Sub-Inhibitory Clindamycin and Azithromycin reduce S. aureus Exoprotein Induced Toxicity, Inflammation, Barrier Disruption and Invasion

Sub-inhibitory concentrations of tigecycline could attenuate the virulence of Staphylococcus aureus by inhibiting the product of α-toxin

Staphylococcus aureus (S. aureus) infection is a serious threat to global health. This study aimed to investigate the anti-virulence efficacy of tigecycline against S. aureus. We used highly virulent S. aureus strains SA75 and JP30 to evaluate the effect of tigecycline on virulence, both of them isolated from the clinic. The MIC value of tigecycline against SA75 was 0.125 µg/mL, and that against JP30 was 0.25 µg/mL. Tigecycline did not affect the growth ability of bacteria at 0.015 µg/mL. Thus, subsequent discussions will focus on the effect of antibiotics at the latter subinhibitory concentrations that did not affect growth. First, the sub-MICs of tigecycline not only enhanced the sensitivity of S. aureus to oxidants and human whole blood but also weakened the hemolytic activity and cell adhesion level of S. aureus. Second, it undermined the survival of S. aureus in RAW264.7 and attenuated the macrophage inflammatory response induced by S. aureus. On the contrary, tigecycline decreased the hemolytic activity, as well as the skin abscess formation and bacterial burden in mice. Most importantly, it significantly decreased the expression of hla, hlgB, hlgC, spa, sbi, saeR, sak, tst, and coa genes by RT-qPCR and the protein expression of α-toxin. Altogether, the sub-MICs of tigecycline might be a promising agent to attenuate the virulence of S. aureus and its host immune response by inhibiting the SaeRS two-component system and the product of α-toxin.IMPORTANCEIn this study, the sub-MICs of tigecycline decreased the resistance of S. aureus to oxidants and human whole blood. Moreover, tigecycline weakened the cell adhesion level of S. aureus and skin abscess formation in mice by reducing bacterial burden. Remarkably, tigecycline decreased the hemolytic activity and significantly downregulated the expression of various virulence genes and α-toxin. This research highlighted that the sub-MICs of tigecycline might be a promising agent to attenuate the virulence of S. aureus by inhibiting the product of α-toxin.

Sub-MIC streptomycin and tetracycline enhanced Staphylococcus aureus Guangzhou-SAU749 biofilm formation, an in-depth study on transcriptomics

Staphylococcus aureus is a major human pathogen, a potential "Super-bug" and a typical biofilm forming bacteria. With usage of large amount of antibiotics, the residual antibiotics in clinical settings further complicate the colonization, pathogenesis and resistance of S. aureus. This study aimed at investigating the phenotypical and global gene expression changes on biofilm formation of a clinical S. aureus isolate treated under different types of antibiotics. Firstly, an isolate Guangzhou-SAU749 was selected from a large sale of previously identified S. aureus isolates, which exhibited weak biofilm formation in terms of biomass and viability. Secondly, 9 commonly prescribed antibiotics for S. aureus infections treatment, together with 10 concentrations ranging from 1/128 to 4 minimum inhibitory concentration (MIC) with 2-fold serial dilution, were used as different antibiotic stress conditions. Then, biofilm formation of S. aureus Guangzhou-SAU749 at different stages including 8 h, 16 h, 24 h, and 48 h, was tested by crystal violet and MTS assays. Thirdly, the whole genome of S. aureus Guangzhou-SAU749 was investigated by genome sequencing on PacBio platform. Fourthly, since enhancement of biofilm formation occurred when treated with 1/2 MIC tetracycline (TCY) and 1/4 MIC streptomycin (STR) since 5 h, the relevant biofilm samples were selected and subjected to RNA-seq and bioinformatics analysis. Last, expression of two component system (TCS) and biofilm associated genes in 4 h, 8 h, 16 h, 24 h, and 48 h sub-MIC TCY and STR treated biofilm samples were performed by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Although most antibiotics lowered the biomass and cell viability of Guangzhou-SAU749 biofilm at concentrations higher than MIC, certain antibiotics including TCY and STR promoted biofilm formation at sub-MICs. Additionally, upon genome sequencing, RNA-seq and RT-qPCR on biofilm samples treated with sub-MIC of TCY and STR at key time points, genes lytR, arlR, hssR, tagA, clfB, atlA and cidA related to TCS and biofilm formation were identified to contribute to the enhanced biofilm formation, providing a theoretical basis for further controlling on S. aureus biofilm formation.

