Assessing the Concordance of MRSA Carriage Screening With MRSA Infections

OBJECTIVES

This study focused on children with confirmed methicillin-resistant Staphylococcus aureus (MRSA) infections to determine MRSA screening utility in guiding empirical anti-MRSA treatment of children without history of MRSA infection. We examined the concordance of screens to assess differences by infection type and used statistical analysis to determine significant contributors to concordance.

METHODS

Pediatric hospital patients admitted from 2002 through 2022 were included. Subjects had MRSA infections subsequent to MRSA surveillance screens performed the preceding year. Statistical analysis identified associations between MRSA screens and infections. Number needed to treat analysis calculated the utility of rescreening.

RESULTS

Among 246 subjects, 39.0% had concordant screens; 151 (61.4%) screens were obtained in the 2 weeks preceding infection. Sensitivity for bacteremia was 50.0% (n = 42), for endotracheal/respiratory 44.4% (n = 81), and 29.4% (n = 102) for skin and soft-tissue infection. For children aged younger than 6 months, sensitivity was 35.9% (n = 78). Multivariable analysis significantly associated days since screening with decreasing likelihood of concordance. Regression modeled the probability of concordance to drop below 50.0% for all infections after 4 days, after 6 days for bacteremia specifically, and 12 days for endotracheal/respiratory infections.

CONCLUSIONS

The concordance of screens was far lower than negative predictive values found previously; earlier studies were possibly impacted by low prevalence and exclusion of children at high risk to inform high negative predictive values. We suggest that negative MRSA screens should not invalidate reasonable suspicion for MRSA infection in patients with high pretest probabilities.

Nanosecond pulsed electric fields increase antibiotic susceptibility in methicillin-resistant Staphylococcus aureus

IMPORTANCE

We have found that treatment with short electric pulses potentiates the effects of multiple antibiotics against methicillin-resistant Staphylococcus aureus. By reducing the dose of antibiotic necessary to be effective, co-treatment with electric pulses could amplify the effects of standard antibiotic dosing to treat S. aureus infections such as skin and soft-tissue infections (SSTIs). SSTIs are accessible to physical intervention and are good candidates for electric pulse co-treatment, which could be adopted as a step-in wound and abscess debridement.

Topical erythritol combined with L-ascorbyl-2-phosphate inhibits staphylococcal growth and alleviates staphylococcal overgrowth in skin lesions of canine superficial pyoderma

Erythritol (ERT) and L-ascorbyl-2-phosphate (APS) are bacteriostatic, but their effects on staphylococcal skin infections remain unknown. We aimed to determine whether ERT combined with APS inhibits the growth of staphylococci that are commonly isolated from pyoderma skin lesions in dogs. We investigated the individual and combined effects of ERT and APS on the growth of Staphylococcus pseudintermedius, S. schleiferi, and S. aureus using turbidity assays in vitro. Skin lesions from 10 dogs with superficial pyoderma were topically treated with 5% ERT and 0.1% APS for 28 days, and swabbed skin samples were then analyzed using 16S rRNA amplicon sequencing and quantitative real-time PCR (qPCR). Results showed that ERT inhibited S. pseudintermedius growth regardless of harboring the mecA gene, and APS increased the inhibitory effects of ERT against S. pseudintermedius, S. schleiferi, and S. aureus in vitro. Moreover, combined ERT and APS decreased the prevalence of staphylococci on canine skin lesions at the genus level. The combination slightly increased the α-diversity but did not affect the β-diversity of the microbiota. The qPCR results revealed that the combination significantly decreased S. pseudintermedius and S. schleiferi in skin lesions. Topical administration of EPS combined with APS can prevent staphylococcal colonization on the surface of mammalian skin. The results of this study may provide an alternative to systemic antibiotics for treating superficial pyoderma on mammalian skin surfaces.

An oral caspase inhibitor as monotherapy or with antibiotics eradicates MRSA skin infections in mice

Staphylococcus aureus is the leading cause of skin and soft tissue infections. With the emergence of antibiotic-resistant bacteria, there is an unmet clinical need to develop immune-based therapies to treat skin infections. Previously, we have shown pan-caspase inhibition as a potential host-directed immunotherapy against community-acquired methicillin-resistant S aureus (CA-MRSA) and other bacterial skin infections. Here, we evaluated the role of irreversible pan-caspase inhibitor emricasan as a monotherapy and an adjunctive with a standard-of-care antibiotic, doxycycline, as potential host-directed immunotherapies against S. aureus skin infections in vivo. We used the established CA-MRSA strain USA300 on the dorsum of WT C57BL/6J mice and monitored lesion size and bacterial burden noninvasively, and longitudinally over 14 days with in vivo bioluminescence imaging (BLI). Mice in four groups placebo (0.5% carboxymethyl cellulose [CMC] solution), placebo plus doxycycline (100 mg/kg), emricasan (40 mg/kg) plus doxycycline, and emricasan only were treated orally twice daily by oral gavage for 7 days, starting at 4 h after injection of S aureus. When compared with placebo, all three groups, placebo plus doxycycline, emricasan plus doxycycline, and emricasan treated group, exhibited biological effect, with reduction of both the lesion size (*p = .0277, ****p < .0001, ****p < .0001, respectively) and bacterial burden (***p = .003, ****p < .0001, ****p < .0001, respectively). Importantly, the efficacy of emricasan against S. aureus was not due to direct antibacterial activity. Collectively, pan-caspase inhibitor emricasan and emricasan plus doxycycline reduced both the lesion size and bacterial burden in vivo, and emricasan is a potential host-directed immunotherapy against MRSA skin infections in a preclinical mouse model.

Skin and soft tissue infections in the elderly

PURPOSE OF REVIEW

To highlight the peculiarity of skin and soft tissue infections (SSTIs) in elderly patients and to provide useful elements for their optimal management.

RECENT FINDINGS

In the COVID-19 era, early discharge from the hospital and implementation of outpatient management is of key importance.

SUMMARY

Elderly patients are at high risk of SSTIs due to several factors, including presence of multiple comorbidities and skin factors predisposing to infections. Clinical presentation may be atypical and some signs of severity, such as fever and increase in C-reactive protein, may be absent or aspecific in this patients population. An appropriate diagnosis of SSTIs in the elderly is crucial to avoid antibiotic overtreatment. Further studies should explore factors associated with bacterial superinfections in patients with pressure ulcers or lower limb erythema. Since several risk factors for methicillin-resistant Staphylococcus aureus (MRSA) may coexist in elderly patients, these subjects should be carefully screened for MRSA risk factors and those with high risk of resistant etiology should receive early antibiotic therapy active against MRSA. Physicians should aim to several objectives, including clinical cure, patient safety, early discharge and return to community. SSTIs in the elderly may be managed using long-acting antibiotics, but clinical follow-up is needed.

Rapid diagnostics for skin and soft tissue infections: the current landscape and future potential

PURPOSE OF REVIEW

Managing antimicrobial therapy in patients with complicated skin and soft tissue infections (SSTI) constitutes a growing challenge due to the wide spectrum of potential pathogens and resistance phenotypes. Today, microbiological documentation relies on cultural methods. This review summarizes the available evidence regarding the clinical input of rapid microbiological diagnostic tools (RMDT) and their impact on the management of antimicrobial therapy in SSTI.

RECENT FINDINGS

Accurate tools are already available for the early detection of methicillin-resistant Staphylococcus aureus (MRSA) in SSTI samples and may help avoiding or shortening empirical anti-MRSA coverage. Further research is necessary to develop and evaluate RMDT detecting group A streptococci (e.g., antigenic test) and Gram-negative pathogens (e.g., multiplex PCR assays), including through point-of-care utilization. Next-generation sequencing (NGS) methods could provide pivotal information for the stewardship of antimicrobial therapy, especially in case of polymicrobial or fungal SSTI and in the immunocompromised host; however, a shortening in the turnaround time and prospective data regarding their therapeutic input are needed to better appraise the clinical positioning of these promising approaches.

