The Small RNA Teg41 Regulates Expression of the Alpha Phenol-Soluble Modulins and Is Required for Virulence inStaphylococcus aureus

ABSTRACTSmall RNAs (sRNAs) remain an understudied class of regulatory molecules in bacteria in general and in Gram-positive bacteria in particular. In the major human pathogenStaphylococcus aureus, hundreds of sRNAs have been identified; however, only a few have been characterized in detail. In this study, we investigate the role of the sRNA Teg41 inS. aureusvirulence. We demonstrate that Teg41, an sRNA divergently transcribed from the locus that encodes the cytolytic alpha phenol-soluble modulin (αPSM) peptides, plays a critical role in αPSM production. Overproduction of Teg41 leads to an increase in αPSM levels and a corresponding increase in hemolytic activity fromS. aureuscells and cell-free culture supernatants. To identify regions of Teg41 important for its function, we performed anin silicoRNA-RNA interaction analysis which predicted an interaction between the 3′ end of Teg41 and the αPSM transcript. Deleting a 24-nucleotide region from theS. aureusgenome, corresponding to the 3′ end of Teg41, led to a 10-fold reduction in αPSM-dependent hemolytic activity and attenuation of virulence in a murine abscess model of infection. Restoration of hemolytic activity in the Teg41Δ3′ strain was possible by expressing full-length Teg41 intrans. Restoration of hemolytic activity was also possible by expressing the 3′ end of Teg41, suggesting that this region of Teg41 is necessary and sufficient for αPSM-dependent hemolysis. Our results show that Teg41 is positively influencing αPSM production, demonstrating for the first time regulation of the αPSM peptides by an sRNA inS. aureus.IMPORTANCEThe alpha phenol-soluble modulins (αPSMs) are among the most potent toxins produced byStaphylococcus aureus. Their biological role during infection has been studied in detail; however, the way they are produced by the bacterial cell is not well understood. In this work, we identify a small RNA molecule called Teg41 that plays an important role in αPSM production byS. aureus. Teg41 positively influences αPSM production. The importance of Teg41 is highlighted by the fact that a strain containing a deletion in the 3′ end of Teg41 produces significantly less αPSMs and is attenuated for virulence in a mouse abscess model of infection. As the search for new therapeutic strategies to combatS. aureusinfection proceeds, Teg41 may represent a novel target.

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A Critical Region in the FlaA Flagellin Facilitates Filament Formation of theVibrio choleraeFlagellum

Journal of Bacteriology ◽

10.1128/jb.00029-18 ◽

2018 ◽

Vol 200 (15) ◽

Cited By ~ 8

Author(s):

Mylea A. Echazarreta ◽

Johnathan L. Kepple ◽

Li-Hua Yen ◽

Yue Chen ◽

Karl E. Klose

Keyword(s):