Antibiotic-Induced Biofilm Formations in Pseudomonas aeruginosa Strains KPW.1-S1 and HRW.1-S3 are Associated with Increased Production of eDNA and Exoproteins, Increased ROS Generation, and Increased Cell Surface Hydrophobicity

Pseudomonas aeruginosa is a medically important opportunistic pathogen due to its intrinsic ability to form biofilms on different surfaces as one of the defense mechanisms for survival. The fact that it can form biofilms on various medical implants makes it more harmful clinically. Although various antibiotics are used to treat Pseudomonas aeruginosa infections, studies have shown that sub-MIC levels of antibiotics could induce Pseudomonas biofilm formation. The present study thus explored the effect of the aminoglycoside antibiotic gentamicin on the biofilm dynamics of two Pseudomonas aeruginosa strains KPW.1-S1 and HRW.1-S3. Biofilm formation was found to be increased in the presence of increased concentrations of gentamicin. Confocal, scanning electron microscopy, and other biochemical tests deduced that biofilm-forming components exoproteins, eDNA, and exolipids as exopolymeric substances in Pseudomonas aeruginosa biofilms were increased in the presence of gentamicin. An increase in reactive oxygen species generation along with increased cell surface hydrophobicity was also seen for both strains when treated with gentamicin. The observed increase in the adherence of the cells accompanied by the increase in the components of exopolymeric substances may have largely contributed to the increased biofilm production by the Pseudomonas aeruginosa strains under the stress of the antibiotic treatment.

Clindamycin-Loaded Nanosized Calcium Phosphates Powders as a Carrier of Active Substances

Bioactive calcium phosphate ceramics (CaPs) are one of the building components of the inorganic part of bones. Synthetic CaPs are frequently used as materials for filling bone defects in the form of pastes or composites; however, their porous structure allows modification with active substances and, thus, subsequent use as a drug carrier for the controlled release of active substances. In this study, four different ceramic powders were compared: commercial hydroxyapatite (HA), TCP, brushite, as well as HA obtained by wet precipitation methods. The ceramic powders were subjected to physicochemical analysis, including FTIR, XRD, and determination of Ca/P molar ratio or porosity. These techniques confirmed that the materials were phase-pure, and the molar ratios of calcium and phosphorus elements were in accordance with the literature. This confirmed the validity of the selected synthesis methods. CaPs were then modified with the antibiotic clindamycin. Drug release was determined on HPLC, and antimicrobial properties were tested against Staphylococcus aureus. The specific surface area of the ceramic has been demonstrated to be a factor in drug release efficiency.

Antimicrobial Treatment of Staphylococcus aureus Biofilms

Staphylococcus aureus is a microorganism frequently associated with implant-related infections, owing to its ability to produce biofilms. These infections are difficult to treat because antimicrobials must cross the biofilm to effectively inhibit bacterial growth. Although some antibiotics can penetrate the biofilm and reduce the bacterial load, it is important to understand that the results of routine sensitivity tests are not always valid for interpreting the activity of different drugs. In this review, a broad discussion on the genes involved in biofilm formation, quorum sensing, and antimicrobial activity in monotherapy and combination therapy is presented that should benefit researchers engaged in optimizing the treatment of infections associated with S. aureus biofilms.

