Le Thuy Thi Nguyen

University of Tsukuba · Infection Biology

SCCmec is a large mobile genetic element that includes the mecA gene and confers resistance to β-lactam antibiotics in methicillin-resistant Staphylococcus aureus (MRSA). There is evidence that SCCmec disseminates among staphylococci, but the transfer mechanisms are unclear. Here, we show that two-component systems mediate the upregulation of natur...

Methicillin-resistant Staphylococcus aureus (MRSA) carries the resistance gene mecA in the staphylococcal cassette chromosome (SCC) that disseminates among staphylococci but the cell-to-cell transmission mechanism of SCC has not been clarified for half a century ¹ . Here, we present evidence for efficient natural transformation in Staphylococcus au...

Objectives Linezolid is one of the last resort antibiotics effectively used in the treatment of infections caused by multidrug-resistant Gram-positive bacteria. Recent outbreaks of Linezolid resistance have been the great concern world wide, while many countries have not experienced it. In this work, we aimed to evaluate the existence of linezolid...

Expression of genes required for natural genetic competence in Staphylococcus aureus is controlled by an alternative transcription sigma factor, SigH. However, even in the SigH-expressing cells, the DNA transformation efficiency varies depending on culture conditions. We report here that cells grown in the competence-inducing medium (CS2 medium) ex...

Staphylococcus aureus is a major opportunistic human pathogen causing a broad spectrum of infections.¹ This bacterium has an extraordinary ability to rapidly acquire resistance to antibiotics, and methicillin-resistant strains (MRSA), the most common cause of nosocomial infections, are now spreading into the community.2, 3 In S. aureus genome, many...

Objectives: Linezolid resistance mediated by the cfr gene represents a global concern due to its dissemination among multiresistant nosocomial pathogens such as MRSA and Enterococcus. In the present work, we have evaluated the in vitro transmission of cfr pSCFS7-like plasmids from two Staphylococcus epidermidis ST2 strains (SE45 and SE50) isolated...

It has long been a question whether Staphylococcus aureus, a major human pathogen, is able to develop natural competence for transformation by DNA. We previously showed that a novel staphylococcal secondary sigma factor, SigH, was a likely key component for competence development, but the corresponding gene appeared to be cryptic as its expression...

Summary of the frequencies of SigH active TetR BgaB-positive colonies in several independent experiments and different genetic backgrounds. Reporter strains carrying the positive selection tetracycline resistance (tet) reporter plasmid (pTet-rep) were grown in drug-free TSB and then selected with 5 µg/ml tetracycline. Shown is the summary of indepe...

Plasmid profile verification of S. aureus transformants. S. aureus cells were transformed with plasmid pT181, and plasmids were purified from twelve transformants using the GeneElute Plasmid Miniprep Kit (Sigma) and submitted to agarose gel electrophoresis. Strain N315 carries an endogenous 24.6 kb plasmid, pN315. Strain N315h carries the pRITsigH...

Comparison of competence genes and their organization in Staphylococcus aureus, Bacillus subtilis and Streptococcus pneumoniae. (TIF)

PCR-based verification of SCCmecII element in S. aureus chromosomal DNA transformants. A) PCR verification of transformants for the horizontal transfer of chromosomal determinants. The SCCmecII element of N315 carries the aadD gene for kanamycin resistance (within pUB110), as well as the mecA gene conferring oxacillin (OX) resistance, located 3.44...

Western blot analysis of SigH-dependent GFP production under different growth conditions A) Western blot analysis of SigH-dependent GFP production in strain N315comGFP. Cells were grown at 37°C in -GS or CS1 medium for 24 or 48 hours with or without shaking under aerobic (upper panel) or anaerobic (lower panel) conditions. Results with the highest...

Nucleotide sequences of SJ duplication junctions in sigH chimeric gene fusions. (TIF)

Phage-dependent “pseudo-transformation" in S. aureus does not require the comG and comE operons, unlike natural genetic competence. Experiments were carried out based on the method previously described [77] with some modifications. In brief, S. aureus cells were grown in TSB medium at 37°C overnight with shaking (180 rpm). Cells were recovered by c...

Plasmid maps of plasmids pMAD-PcomE, pRIT-PcomE-bgaB, and pMAD-tet. Plasmids pMAD-PcomE and pRIT-PcomE-bgaB are intermediates used for constructing plasmid pTet-rep. Plasmid pRIT-PcomE-bgaB was used as a reporter to follow SigH activity in Figure 1C. The Pspa promoter sequence is located between the NdeI and EcoRI sites, and hence does not affect e...

Composition of CS2 medium. (PDF)

In this study, we scanned multiple published databases of gene expression in vivo of M. tuberculosis at different phases of infection in animals and humans, to select 38 proteins that are highly expressed in the active, latent and reactivation phases. The selected proteins were predicted for T and B epitopes. For each proteins, the regions containi...

In this study, we scanned multiple published databases of gene expression in vivo of M. tuberculosis at different phases of infection in animals and humans, to select 38 proteins that are highly expressed in the active, latent and reactivation phases. The selected proteins were predicted for T and B epitopes. For each proteins, the regions containi...