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PubMed1997

[Susceptibility to antibiotics of Staphylococcus aureus strains].

Staphylococcus aureus is a very important pathogen in humans about 20% of all bacterial infections are caused by S. aureus. Because the staphylococcal sensitivity patterns have changed, the aim of this study was to investigate the current susceptibility of the S. aureus strains to 9 antibiotics: penicillin (P), amoxacillin/clavulanic acid (AMC), erythromycin (E), cortimoxazole (SXT), tetracycline (T), chloramphenicol (C), mupirocin (MUP), gentamicin (Ge) and vancomycin (Va). Susceptibility testing was performed by disc diffusion technique, by the procedure outlined by the National Committe for Clinical Laboratory Standards (NCCLS). Susceptibility to methicillin was determined using 5 micrograms methicillin disks. beta-lactamase production in the penicillin-resistant strains was detected with nitrocefin impregnated disk (Cefinase, BBL Microbiology system). The microbiological characteristics of the samples: 338 of the isolates were derived, from noses and the throats 382--from surgical wound secretions. The analysis of the results showed that most S. aureus strains (82.8%) are penicillin resistant and beta-lactamase producing 13.5% of all strains were methicillin-resistant. 16.5%--were erythromycin resistant; 3.2%--were cotrimoxazole resistant; 51.4%--were mupirocin resistant; 20.6%--were gentamicin resistant. All of the strains were vancomycin sensitive.

Drug Resistance, Microbial↗
PubMed1982

Action of antifungal imidazoles on Staphylococcus aureus.

In Staphylococcus aureus, using the imidazoles miconazole and ketoconazole, detailed studies of minimal inhibitory concentrations, kinetics of growth, viability, and release of intracellular K+ confirm that the two imidazoles work differently in this bacterium. Miconazole is bactericidal at low concentrations and causes release of cellular K+. Ketoconazole has no bactericidal effect at any tested concentration and has little effect on K+ permeability of S. aureus; it slows growth at high concentration. This is reflected in a low minimal inhibitory concentration for miconazole and a high one for ketoconazole. The probable mechanisms of the bacteriostatic and bactericidal effects of the imidazoles are discussed in light of these results and the previously described antifungal mechanisms of the drugs. alpha-Tocopherol blocks the action of both imidazoles.

Antifungal Agents↗
PubMed2001

Cloning and functional characterization of an NAD(+)-dependent DNA ligase from Staphylococcus aureus.

A Staphylococcus aureus mutant conditionally defective in DNA ligase was identified by isolation of complementing plasmid clones that encode the S. aureus ligA gene. Orthologues of the putative S. aureus NAD(+)-dependent DNA ligase could be identified in the genomes of Bacillus stearothermophilus and other gram-positive bacteria and confirmed the presence of four conserved amino acid motifs, including motif I, KXDG with lysine 112, which is believed to be the proposed site of adenylation. DNA sequence comparison of the ligA genes from wild type and temperature-sensitive S. aureus strain NT64 identified a single base alteration that is predicted to result in the amino acid substitution E46G. The S. aureus ligA gene was cloned and overexpressed in Escherichia coli, and the enzyme was purified to near homogeneity. NAD(+)-dependent DNA ligase activity was demonstrated with the purified enzyme by measuring ligation of (32)P-labeled 30-mer and 29-mer oligonucleotides annealed to a complementary strand of DNA. Limited proteolysis of purified S. aureus DNA ligase by thermolysin produced products with apparent molecular masses of 40, 22, and 21 kDa. The fragments were purified and characterized by N-terminal sequencing and mass analysis. The N-terminal fragment (40 kDa) was found to be fully adenylated. A fragment from residues 1 to 315 was expressed as a His-tagged fusion in E. coli and purified for functional analysis. Following deadenylation with nicotinamide mononucleotide, the purified fragment could self-adenylate but lacked detectable DNA binding activity. The 21- and 22-kDa C-terminal fragments, which lacked the last 76 amino acids of the DNA ligase, had no adenylation activity or DNA binding activity. The intact 30-kDa C terminus of the S. aureus LigA protein expressed in E. coli did demonstrate DNA binding activity. These observations suggest that, as in the case with the NAD(+)-dependent DNA ligase from B. stearothermophilus, two independent functional domains exist in S. aureus DNA ligase, consisting of separate adenylation and DNA binding activities. They also demonstrate a role for the extreme C terminus of the ligase in DNA binding. As there is much evidence to suggest that DNA ligase is essential for bacterial survival, its discovery in the important human pathogen S. aureus indicates its potential as a broad-spectrum antibacterial target for the identification of novel antibiotics.

