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PubMed1985

Effect of pH on the morphology of Staphylococcus aureus.

Nineteen strains of Staphylococcus aureus (10 sensitive and 9 resistant to oxacillin) were grown for four hours on membranes placed on trypticase soy agar at pH 5, 5.5, 6, 6.5, 7.1, 7.5, 7.8 and 8.3. The morphology was observed by interference phase contrast and by electron microscopy. All strains grown at pH 6 to 7.5 produced cocci of normal size. When grown at pH 5, 5.5, 7.8 and 8.3, however, seven of the oxacillin-resistant strains and seven of the oxacillin-sensitive strains produced bacterial cells 1.5 to 2 micron in diameter. These cells consist of a cluster of staphylococci held together by multiple thick cross walls. Their structure is similar to that of staphylococci grown in the presence of subminimum inhibitory concentrations of beta-lactam antibiotics, which inhibit autolysis of cross walls. It appears that autolysis of cross walls of S. aureus is also inhibited by a low or a high pH.

Autolysis↗

PubMed2003

Phenotypic and genotypic characterization of bovine mastitis isolates of Staphylococcus aureus for biofilm formation.

Staphylococcus aureus is one of the most common pathogens responsible for contagious mastitis in ruminants. The ability of S. aureus to form biofilm in vivo is considered to be a major virulence factor influencing its pathogenesis in mastitis. The objectives of the study were to examine in vitro slime production, biofilm formation, and the presence of the ica gene locus and icaA and icaD genes in S. aureus isolates from bovine mastitis. Thirty-two of the 35 isolates tested produced slime on Congo red agar, whereas only 24 of the isolates were found to produce biofilm in vitro. However, all the 35 isolates possessed the ica locus, icaA and icaD genes. This study indicates a high prevalence of the ica genes among S. aureus mastitis isolates, and their presence is not always associated with in vitro formation of slime or biofilm. A combination of phenotypic and genotypic tests is recommended for investigating biofilm formation in S. aureus.

Animals↗

PubMed1979

Methicillin potentiates the effect of gentamicin on methicillin-resistant Staphylococcus aureus.

Methicillin-resistant Staphylococcus aureus (MRSA) strains show an unusual type of resistance at 37 degrees C; only a small subpopulation of cells is resistant to the beta-lactam antibiotics. Incubation in the presence of methicillin (MET), however, results in the emergence of a homogenous population highly resistant to MET. The purpose of the present study was to determine whether MET, despite its lack of killing effect on MRSA, would promote the bactericidal effect of gentamicin (GM), as demonstrated for MET-susceptible strains of S. aureus. Eleven epidemiologically distinct strains of MRSA were incubated with MET at various concentrations, in the presence or absence of sub-bactericidal concentrations (1/5 or 1/10 of the minimal bactericidal concentration) of GM, and tested for the synergistic action of both antibiotics by three different methods. Population analysis of the 11 strains in the presence of high concentrations of MET showed that the addition of GM at 1/5 or 1/10 of its minimal bactericidal concentration resulted in marked killing of the 11 strains. Time-kill curves obtained with 32 mug of MET per ml and GM at 1/5 or 1/10 of its minimal bactericidal concentration confirmed this synergistic killing at 24 h. These results were further documented by the checkerboard method on two strains. We conclude that the synergism between MET and GM, previously demonstrated for MET-susceptible S. aureus, holds true for MRSA as well and that it can be demonstrated at sub-bactericidal concentrations of GM.

Drug Synergism↗

PubMed2000

Impact of the agr quorum-sensing system on adherence to polystyrene in Staphylococcus aureus.

