 bp and a 132 bp digestion product for ermA and a 333 bp and a 187 bp digestion product for ermC confirmed the authenticity of PCR products. The method could be used to amplify the ermA and ermC genes with as little as 5 pg of template DNA. The use of excess primers or the template DNA resulted in gene-specific amplification and no non-specific amplification was observed by changing the primer to primer or template to primer ratios. Furthermore, no amplification from erythromycin-sensitive S. aureus strain was observed. Using this assay, the poultry strains were found to contain either ermA alone (50%) or a combination of ermA (100%) and ermC (50%) both. The clinical strains contained either ermA (94.5%) or ermC (5.5%) but never both. The gene-specific internal probes were also used to verify the above findings and a high degree of correlation between the multiplex PCR and Southern hybridization data was observed.

Animals↗
PubMed2002

Characterization and molecular cloning of a glutamyl endopeptidase from Staphylococcus epidermidis.

A novel extracellular endopeptidase, designated GluSE, was purified from Staphylococcus epidermidis ATCC 14990 cultured by the dialysis membrane technique, and the structural gene (gseA) was cloned. GluSE was a 27kDa, glutamic acid-specific protease, and the optimal pH was 8.0. The proteolytic activity was specifically inhibited with diisopropyl fluorophosphate, indicating that it is a serine protease. The gseA encoded a single polypeptide of 282 amino acids with a deduced molecular weight of 30,809, in which the first 19 N-terminal amino acids completely matched the deduced sequence starting at Val-67, suggesting that GluSE is synthesized with a propeptide. The amino acid sequence of GluSE exhibited 50.5% identity to Staphylococcus aureus V8-protease (GluV8). Although GluSE lacks a C-terminal 12 repeats of the PBN/PBZ tripeptide of GluV8, a catalytic triad of His-117, Asp-159 and Ser-235 was conserved in GluSE. Southern hybridization analysis revealed that gseA exists as a single copy on the chromosomal DNA. The finding that production of GluSE was obviously observed in the adherent culture conditions of the dialysis membrane technique, but not in the planktonic culture conditions, strongly suggests that GluSE could be involved in an important etiologic process in S.epidermidis infection leading to multiple tissue damages.

Amino Acid Sequence↗
PubMed2001

Photodynamic activity of the haematoporphyrin derivative with rutin and arginine substituents (HpD-Rut(2)-Arg(2)) against Staphylococcus aureus and Pseudomonas aeruginosa.

The impact of the new photosensitizer HpD-Rut(2)-Arg(2)on the growth of methicillin-resistant Staphylococcus aureus(MRSA), methicillin-susceptible Staphylococcus aureus (MSSA) and Pseudomonas aeruginosa clinical strains isolated from infected burn wounds was examined. The susceptibility of the isolates to the photodynamic action of the sensitizer was evaluated by the determination of minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) using the newly developed microdilution method. The results were compared with the previously investigated HpD-Arg(2). All clinical isolates examined proved to be susceptible to the photodynamic action of HpD-Rut(2)-Arg(2). The MIC of this newly synthetized photosensitizer ranged from 0.8 to 12.5 microg ml(-1) for MRSA, from 0.4 to 6.2 microg ml(-1) for MSSA and from 6.2 to 50 microg ml(-1) for P. aeruginosa. While MBC ranged from 1.6 to 12.5 microg ml(-1) for MRSA, 0.4 to 6.2 microg ml(-1) for MSSA and 6.2 to 100 microg ml(-1) for P. aeruginosa. This photosensitizer is more effective in its bactericidal photodynamic action than previously tested HpD-Arg(2).

Anti-Bacterial Agents↗
PubMed1996

Nucleic acid sequence and affiliation of pLUG10, a novel cadmium resistance plasmid from Staphylococcus lugdunensis.

Tolerance of Staphylococcus lugdunensis to relatively high levels of cadmium is mediated by a 3117-bp plasmid, pLUG10. Sequencing reveals three major open reading frames (ORFs) in a single orientation. One ORF encompasses the origin of replication and its predicted product (RepL: 350 amino acids (aa)) shows 70% homology in its deduced aa sequence with Rep proteins of the pT181 family. A lagging strand conversion signal (palA) very similar to that of class 1 plasmids is present outside the rep-ori locus. The other two ORFs of 209 and 116 aa show 92.5% homology between their deduced aa sequences and the CadB and CadX peptides from the pOX6 plasmid of Staphylococcus aureus. The CadX-like peptide is 40% homologous to the S. aureus CadC product. Deletion of the C-terminal cadX gene by restriction enzyme digestion or frame-shift inactivation of the cadB gene reduced, but did not completely abolish, cadmium resistance. The two gene products may act cooperatively to confer cadmium resistance in S. lugdunensis.

