Transcriptomic Adjustments of Staphylococcus aureus COL (MRSA) Forming Biofilms Under Acidic and Alkaline Conditions

Phage SEP1 hijacks Staphylococcus epidermidis stationary cells' metabolism to replicate

In nature, bacteria often survive in a stationary state with low metabolic activity. Phages use the metabolic machinery of the host cell to replicate, and, therefore, their efficacy against non-dividing cells is usually limited. Nevertheless, it was previously shown that the Staphylococcus epidermidis phage SEP1 has the remarkable capacity to actively replicate in stationary-phase cells, reducing their numbers. Here, we studied for the first time the transcriptomic profiles of both exponential and stationary cells infected with SEP1 phage using RNA-seq to gain a better understanding of this rare phenomenon. We showed that SEP1 successfully takes over the transcriptional apparatus of both exponential and stationary cells. Infection was, however, delayed in stationary cells, with genes within the gp142-gp154 module putatively implicated in host takeover. S. epidermidis responded to SEP1 infection by upregulating three genes involved in a DNA modification system, with this being observed already 5 min after infection in exponential cells and later in stationary cells. In stationary cells, a significant number of genes involved in translation and RNA metabolic and biosynthetic processes were upregulated after 15 and 30 min of SEP1 infection in comparison with the uninfected control, showing that SEP1 activates metabolic and biosynthetic pathways necessary to its successful replication.IMPORTANCEMost phage-host interaction studies are performed with exponentially growing cells. However, this cell state is not representative of what happens in natural environments. Additionally, most phages fail to replicate in stationary cells. The Staphylococcus epidermidis phage SEP1 is one of the few phages reported to date to be able to infect stationary cells. Here, we unveiled the interaction of SEP1 with its host in both exponential and stationary states of growth at the transcriptomic level. The findings of this study provide valuable insights for a better implementation of phage therapy since phages able to infect stationary cells could be more efficient in the treatment of recalcitrant infections.

Isolation and characterization of persisters of the pathogenic microorganism Staphylococcus aureus

The presence of antibiotic persisters is one of the leading causes of recurrent and chronic diseases. One challenge in mechanistic research on persisters is the enrichment of pure persisters. In this work, we validated a proposed method to isolate persisters with notorious Staphylococcus aureus cultures. With this, we analyzed the proteome profile of pure persisters and revealed the distinct mechanisms associated with vancomycin and enrofloxacin induced persisters. Furthermore, morphological and metabolic characterizations were performed, indicating further differences between these two persister populations. Finally, we assessed the effect of ATP repression, protein synthesis inhibition, and reactive oxygen species (ROS) level on persister formation. In conclusion, this work provides a comprehensive understanding of S. aureus vancomycin and enrofloxacin induced persisters, facilitating a better mechanistic understanding of persisters and the development of effective strategies to combat them.

A review of chemical signaling mechanisms underlying quorum sensing and its inhibition in Staphylococcus aureus

Staphylococcus aureus is a significant bacterium responsible for multiple infections and is a primary cause of fatalities among patients in hospital environments. The advent of pathogenic bacteria such as methicillin-resistant S. aureus revealed the shortcomings of employing antibiotics to treat bacterial infectious diseases. Quorum sensing enhances S. aureus's survivability through signaling processes. Targeting the key components of quorum sensing has drawn much interest nowadays as a promising strategy for combating infections caused by bacteria. Concentrating on the accessory gene regulator quorum-sensing mechanism is the most commonly suggested anti-virulence approach for S.aureus. Quorum quenching is a common strategy for controlling illnesses triggered by microorganisms since it reduces the pathogenicity of bacteria and improves bacterial biofilm susceptibility to antibiotics, thus providing an intriguing prospect for drug discovery. Quorum sensing inhibition reduces selective stresses and constrains the emergence of antibiotic resistance while limiting bacterial pathogenicity. This review examines the quorum sensing mechanisms involved in S. aureus, quorum sensing targets and gene regulation, environmental factors affecting quorum sensing, quorum sensing inhibition, natural products as quorum sensing inhibitory agents and novel therapeutical strategies to target quorum sensing in S. aureus as drug developing technique to augment conventional antibiotic approaches.

Invited review: Current perspectives for analyzing the dairy biofilms by integrated multiomics

Biofilms formed by pathogenic or spoilage microorganisms have become serious issues in the dairy industry, as this mode of life renders such microorganisms highly resistant to cleaning-in-place (CIP) procedures, disinfectants, desiccation, and other control strategies. The advent of omics techniques, especially the integration of different omics tools, has greatly improved our understanding of the features of microbial biofilms, and provided in-depth knowledge on developing effective methods that are directly against deleterious biofilms. This review provides novel insights into the single use of each omics tool and the application of multiomics tools to unravel the mechanisms of biofilm formation, specific molecular phenotypes exhibited by biofilms, and biofilm control strategies. Challenges and future perspective on the integration of omics tools for biofilm studies are also addressed.