Biofilm formation by Staphylococcus aureus is a serious problem in nosocomial infections. There are great differences in the capacity of S. aureus to express biofilms, but the reasons are unknown. In all, 105 S. aureus strains were tested for a correlation between the agr quorum-sensing system phenotype and the ability of S. aureus to adhere to polystyrene. Some 78% of agr-negative, but only 6% of agr-positive, strains formed a biofilm, demonstrating a profound impact of agr on biofilm formation. This result was confirmed with defined agr mutants and by inhibition of agr with quorum-sensing blockers. The observed effect was not due to differential expression of the autolysin Atl or of the exopolysaccharide polysaccharide intercellular adhesin but seemed to be caused, at least in part, by the surfactant properties of delta-toxin. The detected biofilm-enhancing effect of S. aureus quorum-sensing blockers call into question the proposed therapeutic use of such substances.

Bacterial Adhesion↗

PubMed1995

Isolation and the gene cloning of an alkaline shock protein in methicillin resistant Staphylococcus aureus.

The growth of Staphylococcus aureus occurs at a wide range of pH(5-10), while the optimal is pH 7.0-7.5. The molecular mechanism of such pH tolerant properties should be elucidated because the production of the virulence factors was greatly affected by environmental pH. The effect of pH shift on the composition of cytosolic proteins in S. aureus was examined. A protein with a molecular mass of 23 kDa was remarkably enhanced by a pH upshift from 7 to 10. This alkaline shock protein (ASP23) was isolated and purified by ion-exchange chromatography. The N-terminal sequences of the purified protein and the protease-digested peptides were analyzed. The 320-bp DNA fragment that was designed from the peptide analysis was amplified. Using the amplified fragment as a probe, the ASP gene, asp23, was cloned. The deduced primary sequence of ASP23 comprised 169 amino acids with a calculated molecular weight of 19,191. Northern analysis revealed that asp23 was positively regulated at the transcription level by alkaline shock. Homology search revealed that asp23 is a novel gene. Although the physiological role of ASP23 has yet to be further analysed, we suggest that ASP23 plays a key role in alkaline pH tolerance of S. aureus.

Amino Acid Sequence↗

PubMed2006

Toxicogenomic response of Staphylococcus aureus to peracetic acid.

Staphylococcus aureus is responsible for many incidents of hospital-acquired infection, which causes 90,000 deaths and dollars 4.5 billion loss a year in the United States. Despite a wide use of disinfectants such as peracetic acid in health care environments, we certainly need better understanding of the effects of antimicrobial application on target pathogens to avert infection outbreaks. Consequently, herein, we explored for the first time the toxicogenomic response of S. aureus to a sublethal concentration of peracetic acid (1 mM) by using microarray-based transcriptome analysis. In particular, we investigated the dynamics of global gene expression profiles during its cellular response, which involved initial growth inhibition (10 min) and subsequent partial recovery (20 min). Further, we compared transcriptome responses to peracetic acid between S. aureus and Pseudomonas aeruginosa. Our findings show that (i) the regulation of membrane transport genes was significantly altered, (ii) DNA repair and replication genes were selectively induced, and (iii) primary metabolism-related genes were differently repressed between the two growth states. Most intriguingly, we revealed that many virulence factor genes were induced upon the exposure, which proposes a possibilitythatthe pathogenesis of S. aureus may be stimulated in response to peracetic acid.

Anti-Infective Agents↗

PubMed2006

Alpha-toxin interferes with integrin-mediated adhesion and internalization of Staphylococcus aureus by epithelial cells.

Staphylococcus aureus is an important human and animal pathogen. During infection, this bacterium is able to attach to and enter host cells by using its cell surface-associated factors to bind to the host's extracellular matrix (ECM) proteins. In this study, we determined that a protein exported by S. aureus, alpha-toxin, can interfere with the integrin-mediated adhesion and internalization of S. aureus by human lung epithelial cells (A549). The downregulation of alpha-toxin production significantly increased bacterial adhesion and invasion into the epithelial cells. In contrast, bacterial adhesion and invasion was inhibited by both overproduction of alpha-toxin and the addition of alpha-toxin to the culture medium. Moreover, our results showed that the quantitative effects on invasion closely parallel those of adherence. This suggests that the effect on invasion is probably secondary to, and a consequence of, the reduced adherence caused by alpha-toxin exposure. Specifically, we demonstrated that alpha-toxin interacts with the hosts' ECM protein's receptor, beta1-integrin, which indicates that beta1-integrin may be a potential receptor of alpha-toxin on epithelial cells. Taken together, our results indicate that exported alpha-toxin inhibits the adhesion and internalization of S. aureus by interfering with integrin-mediated pathogen-host cell interactions.