SUMMARY

The clinical input of RMDT in SSTI is currently limited due to the scarcity of available dedicated assays and the polymicrobial feature of certain cases. NGS appears as a relevant tool but requires further developments before its implementation in routine clinical practice.

Nanobased Antibacterial Drug Discovery to Treat Skin Infections of Staphylococcus aureus Using Moringa oleifera-Assisted Zinc Oxide Nanoparticle and Molecular Simulation Study

In addition to the physical barrier, the epidermis acts as a natural barrier against microbial proliferation. It is prone to bacterial infections on the skin and in the nose, such as Staphylococcus aureus, as well as a variety of other skin illnesses. Green nanomaterial production, which eliminates the use of harmful chemicals while simultaneously reducing time, is gaining popularity in the nanotechnology area. Using the leaf extract of the pharmacologically valuable plant Moringa oleifera, we described a green synthesis of ZnO NPs (zinc oxide nanoparticles). ZnO NPs had a particle size of 201.6 nm and a zeta potential of -56.80 mV, respectively. A novel aminoketone antibacterial medication was synthesized and tested for antibacterial activity using ZnO NPs as a phytocatalyst in this work. This method produces high yields while maintaining efficient and gentle reaction conditions. Moringa oleifera extract can reduce ZnO to ZnO NPs in a straightforward manner. FT-IR, 1H-NMR, 13C-NMR, mass spectra, elemental analysis, and morphological analysis were used to synthesize and describe the antibacterial medicines (1a-1g) and (2a-2g). In addition, antibacterial activity was evaluated against bacteria such as Enterococcus faecalis and Staphylococcus aureus, and compound 1c (63 μg/mL, E. faecalis) and compound 2e (0.12 μg/mL, S. aureus) were found to be very active when compared to other medications. mupirocin is used as a reference. In addition, studies of in silico molecular docking for the bacterial DsbA protein were conducted. The strong molecules 1c (-4.3 kcal/mol) and 2e (-5.1 kcal/mol) exhibit a high binding affinity through hydrogen bonding, according to docking tests.

Photonic Hydrogels for Synergistic Visual Bacterial Detection and On-Site Photothermal Disinfection

Rapid and sensitive diagnostics in the early stage of bacterial infection and immediate treatment play critical roles in the control of infectious diseases. However, it remains challenging to develop integrated systems with both rapid detection of bacterial infection and timely on-demand disinfection ability. Herein, we demonstrate a photonic hydrogel platform integrating visual diagnosis and on-site photothermal disinfection by incorporating Fe₃O₄@C nanoparticles into a poly(hydroxyethyl methacrylate)-co-polyacrylamide (PHEMA-co-PAAm) matrix. In vitro experiments demonstrate that such a hydrogel can respond to pH variation caused by bacterial metabolism and generate the corresponding color changes to realize naked-eye observation. Meanwhile, its excellent photothermal conversion ability enables it to effectively kill bacteria by destroying cell membranes under near-infrared irradiation. Moreover, the pigskin infection wound model also verifies the bacterial detection performance and disinfection ability of the hydrogel in vivo. Our strategy demonstrates a new approach for visual diagnosis and treatment of bacterial infections.

Plasmonic Nanozymes: Localized Surface Plasmonic Resonance Regulates Reaction Kinetics and Antibacterial Performance

Among the members of the rapidly growing nanozyme family, plasmonic nanozymes stand out because of their unique localized surface plasmon resonance (LSPR) characteristics and tunable catalytic activity. We prepared a plasmonic nanozyme of Au gold nanoparticles (AuNPs) and Cu metal-organic framework nanosheets (Cu-MOFNs). The Cu-MOFNs have peroxidase-like activity, while AuNPs present unique LSPR characteristics. We found that the as-prepared AuNPs/Cu-MOFNs composite presents 1.6-fold faster reaction kinetics under LSPR excitation compared to that in the dark. Investigations of energy levels, radical capture, and dark-field scattering spectroscopy revealed that LSPR of AuNPs as well as matched energy levels can facilitate efficient hot electron transfer, which could readily cleave the chemical bond of the substrate and accelerate the reaction kinetics. On the basis of these results, we achieved enhanced antibacterial therapy and wound healing using plasmonic AuNPs/Cu-MOFNs. This study spotlights the superiority of plasmonic nanozymes in improving the enzyme-like performance of nanozymes.

Self-Deliverable Peptide-Mediated and Reactive-Oxygen-Species-Amplified Therapeutic Nanoplatform for Highly Effective Bacterial Inhibition

An "antibiotic-free strategy" provides a viable option to address bacterial infections, especially for the "superbug" challenge. However, the undesirable antibacterial activity of antibiotic-free agents hinders their practical applications. In this study, we developed a combination antibacterial strategy of coupling peptide-drug therapy with chemodynamic therapy (CDT) to achieve the effective bacterial inhibition. An amphiphilic oligopeptide (LAOOH-OPA) containing a therapeutic unit of D(KLAK)2 peptide and a hydrophobic linoleic acid hydroperoxide (LAHP) was designed. The positively charged D(KLAK)2 peptide with an α-helical conformation enabled rapid binding with microbial cells via electrostatic interaction and subsequent membrane insertion to deactivate the bacterial membrane. When triggered by Fe2+, moreover, LAHP could generate singlet oxygen (1O2) to elicit lipid bilayer leakage for enhanced bacteria inhibition. In vitro assays demonstrated that the combination strategy possessed excellent antimicrobial activity not only merely toward susceptible strains (Gram-positive Staphylococcus aureus and Gram-negative Escherichia coli) but also toward methicillin-resistant Staphylococcus aureus (MRSA). On the mouse skin abscess model induced by S. aureus, self-assembled LAOOH-OPA exhibited a more significant bacteria reduction (1.4 log10 reduction) in the bioburden compared to that of the standard vancomycin (0.9 log10 reduction) without apparent systemic side effects. This combination antibacterial strategy shows great potential for effective bacterial inhibition.

The Photocatalytic Effects of Modified Hydrothermal Nanotitania Extraction on the Skin and Behavior of Sprague-Dawley Rats

BACKGROUND

Potential antibacterial substances, such as titanium dioxide (TiO2), are being extensively studied throughout the research world. A modified hydrothermal nanotitania extraction was shown to inhibit Staphylococcus aureus growth in the laboratory. However, the toxicity effect of the extract on rats is unknown. In this study, we observed the effects of a modified hydrothermal nanotitania extraction on the skin and behavior of Sprague-Dawley rats.

METHODS

Sprague-Dawley (Rattus norvegicus) rats were used as the experimental animals. The skin around the dorsum of the tested animals was shaved and pasted with 0.1 mg and 0.5 mg of the nanotitania extraction. The color and condition of the pasted area and the behavior of the animals were observed.

RESULTS

0.1 mg nanotitania extraction application on the dorsum of the rat produced no skin color changes at day 1, day 3, day 5, or day 7 postapplication. There were no changes in their behavior up to day 7 with no skin rashes or skin scratches seen or fur changes. However, 0.5 mg of nanotitania extraction resulted in redness and less fur regrowth at day 7.

CONCLUSIONS

A 0.1 mg modified nanotitania extraction was observed to have no effect on the skin of Sprague-Dawley rats.