Amino Acid Motifs↗
PubMed1981

A sandwich ELISA method for detection of Staphylococcus aureus enterotoxins.

Staphylococcus aureus enterotoxins A, B, and C, were detected by means of a four-layer sandwich ELISA method. With toxin produced in broth supernatants, this ELISA method had a detection limit of 0.5 ng enterotoxin per ml. Conjoint with enterotoxin, S. aureus most often produces protein A. The protein A will interfere and produce false positive reactions in a sandwich ELISA, by binding nonspecifically the IgG in different layers, simulating the immunospecific toxin binding. With rabbit IgG coupled to Sepharose CL-4B gel, 99% of protein A could be removed from solutions, bringing the level under the interfering limit in the ELISA.

Adsorption↗
PubMed1996

Identification and characterization of the pckA gene from Staphylococcus aureus.

The Staphylococcus aureus pckA gene was identified and characterized. A pckA mutant lacked detectable phosphoenolpyruvate carboxykinase activity and grew poorly in the absence of glucose. Both enzymatic activity and pckA promoter activity in wild-type cells grown in the absence of glucose were at least 22-fold greater than activities in cells grown in the presence of glucose.

Amino Acid Sequence↗
PubMed1998

Genetic instability of the global regulator agr explains the phenotype of the xpr mutation in Staphylococcus aureus KSI9051.

Staphylococcus aureus KSI9051 has a complex mutation that was associated with the aberrant expression of cell surface and extracellular proteins (M. S. Smeltzer, M. E. Hart, and J. J. Iandolo, J. Bacteriol. 61:919-925, 1993). This mutation was named xpr, although no specific gene was identified. Here this mutation is referred to as Delta1058::Tn551. In this study, we show that in strain KSI9051, the Delta1058::Tn551 mutation occurred coincidentally with a frameshift in agrC that is expected to truncate the sensor component of the known staphylococcal global regulatory locus agr. Remarkably, pleiotropic mutations affecting cell surface and extracellular proteins are generated at frequencies approaching 50% upon the transduction of erythromycin resistance (Emr) encoded by Delta1058::Tn551 from S. aureus KSI905 back to its parental strain, S6C. Three independent isolates created in the manner of KSI9051 contained mutations within agrC. Each isolate had different mutations, suggesting that the transduction of Emr encoded by Delta1058::Tn551 affects the stability of agrC in S6C. In similar experiments with strains from an S. aureus 8325 genetic background, a mutant AgrC phenotype could not be isolated, implying that strain S6 has aberrant genetic behavior. A comparison of the nucleotide sequences of AgrC from several strains revealed seven errors in the GenBank entry for agr (X52543); these data were confirmed with plasmid pRN6650, the original wild-type clone of agr.

Amino Acid Sequence↗
PubMed1992

Antibiotic resistance and plasmids of some human nasal isolates of Staphylococcus aureus.

The Staphylococcus aureus isolates were all susceptible to vancomycin. More than 90% of the isolates were susceptible to rifampicin, ampiclox, methicillin, erythromycin and clindamycin. The isolates were highly resistant to the beta-lactamase-sensitive penicillins, that is 91, 93.2 and 70.4% of the isolates were resistant to penicillin, ampicillin and carbinicillin. Twelve plasmids were found in the isolates, the 35 and 11 Mdal plasmids coded for aminoglycosides and tetracycline resistances, respectively.

Anti-Bacterial Agents↗
PubMed1977

[Utilization of inorganic sulfur sources by Staphylococcus aureus strains].