Bacterial Adhesion↗

PubMed1989

Reduced adherence to traumatized rat heart valves by a low-fibronectin-binding mutant of Staphylococcus aureus.

Isogenic strains of Staphylococcus aureus, differing in fibronectin binding, were constructed for studies of the contribution of fibronectin binding to the in vivo pathogenesis of staphylococcal disease. Mutagenesis of S. aureus 879R4S was accomplished by mating with Enterococcus faecalis FA378 that carried the transposon Tn918. Four low-fibronectin-binding mutants were identified that bound 24- to 35-fold less fibronectin than the parent strain did. A spectinomycin-resistant strain, R4SSp, was transduced by a bacteriophage (80 alpha) lysate propagated on a low-binding mutant of 879R4S to produce R4SSp/1536, which bound less fibronectin, contained a single copy of the transposon, and grew on spectinomycin-containing medium. Using a rat model of endocarditis, we determined the distribution of S. aureus R4SSp and its transductant in normal and cardiac catheterized rats. Cultures of heart tissue showed that catheterized rats challenged with the fibronectin-binding parent strain had over 250-fold more organisms in the left heart than did rats challenged with the low-binding transductant. The ability to bind fibronectin had no effect on the number of S. aureus cells cultured from other tissues. These data suggest that the ability of S. aureus to bind fibronectin is an important factor in establishing adherence to damaged heart valves in vivo.

Animals↗

PubMed1987

[Antibacterial activities of various aminoglycosides against clinically isolated methicillin-resistant Staphylococcus aureus].

Methicillin-resistant Staphylococcus aureus (MRSA) were isolated from samples collected from various patients during 1986, and antibacterial activities of 6 aminoglycosides (AGs) (netilmicin (NTL), gentamicin (GM), sisomicin (SISO), dibekacin (DKB), tobramycin (TOB) and amikacin (AMK] and 4 beta-lactam antibiotics (cefazolin (CEZ), cefmetazole (CMZ), cloxacillin (MCIPC) and methicillin (DMPPC) against these MRSA were evaluated. Among these 6 AGs, NTL was the most potent, and its MIC50 and MIC80 were 1.56 and 3.13 micrograms/ml, respectively. Antibacterial activities of GM, SISO, DKB and TOB were weak, and MIC50's of GM and DKB were both 100 micrograms/ml, while those of SISO and TOB were 50 and greater than 100 micrograms/ml, respectively. Frequency of highly resistant specimens to AMK was rather low and its MIC50 and MIC80 were 12.5 and 25 micrograms/ml, respectively. As for antibacterial activities of the above 4 beta-lactam antibiotics, the MIC50 and MIC80 of CMZ were 6.25 and 12.5 micrograms/ml, respectively, and therefore, its antibacterial activity to MRSA is relatively good. However, MIC50's of CEZ, MCIPC and DMPPC were all greater than 100 micrograms/ml, showing poor antibacterial activities. Recently, MRSA became a problem in various fields of clinical practice, and a number of literatures reporting refractory infections caused by MRSA have been published. Since MRSA is featured as multiply resistant bacteria, it is known that MRSA is resistant to the majority of existing antibiotics (penicillins, cephems, macrolides, AGs, etc.). In 1985, we reported results of our study concerning the antibacterial activities of a number of CEPs and some of AGs against multiply resistant S. aureus including MRSA.(ABSTRACT TRUNCATED AT 250 WORDS)

Amikacin↗

PubMed1998

A second IgG-binding protein in Staphylococcus aureus.