In vitro efficacy of Azadirachta indica leaf extract against methicillin resistant Staphylococci isolated from skin infection

In this cross-sectional study, the isolation and identification of Methicillin Resistant Staphylococcus aureus (MRSA) and Methicillin Resistant S. epidermidis (MRSE) was described from skin infections (n=100). Initial isolation was done by conventional procedures followed by amplification/ sequence analysis of 16S rRNA. Methicillin resistance was determined using cefoxitin discs and resistant isolates were screened for mec-A gene followed by Minimum Inhibitory Concentrations (MIC) determination of vancomycin. In second phase, we investigated extract of Azadirachta indica leaves using Fourier Transformed Infrared Spectroscopy (FTIR-Spectroscopy) and investigated in vitro activity. Initially, total of 28 Staphylococci were identified. 16S rRNA gene sequence confirmed S. aureus (22), S. epidermidis (3) and S. saprophyticus (3) isolates. Cefoxitin discs showed (7/22) MRSA, (3/3) (MRSE) and none of the methicillin resistant S. saprophyticus. MRSA and MRSE isolates showed presence of mec-A gene. However, all isolates were sensitive to vancomycin MIC (0.5-2μg/mL) and sensitive to Linezolid. FTIR-Spectroscopy of A. indica indicated the presence of azadirachtin and nimbolinin. The mean zone of inhibition was measured 14.23±1.37 and 13.66±0.70 against MRSA and MRSE isolates, respectively. Altogether, MRSA and MRSE is significant public health concern. However, vancomycin and linezolid were found effective and extract of A. indica showed in vitro effects.

Universal Antifouling and Photothermal Antibacterial Surfaces Based on Multifunctional Metal-Phenolic Networks for Prevention of Biofilm Formation

Biofilms formed from the pathogenic bacteria that attach to the surfaces of biomedical devices and implantable materials result in various persistent and chronic bacterial infections, posing serious threats to human health. Compared to the elimination of matured biofilms, prevention of the formation of biofilms is expected to be a more effective way for the treatment of biofilm-associated infections. Herein, we develop a facile method for endowing diverse substrates with long-term antibiofilm property by deposition of a hybrid film composed of tannic acid/Cu ion (TA/Cu) complex and poly(ethylene glycol) (PEG). In this system, the TA/Cu complex acts as a multifunctional building block with three different roles: (i) as a versatile "glue" with universal adherent property for substrate modification, (ii) as a photothermal biocidal agent for bacterial elimination under irradiation of near-infrared (NIR) laser, and (iii) as a potent linker for immobilization of PEG with inherent antifouling property to inhibit adhesion and accumulation of bacteria. The resulted hybrid film shows negligible cytotoxicity and good histocompatibility and could prevent biofilm formation for at least 15 days in vitro and suppress bacterial infection in vivo, showing great potential for practical applications to solve the biofilm-associated problems of biomedical materials and devices.

A Universal and Reversible Wet Adhesive via Straightforward Aqueous Self-Assembly of Polyethylenimine and Polyoxometalate

The excellent adhesion of mussels under wet conditions has inspired the development of numerous catechol-based wet adhesives. Nevertheless, the performance of catechol-based wet adhesive suffers from the sensitivity toward temperature, pH, or oxidation stimuli. Therefore, it is of great significance to develop non-catechol-based wet adhesives to fully recapitulate nature's dynamic function. Herein, a novel type of non-catechol-based wet adhesive is reported, which is readily formed by self-assembly of commercially available branched polyethylenimine and phosphotungstic acid in aqueous solution through the combination of electrostatic interaction and hydrogen bonding. This wet adhesive shows reversible, tunable, and strong adhesion on diverse substrates and further exhibits high efficacy in promoting biological wound healing. During the healing of the wound, the as-prepared wet adhesive also possesses inherent antimicrobial properties, thus avoiding inflammations and infections due to microorganism accumulation.

Nonimmunogenic Hydrogel-Mediated Delivery of Antibiotics Outperforms Clinically Used Formulations in Mitigating Wound Infections

Treatment of chronic wound infections caused by Gram-positive bacteria such as Staphylococcus aureus is highly challenging due to the low efficacy of existing formulations, thereby leading to drug resistance. Herein, we present the synthesis of a nonimmunogenic cholic acid-glycine-glycine conjugate (A6) that self-assembles into a supramolecular viscoelastic hydrogel (A6 gel) suitable for topical applications. The A6 hydrogel can entrap different antibiotics with high efficacy without compromising its viscoelastic behavior. Activities against different bacterial species using a disc diffusion assay demonstrated the antimicrobial effect of the ciprofloxacin-loaded A6 hydrogel (CPF-Gel). Immune profiling and gene expression studies after the application of the A6 gel to mice confirmed its nonimmunogenic nature to host tissues. We further demonstrated that topical application of CPF-Gel clears S. aureus-mediated wound infections more effectively than clinically used formulations. Therefore, cholic acid-derived hydrogels are an efficacious matrix for topical delivery of antibiotics and should be explored further.

Light-Activated Biodegradable Covalent Organic Framework-Integrated Heterojunction for Photodynamic, Photothermal, and Gaseous Therapy of Chronic Wound Infection

Chronic wound healing, impeded by bacterial infections and drug resistance, poses a threat to global human health. Antibacterial phototherapy is an effective way to fight microbial infection without causing drug resistance. Covalent organic frameworks (COFs) are a class of highly crystalline functional porous carbon-based materials composed of light atoms (e.g., carbon, nitrogen, oxygen, and borane), showing potential applications in the biomedical field. Herein, we constructed porphyrin-based COF nanosheets (TP-Por CON) for synergizing photodynamic and photothermal therapy under red light irradiation (e.g., 635 nm). Moreover, a nitric oxide (NO) donor molecule, BNN6, was encapsulated into the pore volume of the crystalline porous framework structure to moderately release NO triggered by red light irradiation for realizing gaseous therapy. Therefore, we successfully synthesized a novel TP-Por CON@BNN6-integrated heterojunction for thoroughly killing Gram-negative bacteria Escherichia coli and Gram-positive bacteria Staphylococcus aureus in vitro. Our research identified that TP-Por CON@BNN6 has favorable biocompatibility and biodegradability, low phototoxicity, anti-inflammatory properties, and excellent mice wound healing ability in vivo. This study indicates that the TP-Por CON@BNN6-integrated heterojunction with multifunctional properties provides a potential strategy for COF-based gaseous therapy and microorganism-infected chronic wound healing.

Construction of a Mesoporous Ceria Hollow Sphere/Enzyme Nanoreactor for Enhanced Cascade Catalytic Antibacterial Therapy

Nanozyme has been regarded as one of the antibacterial agents to kill bacteria via a Fenton-like reaction in the presence of H₂O₂. However, it still suffers drawbacks such as insufficient catalytic activity in near-neutral conditions and the requirement of high H₂O₂ levels, which would minimize the side effects to healthy tissues. Herein, a mesoporous ceria hollow sphere/enzyme nanoreactor is constructed by loading glucose oxidase in the mesoporous ceria hollow sphere nanozyme. Due to the mesoporous framework, large internal voids, and high specific surface area, the obtained nanoreactor can effectively convert the nontoxic glucose into highly toxic hydroxyl radicals via a cascade catalytic reaction. Moreover, the generated glucose acid can decrease the localized pH value, further boosting the peroxidase-like catalytic performance of mesoporous ceria. The generated hydroxyl radicals could damage severely the cell structure of the bacteria and prevent biofilm formation. Moreover, the in vivo experiments demonstrate that the nanoreactor can efficiently eliminate 99.9% of bacteria in the wound tissues and prevent persistent inflammation without damage to normal tissues in mice. This work provides a rational design of a nanoreactor with enhanced catalytic activity, which can covert glucose to hydroxyl radicals and exhibits potential applications in antibacterial therapy.