Diarrheal Disease ◽

Critical Role ◽

The Other ◽

Class Iii ◽

Content Type ◽

Important Region ◽

Filament Structure ◽

Flagellar Filament ◽

Necessary And Sufficient ◽

Class Iv

ABSTRACTVibrio choleraeis a Gram-negative bacterium with a monotrichous flagellum that causes the human disease cholera. Flagellum-mediated motility is an integral part of the bacterial life cycle inside the host and in the aquatic environment. TheV. choleraeflagellar filament is composed of five flagellin subunits (FlaA, FlaB, FlaC, FlaD, and FlaE); however, only FlaA is necessary and sufficient for filament synthesis.flaAis transcribed from a class III flagellar promoter, whereas the other four flagellins are transcribed from class IV promoters. However, expressingflaAfrom a class IV promoter still facilitated motility in a strain that was otherwise lacking all five flagellins (ΔflaA-E). Furthermore, FlaA fromV. parahaemolyticus(FlaAVP; 77% identity) supported motility of theV. choleraeΔflaA-Estrain, whereas FlaA fromV. vulnificus(FlaAVV; 75% identity) did not, indicating that FlaA amino acid sequence is responsible for its critical role in flagellar synthesis. Chimeric proteins composed of different domains of FlaAVCand FlaD or FlaAVVrevealed that the N-terminal D1domain (D1N) contains an important region required for FlaA function. Further analyses of chimeric FlaAVC-FlaD proteins identified a lysine residue present at position 145 of the other flagellins but absent from FlaAVCthat can prevent monofilament formation. Moreover, the D1Nregion of amino acids 87 to 153 of FlaAVVinserted into FlaAVCallows monofilament formation but not motility, apparently due to the lack of filament curvature. These results identify residues within the D1Ndomain that allow FlaAVCto fold into a functional filament structure and suggest that FlaAVCassists correct folding of the other flagellins.IMPORTANCEV. choleraecauses the severe diarrheal disease cholera. Its ability to swim is mediated by rotation of a polar flagellum, and this motility is integral to its ability to cause disease and persist in the environment. The current studies illuminate how one specific flagellin (FlaA) within a multiflagellin structure mediates formation of the flagellar filament, thus allowingV. choleraeto swim. This knowledge can lead to safer vaccines and potential therapeutics to inhibit cholera.

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Linezolid Attenuates Lethal Lung Damage during Postinfluenza Methicillin-Resistant Staphylococcus aureus Pneumonia

Infection and Immunity ◽

10.1128/iai.00538-19 ◽

2019 ◽

Vol 87 (10) ◽

Cited By ~ 2

Author(s):

Atul K. Verma ◽

Christopher Bauer ◽

Vijaya Kumar Yajjala ◽

Shruti Bansal ◽

Keer Sun

Keyword(s):

Staphylococcus Aureus ◽

Therapeutic Effect ◽

Critical Role ◽

Lung Damage ◽

Alpha Toxin ◽

Methicillin Resistant ◽

Content Type ◽

Linezolid Therapy ◽

Staphylococcus Aureus Pneumonia ◽

The Impact

ABSTRACT Postinfluenza methicillin-resistant Staphylococcus aureus (MRSA) infection can quickly develop into severe, necrotizing pneumonia, causing over 50% mortality despite antibiotic treatments. In this study, we investigated the efficacy of antibiotic therapies and the impact of S. aureus alpha-toxin in a model of lethal influenza virus and MRSA coinfection. We demonstrate that antibiotics primarily attenuate alpha-toxin-induced acute lethality, even though both alpha-toxin-dependent and -independent mechanisms significantly contribute to animal mortality after coinfection. Furthermore, we found that the protein synthesis-suppressing antibiotic linezolid has an advantageous therapeutic effect on alpha-toxin-induced lung damage, as measured by protein leak and lactate dehydrogenase (LDH) activity. Importantly, using a Panton-Valentine leucocidin (PVL)-negative MRSA isolate from patient sputum, we show that linezolid therapy significantly improves animal survival from postinfluenza MRSA pneumonia compared with vancomycin treatment. Rather than improved viral or bacterial control, this advantageous therapeutic effect is associated with a significantly attenuated proinflammatory cytokine response and acute lung damage in linezolid-treated mice. Together, our findings not only establish a critical role of alpha-toxin in the extreme mortality of secondary MRSA pneumonia after influenza but also provide support for the possibility that linezolid could be a more effective treatment than vancomycin to improve disease outcomes.