Most strains of Staphylococcus aureus express IgG-binding activity and this binding has been considered to be solely mediated by protein A. However, the existence of a second gene in S. aureus strain 8325-4 encoding an IgG-binding polypeptide was recently reported. This novel IgG-binding polypeptide was found after panning a shotgun phage display library, made from chromosomal DNA, against immobilized human IgG. The complete gene (sbi) encoding this novel IgG-binding protein, denoted protein Sbi, has now been cloned and sequenced. Analysis of other S. aureus strains showed that this gene is not unique for strain 8325-4. The protein consists of 436 amino acids and exhibits an immunoglobulin-binding specificity similar to protein A. Furthermore, it is shown that Sbi is highly expressed in strain Newman 4, which shows that IgG-binding activity in S. aureus can be mediated by proteins other than protein A.

Bacterial Outer Membrane Proteins↗

PubMed1994

Molecular characterization of the clumping factor (fibrinogen receptor) of Staphylococcus aureus.

Four mutants of Staphylococcus aureus strain Newman that were defective in the fibrinogen receptor (clumping factor) were isolated by transposon Tn917 mutagenesis. Southern hybridization analysis of the mutants identified transposon-host DNA junction fragments, one of which was cloned and used to generate a probe to identify and clone the wild-type clumping factor locus (clfA). The mutants failed to form clumps in soluble fibrinogen and adhered poorly to polymethylmethacrylate (PMMA) coverslips coated with fibrinogen. A single copy of the clfA gene, when introduced into the chromosome of the mutant strains, fully complemented the clumping deficiency of these strains and restored the ability of these mutants to adhere to fibrinogen-coated PMMA. In addition, the cloned clfA gene on a shuttle plasmid allowed the weakly clumping strain 8325-4 to form clumps with the same avidity as the wild-type strain Newman and also significantly enhanced the adherence of 8325-4 strains. Thus the formation of clumps in soluble fibrinogen correlated with adherence of bacteria to solid-phase fibrinogen. The clfA gene encodes a fibrinogen-binding protein with an apparent molecular mass of c. 130 kDa. The amino acid sequence of the protein was deduced from the DNA sequence; it was predicted that a 896 residue protein (molecular mass 92 kDa) would be expressed. The putative ClfA protein has features that suggest that it is associated with the cell surface. Furthermore it contains a novel 308 residue region comprising dipeptide repeats predominantly of Asp and Ser ending 28 residues upstream from the LPXTG motif common to wall-associated proteins. Significant homology was found between the ClfA protein and the fibronectin-binding proteins of S. aureus, particularly in the N- and C-termini.

Amino Acid Sequence↗

PubMed1990

A new class of conjugative plasmid in Staphylococcus aureus.

Plasmid pWBG637, a Staphylococcus aureus conjugative plasmid having no known resistance phenotype, was compared with other conjugative plasmids in S. aureus by restriction endonuclease analysis, incompatibility testing and DNA-DNA hybridisation. It differed from the other conjugative plasmids on all three criteria and thus belongs to a new class of conjugative plasmids.

DNA Restriction Enzymes↗

PubMedDate not supplied

A gentamycin resistance plasmid in Staphylococcus aureus.

Drug resistance in Staphylococcus aureus is frequently mediated by non-chromosomal DNA molecules referred to as R plasmids. So far, resistance to aminosidic antibiotics was observed with streptomycin [8] and kanamycin-neomycin [3]. Resistance to gentamycin has not been reported in a recent survey by Lacey [7]. In this paper, we describe a strain of S. aureus resistant to gentamycin-kanamycin-tobramycin-sisomycin, and experiments which suggest that the genetic determinant of these resistance characters is plasmid borne.

Anti-Bacterial Agents↗

PubMed2002

Evidence for a continuum of decreased vancomycin susceptibility in unselected Staphylococcus aureus clinical isolates.