Antifracture, Antibacterial, and Anti-inflammatory Hydrogels Consisting of Silver-Embedded Curdlan Nanofibrils

The bacterial exopolysaccharide Curdlan has a unique collagen-like triple helical structure and immune-modulation activities. Although there have been several types of Curdlan gels reported for antibacterial or wound healing purposes, none of them exhibit favorable mechanical properties for clinically applicable wound healing materials. Herein, we present a two-step approach for preparing Ag-embedded Curdlan hydrogels that are highly soft but are very stretchable compared with common polysaccharide-based hydrogels. Ag ions were first reduced in a diluted Curdlan solution to form AgNP-decorated triple helices. Then, the aqueous solution consisting of Curdlan/Ag nanoparticles was mixed with a dimethyl sulfoxide solution consisting of a high concentration of Curdlan. This mixing triggered the conformation transformation of Curdlan random coils into triple helices, and then the helices were further packed into semicrystalline nanofibrils of ∼20 nm in diameter. Due to the presence of semicrystalline fibrils, this novel Curdlan hydrogel exhibits a fracture strain of ∼350% and fracture stress of ∼0.2 MPa at a water content of ∼97%. This nanofibril hydrogel supported the attachment, spreading, and growth of fibroblasts and effectively inhibited the growth of Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus. Moreover, the hydrogels downregulated NO production and proinflammatory gene expression levels in lipopolysaccharide (LPS)-stimulated macrophages but did not change the anti-inflammatory gene expression levels in IL-4-stimulated macrophages. In an animal study, these hydrogels accelerated wound healing in a bacteria-infected mice skin wound model. These results validate the further development of Curdlan/AgNPs nanofibril hydrogels in clinical wound management.

Gold-Platinum Nanodots with High-Peroxidase-like Activity and Photothermal Conversion Efficiency for Antibacterial Therapy

Combined therapeutic strategies for bacterial infection have attracted worldwide attention owing to their faster and more effective therapy with fewer side effects compared with monotherapy. In this work, gold-platinum nanodots (AuPtNDs) are simply and quickly synthesized by a one-step method. They not only exhibit powerful peroxidase-like activity but also confer a higher affinity for hydrogen peroxide (H2O2), which is 3.4 times that of horseradish peroxidase. Under 808 nm laser irradiation, AuPtNDs also have excellent photothermal conversion efficiency (50.53%) and strong photothermal stability. Excitingly, they can combat bacterial infection through the combination of chemodynamic and photothermal therapy. In vitro antibacterial results show that the combined antibacterial strategy has a broad-spectrum antibacterial property against both Escherichia coli (Gram negative, 97.1%) and Staphylococcus aureus (Gram positive, 99.3%). Animal experiments further show that nanodots can effectively promote the healing of bacterial infection wounds. In addition, owing to good biocompatibility and low toxicity, they are hardly traceable in the main organs of mice, which indicates that they can be well excreted through metabolism. These results reveal the application potential of AuPtNDs as a simple and magic multifunctional nanoparticle in antibacterial therapy and open up new applications for clinical anti-infective therapy in the near future.

Small Molecule-Capped Gold Nanoclusters for Curing Skin Infections

With the long-term and extensive abuse of antibiotics, bacteria can mutate into multidrug-resistant (MDR) strains, resist the existing antibiotics, and escape the danger of being killed. MDR bacteria-caused skin infections are intractable and chronic, becoming one of the most significant and global public-health issues. Thus, the development of novel antimicrobial materials is urgently needed. Non-antibiotic small molecule-modified gold nanoclusters (AuNCs) have great potential as a substitute for commercial antibiotics. Still, their narrow antibacterial spectrum hinders their wide clinical applications. Herein, we report that 4,6-diamino-2-pyrimidinethiol (DAPT)-modified AuNCs (DAPT-AuNCs) can fight against Gram-negative and Gram-positive bacterial strains as well as their MDR counterparts. By modifying DAPT-AuNCs on nanofibrous films, we develop an antibiotic film as innovative dressings for curing incised wounds, which exhibits excellent therapeutic effects on wounds infected by MDR bacteria. Compared to the narrow-spectral one, the broad-spectral antibacterial activity of the DAPT-AuNCs-modified film is more suitable for preventing and treating skin infections caused by various kinds of unknown bacteria. Moreover, the antibacterial films display excellent biocompatibility, implying the great potential for clinical applications.

Dialdehyde Nanocrystalline Cellulose as Antibiotic Substitutes against Multidrug-Resistant Bacteria

Antibiotic abuse resulted in the emergence of multidrug-resistant Gram-positive pathogens, which pose a severe threat to public health. It is urgent to develop antibiotic substitutes to kill multidrug-resistant Gram-positive pathogens effectively. Herein, the antibacterial dialdehyde nanocrystalline cellulose (DNC) was prepared and characterized. The antibacterial activity and biosafety of DNC were studied. With the increasing content of aldehyde groups, DNC exhibited high antibacterial activity against Gram-positive pathogens in vitro. DNC3 significantly reduced the amounts of methicillin-resistant Staphylococcus aureus (MRSA) on the skin of infected mice models, which showed low cytotoxicity, excellent skin compatibility, and no acute oral toxicity. DNC exhibited potentials as antibiotic substitutes to fight against multidrug-resistant bacteria, such as ingredients in salves to treat skin infection and other on-skin applications.

Fabrication of Bacterial Cellulose-Based Dressings for Promoting Infected Wound Healing

Bacterial cellulose (BC) holds several unique properties such as high water retention capability, flexibility, biocompatibility, and high absorption capacity. All these features make it a potential material for wound healing applications. However, it lacks antibacterial properties, which hampers its applications for infectious wound healings. This study reported BC-based dressings containing ε-polylysine (ε-PL), cross-linked by a biocompatible and mussel-inspired polydopamine (PDA) for promoting infectious wound healing. BC membranes were coated with PDA by a simple self-polymerization process, followed by treating with different contents of ε-PL. The resulted membranes showed strong antibacterial properties against tested bacteria by both in vitro and in vivo evaluations. The membranes also exhibited hemocompatibility and cytocompatibility by in vitro investigations. Moreover, the functionalized membranes promoted infected wound healing using Sprague-Dawley rats as a model animal. A complete wound healing was observed in the group treated with functionalized membranes, while wounds were still open for control and pure BC groups in the same duration. Histological investigations indicated that the thickness of newborn skin was greater and smoother in the groups treated with modified membranes in comparison to neat BC or control groups. These results revealed that the functionalized membranes have great potential as a dressing material for infected wounds in future clinical applications.

Chitosan modified ultra-thin hollow nanoparticles for photosensitizer loading and enhancing photodynamic antibacterial activities

Antibacterial photodynamic therapy (PDT) has attracted extremely attention due to not inducing bacteria to generate resistance. However, the poor utilization and low reactive oxygen species (ROS) field of photosensitizers hinder their further application for antibacterial. Here, we designed ultra-thin hollow silica nanoparticles (UHSN), followed by pore-engineering including covalent anchoring of chitosan (UHSN@CS) for enhanced loading and photodynamic property of photosensitizer. The UHSN@CS exhibit high loading efficiency (80.6%, pH = 6.0) and controllable pH-responsive release for Ce6. Additionally, UHSN@CS can enhance the ROS yield of photosensitizers and effectively adhere to S. aureus, thus enormously enhancing antibacterial performance toward bacteria. Moreover, UHSN@CS-Ce6 can obliterate mature S. aureus biofilm and cause an 81% decrease in the biomass, showing a better therapeutic effect than Ce6 (59.2%) under laser irradiation. In vivo results confirm that UHSN@CS-Ce6 is effective to promote infectious wound regeneration. As photodynamic-based nanoplatforms, UHSN@CS-Ce6 are potential antibacterial agents for skin infection therapy.

Targeting Antibacterial Effect and Promoting of Skin Wound Healing After Infected with Methicillin-Resistant Staphylococcus aureus for the Novel Polyvinyl Alcohol Nanoparticles

INTRODUCTION

Topical agents typically remain in the wound site for time duration that are too short to effectively eradicate MRSA tradition formation of BZK that can be maintained within the wound site for longer time periods, should be more effective.

METHODS

The novel chitosan and poly (D,L-lactide-co-glycoside) nanoparticles loaded with benzalkonium bromide (BZK) were designed, for the promotion wound healing after MRSA infection. The physical characterization of these nanoparticles, as well as their antibacterial activity in vitro, release profile in simulated wound fluid, cell toxicity, anti-biofilm activity, and their ability to improve the skin wound healing in a mouse model were also studied.