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Disruption of Glycolysis by Nutritional Immunity Activates a Two-Component System That Coordinates a Metabolic and Antihost Response by Staphylococcus aureus

mBio ◽

10.1128/mbio.01321-19 ◽

2019 ◽

Vol 10 (4) ◽

Cited By ~ 4

Author(s):

Paola K. Párraga Solórzano ◽

Jiangwei Yao ◽

Charles O. Rock ◽

Thomas E. Kehl-Fie

Keyword(s):

Staphylococcus Aureus ◽

Metabolic Flux ◽

Bacterial Species ◽

Critical Role ◽

Dependent Manner ◽

Two Component System ◽

Component System ◽

Content Type ◽

Nutritional Immunity ◽

Two Component

ABSTRACT During infection, bacteria use two-component signal transduction systems to sense and adapt to the dynamic host environment. Despite critically contributing to infection, the activating signals of most of these regulators remain unknown. This also applies to the Staphylococcus aureus ArlRS two-component system, which contributes to virulence by coordinating the production of toxins, adhesins, and a metabolic response that enables the bacterium to overcome host-imposed manganese starvation. Restricting the availability of essential transition metals, a strategy known as nutritional immunity, constitutes a critical defense against infection. In this work, expression analysis revealed that manganese starvation imposed by the immune effector calprotectin or by the absence of glycolytic substrates activates ArlRS. Manganese starvation imposed by calprotectin also activated the ArlRS system even when glycolytic substrates were present. A combination of metabolomics, mutational analysis, and metabolic feeding experiments revealed that ArlRS is activated by alterations in metabolic flux occurring in the latter half of the glycolytic pathway. Moreover, calprotectin was found to induce expression of staphylococcal leukocidins in an ArlRS-dependent manner. These studies indicated that ArlRS is a metabolic sensor that allows S. aureus to integrate multiple environmental stresses that alter glycolytic flux to coordinate an antihost response and to adapt to manganese starvation. They also established that the latter half of glycolysis represents a checkpoint to monitor metabolic state in S. aureus. Altogether, these findings contribute to understanding how invading pathogens, such as S. aureus, adapt to the host during infection and suggest the existence of similar mechanisms in other bacterial species. IMPORTANCE Two-component regulatory systems enable bacteria to adapt to changes in their environment during infection by altering gene expression and coordinating antihost responses. Despite the critical role of two-component systems in bacterial survival and pathogenesis, the activating signals for most of these regulators remain unidentified. This is exemplified by ArlRS, a Staphylococcus aureus global regulator that contributes to virulence and to resisting host-mediated restriction of essential nutrients, such as manganese. In this report, we demonstrate that manganese starvation and the absence of glycolytic substrates activate ArlRS. Further investigations revealed that ArlRS is activated when the latter half of glycolysis is disrupted, suggesting that S. aureus monitors flux through the second half of this pathway. Host-imposed manganese starvation also induced the expression of pore-forming toxins in an ArlRS-dependent manner. Cumulatively, this work reveals that ArlRS acts as a sensor that links nutritional status, cellular metabolism, and virulence regulation.

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Importance of Bacillithiol in the Oxidative Stress Response of Staphylococcus aureus

Infection and Immunity ◽

10.1128/iai.01074-13 ◽

2013 ◽

Vol 82 (1) ◽

pp. 316-332 ◽

Cited By ~ 44

Author(s):

Ana C. Posada ◽

Stacey L. Kolar ◽

Renata G. Dusi ◽

Patrice Francois ◽

Alexandra A. Roberts ◽

...

Keyword(s):