Amino Acid Sequence↗
PubMed1995

Expression of Staphylococcus saprophyticus surface properties is modulated by composition of the atmosphere.

Expression of two major surface proteins of Staphylococcus saprophyticus, the haemagglutinin and the Staphylococcus saprophyticus surface-associated protein (Ssp), required carefully defined culture conditions. The Ssp is produced when bacteria are grown on agar, whereas expression of the haemagglutinin requires growth in broth. We sought to identify the environmental signals that are responsible for this modulation. Varying the pH, the osmolarity of the growth medium or the temperature did not influence expression of the proteins. In contrast, growth in an anaerobic atmosphere increased haemagglutination titres and fibronectin binding (both mediated by the haemagglutinin) but suppressed production of the Ssp. As the influence of the CO2 level could be excluded, we conclude that expression of these surface proteins is probably modulated by the O2 content of the atmosphere.

Adhesins, Bacterial↗
PubMed1991

Organization, promoter analysis and transcriptional regulation of the Staphylococcus xylosus xylose utilization operon.

The Staphylococcus xylosus xyl genes were cloned in Staphylococcus carnosus by complementation to xylose utilization. Xylose isomerase assays under inducing (xylose present) and non-inducing (xylose absent) conditions indicated the presence of a regulated xylA gene on the recombinant plasmid. The nucleotide sequence (4520 bases) revealed three open reading frames with the same polarity. They were identified by sequence homologies as xylR, encoding the Xyl repressor, xylA, encoding xylose isomerase and xylB, encoding xylulokinase. Primer extension analyses indicated constitutive transcription of xylR and xylose-inducible transcription of xylA. Promoter consensus sequences were found upstream of both transcriptional start sites. A transcriptional terminator between xylR and xylA separates the different transcriptional units. Potential regulatory elements were identified by sequence analysis and suggest a repressor-operator mechanism for the regulation of xylAB expression.

Aldose-Ketose Isomerases↗
PubMed1994

Genetic and biochemical properties of an extracellular neutral metalloprotease from Staphylococcus hyicus subsp. hyicus.

The gene encoding the extracellular neutral metalloprotease ShpI from Staphylococcus hyicus subsp. hyicus was cloned. DNA sequencing revealed an ORF of 1317 nucleotides encoding a 438 amino acid protein with Mr of 49,698. When the cloned gene was expressed in Staphylococcus carnosus, a 42 kDa protease was found in the culture medium. The protease was purified from both S. carnosus (pCAshp1) and S. hyicus subsp. hyicus. The N-terminal amino acid sequences of the two proteases revealed that ShpI is organized as a pre-pro-enzyme with a proposed 26 amino acid signal peptide, a 75 amino acid hydrophilic pro-region, and a 337 amino acid extracellular mature form with a calculated Mr of 38,394. The N-termini showed microheterogeneity in both host strains. ShpI had a maximum proteolytic activity at 55 degrees C and pH 7.4-8.5. The protease, which had a low substrate specificity, could be inhibited by metal- and zinc-specific inhibitors, such as EDTA and 1,10-phenanthroline. Insensitivity to phosphoramidon separates ShpI from the thermolysin-like family. The conserved Zn2+ binding motif, the only homology to other proteases, and the reactivation of the apoenzyme by Zn2+, indicated that Zn2+ is the catalytic ion. Ca2+ very probably acts as a stabilizer. We also demonstrated the presence of a second extracellular protease in S. hyicus subsp. hyicus.

Amino Acid Sequence↗
PubMed1994

Threonine is present instead of cysteine at the active site of urease from Staphylococcus xylosus.