RESULTS

These novel nanoparticles were found to have a significant antibacterial activity (p<0.01), both in vitro and in vivo test. The stronger anti-biofilm ability of the nanoparticles to inhibit the formation of bacterial biofilms, at a concentration of 3.33 μg/mL, and clear existing bacterial biofilms, at a concentration of 5 mg/mL, compared with its water solution. In addition, significant damage to bacterial cell walls also was found, providing insight into the mechanism of antibacterial activity.

CONCLUSION

Taken together, these results demonstrated the ability of BZK-loaded nanoparticles in the promotion of skin wound healing with MRSA infection. The current findings open a new avenue for nanomedicine development and future clinical applications in the treatment of wounds.

Investigating auranofin for the treatment of infected diabetic pressure ulcers in mice and dermal toxicity in pigs

Bacterial infection of pressure ulcers (PUs) are a notable source of hospitalization for individuals with diabetes. This study evaluated the safety profile and efficacy of auranofin to treat diabetic PUs infected with methicillin-resistant Staphylococcus aureus (MRSA). PUs were infected with MRSA in diabetic TALLYHO/JngJ mice and then treated with topical auranofin (2%), topical mupirocin (2%), or oral clindamycin (30 mg/kg) for four days. PUs were harvested post-treatment to enumerate bacterial burden and determine expression of cytokines/growth factors. Landrace cross pigs were exposed topically to auranofin (1%, 2%, and 3%) for 4-14 days and evaluated for signs of localized or systemic toxicity. Auranofin eradicated MRSA in PUs within four days (7.92-log10 reduction) in contrast to mupirocin (2.15-log10 reduction) and clindamycin (0.73-log10 reduction). Additionally, auranofin treatment resulted in decreased expression of pro-inflammatory cytokines and increased expression of biomarkers associated with re-epithelization of wounded tissue, confirmed with histopathologic analysis. No significant histopathologic lesions were present on porcine skin sites exposed to topical auranofin. Additionally, minimal accumulation of plasma gold and no systemic toxicity was observed in pigs exposed to topical auranofin. Auranofin appears to be a potent and safe topical agent to further investigate for treatment of mild-to-moderate MRSA-infected diabetic PUs.

Acute myeloid leukaemia presenting with ecthyma gangrenosum as the first manifestation: A case report

RATIONALE

Ecthyma gangrenosum (EG) is an uncommon cutaneous infection usually associated with Pseudomonas aeruginosa bacteremia in immunocompromised patients, particularly those with underlying malignant diseases. Despite its rarity, especially in immunocompetent or nondiagnosed immunodeficiency patients, EG can present as the first manifestation of an underlying immunosuppression.

PATIENT CONCERNS

A 42-year-old Japanese man was admitted to our hospital with a 3-day history of a painless red macule on his right forearm and fever.

DIAGNOSES

Blood culture on admission revealed the presence of Pseudomonas aeruginosa, whereas pus culture of the skin lesion showed Pseudomonas aeruginosa and methicillin-susceptible Staphylococcus aureus positivity.

INTERVENTIONS

Additional bone marrow aspirate examination and immunophenotyping were performed to confirm the diagnosis of acute promyelocytic leukaemia with PML-retinoic acid alpha receptor.

OUTCOMES

The patient was successfully treated with a 14-day course of antibiotics, and no evidence of relapse was noted. The patient achieved complete remission after treatment for acute promyelocytic leukaemia.

LESSONS

It should be kept in mind that EG is an important cutaneous infection that is typically associated with P aeruginosa bacteremia and the presence of underlying immunodeficiency, such as acute leukaemia.

Cotrimoxazole and clindamycin in skin and soft tissue infections

PURPOSE OF REVIEW

The aim of this study was to present recent microbiological, experimental, clinical and tolerance data for cotrimoxazole and clindamycin in the specific field of skin and soft tissue infections (SSTIs).

RECENT FINDINGS

Staphylococcus aureus and streptococci remain the leading cause of SSTIs. Cotrimoxazole is a good anti-Gram-positive agent with preserved activity against methicillin-susceptible and methicillin-resistant S. aureus (MRSA) and streptococci. Although clindamycin has good methicillin-susceptible S. aureus activity, a growing number of resistant MRSA and streptococci have been reported. Strong experimental data support the antitoxin activity of clindamycin, but clinical observations remain scarce. Several recent randomized trials involving cotrimoxazole and/or clindamycin demonstrate the efficacy and tolerance of both drugs. The oral formulation of both drugs may facilitate the implementation of early switch and early discharge protocols in clinical practice.

SUMMARY

Recent publications demonstrate that cotrimoxazole and clindamycin remain reliable and realistic therapeutic approaches for SSTIs.

Community-genotype methicillin-resistant Staphylococcus aureus skin and soft tissue infections in Latin America: a systematic review

Background

Community-genotype methicillin-resistant Staphylococcus aureus (CG-MRSA) emerged in the 1990s as a global community pathogen primarily involved in skin and soft tissue infections (SSTIs) and pneumonia. To date, the CG-MRSA SSTI burden in Latin America (LA) has not been assessed.

Objective

The main objective of this study was to report the rate and genotypes of community-genotype methicillin-resistant Staphylococcus aureus (CG-MRSA) causing community-onset skin and soft tissue infections (CO-SSTIs) in LA over the last two decades. In addition, this research determined relevant data related to SSTIs due to CG-MRSA, including risk factors, other invasive diseases, and mortality.

Data sources

Relevant literature was searched and extracted from five major databases: Embase, PubMed, LILACS, SciELO, and Web of Science.

Methods

A systematic review was performed, and a narrative review was constructed.

Results

An analysis of 11 studies identified epidemiological data across LA, with Argentina presenting the highest percentage of SSTIs caused by CG-MRSA (88%). Other countries had rates of CG-MRSA infection ranging from 0 to 51%. Brazil had one of the lowest rates of CG-MRSA SSTI (4.5–25%). In Argentina, being younger than 50 years of age and having purulent lesions were predictive factors for CG-MRSA CO-SSTIs. In addition, the predominant genetic lineages in LA belonged to sequence types 8, 30, and 5 (ST8, ST30, and ST5).

Conclusion

There are significant regional differences in the rates of CG-MRSA causing CO-SSTIs. It is not possible to conclude whether or not CG-MRSA CO-SSTIs resulted in more severe SSTI presentations or in a higher mortality rate.

Levonadifloxacin arginine salt to treat acute bacterial skin and skin structure infection due to S. aureus including MRSA

Acute bacterial skin and skin structure infections (ABSSSIs) are one of the most common types of infections due to methicillin-resistant Staphylococcus aureus (MRSA). The standard of care for ABSSSI includes glycopeptides such as vancomycin, teicoplanin, oxazolidinones and fluoroquinolones, which are potent broad-spectrum antibacterial agents. Unfortunately, due to indiscriminate utilization, resistance to these agents is rising and identification of novel agents is an urgent unmet medical need. In this context, levonadifloxacin (WCK-771) is a novel, hydrate arginine salt of nadifloxacin with improved bactericidal activity against MRSA as well as fluoroquinolone-resistant S. aureus by targeting bacterial DNA supercoiling enzymes DNA gyrase and topoisomerase IV. Levonadifloxacin displays a broad-spectrum bactericidal activity against Gram-positive and Gram-negative bacteria, atypical bacteria, anaerobic bacteria and bioterror pathogens with a very low frequency of mutation. Levonadifloxacin also displays improved activity under low pH biofilm environments. The drug has successfully completed phase I, phase II and phase III clinical trials in India. The U.S. Food and Drug Administration (FDA) granted a Qualified Infectious Disease Product (QIDP) designation to levonadifloxacin for the treatment of MRSA infections in August 2014.