Effect of Ruta graveolens Extract on the Major Virulence Factors in Methicillin Resistant Staphylococcus aureus

Purpose

Rising Antibiotic Resistance has put the world in real threat. Methicillin resistant Staphylococcus aureus (MRSA), is a predominant cause of suppurative chronic skin and soft-tissue infections. Novel insights have focused the light on plant extracts. In this study, Ruta graveolens ethanolic active extract was tested for its potential anti-virulence activities in MRSA.

Materials and Methods

A total of 100 MRSA strains causing skin and soft tissue infections were isolated and antibiotic susceptibility testing was done. Ability to form biofilm was tested phenotypically. Furthermore, the antimicrobial activity of Ruta graveolens was evaluated followed by detection of its Minimum inhibitory concentration (MIC). The inhibitory activity of this extract on biofilm formation was investigated. Afterwards, we investigated its effect on the transcription of biofilm-related genes and mecA gene.

Results

All tested isolates were sensitive to Vancomycin and Linezolid while high resistance was noted with both Fusidic acid (83%) and Gentamicin (68%). (83%) of the isolates were biofilm producers. Ruta graveolens extract showed strong antimicrobial activity against the MRSA strains with MIC 0.78 mg/mL. At subinhibitory concentration (1/2 MIC), the extract had high biofilm inhibitory effects with mean inhibition (70%). Moreover, transcriptional analysis results showed that the mean percentages of inhibition in expression of mecA, icaA and icaD genes were 52.3%, 34.8% and 33.7%, respectively, in which all showed statistically significant difference (p ≤ 0.05).

Conclusion

The current study proposes the ability of Ruta graveolens extract to reduce the biofilm formation and antibiotic resistance of MRSA through downregulation of some biofilm forming genes and mecA gene which confers resistance to B-lactam antibiotics. This may decrease our reliance on antibiotics and improve our ability to effectively treat biofilm-related skin and soft-tissue infections caused by MRSA.

The crafty opponent: the defense systems of Staphylococcus aureus and response measures

Staphylococcus aureus is a serious threat to public health. S. aureus infection can cause acute or long-term persistent infections that are often resistant to antibiotics and are associated with high morbidity and death. Understanding the defensive systems of S. aureus can help clinicians make the best use of antimicrobial drugs and can also help with antimicrobial stewardship. The mechanisms and clinical implications of S. aureus defense systems, as well as potential response systems, were discussed in this study. Because resistance to all currently available antibiotics is unavoidable, new medicines are always being developed. Alternative techniques, such as anti-virulence and bacteriophage therapies, are being researched and may become major tools in the fight against staphylococcal infections in the future, in addition to the development of new small compounds that affect cell viability.

Overcoming bacteriophage insensitivity in Staphylococcus aureus using clindamycin and azithromycinat subinhibitory concentrations

BACKGROUND

Staphylococcus aureus is a pathogen of major concern in both acute infections and chronic conditions such as chronic rhinosinusitis (CRS). Bacteriophage (phage) therapy has recently regained interest for its potential to treat infections caused by antibiotic resistant strains including Methicillin Resistant Staphylococcus aureus (MRSA). However, bacteria can adapt and become resistant to phages. The aim of this study is to determine the potential for antibiotics to overcome phage resistance.

METHODS

The susceptibility of S. aureus clinical isolates (CIs) to phages J-Sa36, Sa83 and Sa87 alone or in combination with protein synthesis inhibitor (PSI) antibiotics clindamycin, azithromycin and erythromycin was assessed using plaque spot assays, minimum inhibitory concentration (MIC) assays, double layer spot assays and resazurin assays. The safety and efficacy of subinhibitory PSI antibiotics in combination with phage was tested in a Sprague Dawley rat model of sinusitis infected with a phage resistant S. aureus CI.

RESULTS

All three antibiotics at subinhibitory concentrations showed synergy when combined with all 3 phages against S. aureus CIs in planktonic and biofilm form and could sensitize phage-resistant S. aureus to promote phage infection. The combination of topical subinhibitory clindamycin or azithromycin and phage was safe and could eradicate S. aureus sinonasal biofilms in vivo.