Impact of cell-free supernatant of lactic acid bacteria on Staphylococcus aureus biofilm and its metabolites

Introduction

A safe bio-preservative agent, lactic acid bacteria (LAB) can inhibit the growth of pathogenic bacteria and spoilage organisms. Its cell-free supernatant (LAB-CFS), which is rich in bioactive compounds, is what makes LAB antibacterial work.

Methods

This study focused on the changes in biofilm activity and related metabolic pathways of S. aureus treated with lactic acid bacteria planktonic CFS (LAB-pk-CFS) and biofilm state (LAB-bf-CFS).

Results

The findings demonstrated that the LAB-CFS treatment considerably slowed Staphylococcus aureus (S. aureus) growth and prevented it from forming biofilms. Additionally, it inhibits the physiological traits of the S. aureus biofilm, including hydrophobicity, motility, eDNA, and PIA associated to the biofilm. The metabolites of S. aureus biofilm treated with LAB-CFS were greater in the LAB-bf-CFS than they were in the LAB-pk-CFS, according to metabolomics studies. Important metabolic pathways such amino acids and carbohydrates metabolism were among the most noticeably altered metabolic pathways.

Discussion

These findings show that LAB-CFS has a strong potential to combat S. aureus infections.

Staphylococcus aureus Fibronectin-Binding Proteins Contribute to Colonization of the Female Reproductive Tract

Methicillin-resistant Staphylococcus aureus (MRSA) is an opportunistic pathogen and frequent colonizer of human skin and mucosal membranes, including the vagina, with vaginal colonization reaching nearly 25% in some pregnant populations. MRSA vaginal colonization can lead to aerobic vaginitis (AV), and during pregnancy, bacterial ascension into the upper reproductive tract can lead to adverse birth outcomes. USA300, the most prominent MRSA lineage to colonize pregnant individuals, is a robust biofilm former and causative agent of invasive infections; however, little is known about how it colonizes and ascends in the female reproductive tract (FRT). Our previous studies showed that a MRSA mutant of seven fibrinogen-binding adhesins was deficient in FRT epithelial attachment and colonization. Using both monolayer and multilayer air-liquid interface cell culture models, we determine that one class of these adhesins, the fibronectin binding proteins (FnBPA and FnBPB), are critical for association with human vaginal epithelial cells (hVECs) and hVEC invasion through interactions with α₅β₁ integrin. We observe that both FnBPs are important for biofilm formation as single and double fnbAB mutants exhibit reduced biofilm formation on hVECs. Using heterologous expression of fnbA and fnbB in Staphylococcus carnosus, FnBPs are also found to be sufficient for hVEC cellular association, invasion, and biofilm formation. In addition, we found that an ΔfnbAB mutant displays attenuated ascension in our murine vaginal colonization model. Better understanding of MRSA FRT colonization and ascension can ultimately inform treatment strategies to limit MRSA vaginal burden or prevent ascension, especially during pregnancy and in those prone to AV.

Unraveling the mechanisms of inhibition of silver-doped bioactive glass-ceramic particles

Infections are a major concern in orthopedics. Antibacterial agents such as silver ions are of great interest as broad-spectrum biocides and have been incorporated into bioactive glass-ceramic particles to control the release of ions within a therapeutic concentration and provide tissue regenerative properties. In this work, the antibacterial capabilities of silver-doped bioactive glass (Ag-BG) microparticles were explored to reveal the unedited mechanisms of inhibition against methicillin-resistant Staphylococcus aureus (MRSA). The antibacterial properties were not limited to the delivery of silver ions but rather a combination of antibacterial degradation by-products. For example, nano-sized debris punctured holes in bacteria membranes, osmotic effects, and reactive oxygen species causing oxidative stress and almost 40% of the inhibition. Upon successive Ag-BG treatments, MRSA underwent phenotypic and genomic mutations which were not only insufficient to develop resistance but instead, the clones became more sensitive as the treatment was re-delivered. Additionally, the unprecedented restorative functionality of Ag-BG allowed the effective use of antibiotics that MRSA resists. The synergy mechanism was mainly identified for combinations targeting cell-wall activity and their action was proven in biofilm-like and virulent conditions. Unraveling these mechanisms may offer new insights into how to tailor healthcare materials to prevent or debilitate infections and join the fight against antibiotic resistance in clinical cases.

Loratadine inhibits Staphylococcus aureus virulence and biofilm formation

There are no anti-virulence and anti-biofilm treatments for Staphylococcus aureus infection. We found that 25 μM loratadine inhibits S. aureus biofilm formation under static or flow-based conditions. Testing of loratadine effects on 255 clinical S. aureus strains with varying biofilm robustness showed inhibition of biofilm formation in medium and strong, but not weak, biofilm-producing strains. At 25 μM, loratadine reduced pigmentation and hemolysis of the bacteria without affecting growth. Loratadine (5 mg/kg) reduced mortality in S. aureus pulmonary infection model mice and acted synergistically with vancomycin to reduce pulmonary bacterial load and levels of inflammatory cytokines in bronchoalveolar lavage fluid. Loratadine analogues (side-chain carbamate moiety changed) inhibited biofilm formation, pigmentation, and hemolysis of S. aureus. Regarding mechanism, loratadine exposure reduced RNA levels of virulence-related S. aureus genes, and loratadine-induced mutations in MgrA reduced loratadine-MgrA binding. Overexpression of mutated mgrA in wild-type S. aureus decreased the biofilm formation inhibition effect of loratadine.