Oxidative Stress ◽

Staphylococcus Aureus ◽

Physiological Role ◽

Content Type ◽

Chromatography Analysis ◽

Expression Of Genes ◽

Fold Reduction ◽

Fosfomycin Resistance ◽

Microarray Analyses

ABSTRACTInStaphylococcus aureus, the low-molecular-weight thiol called bacillithiol (BSH), together with cognateS-transferases, is believed to be the counterpart to the glutathione system of other organisms. To explore the physiological role of BSH inS. aureus, we constructed mutants with the deletion ofbshA(sa1291), which encodes the glycosyltransferase that catalyzes the first step of BSH biosynthesis, andfosB(sa2124), which encodes a BSH-S-transferase that confers fosfomycin resistance, in severalS. aureusstrains, including clinical isolates. Mutation offosBorbshAcaused a 16- to 60-fold reduction in fosfomycin resistance in theseS. aureusstrains. High-pressure liquid chromatography analysis, which quantified thiol extracts, revealed some variability in the amounts of BSH present acrossS. aureusstrains. Deletion offosBled to a decrease in BSH levels. ThefosBandbshAmutants of strain COL and a USA300 isolate, upon further characterization, were found to be sensitive to H2O2and exhibited decreased NADPH levels compared with those in the isogenic parents. Microarray analyses of COL and the isogenicbshAmutant revealed increased expression of genes involved in staphyloxanthin synthesis in thebshAmutant relative to that in COL under thiol stress conditions. However, thebshAmutant of COL demonstrated decreased survival compared to that of the parent in human whole-blood survival assays; likewise, the naturally BSH-deficient strain SH1000 survived less well than its BSH-producing isogenic counterpart. Thus, the survival ofS. aureusunder oxidative stress is facilitated by BSH, possibly via a FosB-mediated mechanism, independently of its capability to produce staphyloxanthin.

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Analysis of the Small RNA Transcriptional Response in Multidrug-Resistant Staphylococcus aureus after Antimicrobial Exposure

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00263-13 ◽

2013 ◽

Vol 57 (8) ◽

pp. 3864-3874 ◽

Cited By ~ 50

Author(s):

Benjamin P. Howden ◽

Marie Beaume ◽

Paul F. Harrison ◽

David Hernandez ◽

Jacques Schrenzel ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Expression Profiles ◽

Critical Role ◽

Nonnegative Matrix ◽

Transcriptional Response ◽

Antibiotic Exposure ◽

Data Set ◽

Remarkable Feature ◽

Content Type

ABSTRACTThe critical role of noncoding small RNAs (sRNAs) in the bacterial response to changing conditions is increasingly recognized. However, a specific role for sRNAs during antibiotic exposure has not been investigated inStaphylococcus aureus. Here, we used Illumina RNA-Seq to examine the sRNA response of multiresistant sequence type 239 (ST239)S. aureusafter exposure to four antibiotics (vancomycin, linezolid, ceftobiprole, and tigecycline) representing the major classes of antimicrobials used to treat methicillin-resistantS. aureus(MRSA) infections. We identified 409 potential sRNAs and then compared global sRNA and mRNA expression profiles at 2 and 6 h, without antibiotic exposure and after exposure to each antibiotic, for a vancomycin-susceptible strain (JKD6009) and a vancomycin-intermediate strain (JKD6008). Exploration of this data set by multivariate analysis using a novel implementation of nonnegative matrix factorization (NMF) revealed very different responses for mRNA and sRNA. Where mRNA responses clustered with strain or growth phase conditions, the sRNA responses were predominantly linked to antibiotic exposure, including sRNA responses that were specific for particular antibiotics. A remarkable feature of the antimicrobial response was the prominence of antisense sRNAs to genes encoding proteins involved in protein synthesis and ribosomal function. This study has defined a large sRNA repertoire in epidemic ST239 MRSA and shown for the first time that a subset of sRNAs are part of a coordinated transcriptional response to specific antimicrobial exposures inS. aureus. These data provide a framework for interrogating the role of staphylococcal sRNAs in antimicrobial resistance and exploring new avenues for sRNA-based antimicrobial therapies.

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Impact of the Novel Prophage ϕSA169 on Persistent Methicillin-Resistant Staphylococcus aureus Endovascular Infection

mSystems ◽

10.1128/msystems.00178-20 ◽

2020 ◽

Vol 5 (3) ◽

Author(s):