CONCLUSION

Subinhibitory concentrations of PSI antibiotics could sensitize phage-resistant S. aureus and MRSA strains to phages in vitro and in vivo. This data supports the potential use of phage-PSI antibiotic combination therapies, in particular for difficult-to-treat infections with phage-resistant S. aureus and MRSA strains.

Trimellitic anhydride facilitates transepithelial permeability disrupting tight junctions in sinonasal epithelial cells

Trimellitic anhydride (TMA) is a chemical agent classified as a low molecular weight (LMW) agent causing occupational rhinitis (OR) or asthma. Although TMA is recognized as a respiratory sensitizer, the direct and non-immunologic effects of TMA remain unclear. Air- liquid interface (ALI) cultured human nasal epithelial cells (HNECs) derived from control subjects were treated with TMA, followed by measurement of the transepithelial electrical resistance (TEER), paracellular permeability of fluorescein isothiocyanate (FITC)-dextran and immunofluorescence of tight junction proteins claudin-1 and zonula occludens-1 (ZO-1). The cytotoxicity of TMA was evaluated by lactate dehydrogenase (LDH) assay. TMA at concentrations of 2 and 4 mg/mL significantly reduced the TEER within 10 min (p = 0.0177 on 2 mg/mL; p < 0.0001 on 4 mg/mL). The paracellular permeability of FITC-dextran was significantly increased upon challenge with 4 mg/mL TMA for 3 h (p = 0.0088) and 6 h (p = 0.0004). TMA treatment induced a reduction in the fluorescence intensity of claudin-1 and ZO-1 in a dose-dependent manner. LDH assay revealed 4 mg/mL TMA induced cytotoxicity only after 6 h incubation, while 1 or 2 mg/mL TMA caused no cytotoxicity. Our results suggest that TMA has a potential to penetrate the epithelial barrier by disrupting claudin-1 and ZO-1, indicating an important role for sensitization and OR development.

Maximum levels of cross-contamination for 24 antimicrobial active substances in non-target feed. Part 5: Lincosamides: lincomycin

The specific concentrations of lincomycin in non-target feed for food-producing animals, below which there would not be an effect on the emergence of, and/or selection for, resistance in bacteria relevant for human and animal health, as well as the specific antimicrobial concentrations in feed which have an effect in terms of growth promotion/increased yield were assessed by EFSA in collaboration with EMA. Details of the methodology used for this assessment, associated data gaps and uncertainties, are presented in a separate document. To address antimicrobial resistance, the Feed Antimicrobial Resistance Selection Concentration (FARSC) model developed specifically for the assessment was applied. However, due to the lack of data on the parameters required to calculate the FARSC, it was not possible to conclude the assessment until further experimental data become available. To address growth promotion, data from scientific publications obtained from an extensive literature review were used. Levels of lincomycin in feed that showed to have an effect on growth promotion/increased yield were reported. It was recommended to carry out studies to generate the data that are required to fill the gaps which prevented the calculation of the FARSC for lincomycin.

Antimicrobial Activities of Alginate and Chitosan Oligosaccharides Against Staphylococcus aureus and Group B Streptococcus

The bacterial pathogens Streptococcus agalactiae (GBS) and Staphylococcus aureus (S. aureus) cause serious infections in humans and animals. The emergence of antibiotic-resistant isolates and bacterial biofilm formation entails the urge of novel treatment strategies. Recently, there is a profound scientific interest in the capabilities of non-digestible oligosaccharides as antimicrobial and anti-biofilm agents as well as adjuvants in antibiotic combination therapies. In this study, we investigated the potential of alginate oligosaccharides (AOS) and chitosan oligosaccharides (COS) as alternative for, or in combination with antibiotic treatment. AOS (2-16%) significantly decreased GBS V growth by determining the minimum inhibitory concentration. Both AOS (8 and 16%) and COS (2-16%) were able to prevent biofilm formation by S. aureus wood 46. A checkerboard biofilm formation assay demonstrated a synergistic effect of COS and clindamycin on the S. aureus biofilm formation, while AOS (2 and 4%) were found to sensitize GBS V to trimethoprim. In conclusion, AOS and COS affect the growth of GBS V and S. aureus wood 46 and can function as anti-biofilm agents. The promising effects of AOS and COS in combination with different antibiotics may offer new opportunities to combat antimicrobial resistance.