DNA sequence analysis of the structural urease genes from Staphylococcus xylosus revealed that three enzyme subunits are encoded in the order of 11,000, 15,400 and 61,000 (mol. mass), which correspond to the single polypeptide chain of jack bean urease (90,800). Comparing the deduced amino acid sequence of S. xylosus urease with the amino acid sequence of jack bean urease an overall portion of 56% identical residues was found. For S. xylosus urease a subunit structure of (alpha beta gamma)4 was proposed, based on the comparison of the deduced amino acid content of the enzyme subunits with the total amino acid content of the purified enzyme. The staphylococcal enzyme contained no cysteine, as deduced from DNA sequence and confirmed by the determination of the total amino acid content in the purified enzyme. Instead of cysteine, known to be catalytically essential in the plant enzyme, and conserved among all bacterial ureases analyzed so far, threonine was found in S. xylosus. This amino acid-exchange was located within a highly conserved domain of 17 amino acids, supposed to be part of the active site. Sequence analysis of the respective region of Staphylococcus saprophyticus urease showed that it also contains threonine instead of cysteine. In contrast to jack bean urease S. xylosus urease was not affected by the SH-group inhibitor dipyridyl disulfide but was completely inhibited by the serine protease inhibitor phenylmethanesulfonyl fluoride. The presented results indicate that in these staphylococcal strains urea hydrolysis might function in a manner similar to the peptide bond cleavage by chymotrypsin.

Amino Acid Sequence↗
PubMed1986

Enterotoxin A production in Staphylococcus aureus: inhibition by glucose.

In this study, we investigated the relationship between carbohydrate metabolism and repression of staphylococcus enterotoxin A (SEA) in Staphylococcus aureus 196E and a pleiotrophic mutant derived from strain 196E. The mutant, designated at strain 196E-MA, lacked a functional phosphoenolpyruvate phosphotransferase system (PTS). The mutant produced acid, under aerobic conditions, from only glucose and glycerol. The parent strain contained an active PTS, and aerobically produced acid from a large number of carbohydrates. Prior growth in glucose led to repression of SEA synthesis in the parent strain; addition to the casamino acids enterotoxin production medium (CAS) led to more severe repression of toxin synthesis. The repression was not related to pH decreases produced by glucose metabolism. When S. aureus 196E was grown in the absence of glucose, there was inhibition of toxin production as glucose level was increased in CAS. The inhibition was related to pH decrease and was unlike the repression observed with glucose-grown strain 196E. The inhibition of SEA synthesis in mutant strain 196E-MA was approximately the same in cells grown with or without glucose and was pH related. Repression of SEA synthesis similar to that seen with glucose-grown S. aureus 196E could not be demonstrated in the mutant. In addition, glucose-grown S. aureus 196E neither synthesized beta-galactosidase nor showed respiratory activity with certain tricarboxylic acid (TCA) cycle compounds. Glucose-grown strain 196E-MA, however, did not show suppressed respiration of TCA cycle compounds; beta-galactosidase was not synthesized because the mutant lacked a functional PTS.(ABSTRACT TRUNCATED AT 250 WORDS)

Carbohydrate Metabolism↗
PubMed1977

The formation of germtubes by Candida albicans, when grown with Staphylococcus pyogene, Escherichia coli, Klebsiella pneumoniae, Lactobacilius acidophilus and Proteus vulgaris.

The formation of germtubes by twelve clinical isolates of C. albicans was studied in human serum containing per millilitre 10(3) to 10(9) organisms as: Staphylococcus pyegene, Escherichia coli, Klebsiella pneumoniae, Lactobacillus acidophilus and Proteus vulgaris. All the five bacteria inhibited formation of germtubes by C. albicans at all concentrations and the percent germtube formed diminished with increasing concentration of the bacteria. Lactobacillus acidophilus inhibited the formation of germtubes maximally followed by Staphylococcus pyogene, Escherichia coli and Klebsiella pneumoniae. Proteus vulgaris in the concentrations of 10(3) to 10(7) bacteria per millilitre produced only insignificant inhibition of formation of germtubes by C. albicans. Since germtubes of C. albicans are invasive, it is suggested that inhibition of "blastospore-germtube transformation" may be significantly responsible for prevention of infection by C. albicans by coexisting bacterial flora.

Candida albicans↗
PubMed1977

Antibacterial activity of amniotic fluid against Staphylococcus aureus, Candida albicans and Brucella abortus.

Sixty amniotic fluid samples from sixty patients between 14--42 weeks gestation were studied for antibacterial activity against Staphylococcus aureus, Brucella abortus and antifungal activity against Candida albicans. Both antibacterial and antifungal activity of the amniotic fluid were observed. When antimicrobial activity was correlated with gestational age, it was found to increase with the period of gestation. Maximum antimicrobial activity of the amniotic fluid was found to be present in the samples obtained between 36--42 weeks of gestation. All samples before 20 weeks gestation showed week antibacterial activity against Staphylococcus aureus, but comparatively strong reaction against Candida albicans and Brucella abortus.