Liang Li ◽

Genzhu Wang ◽

Yi Li ◽

Patrice Francois ◽

Arnold S. Bayer ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Hot Spot ◽

Critical Role ◽

Bacteriophage Therapy ◽

Methicillin Resistant ◽

Content Type ◽

Antimicrobial Resistance Genes

ABSTRACT Persistent methicillin-resistant Staphylococcus aureus (MRSA) endovascular infections are life-threatening syndromes with few therapeutic options. The potential impact of bacteriophages on the persistent outcome has not been well studied. In this study, we investigated the role of a novel prophage (ϕSA169) in MRSA persistence by using a lysogen-free clinically resolving bacteremia (RB) isolate and comparing it to a derivative which was obtained by infecting the RB strain with ϕSA169, which has been lysogenized in a clinical persistent MRSA bacteremia (PB) isolate. Similar to the PB isolate, the ϕSA169-lysogenized RB strain exhibited well-defined in vitro and in vivo phenotypic and genotypic signatures related to the persistent outcome, including earlier activation of global regulators (i.e., sigB, sarA, agr RNAIII, and sae); higher expression of a critical purine biosynthesis gene, purF; and higher growth rates accompanied by lower ATP levels and vancomycin (VAN) susceptibility and stronger δ-hemolysin and biofilm formation versus its isogenic parental RB isolate. Notably, the contribution of ϕSA169 in persistent outcome with VAN treatment was confirmed in an experimental infective endocarditis model. Taken together, these results indicate the critical role of the prophage ϕSA169 in persistent MRSA endovascular infections. Further studies are needed to identify the mechanisms of ϕSA169 in mediating the persistence, as well as establishing the scope of impact, of this prophage in other PB strains. IMPORTANCE Bacteriophages are viruses that invade the bacterial host, disrupt bacterial metabolism, and cause the bacterium to lyse. Because of its remarkable antibacterial activity and unique advantages over antibiotics, for instance, bacteriophage is specific for one species of bacteria and resistance to phage is less common than resistance to antibiotics. Indeed, bacteriophage therapy for treating infections due to multidrug-resistant pathogens in humans has become a research hot spot. However, it is also worth considering that bacteriophages are transferable and could cotransfer host chromosomal genes, e.g., virulence and antimicrobial resistance genes, while lysogenizing and integrating into the bacterial chromosome (prophage), thus playing a role in bacterial evolution and virulence. In the current study, we identified a novel prophage, ϕSA169, from a clinical persistent MRSA bacteremia isolate, and we determined that ϕSA169 mediated well-defined in vitro and in vivo phenotypic and genotypic signatures related to the persistent outcome, which may represent a unique and important persistent mechanism(s).

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Identification of a Novel LysR-Type Transcriptional Regulator in Staphylococcus aureus That Is Crucial for Secondary Tissue Colonization during Metastatic Bloodstream Infection

mBio ◽

10.1128/mbio.01646-20 ◽

2020 ◽

Vol 11 (4) ◽

Author(s):

Michaela Groma ◽

Sarah A. Horst ◽

Sudip Das ◽

Bruno Huettel ◽

Maximilian Klepsch ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Bloodstream Infection ◽

