The toxin-antitoxin system YefM-YoeB is associated with antibiotic tolerance and extracellular dependent biofilm formation.

The high antibiotic tolerance of biofilms is associated with challenges for treating periprosthetic joint infection. The toxin-antitoxin system, YefM-YoeB, is thought to be a regulator for antibiotic tolerance, but its physiological role is unknown. The objective of this study was to determine the biofilm and antibiotic susceptibility phenotypes associated with yoeB homologs.

Role of the Staphylococcus aureus Extracellular Loop of GraS in Resistance to Distinct Human Defense Peptides in PMN and Invasive Cardiovascular infections.

GraS is a membrane sensor in Staphylococcus aureus that induces and expression to alter the surface positive charge upon exposure to cationic human defense peptides (HDPs). The sensing domain of GraS likely resides in the 9-residue extracellular loop (EL). In this study, we assessed a hospital-acquired methicillin-resistant S.

The Stringent Response Contributes to Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection Through the Purine Biosynthetic Pathway.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections represent a significant clinical-therapeutic challenge. Of particular concern is antibiotic treatment failure in infections caused by MRSA that are "susceptible" to antibiotic in vitro. In the current study, we investigate specific purine biosynthetic pathways and stringent response mechanism(s) related to this life-threatening syndrome using genetic matched persistent and resolving MRSA clinical bacteremia isolates (PB and RB, respectively), and isogenic MRSA strain sets.

The Toxin-Antitoxin MazEF Drives Staphylococcus aureus Biofilm Formation, Antibiotic Tolerance, and Chronic Infection.

is the major organism responsible for surgical implant infections. Antimicrobial treatment of these infections often fails, leading to expensive surgical intervention and increased risk of mortality to the patient. The challenge in treating these infections is associated with the high tolerance of biofilm to antibiotics.

Interspecies interactions induce exploratory motility in .

Microbes often live in multispecies communities where interactions among community members impact both the individual constituents and the surrounding environment. Here, we developed a system to visualize interspecies behaviors at initial encounters. By imaging two prevalent pathogens known to be coisolated from chronic illnesses, and , we observed can modify surface motility in response to secreted factors from .

CspA regulation of Staphylococcus aureus carotenoid levels and σ activity is controlled by YjbH and Spx.

Staphyloxanthin, a carotenoid in S. aureus, is a powerful antioxidant against oxidative stresses. The crtOPQMN operon driving pigment synthesis is under the control of σ .

Role of Purine Biosynthesis in Persistent Methicillin-Resistant Staphylococcus aureus Infection.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia (PB) represents an important subset of S. aureus endovascular infections. In this study, we investigated potential genetic mechanisms underlying the persistent outcomes.

Healthcare Antibiotic Resistance Prevalence - DC (HARP-DC): A Regional Prevalence Assessment of Carbapenem-Resistant Enterobacteriaceae (CRE) in Healthcare Facilities in Washington, District of Columbia.

OBJECTIVE Carbapenem-resistant Enterobacteriaceae (CRE) are a significant clinical and public health concern. Understanding the distribution of CRE colonization and developing a coordinated approach are key components of control efforts. The prevalence of CRE in the District of Columbia is unknown.

Bypassing the Restriction System To Improve Transformation of Staphylococcus epidermidis.

is the leading cause of infections on indwelling medical devices worldwide. Intrinsic antibiotic resistance and vigorous biofilm production have rendered these infections difficult to treat and, in some cases, require the removal of the offending medical prosthesis. With the exception of two widely passaged isolates, RP62A and 1457, the pathogenesis of infections caused by clinical strains is poorly understood due to the strong genetic barrier that precludes the efficient transformation of foreign DNA into clinical isolates.

Persister formation in Staphylococcus aureus is associated with ATP depletion.

Persisters are dormant phenotypic variants of bacterial cells that are tolerant to killing by antibiotics(1). Persisters are associated with chronic infections and antibiotic treatment failure(1-3). In Escherichia coli, toxin-antitoxin modules have been linked to persister formation(4-6).

Persister formation in is associated with ATP depletion.

Persisters are dormant phenotypic variants of bacterial cells that are tolerant to killing by antibiotics. Persisters are associated with chronic infections and antibiotic treatment failure. In , toxin/antitoxin (TA) modules have been linked to persister formation.

Effect of clpP and clpC deletion on persister cell number in Staphylococcus aureus.

Staphylococcus aureus is responsible for a wide variety of infections that include superficial skin and soft tissue infections, septicaemia, central nervous system infections, endocarditis, osteomyelitis and pneumonia. Others have demonstrated the importance of toxin-antitoxin (TA) modules in the formation of persisters and the role of the Clp proteolytic system in the regulation of these TA modules. This study was conducted to determine the effect of clpP and clpC deletion on S.

The GraS Sensor in Staphylococcus aureus Mediates Resistance to Host Defense Peptides Differing in Mechanisms of Action.

Staphylococcus aureus uses the two-component regulatory system GraRS to sense and respond to host defense peptides (HDPs). However, the mechanistic impact of GraS or its extracellular sensing loop (EL) on HDP resistance is essentially unexplored. Strains with null mutations in the GraS holoprotein (ΔgraS) or its EL (ΔEL) were compared for mechanisms of resistance to HDPs of relevant immune sources: neutrophil α-defensin (human neutrophil peptide 1 [hNP-1]), cutaneous β-defensin (human β-defensin 2 [hBD-2]), or the platelet kinocidin congener RP-1.