Staphylococcus aureus strains of different host-adapted variants (Meyer 1966) have been tested for their ability to use inorganic sulfur sources. All the 25 strains tested were able to utilize sodium sulfide as sulfur source in a medium similar to that described by Kloos and Pattee (1965). Using S. aureus strain 116/74 grown in a medium containing Na2-35S as the only sulfur source we studied incorporation and insertion of inorganic sulfide into sulfur containing amino acids. In disintegrated and fractionated cellular material we could find 35S labelled homocystine and methionine as major compounds, and cystine, cysteic acid, homocysteic acid, and beta-sulphopyruvate as minor compounds. The occurrence of homocystine and the sulfonic acids in bacterial proteins is rather uncommon.

Bacterial Proteins↗
PubMed2000

Identification of a new repetitive element in Staphylococcus aureus.

The Staphylococcus aureus repeat (STAR) element is a sequence identified in two intergenic regions in S. aureus. The element is found in 13 to 21 copies in individual S. aureus strains, and elements in the homologous intergenic location are variable in length. The element sequence consists of several small and unusually GC-rich direct repeats with recurring intervening sequences. In addition, STAR-like elements may be present in related staphylococcal species.

Adenosine Triphosphatases↗
PubMed2001

Structure, activity and evolution of the group I thiolactone peptide quorum-sensing system of Staphylococcus aureus.

In Staphylococcus aureus, the agr locus is responsible for controlling virulence gene expression via quorum sensing. As the blockade of quorum sensing offers a novel strategy for attenuating infection, we sought to gain novel insights into the structure, activity and turnover of the secreted staphylococcal autoinducing peptide (AIP) signal molecules. A series of analogues (including the L-alanine and D-amino acid scanned peptides) was synthesized to determine the functionally critical residues within the S. aureus group I AIP. As a consequence, we established that (i) the group I AIP is inactivated in culture supernatants by the formation of the corresponding methionyl sulphoxide; and (ii) the group I AIP lactam analogue retains the capacity to activate agr, suggesting that covalent modification of the AgrC receptor is not a necessary prerequisite for agr activation. Although each of the D-amino acid scanned AIP analogues retained activity, replacement of the endocyclic amino acid residue (aspartate) located C-terminally to the central cysteine with alanine converted the group I AIP from an activator to a potent inhibitor. The screening of clinical S. aureus isolates for novel AIP groups revealed a variant that differed from the group I AIP by a single amino acid residue (aspartate to tyrosine) in the same position defined as critical by alanine scanning. Although this AIP inhibits group I S. aureus strains, the producer strains possess a functional agr locus dependent on the endogenous peptide and, as such, constitute a fourth S. aureus AIP pheromone group (group IV). The addition of exogenous synthetic AIPs to S. aureus inhibited the production of toxic shock syndrome toxin (TSST-1) and enterotoxin C3, confirming the potential of quorum-sensing blockade as a therapeutic strategy.

Bacterial Proteins↗
PubMed2004

Diversity of toxic shock syndrome toxin 1-positive Staphylococcus aureus isolates.

Staphylococcus aureus isolates from women with nasal, anal, or vaginal colonization were evaluated for population diversity by pulsed-field gel electrophoresis. Cluster analysis of restriction patterns revealed diversity indices of 0.89 and 0.99 for toxic shock syndrome toxin 1-positive and -negative isolates, respectively. Toxin-producing strains were isolated more frequently from the nares than from other sites.

Anal Canal↗
PubMed2001

PerR controls oxidative stress resistance and iron storage proteins and is required for virulence in Staphylococcus aureus.

The Staphylococcus aureus genome encodes three ferric uptake regulator (Fur) homologues: Fur, PerR, and Zur. To determine the exact role of PerR, we inactivated the gene by allelic replacement using a kanamycin cassette, creating strain MJH001 (perR). PerR was found to control transcription of the genes encoding the oxidative stress resistance proteins catalase (KatA), alkyl hydroperoxide reductase (AhpCF), bacterioferritin comigratory protein (Bcp), and thioredoxin reductase (TrxB). Furthermore, PerR regulates transcription of the genes encoding the iron storage proteins ferritin (Ftn) and the ferritin-like Dps homologue, MrgA. Transcription of perR was autoregulated, and PerR repressed transcription of the iron homeostasis regulator Fur, which is a positive regulator of catalase expression. PerR functions as a manganese-dependent, transcriptional repressor of the identified regulon. Elevated iron concentrations produced induction of the PerR regulon. PerR may act as a peroxide sensor, since addition of external hydrogen peroxide to 8325-4 (wild type) resulted in increased transcription of most of the PerR regulon, except for fur and perR itself. The PerR-regulated katA gene encodes the sole catalase of S. aureus, which is an important starvation survival determinant but is surprisingly not required for pathogenicity in a murine skin abscess model of infection. In contrast, PerR is not necessary for starvation survival but is required for full virulence (P < 0.005) in this model of infection. PerR of S. aureus may act as a redox sentinel protein during infection, analogous to the in vitro activities of OxyR and PerR of Escherichia coli and Bacillus subtilis, respectively. However, it differs in its response to the metal balance within the cell and has the added capability of regulating iron uptake and storage.