Murine Model ◽

Bacterial Colonization ◽

Critical Role ◽

Transcriptional Regulator ◽

Metabolic Adaptation ◽

Mutant Library ◽

Copper Transporter ◽

Content Type

ABSTRACT Staphylococcus aureus is a common cause of bacteremia that can lead to severe complications once the bacteria exit the bloodstream and establish infection in secondary organs. Despite its clinical relevance, little is known about the bacterial factors facilitating the development of these metastatic infections. Here, we used an S. aureus transposon mutant library coupled to transposon insertion sequencing (Tn-Seq) to identify genes that are critical for efficient bacterial colonization of secondary organs in a murine model of metastatic bloodstream infection. Our transposon screen identified a LysR-type transcriptional regulator (LTTR), which was required for efficient colonization of secondary organs such as the kidneys in infected mice. The critical role of LTTR in secondary organ colonization was confirmed using an isogenic mutant deficient in the expression of LTTR. To identify the set of genes controlled by LTTR, we used an S. aureus strain carrying the LTTR gene in an inducible expression plasmid. Gene expression analysis upon induction of LTTR showed increased transcription of genes involved in branched-chain amino acid biosynthesis, a methionine sulfoxide reductase, and a copper transporter as well as decreased transcription of genes coding for urease and components of pyrimidine nucleotides. Furthermore, we show that transcription of LTTR is repressed by glucose, is induced under microaerobic conditions, and required trace amounts of copper ions. Our data thus pinpoints LTTR as an important element that enables a rapid adaptation of S. aureus to the changing host microenvironment. IMPORTANCE Staphylococcus aureus is an important pathogen that can disseminate via the bloodstream and establish metastatic infections in distant organs. To achieve a better understanding of the bacterial factors facilitating the development of these metastatic infections, we used in this study a Staphylococcus aureus transposon mutant library in a murine model of intravenous infection, where bacteria first colonize the liver as the primary infection site and subsequently progress to secondary sites such as the kidney and bones. We identified a novel LysR-type transcriptional regulator (LTTR), which was specifically required by S. aureus for efficient colonization of secondary organs. We also determined the transcriptional activation as well as the regulon of LTTR, which suggests that this regulator is involved in the metabolic adaptation of S. aureus to the host microenvironment found in secondary infection sites.

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Fate of Mutation Rate Depends onagrLocus Expression during Oxacillin-Mediated Heterogeneous-Homogeneous Selection in Methicillin-Resistant Staphylococcus aureus Clinical Strains

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01119-09 ◽

2011 ◽

Vol 55 (7) ◽

pp. 3176-3186 ◽

Cited By ~ 11

Author(s):

Konrad B. Plata ◽

Roberto R. Rosato ◽

Adriana E. Rosato

Keyword(s):

Staphylococcus Aureus ◽

Mutation Rate ◽

Selection Process ◽

Critical Role ◽

Ectopic Expression ◽

Regulatory System ◽

Methicillin Resistant ◽

Content Type ◽

Heterogeneous Expression ◽

Mrsa Strains

ABSTRACTMethicillin-resistantStaphylococcus aureus(MRSA) strains are characterized by a heterogeneous expression of resistance. We have previously shown in clinical oxacillin-susceptible,mecA-positive MRSA strains that selection from a very heterogeneous (HeR) to highly homogeneous (HoR) resistant phenotype was mediated by acquisition of mutations through an oxacillin-induced SOS response. In the present study, we used a spotted DNA microarray to evaluate differential gene expression during HeR-HoR selection and found increased expression of theagrtwo-component regulatory system. We hypothesized that increased expression ofagrrepresents a mechanistically relevant component of this process. We demonstrated that inactivation ofagrduring the HeR-HoR selection process results in a significant increase in mutation rate; these effects were reversed by complementing theagrmutant. Furthermore, we found that extemporal ectopic expression ofagrand, more specifically, RNAII inagr-null mutant HeR cells suppressed mutation frequency and the capacity of these cells to undergo the HeR-HoR selection. These findings sustain the concept that increased expression ofagrduring HeR-HoR selection plays a critical role in regulating the β-lactam-induced increased mutation rate in very heterogeneous MRSA strains. Moreover, they indicate that a temporally controlled increase inagrexpression is required to tightly modulate SOS-mediated mutation rates, which then allows for full expression of oxacillin homogeneous resistance in very heterogeneous clinical MRSA strains.

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Platelets Enhance Dendritic Cell Responses againstStaphylococcus aureusthrough CD40-CD40L

Infection and Immunity ◽

10.1128/iai.00186-18 ◽

2018 ◽

Vol 86 (9) ◽

Cited By ~ 8

Author(s):

Sharmeen Nishat ◽

Leah M. Wuescher ◽

Randall G. Worth

Keyword(s):

