Figure 5. Detection of cytokines and chemokines secreted by macrophages infected with S. We determined the multilocus genotype of 60 SIHP isolates collected from patients admitted in our hospital between and The seven-locus scheme recommended in the S. Hemolysin is one of the most important virulence factors for S. The combined effects of each of the four kinds of hemolysin result in the destruction of the red cell membrane which leads to the formation of the full transparent hemolytic ring on blood agar plates.
In this study, we sought to identify these strains and study their characteristics in microbiology. Initially, we used different commercial or self-prepared sheep blood agar plates to isolate, incubate and serially passage the strains. We showed that there are some strains that exhibit and maintain an incomplete hemolytic phenotype even after prolonged sub-culture. Thus, the possibility that this phenotype is induced by non-bacterial factors can be excluded.
Berube et al. In this study, we showed that the expression of four hemolysins of SIHP strains and SCHP strains has significantly different transcriptional expression profiles.
These results suggest that the observed incomplete phenotype of SIHP strains is most likely the effects of all four hemolysins which are expressed in a different way compared to the SCHP strains. In this study, all of the patients infected with SIHP received long-term treatment of broad-spectrum antibiotics, whether this selective pressure induced over-expression of drug-resistant genes and interfered with the expression of the hemolysin genes remains a possibility that needs further examination.
To explore the microbiological characteristics of SIHP, we conducted antimicrobial susceptibility tests and chose the virulence gene tst which are associated with S. The results of antimicrobial susceptibility tests showed that even after 10 passages, of these 60 SIHP strains, the MIC-values of linezolid and teicoplanin of only three SIHP strains have changed little. However, these changes of MIC values did not influence the assessment of the results of antimicrobial susceptibility.
As a super antigen, TSST-1 enhances the shock and immune suppression responses induced by endotoxins Kulhankova et al. Recently, many reports showed that S. In addition, patient data analysis showed that the effect of anti-infective therapy in most of the patients infected with SIHP strains was worse than that of the similar patients infected with SCHP strains data not shown.
Our study provides preliminary experimental evidence for the speculation that SIHP strains possess a potential high virulence. During the infection process of invasive S. It was reported that the secretion of inflammatory cytokines IL-6 increased with increasing concentrations of S. In addition, superantigenic S. Moreover, these SIHP strains were grouped together in the spa type of t data not shown. Taken together, SIHP may be a new subset of MRSA with potential high virulence, and more attention should be paid in controlling and treatment of these strains in hospitals.
The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest. Al Laham, N. Andrey, D. Bekeredjian-Ding, I. The innate immune response against Staphylococcus aureus. Berube, B. Toxins Basel. Changchien, C. BMC Infect Dis. Chen, Q. Inflammation 39, — Clinical and Laboratory Standards Institute Detection of alpha-toxin and other virulence factors in biofilms of Staphylococcus aureus on polystyrene and a human epidermal model.
Evangelista Sde, S. Community-acquired methicillin-resistant Staphylococcus aureus : a global problem. Giai, C. Innate Immun. Goerke, C. Ciprofloxacin and trimethoprim cause phage induction and virulence modulation in Staphylococcus aureus. Antimicrob Agents Chemother. Heym, B. Hildebrand, A. Staphylococcus aureus alpha-toxin. Dual mechanism of binding to target cells. PubMed Abstract Google Scholar. Huseby, M. Beta toxin catalyzes formation of nucleoprotein matrix in staphylococcal biofilms.
Islander, U. Partial hemolysis is termed alpha-hemolysis. Colonies typically are surrounded by a green, opaque zone. Streptococcus pneumoniae and Streptococcus mitis are a-hemolytic the picture in the middle below shows the a-hemolysis of S. If no hemolysis occurs, this is termed gamma-hemolysis. There are no notable zones around the colonies. Staphylococcus epidermidis is gamma-hemolytic.
Often when inoculating a BAP to observe hemoloysis patterns, investigators will also stab several times through the agar using an inoculating loop. We will be doing the ONPG test the next session. That test requires the turning on of a set of genes, the lac operon.
To induce this activity, the bacterium has to be exposed to lactose. This is why you will also inoculate a tube of phenol red lactose broth. Staph aureus produces alpha toxin which typically causes wide zones of beta complete hemolysis. Check the SM for growth and for pigment. Nutrients and vitamins in this medium enhance the pigmentation of the pathogenic Staphylococcus , those colonies becoming ayellow-orange colony.
Run the coagulase test: there is a linked exercise for this test. There are only a few species of Staphylococcus that are positive for the coagulase test see table below , and S. Since there are 2 kinds of coagulase enzyme—bound and freethere are 2 different tests that can be used to identify these enzymes. The TUBE method is the definitive test of the 2, the most reliable. The coagulase test exercise in the lab manual clearly describes these 2 versions. The ONPG test will be run.
Look in your lab exercises for this test for the directions on how to run the test. Since there is very little liquid in the tube, you will want to cover the top of the tube will parafilm and then place the tube top over that.
This reduces dehydration. The test media that you will run for identification depends on which category your organism falls in. You may want to run some of the following tests. Available media : arginine and ornithine decarboxylase broths urea broth ONPG sucrose, trehalose, maltose sugars VP broth nitrate broth If you have a coagulase positive Staph , there are only a few species available as your choice: there is a table with those species below.
Run necessary tests for identification.
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