Der p 1 Disrupts the Epithelial Barrier and Induces IL-6 Production in Patients With House Dust Mite Allergic Rhinitis

Background:Dermatophagoides pteronyssinus 1/2 (Der p 1/Der p 2) are regarded as important allergens of house dust mite (HDM). However, the effect of both products on the epithelial barrier and immune response of patients with and without HDM allergic rhinitis (AR) remains unclear.

Methods: Air–liquid interface (ALI) cultured human nasal epithelial cells (HNECs) derived from control subjects (non-AR) (n = 9) and HDM-AR patients (n = 9) were treated with Der P 1 and Der P 2, followed by testing the transepithelial electrical resistance (TEER), paracellular permeability of fluorescein isothiocyanate (FITC)-dextrans and immunofluorescence of claudin-1 and ZO-1. Interleukin-6 (IL-6) production was evaluated by ELISA.

Results: Der p 1 reduced TEER significantly in a transient and dose-dependent manner in HNEC-ALI cultures from HDM-AR and non-AR patients, whilst the paracellular permeability was not affected. TEER was significantly reduced by Der p 1 at the 10-min time point in HDM-AR patients compared to non-AR patients (p = 0.0259). Compared to no-treatment control, in HNECs derived from HDM-AR patients, Der p 1 significantly cleaved claudin-1 after 30 min exposure (72.7 ± 9.5 % in non-AR group, 39.9 ± 7.1 % in HDM-AR group, p = 0.0286) and induced IL-6 secretion (p = 0.0271).

Conclusions: Our results suggest that patients with HDM-AR are more sensitive to Der p 1 than non-AR patients with increased effects of Der p1 on the mucosal barrier and induction of inflammation, indicating an important role for Der p1 in sensitization and HDM-AR development.

Staphylococcus aureus Biofilm: Morphology, Genetics, Pathogenesis and Treatment Strategies

Staphylococcus aureus is a nosocomial bacterium causing different infectious diseases, ranging from skin and soft tissue infections to more serious and life-threatening infections such as septicaemia. S. aureus forms a complex structure of extracellular polymeric biofilm that provides a fully secured and functional environment for the formation of microcolonies, their sustenance and recolonization of sessile cells after its dispersal. Staphylococcus aureus biofilm protects the cells against hostile conditions, i.e., changes in temperature, limitations or deprivation of nutrients and dehydration, and, more importantly, protects the cells against antibacterial drugs. Drugs are increasingly becoming partially or fully inactive against S. aureus as they are either less penetrable or totally impenetrable due to the presence of biofilms surrounding the bacterial cells. Other factors, such as evasion of innate host immune system, genome plasticity and adaptability through gene evolution and exchange of genetic material, also contribute to the ineffectiveness of antibacterial drugs. This increasing tolerance to antibiotics has contributed to the emergence and rise of antimicrobial resistance (AMR), a serious problem that has resulted in increased morbidity and mortality of human and animal populations globally, in addition to causing huge financial losses to the global economy. The purpose of this review is to highlight different aspects of S. aureus biofilm formation and its overall architecture, individual biofilm constituents, clinical implications and role in pathogenesis and drug resistance. The review also discusses different techniques used in the qualitative and quantitative investigation of S. aureus biofilm and various strategies that can be employed to inhibit and eradicate S. aureus biofilm.