Panton-Valentine leukocidin-positive Staphylococcus aureus in skin and soft tissue infections from primary care patients

OBJECTIVES

To characterize deep skin and soft tissue infections (dSSTI) caused by Panton-Valentine leukocidin (PVL)-positive versus PVL-negative Staphylococcus aureus isolates.

METHODS

We performed a retrospective analysis of patients' records including S. aureus isolates from outpatients with dSSTI. Samples had been submitted by primary care physicians, i.e. general practitioners, surgeons, dermatologists and paediatricians, located in Berlin, Germany, in 2007-2017. Bacterial isolates were identified and tested for antimicrobial susceptibility by VITEK 2; PVL was detected by PCR.

RESULTS

In total, 1199 S. aureus isolates from 1074 patients with dSSTI were identified, and 613 (51.1%) of 1199 samples were PVL⁺. The median age of patients with PVL⁺S. aureus was lower than in patients with PVL- S. aureus (34 years, range 0-88 years, vs. 44 years, range 0-98 years; p < 0.0001). PVL was associated with repeated/multiple samples compared to single sample submission (69/92, 75% vs. 448/982, 45.6%, p < 0.0001; odds ratio (OR), 3.6; 95% confidence interval (CI), 2.2-5.8). Interestingly, the highest PVL positivity rate was found in isolates from gluteal (82/108, 75.9%; OR, 3.6; 95% CI, 2-5) or axillary (76/123, 61.8%; OR, 2; 95% CI, 1.1-3.3) localizations compared to isolates from the arm. The PVL positivity rate did not increase over time. Yet we noticed an increase in the trimethoprim/sulfamethoxazole (SXT) resistance rate in PVL⁺ isolates, mainly methicillin-sensitive S. aureus, when considering SXT resistance rates of 2007-2012 versus 2013-2017 (35/226, 15.5% vs. 74/289, 25.6%; p 0.01).

CONCLUSIONS

In outpatients, gluteal and axillary dSSTI are indicative of PVL⁺S. aureus. Providing SXT as a complementary treatment for dSSTI should be based on susceptibility testing.

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in erythrodermic cutaneous T-cell lymphoma (CTCL) patients

Erythroderma can occur in cutaneous T-cell lymphoma (CTCL). Staphylococcus aureus (S. aureus) prevalence is increased in CTCL patients and contributes to CTCL disease flares. Our primary aim was to describe S. aureus infections, including resistance patterns and the antibiotic treatment regimens used, in erythrodermic CTCL patients. This was a retrospective chart review of erythrodermic CTCL patients who had S. aureus infection or colonization and were treated at the UT MD Anderson Cancer Center's Melanoma Skin Center between 2012 and 2016. Twenty-six erythrodermic CTCL patients had 50 documented S. aureus colonization or infection events. Patients had an improvement in body surface area (BSA) or modified Severity Weighted Assessment Tool (mSWAT) in 53% events treated for S. aureus. Seventeen of the 50 (34%) events were due to methicillin-resistant S. aureus (MRSA). One-third (33%) of MRSA events were initially treated with dicloxacillin. The MRSA isolates were sensitive to trimethoprim-sulfamethoxazole (92%) and doxycycline (88%). Patients treated in the outpatient setting (OR 0.073; 95% CI 0.008-0.627; p = 0.017) and patients with a previous history of topical anti-S. aureus decolonization treatments before S. aureus event as stand-alone (OR 0.125; 95% CI 0.018-0.887; p = 0.038) or in combination treatment with systemic antibiotics (OR 0.094; 95% CI 0.009-0.944; p = 0.045) were less likely to see improvement in BSA or mSWAT from S. aureus treatment. Treatment of S. aureus improved CTCL skin score in a high number of erythrodermic patients. The MRSA prevalence was high in erythrodermic CTCL patients. Clinicians should consider using empiric MRSA antibiotic coverage for these patients.

Skin Infections Caused by Staphylococcus aureus

Staphylococcus aureus is the most common pathogen involved in skin infections worldwide, regardless of the patient’s age, the climate or geographical area. The main skin clinical manifestations can be linked to a few toxins produced by the bacteria, which give rise to a rich and varied clinical spectrum. Panton Valentine leucocidin, exfoliatins, enterotoxins and toxin shock syndrome toxin 1 are the main toxins involved in most dermatological manifestations associated with S. aureus. Other less frequent cutaneous manifestations can occur in endocarditis, bacteraemia. Currently, the most important event is worldwide emergence of community-acquired S. aureus resistant to methicillin (CA-MRSA), mainly causing skin infections.

Antibiotic use among twelve Canadian First Nations communities: a retrospective chart review of skin and soft tissue infections

BACKGROUND

Previous publications indicated an emerging issue with community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA), particularly skin and soft tissue infections (SSTIs), in Indigenous communities in Canada. The objectives of this analysis were to explore the prevalence of SSTIs due to CA-MRSA and patterns of antimicrobial use in the community setting.

METHODS

A retrospective chart review was conducted as part of an environmental scan to assess antibiotic prescriptions in 12 First Nations communities across five provinces in Canada including Alberta, Saskatchewan, Manitoba, Ontario, and Québec. Charts were randomly selected from nursing stations and patients who had accessed care in the previous 12 months and were ≥ 18 years were included in the review. Data was collected from September to December, 2013 on antibiotic prescriptions, including SSTIs, clinical symptoms, diagnostic information including presence of CA-MRSA infection, and treatment.

RESULTS

A total of 372 charts were reviewed, 60 from Alberta, 70 from Saskatchewan, 120 from Manitoba, 100 from Ontario, and 22 from Québec. Among 372 patients, 224 (60.2%) patients had at least one antibiotic prescription in the previous 12 months and 569 prescriptions were written in total. The prevalence of SSTIs was estimated at 36.8% (137 cases of SSTIs in 372 charts reviewed). In 137 cases of SSTIs, 34 (24.8%) were purulent infections, and 55 (40.2%) were due to CA-MRSA.

CONCLUSIONS

This study has identified a high prevalence of antibiotic use and SSTIs due to CA-MRSA in remote and isolated Indigenous communities across Canada. This population is currently hard to reach and under-represented in standard surveillance system and randomized retrospective chart reviews can offer complimentary methodology for monitoring disease burden, treatment and prevention.

Insights into idarubicin antimicrobial activity against methicillin-resistant Staphylococcus aureus

BACKGROUND

MRSA is a major concern in community settings and in health care. The emergence of biofilms and persister cells substantially increases its antimicrobial resistance. It is very urgent to develop new antimicrobials to solve this problem.

OBJECTIVE

Idarubicin was profiled to assess its antimicrobial effects in vitro and in vivo, and the underlying mechanisms.

METHODS

We investigated the antimicrobial effects of idarubicin against MRSA by time-kill analysis. The antibiofilm efficacy of idarubicin was assessed by crystal violet and XTT staining, followed by laser confocal microscopy observation. The mechanisms underlying the antimicrobial effects were studied by transmission electron microscopy, all-atom molecular dynamic simulations, SYTOX staining, surface plasma resonance, and DNA gyrase inhibition assay. Further, we addressed the antimicrobial efficacy in wound and subcutaneous abscess infection in vivo.

RESULTS

Idarubicin kills MRSA cells by disrupting the lipid bilayers and interrupting the DNA topoisomerase IIA subunits, and idarubicin shows synergistic antimicrobial effects with fosfomycin. Through synergy with a single dose treatment fosfomycin and the addition of the cell protector amifostine, the cytotoxicity and cardiotoxicity of idarubicin were significantly reduced without affecting its antimicrobial effects. Idarubicin alone or in combination with fosfomycin exhibited considerable efficacy in a subcutaneous abscess mouse model of MRSA infection. In addition, idarubicin also showed a low probability of causing resistance and good postantibiotic effects.

CONCLUSIONS

Idarubicin and its analogs have the potential to become a new class of antimicrobials for the treatment of MRSA-related infections.