Improving transformation of Staphylococcus aureus belonging to the CC1, CC5 and CC8 clonal complexes.

Methicillin resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen found in hospital and community environments that can cause serious infections. A major barrier to genetic manipulations of clinical isolates has been the considerable difficulty in transforming these strains with foreign plasmids, such as those from E. coli, in part due to the type I and IV Restriction Modification (R-M) barriers.

Site-specific mutation of the sensor kinase GraS in Staphylococcus aureus alters the adaptive response to distinct cationic antimicrobial peptides.

The Staphylococcus aureus two-component regulatory system, GraRS, is involved in resistance to killing by distinct host defense cationic antimicrobial peptides (HD-CAPs). It is believed to regulate downstream target genes such as mprF and dltABCD to modify the S. aureus surface charge.

Role of adaptor TrfA and ClpPC in controlling levels of SsrA-tagged proteins and antitoxins in Staphylococcus aureus.

Staphylococcus aureus responds to changing extracellular environments in part by adjusting its proteome through alterations of transcriptional priorities and selective degradation of the preexisting pool of proteins. In Bacillus subtilis, the proteolytic adaptor protein MecA has been shown to play a role in assisting with the proteolytic degradation of proteins involved in competence and the oxidative stress response. However, the targets of TrfA, the MecA homolog in S.

In vivo bioluminescence imaging to evaluate systemic and topical antibiotics against community-acquired methicillin-resistant Staphylococcus aureus-infected skin wounds in mice.

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) frequently causes skin and soft tissue infections, including impetigo, cellulitis, folliculitis, and infected wounds and ulcers. Uncomplicated CA-MRSA skin infections are typically managed in an outpatient setting with oral and topical antibiotics and/or incision and drainage, whereas complicated skin infections often require hospitalization, intravenous antibiotics, and sometimes surgery. The aim of this study was to develop a mouse model of CA-MRSA wound infection to compare the efficacy of commonly used systemic and topical antibiotics.

Crystallization of the Staphylococcus aureus MazF mRNA interferase.

mazEF modules encode toxin-antitoxin pairs that are involved in the bacterial stress response through controlled and specific degradation of mRNA. Staphylococcus aureus MazF and MazE constitute a unique toxin-antitoxin module under regulation of the sigB operon. A MazF-type mRNA interferase is combined with an antitoxin of unknown fold.

Noninvasive in vivo imaging to evaluate immune responses and antimicrobial therapy against Staphylococcus aureus and USA300 MRSA skin infections.

Staphylococcus aureus skin infections represent a significant public health threat because of the emergence of antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA). As greater understanding of protective immune responses and more effective antimicrobial therapies are needed, a S.

The staphylococcus-specific gene rsr represses agr and virulence in Staphylococcus aureus.

The expression of virulence factors in Staphylococcus aureus is tightly coordinated by a vast network of regulatory molecules. In this report, we characterize a genetic locus unique to staphylococci called rsr that has a role in repressing two key virulence regulators, sarR and agr. Using strain SH1000, we showed that the transcription of virulence effectors, such as hla, sspA, and spa, is altered in an rsr mutant in a way consistent with agr upregulation.

Proteolytic regulation of toxin-antitoxin systems by ClpPC in Staphylococcus aureus.

Bacterial toxin-antitoxin (TA) systems typically consist of a small, labile antitoxin that inactivates a specific longer-lived toxin. In Escherichia coli, such antitoxins are proteolytically regulated by the ATP-dependent proteases Lon and ClpP. Under normal conditions, antitoxin synthesis is sufficient to replace this loss from proteolysis, and the bacterium remains protected from the toxin.

Confinement-induced quorum sensing of individual Staphylococcus aureus bacteria.

It is postulated that in addition to cell density, other factors such as the dimensions and diffusional characteristics of the environment could influence quorum sensing (QS) and induction of genetic reprogramming. Modeling studies predict that QS may operate at the level of a single cell, but, owing to experimental challenges, the potential benefits of QS by individual cells remain virtually unexplored. Here we report a physical system that mimics isolation of a bacterium, such as within an endosome or phagosome during infection, and maintains cell viability under conditions of complete chemical and physical isolation.

Regulation of the mazEF toxin-antitoxin module in Staphylococcus aureus and its impact on sigB expression.

In Staphylococcus aureus, the sigB operon codes for the alternative sigma factor sigma(B) and its regulators that enable the bacteria to rapidly respond to environmental stresses via redirection of transcriptional priorities. However, a full model of sigma(B) regulation in S. aureus has not yet emerged.

Overexpression of MazFsa in Staphylococcus aureus induces bacteriostasis by selectively targeting mRNAs for cleavage.

The role of chromosomally encoded toxin-antitoxin (TA) loci in bacterial physiology has been under debate, with the toxin proposed as either an inducer of bacteriostasis or a mediator of programmed cell death (PCD). We report here that ectopic expression of MazF(Sa), a toxin of the TA module from Staphylococcus aureus, led to a rapid decrease in CFU counts but most cells remained viable as determined by differential Syto 9 and propidium iodide staining after MazF(Sa) induction. This finding suggested that the toxin MazF(Sa) induced cell stasis rather than cell death.

Candida bloodstream infections in hemodialysis recipients.

Candidemia is a major cause of morbidity and mortality in patients undergoing hemodialysis but it has not been well defined in this patient population. We performed a retrospective case-control study to characterize the epidemiology, microbiology, and outcomes of hemodialysis-associated candidemia. All cases of candidemia at our institution were evaluated from 1 January 2000 until 1 September 2004.