Virulence alterations in staphylococcus aureus upon treatment with the sub-inhibitory concentrations of antibiotics

Background

The treatment of patients with Staphylococcus aureus infections mainly relies on antistaphylococcal regimens that are established with effective antibiotics. In antibiotic therapy or while living in nature, pathogens often face the sub-inhibitory concentrations (sub-MICs) of antibiotics due to drug pharmacokinetics, diffusion barriers, waste emission, resistant organism formation, and farming application. Different categories of antibiotics at sub-MICs have diverse effects on the physiological and chemical properties of microorganisms. These effects can result in virulence alterations. However, the mechanisms underlying the actions of antibiotics at sub-MICs on S. aureus virulence are obscure.

Aim of review

In this review, we focus on the effects of sub-MICs of antibiotics on S. aureus virulence from the aspects of cell morphological change, virulence factor expression, bacterial adherence and invasion, staphylococcal biofilm formation, and small-colony variant (SCV) production. The possible mechanisms of antibiotic-induced S. aureus virulence alterations are also addressed.

Key scientific concepts of review

Five main aspects of bacterial virulence can be changed in S. aureus exposure to the sub-MIC levels of antibiotics, resulting in deformed bacterial cells to stimulate abnormal host immune responses, abnormally expressed virulence factors to alter disease development, changed bacterial adhesion and invasion abilities to affect colonization and diffusion, altered biofilm formation to potentate material-related infections, and increased SCV formation to achieve persistent infection and recurrence. These advanced findings expand our knowledge to rethink the molecular signaling roles of antibiotics beyond their actions as antimicrobial agents.

Azithromycin and ciprofloxacin inhibit interleukin-8 secretion without disrupting human sinonasal epithelial integrity in vitro

BACKGROUND

We recently developed a ciprofloxacin and azithromycin sinus stent (CASS) to target recalcitrant infections in chronic rhinosinusitis (CRS). The objective of this study was to evaluate the anti-inflammatory activity of azithromycin released from the CASS and assess the impact on the integrity and function of primary human sinonasal epithelial cells (HSNECs).

METHODS

Pseudomonas aeruginosa lipopolysaccharide (LPS)-stimulated HSNECs were treated with azithromycin and/or ciprofloxacin at concentrations attainable from CASS release. Interleukin-8 (IL-8) secretion was quantified by enzyme-linked immunosorbent assay (ELISA). Epithelial integrity (transepithelial resistance [TEER], paracellular permeability [fluorescein isothiocyanate-labeled dextran], lactate dehydrogenase [LDH] assays) and function (ciliary beat frequency [CBF]) were also evaluated.

RESULTS

Azithromycin significantly reduced secreted IL-8 from P. aeruginosa LPS-stimulated HSNECs at all concentrations tested (mean ± standard deviation; control = 5.77 ± 0.39 ng/mL, azithromycin [6 μg/mL] = 4.58 ± 0.40 ng/mL, azithromycin [60 µg/mL] = 4.31 ± 0.06, azithromycin [180 µg/mL] = 4.27 ± 0.26 ng/mL, p < 0.05). Co-incubation with azithromycin (6 µg/mL) and ciprofloxacin (2.4 µg/mL) in LPS-stimulated HSNECs also displayed a significant reduction in secreted IL-8 when compared to P. aeruginosa LPS alone (co-treatment = 4.61 ± 0.29 ng/mL, P. aeruginosa LPS = 7.35 ± 0.89 ng/mL, p < 0.01). The drugs did not negatively impact TEER, paracellular permeability, LDH release, or CBF, indicating retention of cell integrity and function.

CONCLUSION

Azithromycin decreased P. aeruginosa LPS IL-8 production in HSNECs at drug concentrations attainable with sustained release of azithromycin from the CASS. In addition to antibacterial activity, anti-inflammatory properties of the CASS should provide further benefit for patients with recalcitrant CRS.