Quaternized Chitosan-Coated Montmorillonite Interior Antimicrobial Metal-Antibiotic in Situ Coordination Complexation for Mixed Infections of Wounds

Conventional drug delivery systems for natural clay materials still face critical challenges in their practical application, including multiple bacterial infections, combined infection of bacteria and fungi, and low sterilization efficiency. In this work, we address these challenges using the multifunctional montmorillonite nanosheet-based (MMT-based) drug nanoplatform, which involves the antibiotic 5-fluorocytosine (5-FC), antibacterial metal copper ions, and quaternized chitosan (QCS). Composite material QCS/MMT/5-FCCu can can strongly inhibit Staphylococcus aureus (a typical Gram-positive bacterium), Escherichia coli (a typical Gram-negative bacterium), and Candida albicans (a fungus) because 5-FC coordinates with copper ions in situ and due to the deposition of QCS. The subsequent drug release behavior of 5-FCCu was studied, and the results show an initial high concentration kills microorganisms and long-acting sustained release inhibition. Moreover, in vivo wound experiments and toxicity experiments show the promotion of wound healing and excellent biocompatibility. As a demonstration of the utility of the latter, we have shown that the MMT-based smart platform can be used for the treatment of mixed infections of wounds.

Local Treatment of Local Staphylococcal Infection with Complex Preparations Based on Metal Nanoparticles in the Experiment

Antibacterial activity of powdered preparations based on copper and silver nanoparticles was compared with activity of the reference preparation Baneocin on the model of local staphylococcal infection in white rats. The developed preparations exhibited pronounced antibacterial activity against methicillin-resistant S. epidermidis strains in vivo significantly (p<0.001) exceeding that of Baneocin, reduced microbial contamination of the wound on day 5 of study by 2 lg and more in comparison with bacterial load before treatment, and provided effective decontamination of the wound within 7-10 days.

Eradication of meticillin-resistant Staphylococcus aureus from human skin by the novel LL-37-derived peptide P10 in four pharmaceutical ointments

Skin bacterial colonization/infection is a frequent cause of morbidity in patients with chronic wounds and allergic/inflammatory skin diseases. This study aimed to develop a novel approach to eradicate meticillin-resistant Staphylococcus aureus (MRSA) from human skin. To achieve this, the stability and antibacterial activity of the novel LL-37-derived peptide P10 in four ointments was compared. Results indicate that P10 is chemically stable and antibacterial in hypromellose gel and Softisan-containing cream, but not in Cetomacrogol cream (with or without Vaseline), at 4 ^°C for 16 months. Reduction in MRSA counts on Leiden human epidermal models (LEMs) by P10 in hypromellose gel was greater than that of the peptide in Cetomacrogol cream or phosphate buffered saline. P10 did not show adverse effects on LEMs irrespective of the ointment used, while Cetomacrogol with Vaseline and Softisan cream, but not hypromellose gel or Cetomacrogol cream, destroyed MRSA-colonized LEMs. Taking all this into account, P10 in hypromellose gel dose-dependently reduced MRSA colonizing the stratum corneum of the epidermis as well as biofilms of this bacterial strain on LEMs. Moreover, P10 dose-dependently reduced MRSA counts on ex-vivo human skin, with P10 in hypromellose gel being more effective than P10 in Cetomacrogol and Softisan creams. P10 in hypromellose gel is a strong candidate for eradication of MRSA from human skin.

Infection with persister forms of Staphylococcus aureus causes a persistent skin infection with more severe lesions in mice: failure to clear the infection by the current standard of care treatment

Staphylococcus aureus can cause persistent infections and is known to develop persister cells in vitro. However, the in vivo significance of in vitro persisters in general is largely unclear. Here, we evaluated S. aureus stationary phase cultures and biofilm bacteria enriched in persister bacteria in comparison with actively growing log phase bacteria in terms of their ability to cause disease in a mouse skin infection model. We found that mice infected with the stationary phase and biofilm bacteria, which were enriched with persisters, produced more pronounced skin lesions that took longer to heal, and had more severe skin pathology and higher bacterial load than mice infected with log phase bacteria. Using our persistent infection mouse model, we showed that the clinically recommended treatment for recurrent S. aureus skin infection, doxycycline + rifampin, was not effective in eradicating the bacteria in mice. Analogous findings were observed in a Caenorhabditis elegans model, where stationary phase S. aureus caused greater virulence or mortality than log phase bacteria as early as two days post-infection. Our findings associate in vitro persisters and biofilm bacteria with more persistent and more severe infections and emphasize the importance of quality or metabolic status of the inoculum bacteria (persister bacteria versus growing bacteria) not just the number of bacteria in causing disease. The persistent infection mouse model we developed with persister inocula should have implications for understanding the process of disease establishment and pathogenesis, for developing persistent infection animal models, and for developing more effective treatments for chronic persistent infections in general.

Evaluation of Platensimycin and Platensimycin-Inspired Thioether Analogues against Methicillin-Resistant Staphylococcus aureus in Topical and Systemic Infection Mouse Models

Staphylococcus aureus is one of the most common pathogens causing hospital-acquired and community-acquired infections. Methicillin-resistant S. aureus (MRSA)-formed biofilms in wounds are difficult to treat with conventional antibiotics. By targeting FabB/FabF of bacterial fatty acid synthases, platensimycin (PTM) was discovered to act as a promising natural antibiotic against MRSA infections. In this study, PTM and its previously synthesized sulfur-Michael derivative PTM-2t could reduce over 95% biofilm formation by S. aureus ATCC 29213 when used at 2 μg/mL in vitro. Topical application of ointments containing PTM or PTM-2t (2 × 4 mg/day/mouse) was successfully used to treat MRSA infections in a BABL/c mouse burn wound model. As a potential prodrug lead, PTM-2t showed improved in vivo efficacy in a mouse peritonitis model compared with PTM. Our study suggests that PTM and its analogue may be used topically or locally to treat bacterial infections. In addition, the use of prodrug strategies might be instrumental to improve the poor pharmacokinetic properties of PTM.

Newborn with desquamating rash

A 9-day-old boy was brought to the emergency department by his mother. The infant had been doing well until his most recent diaper change when his mother noticed a rash around the umbilicus, genitalia, and anus. The infant was born at term via spontaneous vaginal delivery. The pregnancy was uncomplicated; the infant's mother was group B strep negative. Following a routine postpartum course, the infant underwent an elective circumcision before hospital discharge on his second day of life. There were no interval reports of irritability, poor feeding, fevers, vomiting, or changes in urine or stool output.

Antimicrobial Activity of Omadacycline Tested against Clinical Bacterial Isolates from Hospitals in Mainland China, Hong Kong, and Taiwan: Results from the SENTRY Antimicrobial Surveillance Program (2013 to 2016)

Omadacycline is a derivative of minocycline and the first agent of the aminomethylcycline class. A total of 3,282 organisms (1 per patient) were consecutively collected from patients hospitalized in China (including Hong Kong) and Taiwan. Susceptibility testing was performed by broth microdilution methods in a central laboratory (JMI Laboratories). The collection included Gram-positive and Gram-negative organisms from patients with pneumonia, bloodstream, skin, community-acquired respiratory, and other infections. Omadacycline was very potent against Staphylococcus aureus (n = 689; MIC50/90, 0.12/0.25 mg/liter), including methicillin-resistant Staphylococcus aureus (MRSA; n = 299; MIC50/90, 0.12/0.5 mg/liter), and had similar activity across geographic regions. Omadacycline was very active against Streptococcus pneumoniae (highest MIC, 0.25 mg/liter), β-hemolytic streptococci (highest MIC, 1 mg/liter), viridans group streptococci (highest MIC, 0.25 mg/liter), and Enterococcus spp. (highest MIC, 0.5 mg/liter) from all geographic regions. Overall, 53.8% of S. pneumoniae isolates were penicillin resistant (penicillin MIC, ≥2 mg/liter) and 10.7% of enterococci (21.2% among E. faecium isolates) were vancomycin resistant. Omadacycline was active against Haemophilus influenzae (MIC50/90, 0.5/1 mg/liter) regardless of β-lactamase production and was active against Moraxella catarrhalis (MIC50/90, ≤0.12/0.25 mg/liter). Against Enterobacteriaceae, omadacycline was most active against Escherichia coli (MIC50/90, 1/2 mg/liter), Klebsiella oxytoca (MIC50/90, 1/4 mg/liter), and Enterobacter cloacae (MIC50/90, 2/4 mg/liter). Omadacycline had potent in vitro activity against Gram-positive and Gram-negative pathogens isolated from China and Taiwan and retained activity against problem pathogens, such as MRSA, vancomycin-resistant enterococci (VRE), penicillin-resistant S. pneumoniae (PRSPN), and extended-spectrum β-lactamase-producing E. coli The observed MIC profile in Chinese isolates was very similar to that seen in the U.S. and European surveillance studies.