Amino Acid Sequence↗
PubMed2006

Clonal distribution and differential occurrence of the enterotoxin gene cluster, egc, in carriage- versus bacteremia-associated isolates of Staphylococcus aureus.

The Staphylococcus aureus enterotoxin gene cluster, egc, was detected in isolates from healthy individuals and in those from patients with bacteremia. The egc genes cooccur and are slightly enriched in strains from healthy carriers (present in 63.7% of carriage-associated isolates versus 52.9% of invasive isolates; P = 0.03). Multilocus sequence typing revealed that successful staphylococcal clones usually harbor the egc locus.

Bacteremia↗
PubMed1979

Antibiotic sensitivity and synergism of 'penicillin-tolerant' Staphylococcus aureus.

15 Staphylococcus aureus strains were isolated from 15 patients with staphylococcal bacteremia. Eight of these strains were shown to be tolerant for cloxacillin. Cloxacillin-tolerant strains were also tolerant for most of the cephalosporins tested except for cephapirin. Strains were not tolerant for clindamycin and gentamicin. Penicillin-tolerant staphylococci showed a high degree of synergism between gentamicin and cloxacillin or cephalothin and gentamicin.

Anti-Bacterial Agents↗
PubMed1992

The facts about methicillin-resistant Staphylococcus aureus.

1. Staphylococcus aureus is a gram-positive organism that can be cultured from the anterior nares of 30% to 40% of the general population. S aureus causes about 10% of all nosocomial infections, and is the leading cause of surgical wound infections. 2. Several factors can influence the recovery of MRSA from specimens, including mixed cultures in the person, a person who is an intermittent carrier, and a culture that is taken or transported incorrectly. 3. Two approaches can be used to reduce the risk of cross-transmission of organisms among patients and health-care workers: a generic infection precautions strategy for all patients, and identifying patients infected or colonized with MRSA and treating them differently than other patients.

Bacteriological Techniques↗
PubMed2001

In-vivo transfer of mecA DNA to Staphylococcus aureus [corrected].

Staphylococcus aureus is thought to have acquired mecA DNA by horizontal transfer. DNA fingerprints made by restriction nucleases that cut certain sequences of DNA are used to compare complete genomes or particular genes between bacteria. We isolated an epidemic mecA(-) meticillin-susceptible S aureus genotype and, subsequently, a rare isogeneic mecA(+) meticillin-resistant S aureus (MRSA) genotype from a neonate who had never been in contact with MRSA. This MRSA contained mecA DNA that was identical to that in a coagulase-negative staphylococcal strain isolated from this patient, but different from other MRSA genotypes. We believe that this MRSA was formed in vivo by horizontal transfer of the mecA DNA between two staphylococcal species.

Bacteremia↗
PubMed2004

[New Staphylococcus aureus strains].

Staphylococcus aureus strains are present in the nose of 30% of healthy humans and are responsible for skin and soft tissue infections. Deep seated infections secondarily occurred such as osteomyelitis or infective endocarditis. New toxin-associated clinical entities have been recognized such as the toxin shock syndrome, the staphylococcal scarlet fever, the staphylococcal scalded skin syndrome or the necrotising pneumonia. This later syndrome is associated with Panton Valentine leukocidin producing strains. It occurs mainly in children and has a lethality of 75%. New antibiotic resistances are also emerging, for vancomycin in hospital-acquired infections and for methicillin in community-acquired infections.

Dermatitis, Exfoliative↗