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Loratadine inhibits S. aureus biofilm formation under static or flow conditions

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Loratadine reduced mortality in S. aureus pulmonary infection model mice

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Loratadine synergistically with vancomycin reduced pulmonary bacterial load

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Loratadine-induced mutations in MgrA reduced loratadine-MgrA binding

Genomic comparisons and phylogenetic analysis of mastitis-related staphylococci with a focus on adhesion, biofilm, and related regulatory genes

Mastitis is a common and costly disease on dairy farms, commonly caused by Staphylococcus spp. though the various species are associated with different clinical outcomes. In the current study, we performed genomic analyses to determine the prevalence of adhesion, biofilm, and related regulatory genes in 478 staphylococcal species isolated from clinical and subclinical mastitis cases deposited in public databases. The most prevalent adhesin genes (ebpS, atl, pls, sasH and sasF) were found in both clinical and subclinical isolates. However, the ebpS gene was absent in subclinical isolates of Staphylococcus arlettae, S. succinus, S. sciuri, S. equorun, S. galinarum, and S. saprophyticus. In contrast, the coa, eap, emp, efb, and vWbp genes were present more frequently in clinical (vs. subclincal) mastitis isolates and were highly correlated with the presence of the biofim operon (icaABCD) and its transcriptional regulator, icaR. Co-phylogenetic analyses suggested that many of these adhesins, biofilm, and associated regulatory genes could have been horizontally disseminated between clinical and subclinical isolates. Our results further suggest that several adhesins, biofilm, and related regulatory genes, which have been overlooked in previous studies, may be of use for virulence profiling of mastitis-related Staphylococcus strains or as potential targets for vaccine development.

Confocal spectral microscopy, a non-destructive approach to follow contamination and biofilm formation of mCherry Staphylococcus aureus on solid surfaces

Methods to test the safety of wood material for hygienically sensitive places are indirect, destructive and limited to incomplete microbial recovery via swabbing, brushing and elution-based techniques. Therefore, we chose mCherry Staphylococcus aureus as a model bacterium for solid and porous surface contamination. Confocal spectral laser microscope (CSLM) was employed to characterize and use the autofluorescence of Sessile oak (Quercus petraea), Douglas fir (Pseudotsuga menziesii) and poplar (Populus euramericana alba L.) wood discs cut into transversal (RT) and tangential (LT) planes. The red fluorescent area occupied by bacteria was differentiated from that of wood, which represented the bacterial quantification, survival and bio-distribution on surfaces from one hour to one week after inoculation. More bacteria were present near the surface on LT face wood as compared to RT and they persisted throughout the study period. Furthermore, this innovative methodology identified that S. aureus formed a dense biofilm on melamine but not on oak wood in similar inoculation and growth conditions. Conclusively, the endogenous fluorescence of materials and the model bacterium permitted direct quantification of surface contamination by using CSLM and it is a promising tool for hygienic safety evaluation.

Comparative study of the immune responses to the HMS-based fusion protein and capsule-based conjugated molecules as vaccine candidates in a mouse model of Staphylococcus aureus systemic infection

Staphylococcus aureus is a powerful pathogen that causes a wide range of infectious diseases and results in a high mortality rate in humans. Treating S. aureus-related infections is extremely difficult because of its ability to resist many antibiotics; therefore, developing an effective vaccine against this infection can be an alternative and promising approach. In this study, we evaluated the protective effects of a Hla-MntC-SACOL0723 multi-epitope protein (HMS) compared with HMS conjugated to polysaccharides 5 and 8 (CP5 and CP8) of S. aureus and CP5 and CP8 in a mouse sepsis model. To evaluate the type of induced immune response, specific IgG, and antibody isotypes (IgG1 and IgG2a) were determined using the ELISA method. The functional activity of these vaccine candidates was assessed by opsonophagocytosis. Mice were infected with S. aureus COL strain and evaluated for bacterial load in the kidney and spleen homogenates. Th1, Th2, and Th17-related cytokines in the spleen cell supernatants were assessed by flow cytometry. The therapeutic effect of specific anti-HMS protein IgG antibodies against S. aureus COL strain infection was evaluated by passive immunization. HMS recombinant protein induced a higher level of Th1, Th2, and Th17-related cytokines compared with conjugated molecules. Also, mice immunized with the HMS protein reduced the bacterial load in the kidney and spleen more than the one that received the conjugated molecules. Our study suggests that the HMS fusion protein and conjugate molecule vaccine candidates could be suitable candidates for the removal of S. aureus in the mouse sepsis model but HMS protein can be a more effective candidate.