Ceftaroline fosamil doses and breakpoints for Staphylococcus aureus in complicated skin and soft tissue infections

Objectives

To describe the pharmacokinetic/pharmacodynamic (PK/PD) modelling and microbiological data that were used to support the recent European approval of ceftaroline fosamil 600 mg q8h by 2 h intravenous (iv) infusion for patients with complicated skin and soft tissue infections (cSSTIs) caused by Staphylococcus aureus with ceftaroline MICs of 2 or 4 mg/L, and the associated EUCAST MIC breakpoint update for q8h dosing (intermediate = 2 mg/L and resistant >2 mg/L).

Methods

A population PK model for ceftaroline and ceftaroline fosamil was developed using PK data from 21 clinical studies. The final model was used to simulate PTA in patients with cSSTI receiving ceftaroline fosamil 600 mg q12h by 1 h iv infusion or 600 mg q8h by 2 h iv infusion. PTA was calculated by MIC for S. aureus PK/PD targets derived from preclinical studies (27% fT>MIC for stasis, 31% fT>MIC for 1 log10 kill and 35% fT>MIC for 2 log10 kill) and compared with S. aureus ceftaroline MIC distributions from a 2013 global surveillance study.

Results

The final population PK model based on 951 subjects adequately described ceftaroline and ceftaroline fosamil PK. High PTA (>90%) was predicted for the ceftaroline fosamil 600 mg q12h dosage regimen against S. aureus isolates with ceftaroline MICs ≤2 mg/L. Greater than 90% PTA was predicted for the ceftaroline fosamil 600 mg q8h dosage regimen against S. aureus with ceftaroline MICs ≤4 mg/L.

Conclusions

The approved ceftaroline fosamil dosage regimens for adults and adolescents with cSSTI achieve high PTA against S. aureus at the associated EUCAST breakpoints.

Mouse Model of Staphylococcus aureus Skin Infection

Bacterial skin and soft tissue infections are abundant worldwide, and many are caused by Staphylococcus aureus. Indeed, S. aureus is the leading cause of skin and soft tissue infections in the USA. Here we describe a mouse model of skin and soft tissue infection induced by subcutaneous inoculation of S. aureus. This animal model can be used to investigate a number of factors related to the pathogenesis of skin and soft tissue infections, including strain virulence and the contribution of specific bacterial molecules to disease, and it can be employed to test the potential effectiveness of antibiotic therapies or vaccine candidates.

Variation in Antibiotic Selection and Clinical Outcomes in Infants <60 Days Hospitalized With Skin and Soft Tissue Infections

OBJECTIVES

To describe variation in empirical antibiotic selection in infants <60 days old who are hospitalized with skin and soft-tissue infections (SSTIs) and to determine associations with outcomes, including length of stay (LOS), 30-day returns (emergency department revisit or readmission), and standardized cost.

METHODS

Using the Pediatric Health Information System, we conducted a retrospective study of infants hospitalized with SSTI from 2009 to 2014. We analyzed empirical antibiotic selection in the first 2 days of hospitalization and categorized antibiotics as those typically administered for (1) staphylococcal infection, (2) neonatal sepsis, or (3) combination therapy (staphylococcal infection and neonatal sepsis). We examined the association of antibiotic selection and outcomes using generalized linear mixed-effects models.

RESULTS

A total of 1319 infants across 36 hospitals were included; the median age was 30 days (interquartile range [IQR]: 17-42 days). We observed substantial variation in empirical antibiotic choice, with 134 unique combinations observed before categorization. The most frequently used antibiotics included staphylococcal therapy (50.0% [IQR: 39.2-58.1]) and combination therapy (45.4% [IQR: 36.0-56.0]). Returns occurred in 9.2% of infants. Compared with administration of staphylococcal antibiotics, use of combination therapy was associated with increased LOS (adjusted rate ratio: 1.35; 95% confidence interval: 1.17-1.53) and cost (adjusted rate ratio: 1.39; 95% confidence interval: 1.21-1.58), but not with 30-day returns.

CONCLUSIONS

Infants who are hospitalized with SSTI experience wide variation in empirical antibiotic selection. Combination therapy was associated with increased LOS and cost, with no difference in returns. Our findings reveal the need to identify treatment strategies that can be used to optimize resource use for infants with SSTI.

MRGPR-mediated activation of local mast cells clears cutaneous bacterial infection and protects against reinfection

Mast cells (MCs) are strategically distributed at barrier sites and prestore various immunocyte-recruiting cytokines, making them ideal targets for selective activation to treat peripheral infections. Here, we report that topical treatment with mastoparan, a peptide MC activator (MCA), enhances clearance of Staphylococcus aureus from infected mouse skins and accelerates healing of dermonecrotic lesions. Mastoparan functions by activating connective tissue MCs (CTMCs) via the MRGPRX2 (Mas-related G protein-coupled receptor member X2) receptor. Peripheral CTMC activation, in turn, enhances recruitment of bacteria-clearing neutrophils and wound-healing CD301b⁺ dendritic cells. Consistent with MCs playing a master coordinating role, MC activation also augmented migration of various antigen-presenting dendritic cells to draining lymph nodes, leading to stronger protection against a second infection challenge. MCAs therefore orchestrate both the innate and adaptive immune arms, which could potentially be applied to combat peripheral infections by a broad range of pathogens.

In vitro activity of tedizolid and other comparator drugs in methicillin-resistant Staphylococcus aureus isolates in skin and soft tissue infections in seven Colombian hospitals

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) causes severe skin and soft tissue infections in hospitals and, more recently, in the community. Tedizolid is a new second-generation oxazolidinone derivative having greater in vitro potency than linezolid against this type of microorganism. Objectives: To evaluate the antimicrobial activity of tedizolid and other comparator antibiotics in MRSA isolates causing skin and soft tissue infections in Colombian hospitals. Materials and methods: We conducted a prospective, multi-center descriptive study in seven tertiary-level hospitals in Colombia along a 12-month period. MRSA isolates were collected from adult patients with skin and soft tissue infections. Tedizolid, linezolid, vancomycin, daptomycin, trimethoprim-sulfamethoxazole, and clindamycin minimum inhibitory concentration (MIC) was determined by ETEST® (bioMérieux). Results: MRSA isolates were obtained from 102 patients with an average age of 46.8 years of whom 56 (54.9%) were men. Infection was community-acquired in 77 cases (75.4%). Abscess-related samples predominated (69 patients: 67.6%). All isolates were susceptible to tedizolid, linezolid, daptomycin, trimethoprim-sulfamethoxazole, and vancomycin. Tedizolid had greater in vitro activity than linezolid. Tedizolid MIC intervals ranged from 0.125 μg/mL to 0.5 μg/mL while those of linezolid ranged from 1μg/mL to 2μg/mL. Conclusions: MRSA strains circulating in Colombia are highly susceptible to tedizolid and can be considered a therapeutic alternative for hospitals and/or community-acquired skin and soft tissue infections.