Staphylococcus Aureus ◽

Dendritic Cells ◽

Dendritic Cell ◽

Critical Role ◽

Interleukin 12 ◽

Necrosis Factor Alpha ◽

Content Type ◽

Enhanced Production ◽

Bacterial Uptake ◽

Direct Killing

ABSTRACTStaphylococcus aureusis a major human pathogen that can cause mild to severe life-threatening infections in many tissues and organs. Platelets are known to participate in protection againstS. aureusby direct killing and by enhancing the activities of neutrophils and macrophages in clearingS. aureusinfection. Platelets have also been shown to induce monocyte differentiation into dendritic cells and to enhance activation of dendritic cells. Therefore, in the present study, we explored the role of platelets in enhancing bone marrow-derived dendritic cell (BMDC) function againstS. aureus. We observed a significant increase in dendritic cell phagocytosis and intracellular killing of a methicillin-resistantStaphylococcus aureus(MRSA) strain (USA300) by thrombin-activated platelets or their releasates. Enhancement of bacterial uptake and killing by DCs is mediated by platelet-derived CD40L. Coculture of USA300 and BMDCs in the presence of thrombin-activated platelet releasates invokes upregulation of the maturation marker CD80 on DCs and enhanced production of the proinflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin 12 (IL-12), and IL-6. Overall, these observations support our hypothesis that platelets play a critical role in the host defense againstS. aureusinfection. Platelets stimulate DCs, leading to direct killing ofS. aureusand enhanced DC maturation, potentially leading to adaptive immune responses againstS. aureus.

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

mBio ◽

10.1128/mbio.01658-19 ◽

2019 ◽

Vol 10 (6) ◽

Cited By ~ 11

Author(s):

Dongzhu Ma ◽

Jonathan B. Mandell ◽

Niles P. Donegan ◽

Ambrose L. Cheung ◽

Wanyan Ma ◽

...

Keyword(s):

Staphylococcus Aureus ◽

Biofilm Formation ◽

Chronic Infection ◽

Critical Role ◽

Antimicrobial Treatment ◽

Antibiotic Tolerance ◽

Chronic Infections ◽

Content Type ◽

Increased Risk

ABSTRACT Staphylococcus aureus 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 S. aureus biofilm to antibiotics. MazEF, a toxin-antitoxin system, is thought to be an important regulator of this phenotype, but its physiological function in S. aureus is controversial. Here, we examined the role of MazEF in developing chronic infections by comparing growth and antibiotic tolerance phenotypes in three S. aureus strains to their corresponding strains with disruption of mazF expression. Strains lacking mazF production showed increased biofilm growth and decreased biofilm antibiotic tolerance. Deletion of icaADBC in the mazF::Tn background suppressed the growth phenotype observed with mazF-disrupted strains, suggesting the phenotype was ica dependent. We confirmed these phenotypes in our murine animal model. Loss of mazF resulted in increased bacterial burden and decreased survival rate of mice compared to its wild-type strain demonstrating that loss of the mazF gene caused an increase in S. aureus virulence. Although lack of mazF gene expression increased S. aureus virulence, it was more susceptible to antibiotics in vivo. Combined, the ability of mazF to inhibit biofilm formation and promote biofilm antibiotic tolerance plays a critical role in transitioning from an acute to chronic infection that is difficult to eradicate with antibiotics alone. IMPORTANCE Surgical infections are one of the most common types of infections encountered in a hospital. Staphylococcus aureus is the most common pathogen associated with this infection. These infections are resilient and difficult to eradicate, as the bacteria form biofilm, a community of bacteria held together by an extracellular matrix. Compared to bacteria that are planktonic, bacteria in a biofilm are more resistant to antibiotics. The mechanism behind how bacteria develop this resistance and establish a chronic infection is unknown. We demonstrate that mazEF, a toxin-antitoxin gene, inhibits biofilm formation and promotes biofilm antibiotic tolerance which allows S. aureus to transition from an acute to chronic infection that cannot be eradicated with antibiotics but is less virulent. This gene not only makes the bacteria more tolerant to antibiotics but makes the bacteria more tolerant to the host.

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