Amniocentesis↗
PubMed1981

Studies on isolated gut mucosal lymphocytes in inflammatory bowel disease. Detection of activated T cells and enhanced proliferation to Staphylococcus aureus and lipopolysaccharides.

To determine whether a defective proliferation of gut mucosal lymphocytes is a contributory factor to the pathogenesis of inflammatory bowel disease, we assessed their reactivity toward mitogens and bacterial antigens. Spontaneous replication of intestinal lymphoid cells was higher than that of patient-matched peripheral blood lymphocytes. That gut mucosal lymphocytes appear to be activated in loco was confirmed by a striking, time-dependent increase in the number of stable E rosettes generated by culturing unstimulated Crohn's disease intestinal lymphoid cells. The responses of lymphocytes from inflamed and normal mucosa to polyclonal mitogens were not only comparable to each other, but to those of corresponding peripheral lymphocytes, as well. Peripheral blood lymphocytes from patients with Crohn's disease showed less proliferation to Bacteroides and lipopolysaccharide antigens than did those from control individuals, but replicated similarly in response to Staphylococcus aureus and the enterobacterial common antigen: In contrast, when cultured with Staphylococcus aureus or with lipopolysaccharides, but mucosal lymphocytes from Crohn's disease proliferated 3-5 times more than did those from normal mucosa, while lymphoid cells from both sources were equally stimulated by Kunin antigen. Overall, this study found no evidence for a defective proliferative capacity of immune competent cells at the gut mucosal level in inflammatory bowel disease.

Colitis↗
PubMed1995

Molecular structure of staphylococcus and streptococcus superantigens.

Staphylococcus aureus and streptococci, notably those belonging to group A, make up a large family of true exotoxins referred to as pyrogenic toxin superantigens. These toxins cause toxic shock-like syndromes and have been implicated in several allergic and autoimmune diseases. Included within this group of proteins are the staphylococcal enterotoxins, designated serotypes A, B, Cn, D, E, and G; two forms of toxic shock syndrome toxin-1 also made by Staphylococcus aureus; the group A streptococcal pyrogenic exotoxins, serotypes A, B, and C; and recently described toxins associated with groups B, C, F, and G streptococci. The nucleotide sequences of the genes for all of the toxins except those from the groups B, C, F, and G streptococcal strains have been sequenced. The sequencing studies indicate that staphylococcal enterotoxins B and C and streptococcal pyrogenic exotoxin A share highly significant sequence similarity; staphylococcal enterotoxins A, D, and E share highly significant sequence similarity; and toxic shock syndrome toxin-1 and streptococcal pyrogenic exotoxin B and C share little, if any, sequence similarity with any of the toxins. Despite the dissimilarities seen in primary amino acid sequence among some members of the toxin family, it was hypothesized that there was likely to be significant three-dimensional structure similarity among all the toxins. The three-dimensional structures of three of the pyrogenic toxin superantigens have been determined recently. The structural features of two of these, toxic shock syndrome toxin-1 and enterotoxin C3, are presented. Toxic shock syndrome-1 exists as a protein with two major domains, referred to as A and B. The molecule begins with a short N-terminal alpha-helix that then leads into a clawshaped structure in domain B that is made up of beta strands.

Bacterial Toxins↗
PubMedDate not supplied

Clinical significance of Staphylococcus aureus in cystic fibrosis.

Staphylococcus aureus is usually the first bacterial pathogen detected in the respiratory secretions of patients with cystic fibrosis. This review briefly examines the characteristics of this host-parasite relationship in terms of current knowledge about the toxicity of the organism, mechanisms of respiratory tract injury, therapy and prevention. Recent evidence indicates that viral infection plays a role in the initial damage of the respiratory epithelial cells and staphylococcal colonization ensues. Affinity of staphylococcus for cystic fibrosis mucus, mucociliary abnormalities and unknown factors contribute to persistent colonization with this organism causing progressive pulmonary damage and possibly influencing Pseudomonas infection. Most of the evidence today indicates that aggressive antibiotic management directed against S. aureus is warranted in all stages of bronchopulmonary infection in cystic fibrosis. Future efforts to prevent colonization and the toxic and immunopathic consequences of staphylococcal infection are also important. One study is in progress that examines antibiotic prevention in the early stages of cystic fibrosis. Future investigations need to address other strategies including vaccines, antitoxins, anti-inflammatory agents, immunomodulators, and antibiotic regimens.

Anti-Bacterial Agents↗