Some Staphylococcus aureus isolates have glycopeptide minimal inhibitory concentrations (MICs) in the susceptible range but have subpopulations that grow on >or=4 microg/mL vancomycin. Clinical laboratory methods for determining susceptibility have proven to be inadequate for detecting these strains. Among methicillin-resistant S. aureus (MRSA) and methicillin-susceptible S. aureus (MSSA) clinical isolates, 149 (66.2%) of 225 and 17 (56.6%) of 30, respectively, grew on brain-heart infusion (BHI) medium containing 2 microg/mL vancomycin; 17 (7.5%) of the MRSA and 2 (6.6%) of the MSSA isolates grew on BHI screening plates containing 4 microg/mL vancomycin. One isolate grew on plates containing 6 microg/mL vancomycin. This isolate escaped detection by routine testing but had a vancomycin MIC of 6 microg/mL when tested in BHI medium. This isolate also had decreased Triton X-100-induced autolysis and killing when incubated in broth media containing vancomycin, properties accorded to glycopeptide-intermediate S. aureus isolates. These observations suggest that glycopeptide-intermediate-like S. aureus isolates are circulating undetected and that a continuum of decreased susceptibility exists in unselected isolates.

Adult↗

PubMed1983

Rapid isolation of DNA from Staphylococcus aureus.

We describe a Staphylococcus aureus bulk DNA isolation procedure which uses detergent and guanidine hydrochloride to free the nucleic acid from contaminants. The procedure is rapid and yields high-molecular-weight DNA suitable for molecular biological procedures.

DNA, Bacterial↗

PubMed1995

Molecular population genetic analysis of Staphylococcus aureus recovered from cows.

Staphylococcus aureus is one of the most common causes of bovine mastitis. To estimate genetic relationships among S. aureus strains recovered from cows, 357 isolates from milk samples from worldwide localities were examined for electrophoretic variation at 13 metabolic-enzyme loci. Thirty-nine electrophoretic types which represented distinctive multilocus enzyme genotypes were identified, and nearly 90% of all isolates were assigned to one of eight clones. Genetic heterogeneity was found among organisms recovered from dairy herds from which multiple isolates were obtained, indicating that the S. aureus population in a single herd can be multiclonal. Although humans and cows shared 7 of the 39 S. aureus clones, each clone was predominantly associated with one of these host species. These results are consistent with the concept of host specialization among S. aureus clones and imply that successful transfer of bacteria between humans and cows is limited.

Alleles↗

PubMed1995

Internalization of Staphylococcus aureus by cultured osteoblasts.

Staphylococcus aureus is the most common cause of both acute and chronic osteomyelitis; however, the pathogenesis of osteomyelitis is poorly understood. We investigated the ability of S. aureus to associate with chick osteoblasts in culture and have demonstrated internalization of bacteria by the osteoblasts. Two strains of S. aureus were examined that were ingested by osteoblasts to different extents, suggesting strain differences in uptake. Initial association of S. aureus strains with osteoblasts was independent of the presence of matrix collagen produced by the osteoblasts. Internalization of bacteria required live osteoblasts, but not live S. aureus, indicating osteoblasts are active in ingesting the organisms. The bacteria were not killed by the osteoblasts, since viable bacteria were cultured several hours after ingestion.

Animals↗

PubMed1991

Non-specific immunoprecipitation of rotavirus Vp6 protein with Staphylococcus aureus.

The specificity of Staphylococcus aureus and protein A-Sepharose (PA-S) were compared in the radioimmunoprecipitation assay for the characterization of monoclonal antibodies (mAbs) against rotavirus proteins. Five mAbs directed against bovine rotavirus Q17 proteins Vp6 and Vp7 and one mAb directed against human rotavirus protein Vp4 were used in this study. mAbs directed against other viruses, NS-1 culture supernatant and ascitic fluid, were used as control reagents. A non-specific immunoprecipitation of the viral protein Vp6 was always found with S. aureus, but not with PA-S. mAb 74 reacted with rotavirus antigens in ELISA and in indirect immunofluorescence assay but did not immunoprecipitate a viral protein with PA-S. This mAb immunoprecipitated the viral protein Vp6 when S. aureus reagent was used. This false positive reaction was always present and could lead to confusing results in the analysis and characterization of mAbs against rotavirus.

Antibodies, Monoclonal↗